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GENERAL PLANT AND ANIMALANATOMY AND PHYSIOLOGY

1. Define the term parthenogenesis

Parthenogenesis is the spontaneous development of an embryo from an unfertilized egg cell. Parthenogenesis is the phenomenon in which a female gamete directly develops into a new organism. It is seen in some birds (Turkey), rotifers and honeybee and some plants

2. State four advantages of plant reproduction by seeds

Seeds are surrounded by a protective cover called the seed coat. The seed coat protects the embryo from harsh environmental conditions.

They provide nourishment and parental care to the developing embryo.

The dispersal of the seeds to far-off places prevents competition among the members of the same species, thus preventing their extinction.

3. Differentiate between oviparous and viviparous animals.

 In oviparous animals, embryo develops outside the body of female in eggs, e.g. reptiles On the contrary in viviparous animals, embryo develops inside body of female. They give birth to babies, e.g. humans.

4. Distinguish between viability and vigour in seed germination

Seed viability refers to a seed’s capacity to germinate and produce a healthy seedling. Seed vigor refers to how quickly seeds germinate. The viability test is used to determine if a seed sample contains alive or dead seeds. The seed vigor test distinguishes between high and low vigor seeds.

5. State three stages in seed germination process

6.Name four types of fruit ovules

Simple Fruit:

1.Simple natural products are those kinds of natural products that are created from the monocarpellary ovary or multicarpellary syncarpous ovary and the main organic product is framed by the gynoecium.

Aggregate Fruits :

1.Aggregate Fruits are the sorts of organic products that begin from the multicarpellary apocarpous ovary.

2.This natural product turns into a fruitlet in light of the fact that every carpel is isolated from the other in the apocarpous ovary.

3.Total organic products spread the word about a lot of fruits which are as etaerio

4.Fruits from many flowers are packed together such as pineapple, blackberry, and raspberry.

Multiple Fruits:

1.Multiple fruits, also known as collective fruits, are fruiting structures that develop from an inflorescence, which is a cluster of flowers.

2.The fruits that are produced by each flower in the inflorescence eventually combine into a single mass.

3.The mass that forms after flowering is known as an infructescence.

4.The fig, pineapple, mulberry, osage-orange, and jackfruit are other examples.

5.An aggregation fruit, like a raspberry, grows from several ovaries of a single flower in contrast.

6.The meanings of “many” and “aggregate” fruit are flipped in languages other than English, causing multiple fruits to combine several pistils into a single blossom.

7.Examples are the fig, pineapple, mulberry, osage-orange, and jackfruit.

Accessory Fruit:

1.When some of the fruit’s flesh originates from tissue nearby the carpel rather than the floral ovary, the fruit is said to be an accessory fruit.

2.The petals establish the symmetry of the flower.

3.The term “regular” or “actinomorphic” refers to a flower that has radial symmetry and has petals that are equal in size, shape, and distance from one another (e.g., buttercup, Ranunculus; Ranunculaceae).

6. What is the major difference you observe in the offsprings produced by asexual reproduction and in the progeny produced by sexual reproduction?     

Offsprings -produced by asexual reproduction are genetically identical to parents and to each other. On the contrary, progeny produced as a result of meiosis and gametic fusion in sexual reproduction show variations and differences from the two parents as well as among themselves.    

7. Distinguish between  each of the following

• Bulb and corn

Bulbs are structurally short stems with fleshy leaves or leaf bases. Corms are rounded, underground storage organs consisting of a swollen stem base covered with scale leaves. Bulbs are modified leaves that store nutrients. Corms are swollen stem bases.

• Stolon  and runner

Stolons develop underground stems that grow horizontally and bear nodes and internodes. Stolons are very similar to runners except that they are underground and are produced below the soil surface.

• Stem tuber and rhizome

Rhizome is the main underground stem that creeps horizontally below the surface of the soil is the rhizome.This is fleshy and helps in storage.For example, ginger.

Tuber is the underground part of the root of the structure derived from the tip of underground branches is the tuber. This helps in the storage of starch.For example, potatoes and beetroot.

8. Draw a diagram of a matured microspore of an angiosperm. Label its cellular components only.
   

The labelled diagram of a mature microspore of an angiosperm with its cellular components is given below:

9. Draw a diagram of a male gametophyte of an angiosperm. Label any four parts. Why is sporopollenin considered the most resistant organic material?

(i)The structure of a male gametophyte of an angiosperm is:

(ii)Sporopollenin is one of the hardest or resistant organic material known. It can withstand high temperatures, strong acids and alkalis. No enzyme that degrades sporopollenin is so far known.That’s why it is considered the most .

10. Draw a labelled diagram of sectional view of a mature embryo sac of an angiosperm.
    

The sectional view of a mature embryo sac in an angiospermis. Chalazal end Antipodals resistant organic material

8. Explain the phenomenon of double fertilisation.  

The phenomenon of double fertilisation occur in following steps:
(i) In an angiospermic plant, two male gametes are discharged by a pollen tube into the embryo sac.
(ii) One of the male gametes fuses with the egg to form a zygote. This process is called syngamy.

1. Other male gamete fuses with the secondary nucleus to form the primary endosperm nucleus, this process is called triple fusion.
   (iv) Since, there are two fusions (syngamy and triple fusion), inside an ovule during fertilisation, it is known as double fertilization

11. Name two

• Growth inhibitors in plants

 Abscisic acid and Ethylene are grouped into Plant growth inhibitors.

• Growth promotors in plants

Auxins, Gibberellins, and Cytokinins are grouped into Plant growth promoters while

 

12. Explain the necessity of transport in plants and animals.

Transport is an important part of sustaining life in both plants and animals. Transport of substances and waste products is achieved through cellular mechanisms such as pumps, channels, carrier and ducts.

Transport is a necessity for the growth and survival of all living things. Molecules need to be transported from one area of the cell to another, or from one area of the organism to another to sustain life. For example, the food that is eaten by animals is digested in the stomach and absorbed in the small intestine. The nutrients from that food need to be transported to other cells in the body so they can use it as energy and building blocks to create cellular materials. If the nutrients remained at the small intestine, the other organs of the body would run out of energy and die off. The same goes for plants, the water and nutrients the roots pulled from the soil need to be delivered to the rest of the plant so that it can grow and survive. If the transport tubes of the plant, xylem, and phloem, were non-existent, the plant would die as the stalk and leaves would not receive any energy. Transport of waste products is also necessary to rid the body of toxic substances that would otherwise accumulate and kill the organism.

13. Explain the process of fertilization in  a flowering plant

Flowers are the reproductive structures of angiosperms. They vary greatly physically and are of great diversity in methods of reproduction. The process of fertilization in plants occurs when gametes in haploid conditions meet to create a zygote which is diploid. The male gametes of the flower are transferred on to the female reproductive organs through pollinators. The final product of this process is the formation of embryo in a seed.

14. Describe the process by which plants prepare their food using different raw materials.
The process by which green plants can prepare their own food is called photosynthesis. Green plants possess chlorophyll in their leaf and utilises carbon dioxide (from air) water, minerals (from soil, through root) as raw material and sunlight as source of energy and convert light energy into chemical energy. The food thus synthesised is in the form of starch (carbohydrate). The overall reaction for photosynthesis can be given as follows:

15. Define the following terms  as used in vegetative propagation

scion

 The scion is the part of the grafted plant that will produce the plant’s shoots. It will, in the future, give rise to all of the plant’s leaves, stems, flowers, and fruits. The scion is typically the top part of the grafted plant.

Root stock

A rootstock is part of a plant, often an underground part, from which new above-ground growth can be produced. It could also be described as a stem with a well developed root system, to which a bud from another plant is grafted. It can refer to a rhizome or underground stem.

16. Explain four methods of vegetative propagation

Vegetative propagation methods include: • rooting of cuttings, • layering or marcotting, • grafting, • micropropagation. Propagation is the natural mechanism by which plants regenerate.

17. State four advantages  and disadvantages of vegetative propagation

Advantages of vegetative propagation

Quicker and more certain.

Produces identical quality as the parent.

Plants that do not have viable seed, can be reproduced.

Flowers produced are of superior quality.

Desirable character of fruit can be maintained.

Disadvantages of vegetative reproduction

Does not produce new variety.

Leads to overcrowding around the parent plant.

Very little possibility of dispersal.

 

18. Write the differences between wind pollinated and insect pollinated flowers. Give an example of each type. 

The differences between wind pollinated and insect pollinated flowers are:

7. Draw a Longitudinal Section (LS) of a post-pollinated pistil showing entry of pollen tube into a mature embryo sac. Label filiform apparatus, chalazal end, hilum, antipodals, male gametes and secondary nucleus.    
   Longitudinal Section (LS) of a post-pollinated pistil is given below:
   
8. Banana is a parthenocarpic fruit, whereas oranges show polyembryony. How are they different from each other with respect to seeds?    
   Since, banana is a parthenocarpic fruit, it is seedless, whereas oranges show polyembryony that leads to formation of many seed
9. Why are humans testes located outside the abdominal cavity?Name the pouch in which they are present.    Human testes are located outside the abdominal cavity as it helps in maintaining low temperature, (2-2.5°C lower than body temperature), required for spermatogenesis.Testes are enclosed in a pouch called scrotum.
10. List the different parts of human oviduct through which the ovum travels till it meets the sperm for fertilisation.
11. The different parts of human female oviduct through which the ovum travels, till it gets fertilised are given below in the sequence.
    • Fimbriae, finger-like projections Collect or catch the ovum, after ovulation.
    • Infundibulum Ovum from fimbriae is guided into funnel-shaped infundibulum, part of Fallopian tube.
    • Ampulla A wider part of oviduct that leads ovun into isthmus.
    • Isthmus With narrow lumen, and in the portion or junction of ampulla-isthmus, the ovum gets fertilised..
12. Write the location and function of Sertoli cells in humans.
    Location of Sertoli cells Within the lining of seminiferous tubule of testis.
    Function of Sertoli cells They provide nutrition to the developing sperm cells.
13. Where are fimbriae present in a human female reproductive system. Give their function.    
    Fimbriae are present in funnel-shaped edges of the Fallopian tube or oviduct in human female reproductive system. They help in the collection of ovum/secondary oocyte after ovulation. 
14. When do the oogenesis and the spermatogenesis initiate in human females and males, respectively?
    .Oogenesis initiates in foetal or embryonic
    stage of females, whereas spermatogenesis, in males starts at puberty.
15. Mention the differences between spermiogenesis and spermiation
16. 
    
17. 
    
18. Difference between spermiogenesis and spermiation is:
    
19. State and Explain the role of any two accessory glands in human male reproductive system.

(I) Oogenesis begins during the embryonic development stage when a million gamete mother cells (oogonia) are formed within each foetal ovary.

(ii) (a) Sertoli cells are located on the inside lining of seminiferous tubule. These cells provide nutrition to the germ cells.
    (b) Leydig cells or interstitial cells are located in the regions outside the seminiferous tubule called interstitial spaces. These cells synthesise and secrete testicular hormone called androgens.
Primary spermatocytes Located inside the seminiferous tubule and involved in the formation of spermatozoa.

(c) Prostate and seminal vesicles Their secretion provide a fluid medium for the sperms to swim towards the ovum. They provide nutrition to sperms.

(d) Bulbourethral glands ;Their secretion helps in the lubrication of penis.

24. State the function of  Vas deferens tube

Typically, you have a vas deferens (also called a sperm duct or a ductus deferens) in each testicle. The job of these ducts is to move sperm away from its storage place in the testicle. The ducts can be affected by scar tissue or infections.

17. state four functions of placenta

The placenta is an organ that develops in the uterus during pregnancy. This structure provides oxygen and nutrients to a growing baby. It also removes waste products from the baby’s blood.

18. describe the features common  to both male and female reproductive systems  in mammals

The reproductive system is the human organ system responsible for the production and fertilization of gametes (sperm or eggs) and, in females, the carrying of a fetus. Both male and female reproductive systems have organs called gonads that produce gametes. A gamete is a haploid cell that combines with another haploid gamete during fertilization, forming a single diploid cell called a zygote. Besides producing gametes, the gonads also produce sex hormones.

1. state the eight steps  of fertilization process in human

When sperms come in contact with an egg, one of the sperms may fuse with the egg. Such fusion of the egg and the sperm is called fertilization. During fertilization, the nuclei of the sperm and the egg fuse to form a single nucleus. This results in the formation of a fertilized egg or zygote.The process of fertilization is the meeting of an egg cell from the mother and a sperm cell from the father. So, the new individual inherits some characteristics from the mother and some from the father.

22. State and explain the function of acrosome. In humans, the acrosome is present in the anterior portion of head of the human sperm. Function Enzymes present in acrosome help in contact and penetration into egg, during fertilisation of the ovum
23. List the changes the primary oocyte undergoes in the tertiary follicular stage in human embryo..
    In human embryo, the primary oocyte grows in size, completes meiosis-l and forms a larger cell, the secondary oocyte and a smaller cell, the first polar body.
24. Draw and label the parts of the head region only of a human sperm.
    

Diagram showing head of human sperm
(i) The acrosome is filled with enzymes that help in fertilisation of the ovum.

Neck contains two centrioles, a proximal centriole which is necessary for first cleavage division of zygote and a distal centriole, that gives rise to axial filament of tail
(ii)Middle piece possesses many mitochondria to produce energy for the movement of tail to facilitate sperm motility.
(iii)Tail of the sperm consists of an axial filament. Its role is to help movement inside the female reproductive tract towards the ovum for fertilisation.

22. Spermatogenesis in human males is a hormone regulated process. Justify.  
    Hormonal control of spermatogenesis in human males:
    (i) Gonadotropin Releasing Hormone (GnRH) is released significantly from the hypothalamus during puberty.
    (ii) GnRH stimulate anterior pituitary to secrete gonadotropins, i.e. LH and FSH or Interstitial Cell Stimulating Hormone (ICSH).

(iii)Leuteinising Hormone (LH) acts on Leydig cells to stimulate synthesis and secretion of androgens. Androgens stimulates the process of spermatogenesis.
(iv) Follicle Stimulating Hormone (FSH) acts on Sertoli cells and stimulates them to secrete certain factors which are necessary for the process of spermiogenesis.

23. Identify  the parts of the reproductive system  where each of the following process takes place

• Oogenesis

Oogenesis occurs in the outermost layers of the ovaries. Oogenesis starts with a germ cell called oogonium and undergoes mitosis to increase in number.

• Fertilization

Fertilization usually takes place in a fallopian tube that links an ovary to the uterus. If the fertilized egg successfully travels down the fallopian tube and implants in the uterus, an embryo starts growing.

• Implantation

Once fertilized, the cells start to multiply and grow. The zygote, or fertilized egg, travels down into the uterus and becomes what’s called a morula. In the uterus, the morula becomes a blastocyst and eventually burrows into the uterine lining in a process called implantation.

• Formation of sperms

Sperm production in the testes takes place in coiled structures called seminiferous tubules. Along the top of each testicle is the epididymis. This is a cordlike structure where the sperm mature and are stored. The release process starts when the penis fills with blood and becomes erect

24. State the function of each of the following in a male reproductive system

• Prostrate gland

The prostate gland is located just below the bladder in men and surrounds the top portion of the tube that drains urine from the bladder (urethra). The prostate’s primary function is to produce the fluid that nourishes and transports sperm (seminal fluid).

• Seminal vessicle

The seminal vesicle is part of the reproductive system. The vesicles have both glandular tissue and muscular tissue. The muscular tissue contracts to move seminal fluid and sperm into the urethra and out through the penis.

• Cowpers gland

Cowper’s glands are pea sized glands present inferior to the prostate gland in the male reproductive system. They produce thick clear mucus prior to ejaculation that drains into the spongy urethra.

25. Describe fertilization in flowering plants

In plants, fertilization is a process of sexual reproduction, which occurs after pollination and germination.

Fertilization can be defined as the fusion of the male gametes (pollen) with the female gametes (ovum)  to form a diploid zygote. It is a physicochemical process which occurs after the pollination of the carpel. The complete series of this process takes place in the zygote to develop into a seed.

In the fertilization process, flowers play a significant role as they are the reproductive structures of angiosperms (flowering plants). The method of fertilization in plants occurs when gametes in haploid conditions fuse to produce a diploid zygote.

In the course of fertilization, male gametes get transferred into the female reproductive organs through pollinators (honey bees, birds, bats, butterflies, flower beetles) and the final product will be the formation of the embryo in a seed.

In flowers, the pollen grain germinates after the pollination of the carpel and grows into the style by creating the pathway for the pollen grain to move down to the ovary.

The pollen tube opens into the ovule through the micropyle and bursts into the embryo sac. Here, the male nucleus unites with the nucleus of an egg inside the ovule forming a diploid zygote, which later swells up and develops into a fruit.

26. How is the entry of only one sperm ensured into an ovum during fertilisation in humans.

.During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum and induces changes (depolarisation) in the membrane that blocks the entry of additional sperms. This ensures that only one sperm can fertilise an ovum

27. .(i)Explain the events taking place at the time of fertilisation of an ovum in a human female.

    The process of fertilization in a human female involves a series of events that lead to the fusion of a sperm cell with an ovum (egg). Here are the key events that take place during fertilization:

    ü Ovulation: Ovulation is the release of a mature egg from the ovary. Typically, one egg is released during each menstrual cycle. The egg is surrounded by a protective layer called the zona pellucida and is swept into the fallopian tube (also known as the oviduct).

    ü Sperm Transport: Sperm cells, which are deposited in the vagina during sexual intercourse, need to travel through the cervix, uterus, and into the fallopian tube where fertilization occurs. Sperm cells undergo capacitation, a process that involves changes in their structure and mobility, enabling them to swim more effectively towards the egg.

    ü Penetration of the Zona Pellucida: When sperm cells reach the egg in the fallopian tube, they must penetrate the zona pellucida, the protective layer surrounding the egg. Sperm cells release enzymes that help them break through the zona pellucida and reach the surface of the egg.

    ü Fusion of Sperm and Egg: Once a sperm cell reaches the surface of the egg, it binds to specific receptors on the egg’s surface. This binding triggers a series of changes in the egg’s membrane, preventing other sperm cells from binding. The sperm then undergoes the process of acrosomal reaction, where the acrosome at the tip of the sperm releases enzymes to help it penetrate the egg’s membrane. The sperm’s nucleus enters the egg, and the membranes of the sperm and egg fuse, combining their genetic material.

    ü Activation of the Egg: The fusion of the sperm and egg triggers various changes in the egg, including the completion of meiosis (the division of chromosomes), forming the female pronucleus. The male pronucleus, derived from the sperm, forms as well. The pronuclei contain the genetic material from each parent.

    ü Formation of Zygote: The male and female pronuclei migrate towards each other within the egg. When they meet, they fuse, combining the genetic material from the sperm and egg. This fusion forms a diploid cell called a zygote, which now contains the complete set of chromosomes required to develop into a human being.

    ü Implantation: After fertilization, the zygote starts dividing rapidly as it travels down the fallopian tube towards the uterus. Once it reaches the uterus, it undergoes further cell divisions and forms a blastocyst, a hollow structure consisting of an outer layer of cells and an inner cell mass. The blastocyst then implants itself into the uterine lining, where it will develop further.

(ii)Trace the development of the zygote up to its implantation in the uterus.

After fertilization, the zygote undergoes several stages of development before it implants in the uterus. Here is a step-by-step trace of the zygote’s development:

ü Zygote Formation: Fertilization occurs when a sperm cell fuses with an egg cell, resulting in the formation of a diploid zygote. The zygote contains the complete set of chromosomes required for human development, with half of the chromosomes from the sperm and half from the egg.

ü Cleavage: The zygote begins a process called cleavage, where it undergoes rapid cell divisions without growth in size. During cleavage, the zygote divides into smaller cells called blastomeres. These divisions result in the formation of a solid ball of cells called a morula.

ü Blastocyst Formation: The morula continues to divide and forms a fluid-filled cavity in the center. This fluid-filled structure is known as the blastocoel. The embryo at this stage is called a blastocyst. The blastocyst consists of two distinct cell populations: the outer layer of cells called the trophoblast and the inner cell mass.

ü Differentiation of Trophoblast and Inner Cell Mass: The trophoblast cells give rise to the placenta, which will nourish and support the developing embryo. The inner cell mass, which is a cluster of cells within the blastocyst, gives rise to the embryo itself.

ü Implantation: The blastocyst undergoes implantation in the uterus. It attaches to the endometrium, the lining of the uterus. The trophoblast cells secrete enzymes that allow the blastocyst to penetrate the uterine wall. Once implanted, the trophoblast cells continue to proliferate, forming finger-like projections called chorionic villi. The chorionic villi play a crucial role in establishing a connection between the maternal blood supply and the developing embryo.

ü Formation of Placenta and Amniotic Sac: The trophoblast cells differentiate further and form the chorion, which surrounds the amniotic sac. The amniotic sac contains the amniotic fluid, which protects and cushions the developing embryo. The chorion, along with the endometrium, forms the placenta, a vital organ that allows nutrient and gas exchange between the mother and the developing embryo.

ü Further Embryonic Development: Once implanted, the inner cell mass continues to differentiate and form the three germ layers: ectoderm, mesoderm, and endoderm. These germ layers give rise to different tissues and organs of the developing embryo.

(iii)Name and draw a labelled sectional view of the embryonic stage that gets implanted.

(i)In humans, the fertilisation of ovum takes place in ampullary-isthmic junction of Fallopian tube.

The events that occur during the process of fertilisation are:
(a) The sperm reaches the junction of ampulla and isthmus and comes in contact with zona pellucida layer of ovum.
(b) Acrosome of sperm head release sperm lysin enzymes that dissolves corona radiata and digests zona pellucida layer and enters cytoplasm.

(c) Entry of sperm stimulates secondary oocyte to complete its suspended second meiotic division, thus producing haploid egg or ovum and second polar body.

(d)Nucleus of sperm and of ovum fuses to form a diploid zygote.
(ii)Development of zygote up to implantation takes place in following sequence

• Cleavage division (mitotic) starts in zygote as it moves through the isthmus of Fallopian tube towards the uterus.
• This division results into 2, 4, 8 and 16 daughter cells called blastomeres.
• The embryo with 8-16 blastomeres is called morula.
• Morula continues to divide and transforms into blastocyst as it moves further into uterus.
• Blastomeres in the blastocyst are arranged into an outer layer called trophoblast and inner group of cells attached to trophoblast called inner cell mass.
• Trophoblast layer then gets attached to the endometrium and the inner cell mass gets differentiated as the embryo.
• After attachment, the uterine cells divide rapidly and cover the blastocyst.
• It leads to blastocyst’s embedding in the endometrium of the uterus. This is called implantation.

(iii) Blastocyst stage implants in the uterus.

28. Draw the structure of a neuron and explain its function.
    

Nerve cell or neuron is the functional unit of nervous system. A nerve cell has three parts-

1. cell body
2. dendrite

1. axon
   Function : The function of nerve cells is to carry information in the form of electrical signals which are called nerve impulses. Cells receive stimulus to send it to spinal cord and brain and carry the message from brain to the target organ.

29. How does pancreas control glucose level of blood ?
    Pancreas produces two hormones

Insulin from P-cells of islet of Langerhans and

Glucagon from a- cells of islets of langerhans.

Insulin is produced when glucose level of blood rises. Insulin helps the cells to withdraw glucose from blood. It also converts glucose into glycogen in liver and muscles.

30. How is the small intestine designed to absorb digested food ?

The small intestine is designed to provide maximum area for absorption of digested food and its transfer into the blood for its circulation into the body. For this the inner lining of the small intestine has numerous finger-like projections called villi. The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body.

31. State four functions of non-ruminant stomach in digestion

Ruminant animals have a stomach with four compartments while the stomach of non-ruminant animals is composed of a single compartment. Furthermore, ruminant animals digest plant materials such as cellulose through fermentation while non-ruminant animals eliminate cellulose as an undigested material. The main difference between ruminant and non-ruminant animals is the type of digestion and the structure of the digestive system.

32. State the functions of each of the following mouth parts of insect

• Mandible

Insect mandibles are a pair of appendages near the insect’s mouth, and the most anterior of the three pairs of oral appendages (the labrum is more anterior, but is a single fused structure). Their function is typically to grasp, crush, or cut the insect’s food, or to defend against predators or rivals.

• Maxillae

Maxillae (singular Maxilla) are part of an insect’s mouthparts. The maxilla are paired and arranged behind the mandibles. Maxillae usually end in a sharp point and so the maxillae act like pincers. They are used to hold and manipulate food so that it can be chewed or sliced by the mandibles.

• Labrium

The labrum is often called an insect’s upper lip. The labrum is flattened piece of cuticle at the base of the insect’s “face” and above the mouthparts. The labrum partially or completely obscures the mandibles and helps hold food in a position when the insect feeds.

• Hypopharynix

The hypopharynx, a tongue-like structure in insects with chewing mouthparts (Fig. 2.2A), is also styletiform in mosquitoes and is used to pierce host tissue. Running the length of the hypopharynx is a channel that delivers saliva to the apical portion of the mouthparts during feeding.

33. Relate the structure of human stomach to its function

The stomach is a J-shaped organ that digests food. It produces enzymes (substances that create chemical reactions) and acids (digestive juices). This mix of enzymes and digestive juices breaks down food so it can pass to your small intestine.

Your stomach is part of the gastrointestinal (GI) tract. The GI tract is a long tube that starts at your mouth. It runs to your anus, where stool (poop) leaves your body. The GI tract is a key part of your digestive system.

What is the stomach’s function?

Your stomach’s purpose is to digest food and send it to your small intestine. It has three functions:

• Temporarily store food.
• Contract and relax to mix and break down food.
• Produce enzymes and other specialized cells to digest food.

How does the stomach work with the rest of the GI tract?

Each part of your GI tract breaks down food and liquid and carries it through your body. During the digestive process, your body absorbs nutrients and water. Then, you expel the waste products of digestion through your large intestine.

Food moves through your GI tract in a few steps:

1. Mouth:As you chew and swallow, your tongue pushes food into your throat. A small piece of tissue called the epiglottis covers your windpipe. The epiglottis prevents choking.
2. Esophagus:Food travels down a hollow tube called the esophagus. At the bottom, your esophageal sphincter relaxes to let food pass to your stomach. (A sphincter is a ring-shaped muscle that tightens and loosens.)
3. Stomach:Your stomach creates digestive juices and breaks down food. It holds food until it is ready to empty into your small intestine.
4. Small intestine: Food mixes with the digestive juices from your intestine, liverand pancreas. Your intestinal walls absorb nutrients and water from food and send waste products to the large intestine.
5. Large intestine: Your large intestine turns waste products into stool. It pushes the stool into your rectum.
6. Rectum: The rectum is the lower portion of your large intestine. It stores stool until you have a bowel movement.

Where is the stomach located?

Your stomach sits in your upper abdomen on the left side of your body. The top of your stomach connects to a valve called the esophageal sphincter (a muscle at the end of your esophagus). The bottom of your stomach connects to your small intestine.

How big is your stomach?

The size of the stomach varies from person to person. Your stomach expands when full and deflates when empty. Because of this, your stomach size can vary depending on how recently and how much you have eaten.

What are the parts of the stomach’s anatomy?

Your stomach has five distinct sections:

• The cardia is the top part of your stomach. It contains the cardiac sphincter, which prevents food from traveling back up your esophagus.
• The fundus is a rounded section next to the cardia. It’s below your diaphragm (the dome-shaped muscle that helps you breathe).
• The body (corpus) is the largest section of your stomach. In the body, your stomach contracts and begins to mix food.
• The antrum lies below the body. It holds food until your stomach is ready to send it to your small intestine.
• The pylorus is the bottom part of your stomach. It includes the pyloric sphincter. This ring of tissue controls when and how your stomach contents move to your small intestine.

What is the stomach’s structure?

Several layers of muscle and other tissues make up your stomach:

• Mucosais your stomach’s inner lining. When your stomach is empty, the mucosa has small ridges (rugae). When your stomach is full, the mucosa expands, and the ridges flatten.
• Submucosacontains connective tissue, blood vessels, lymph vessels (part of your lymphatic system) and nerve cells. It covers and protects the mucosa.
• Muscularis externa is the primary muscle of your stomach. It has three layers that contract and relax to break down food.
• Serosa is a layer of membrane that covers your stomach.

 

34. (a)List five enzymes found in pancreatic juice

 Pancreas creates natural juices called pancreatic enzymes to break down foods. These juices travel through your pancreas via ducts. They empty into the upper part of your small intestine called the duodenum. Each day, your pancreas makes about 8 ounces of digestive juice filled with enzymes. These are the different enzymes:

1. This enzyme works together with bile, which your liver produces, to break down fat in your diet. If you don’t have enough lipase, your body will have trouble absorbing fat and the important fat-soluble vitamins (A, D, E, K). Symptoms of poor fat absorption include diarrhea and fatty bowel movements.

1. This enzyme breaks down proteins in your diet. It also helps protect you from germs that may live in your intestines, like certain bacteria and yeast. Undigested proteins can cause allergic reactions in some people.

1. This enzyme helps break down starches into sugar, which your body can use for energy. If you don’t have enough amylase, you may get diarrhea from undigested carbohydrates.
2. Gastrin and amylin. Gastrin is primarily made in the G cells in your stomach, but some is made in the pancrease, too. It stimulates your stomach to make gastric acid. Amylin is made in beta cells and helps control appetite and stomach emptying.
3. State the function of each of the following in human intestines

• Capilaries

The mucosa that lines the small intestine is covered with fingerlike projections called villi. There are blood capillaries and special lymph capillaries, called lacteals, in the center of each villus. The blood capillaries absorb most nutrients, but the fats and fat-soluble vitamins are absorbed by the lacteals.

• Lactael

A lacteal is the blunt‐ended lymphatic capillary at the center of each villus in the small intestine, is a main route for drainage of dietary lipids and lipid‐soluble nutrients in the form of lymph, which returns to the systemic circulation via the thoracic duct

36. Outline digestion in the small intestines

Food moves through your GI tract by a process called peristalsis. The large, hollow organs of your GI tract contain a layer of muscle that enables their walls to move. The movement pushes food and liquid through your GI tract and mixes the contents within each organ. The muscle behind the food contracts and squeezes the food forward, while the muscle in front of the food relaxes to allow the food to move.

The digestive process starts when you put food in your mouth.

Mouth. Food starts to move through your GI tract when you eat. When you swallow, your tongue pushes the food into your throat. A small flap of tissue, called the epiglottis, folds over your windpipe to prevent choking and the food passes into your esophagus.

Esophagus. Once you begin swallowing, the process becomes automatic. Your brain signals the muscles of the esophagus and peristalsis begins.

Lower esophageal sphincter. When food reaches the end of your esophagus, a ringlike muscle—called the lower esophageal sphincter —relaxes and lets food pass into your stomach. This sphincter usually stays closed to keep what’s in your stomach from flowing back into your esophagus.

Stomach. After food enters your stomach, the stomach muscles mix the food and liquid with digestive juices. The stomach slowly empties its contents, called chyme, into your small intestine

Small intestine. The muscles of the small intestine mix food with digestive juices from the pancreas, liver, and intestine, and push the mixture forward for further digestion. The walls of the small intestine absorb water and the digested nutrients into your bloodstream. As peristalsis continues, the waste products of the digestive process move into the large intestine.

Large intestine. Waste products from the digestive process include undigested parts of food, fluid, and older cells from the lining of your GI tract. The large intestine absorbs water and changes the waste from liquid into stool. Peristalsis helps move the stool into your rectum.

Rectum. The lower end of your large intestine, the rectum, stores stool until it pushes stool out of your anus during a bowel movement.

39. How are the lungs designed in human beings to maximise the area for exchange of gases ?
    • Within the lungs, the air passage divides into smaller and smaller tubes, called bronchi which in turn form bronchioles. The bronchioles terminate in balloon-like structures, called alveoli. The alveoli present in the lungs provide maximum surface for exchange of gases. The alveoli have vary thin walls and contain an extensive network of blood vessels to facilitate exchange of gases.
40. What are the components of the transport system in human beings ? What are the functions of these components ?

The transport system (circulatory system) in human beings mainly consists of heart, blood and blood vessels.

1. Function of heart : The heart receives deoxygenated blood from the body parts and pumps it to lungs for enriching with oxygen. It receives purified blood from lungs and pumps it around the body.
   (ii) Function of blood : Blood transports oxygen, carbon dioxide, digested food, hormones and nitrogeneous waste like urea. It also protects the body from diseases and regulates the body temperature.
2. Function of blood vessels : The blood pushed by the heart flows through the blood vessels (arteries, veins and capillaries) and also comes back to the heart through them.

State four characteristics  of class insecta that  that differentiate it from other classes of animals

1. These are tracheated arthropods.
2. It possesses 3 pairs of jointed legs.
3. Body is segmented .
4. Insect body is divided into 3 regions viz., head, thorax and abdomen
5. It possesses a pair of compound eyes & antennae.
6. Two pairs of wings are present in adult stage.

Differentiate between a nervous system and endocrine system

One of the most significant differences between the nervous system and endocrine system is that the nervous system uses electrical impulses to send messages through neurons while endocrine glands use hormones to send messages to the target cells through the bloodstream. However ,both the nervous system and endocrine system give signals to the internal body parts.

Nervous System	Endocrine System
Electrical impulses are the messengers in the nervous system	Hormones are the chemical messengers in the endocrine system that target cells through the bloodstream
Brain and the spinal cord constitute the nervous system	Glands and organs like thyroid, pituitary glands and reproductive organs (ovaries and testes) are involved in the endocrine system
Nerve impulses are transmitted through neurons	Hormones are transmitted through blood vessels
The nervous system is under both voluntary and involuntary control	The endocrine system is under involuntary control
Nerve impulses make use of the neurotransmitters at synaptic clefts and sodium and potassium channels and enter the target cells.	The hormones enter into the target cells by diffusing through the plasma membrane or by binding to the cell receptors
Responses are localised	Responses are widespread

38. Distinguish between Oesteology and Ornithology

While osteology focuses on the study of bones, their structure, and functions across various organisms, ornithology specifically concentrates on birds, covering their classification, behavior, ecology, and conservation.

39. What are the components of the transport system in highly organised plants?

In highly organised plants there are two conducting tissues xylem and phloem.

Xylem consists of vessels, tracheids and other xylem tissues. The interconnected vessels and tracheids form a continuous system of water conducting channels reaching all parts of the plant. Xylem carries water and minerals.

Phloem conducts soluble products of photosynthesis from leaves to different parts of the plant body.

37. How are water and minerals transport in plants ?

The roots of a plant have hair called root hair.
The root hair are directly in contact with the film of water in between the soil particles. Water and dissolved minerals get into the root hair by the process of diffusion. The water and minerals absorbed by the root hair from the soil pass from cell to cell by osmosis through the epidermis, root cortex, endodermis and reach the root xylem.
The xylem vessels of the root of the plant are connected to the xylem vessels of its stem.

Therefore the water containing dissolved minerals enters the root xylem vessels into stem xylem vessels. The xylem vessels of the stem branch into the leaves of the plants. So, the water and minerals carried by the xylem vessels in the stem reach the leaves through the branched xylem vessels which enter from the petiole (stalk of the leaf) into each and every part of the leaf. Thus the water and minerals from the soil reach through the root and stem to the leaves of the plants. Evaporation of water molecules from the cells of a leaf creates a suction which pulls water from the xylem cells of roots. The loss of water in the form of vapour from the aerial parts of the plant is known as transpiration.
38. How is food transported in plants ?

The movement of food in phloem (or translocation) takes place by utilizing energy. The sugar (food) made in leaves is loaded into the sieve tubes of phloem tissue by using energy from ATP Water now enters the sieve tubes containing sugar by the process of osmosis due to which the pressure in the phloem tissue rises. This high pressure produced in the phloem tissue moves the food to all parts of the plant having less pressure in their tissues. This allows the phloem to transport food according to the needs of the plant.

38. State the importance of excretion in living  organisms

Excretion, the process by which animals rid themselves of waste products and of the nitrogenous by-products of metabolism. Through excretion organisms control osmotic pressure—the balance between inorganic ions and water—and maintain acid-base balance. The process thus promotes homeostasis, the constancy of the organism’s internal environment.

39. List four functions of kidney
40. Filtration and Waste Removal: The primary function of the kidneys is to filter waste products, toxins, and excess substances from the bloodstream. They selectively remove waste molecules, such as urea, creatinine, and uric acid, along with excess water and electrolytes, while retaining essential substances like glucose and proteins. These waste products and excess fluids are then eliminated from the body through urine formation.
41. Regulation of Fluid and Electrolyte Balance: The kidneys play a crucial role in maintaining the balance of fluids and electrolytes in the body. They help regulate the concentration of substances like sodium, potassium, calcium, and phosphate in the bloodstream. By selectively reabsorbing or excreting these substances, the kidneys help maintain proper hydration, blood pressure, and pH balance within the body.
42. Acid-Base Balance: The kidneys contribute significantly to maintaining the body’s acid-base balance, also known as pH homeostasis. They help regulate the levels of bicarbonate ions (HCO3-) in the bloodstream, which act as a buffer to maintain the blood’s pH within a narrow range. The kidneys can excrete hydrogen ions (H+) to reduce acidity or reabsorb and regenerate bicarbonate ions to reduce alkalinity, helping to maintain proper pH levels.
43. Hormone Production: The kidneys are involved in the production and secretion of important hormones that have various regulatory functions in the body. Two notable hormones produced by the kidneys are:

• Renin: Renin plays a crucial role in regulating blood pressure. It helps control the constriction and dilation of blood vessels, the release of aldosterone (which influences sodium and potassium levels), and the overall balance of fluids in the body.
• Erythropoietin (EPO): EPO is responsible for stimulating the production of red blood cells in the bone marrow. It plays a vital role in maintaining adequate oxygen-carrying capacity in the bloodstream and helps regulate the body’s response to low oxygen levels.

39. Name two substances excreted through liver

Liver produces excretory wastes such as urea, ammonia, uric acid etc. It also produces and excretes bile pigments such as bilirubin and biliverdin formed by the breakdown of dead RBCs.

40. Explain the role of mammalian skin  in excretion

• The mammalian skin plays a significant role in the excretion of certain waste products from the body. While the primary organs involved in excretion are the kidneys and respiratory system, the skin contributes to the elimination of certain substances through the process of perspiration or sweating.
• Sweating is the body’s mechanism to regulate temperature, but it also aids in the excretion of waste products. The sweat glands present in the skin produce sweat, which is primarily composed of water, electrolytes (such as sodium, chloride, and potassium), and small amounts of metabolic waste products.
• The waste products excreted through sweat include urea, ammonia, uric acid, and lactic acid. Urea, which is a byproduct of protein metabolism, is one of the most significant waste products excreted through sweating. Ammonia and uric acid are nitrogenous waste products resulting from the breakdown of proteins and nucleic acids. Lactic acid is produced during muscle metabolism.
• When sweat is released onto the skin’s surface, it evaporates, helping to cool the body and regulate body temperature. Simultaneously, the waste products dissolved in sweat are eliminated from the body. This excretory function of the skin is relatively minor compared to the main excretory functions of the kidneys and respiratory system. However, in certain situations, such as during intense physical activity or in high-temperature environments, sweating and subsequent excretion through the skin can become more pronounced.

41. (a) Relate the structure of  proximal convoluted tubule  to its function

The proximal convoluted tubule (PCT) is a segment of the renal tubule responsible for the reabsorption and secretion of various solutes and water. The PCT is located in the renal cortex, the outer part of the kidney, and is the first segment of the renal tubule, where it receives the filtrate from the renal corpuscle.

• Name the substance  reabsorbed in the proximal convoluted tubules

The proximal tubule completes the reabsorption of glucose, amino acids, and important anions, including phosphate and citrate, because it is the sole site of transport of these filtered solutes.

42. Explain the importance of water  in the body of living things

Living organisms need water because it plays a vital role in the reactions taking place within organism’s cells and body. Water acts as a universal solvent, providing a medium for the chemical reactions to occur. Substances are also transported from one part of body to the other in the dissolved state.

43. List the blood vessels and organs , in sequence through which urea passes to reach the kidney  from the liver

Urea is produced in the liver and eliminated from the body through kidneys, from liver it travels to heart then lungs followed by heart.

44. Explain three effects of exercise on

• Respiratory system

When you exercise and your muscles work harder, your body uses more oxygen and produces more carbon dioxide. To cope with this extra demand, your breathing has to increase from about 15 times a minute (12 litres of air) when you are resting, up to about 40–60 times a minute (100 litres of air) during exercise

• Cardiovascular system

Frequent exercise is robustly associated with a decrease in cardiovascular mortality as well as the risk of developing cardiovascular disease. Physically active individuals have lower blood pressure, higher insulin sensitivity, and a more favorable plasma lipoprotein profile

39. Describe the structure and functions of nephrons.
    Structure of nephron : Each nephron is composed of two parts. First one is a cup-shaped bag at its upper end which is called Bowman’s capsule.

The Bowman’s capsule contains a bundle of blood capillaries which is called glomerulus. One end of the glomerulus is attached to the renal artery which brings the impure blood containing the urea waste into it. These impurities are filtered. The other part of the nephron is coiled. In this part, the substances like sugar (glucose), amino acid, ions and excess water which are required by the body, are reabsorbed. The substance remained in the nephron is mainly urine containing dissolved urea in water which is expelled from the body through urethra from time to time.

45. Functions of nephron: Filtration of blood takes place in Bowman’s capsule from the capillaries of glomerulus. The filtrate passes into the tubular part of the nephron. This filtrate contains glucose, amino acids, urea, uric acid, salts and water.
    Reabsorption : As the filtrate flows along the tubule, useful substances such as glucose, amino acids, salts and water are selectively reabsorbed into the blood by capillaries surrounding the nephron tubule.
    Urine : The filtrate which remained after reabsorption is called urine. Urine contains dissolved nitrogenous waste like urea and uric acid, excess salts and water. Urine is collected from nephrons to carry it to the ureter from where it passes into urinary bladder.
46. How is the amount of urine produced regulated ?

The amount of urine is regulated by kidney. It depends on the quantity of excess water and wastes dissolved in water.

(i)Quantity of water : When water is abundant in the body tissues, large quantities of dilute urine is excreted out. When water is less in quantity in the body tissues, a small quantity of concentrate urine is excreted.

(ii) Quantity of dissolved wastes : Dissolved wastes, especially nitrogenous wastes, like urea and uric acid and salts are excreted from the body. When there is more quantity of dissolved wastes in the body, more quantity of water is required to excrete them. Therefore, the amount of urine produced increases.

(iii) Hormones : The amount of urine produced is also regulated by certain hormones which control the movement of water and Na+ ions in and out of the nephrons.

What are the methods used by plants to get rid of excretory products ?
(i) The plants get rid of gaseous products-through stomata in leaves and lenticels in stems.

• The plants get rid of stored solid and liquid waste by the shedding off leaves, peeling off bark and felling off fruits.
• The plants get rid of wastes by secreting them in the form of gum s and resins
• Plants also excrete some waste substances into the soil around them.

47. Outline conditions for efficient gaseous exchange  in mammals

The specialised respiratory surface must have a large surface area to volume ratio (SA : V). The specialised respiratory surface must be moist. The the specialised respiratory surface must be thin. And there must be a large concentration gradient across the respiratory surface.

48. (a) Name four types of respiratory surfaces found in animals

There are three major types of respiratory structures in the vertebrates: gills, integumentary exchange areas, and lungs.

49. Explain four adaptation  of alveoli  for gaseous exchange in animals

Alveoli are tiny air sacs present in the lungs that aid in the transport and exchange of gases. Adaptation of alveoli: The alveoli present in the lungs have thin walls composed only of a single layer of cells in order to minimize the diffusion distance. Their walls are moist which helps the gases to diffuse better.

50. Distinguish between  each of the following lung volumes

• Tidal volume and Vital volume

Tidal volume is essentially every breath a person takes. It is one of the main determinants of minute ventilation and alveolar ventilation. Minute ventilation, also known as total ventilation, is a measurement of the amount of air that enters the lungs per minute. It is the product of respiratory rate and tidal volume.

• Residual volume and dead space

Residual volume is a normal phenomenon but the dead space volume(physiological dead space) occurs due to lack of the blood supply into the alveoli resulting in the improper gaseous exchange of the alveoli.

42. How is oxygen and carbon dioxide transported in human beings ?
43. (i) Transport of oxygen : Haemoglobin present in the blood takes up the oxygen from the air in the lungs. It carries the oxygen to tissues which are deficient in oxygen before releasing it.
    (ii) Transport of carbon dioxide : Carbon dioxide is more soluble in water. Therefore, it is mostly transported from body tissues in the dissolved form in our blood plasma to lungs. Here it diffuses from blood to air in the lungs.
44. Describe gaseous exchange in the alveoli

During gas exchange oxygen moves from the lungs to the bloodstream. At the same time carbon dioxide passes from the blood to the lungs. This happens in the lungs between the alveoli and a network of tiny blood vessels called capillaries, which are located in the walls of the alveoli

49. How are the alveoli designed to maximise the exchange of gases?

A small sac called alveoli helps with gas exchange.

Alveoli  are numerous  and have thin walls and a close network of blood arteries to allow gas exchange between blood and air-filled alveoli.

They have a balloon-like structure to maximize surface area in exchange for gas.
50 Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.

Alveoli	Nephron
Alveoli are functional unit of lungs.	Nephrons are functional unit of kidney.
A mature lung has about 30 crore alveoli.	A kidney has about 100000 nephrons.
Alveoli provide a wide surface for gaseous exchange.	The surface area of a nephron is not much more.
The exchange of O2 and CO2 takes place through the network of capillaries in alveoli.	. The Bowman’s capsule in nephron regulates the concentration of water and salts.

51. How are the lungs designed in human beings to maximise the area for exchange of gases ?

Within the lungs, the air passage divides into smaller and smaller tubes, called bronchi which in turn form bronchioles. The bronchioles terminate in balloon-like structures, called alveoli. The alveoli present in the lungs provide maximum surface for exchange of gases. The alveoli have vary thin walls and contain an extensive network of blood vessels to facilitate exchange of gases.

52. How are the alveoli designed to maximise the exchange of gases ?

The alveoli are thin walled and richly supplied with a network of blood vessels to facilitate exchange of gases between blood and the air filled in alveoli.

• Alveoli have balloon-like structure. Hence, provide maximum surface for exchange of gases.

53. Distinguish between aerobic and anaerobic respiration

Aerobic respiration	Anaerobic respiration
It takes place in the presence of oxygen.	It takes place in the absence of oxygen.
Complete breakdown of food occurs in aerobic respiration.	Partial breakdown of food occurs in anaerobic respiration.
The end products in aerobic respiration are carbon dioxide and water.	The end products in anaerobic respiration may be ethanol and carbon dioxide (as in yeast plants) or lactic acid (as in animal muscles).
Aerobic respiration produces a considerable amount of energy.	Much less energy is produced in anaerobic respiration.

 

54. State four functions of synovial fluid

Synovial fluid is a viscous solution found in the cavities of synovial joints. The principal role of synovial fluid is

• To reduce friction between the articular cartilages of synovial joints during movement.
• It lubricates the joint and allows the ends of the bones to move without friction.
• It contains nutrients needed for the cartilage at the ends of the bones and carries away waste from within the joint capsule.
• It acts as a shock absorber within the joint.

55. State four functions of vertebral skeleton

The major function of the vertebral column is protection of the spinal cord; it also provides stiffening for the body and attachment for the pectoral and pelvic girdles and many muscles. In humans an additional function is to transmit body weight in walking and standing.

56. Relate the structural modification of nephron of a desert animal to its habitat

Desert animals have adapted various structural modifications in their nephrons, which are the functional units of the kidneys, to help them cope with the challenges of their arid habitat. These adaptations allow for efficient water conservation and electrolyte balance in the body. Here are some structural modifications of the nephron in desert animals and their relationship to the desert environment:

• Longer Loop of Henle: The Loop of Henle, a part of the nephron, plays a crucial role in water conservation. Desert animals typically have longer loops compared to those of non-desert species. This adaptation allows for increased reabsorption of water from the filtrate, reducing the amount of water lost in urine. The longer Loop of Henle enables a more concentrated urine output, helping to conserve precious water resources in the arid desert environment.
• Increased Medullary Thickness: The medulla, the inner region of the kidney, is responsible for creating a concentration gradient that facilitates water reabsorption. Desert animals have relatively thicker medullae, which provide a larger area for the reabsorption of water and help in producing concentrated urine. The increased medullary thickness aids in the efficient conservation of water by allowing the kidneys to extract as much water as possible from the filtrate before excretion.
• Well-Developed Renal Corpuscle: The renal corpuscle consists of the glomerulus and Bowman’s capsule, where the initial filtration of blood occurs. Desert animals may have well-developed renal corpuscles, enabling efficient filtration. This adaptation ensures that necessary substances are retained in the body, while excess water and waste products are selectively filtered out for excretion. It helps to prevent excessive water loss and maintain electrolyte balance, both of which are crucial in the arid desert environment.
• Efficient Tubular Reabsorption: The tubules of the nephron are responsible for the reabsorption of water, electrolytes, and essential substances back into the bloodstream. Desert animals have highly efficient tubular reabsorption mechanisms, allowing them to maximize water reabsorption and minimize water loss in the urine. The tubular cells may have increased permeability to water or specialized transport mechanisms for electrolyte reabsorption, ensuring effective water conservation and electrolyte balance in the body.

These structural modifications in the nephron of desert animals enable them to conserve water, produce concentrated urine, and maintain the proper balance of electrolytes in their bodies. These adaptations are essential for their survival in the harsh desert environment where water is scarce, and the risk of dehydration is high. By efficiently conserving water and minimizing water loss through urine, desert animals can thrive in their arid habitats.

57. Relate the structure of nephrone to its function

The structure of the nephron is intricately related to its function in the kidney. The nephron is the functional unit responsible for the filtration, reabsorption, and secretion processes involved in urine formation. Let’s explore the relationship between the structure and function of the nephron:

1. Renal Corpuscle:

• Structure: The nephron begins with the renal corpuscle, consisting of the glomerulus and Bowman’s capsule. The glomerulus is a network of capillaries, while Bowman’s capsule is a cup-like structure that surrounds the glomerulus.
• Function: The renal corpuscle is responsible for the filtration of blood. Blood pressure forces fluid and solutes out of the glomerular capillaries and into the Bowman’s capsule, forming the filtrate. This filtration process allows for the removal of waste products, excess water, and other substances from the blood.

1. Proximal Convoluted Tubule (PCT):

• Structure: The PCT is a highly coiled and convoluted tubule located after the Bowman’s capsule.
• Function: The PCT is involved in the reabsorption of water, glucose, amino acids, electrolytes, and other essential substances from the filtrate back into the bloodstream. It has microvilli on its cells, increasing its surface area for efficient reabsorption.

1. Loop of Henle:

• Structure: The Loop of Henle is a U-shaped tubule with a descending limb and an ascending limb. The descending limb is permeable to water, while the ascending limb is impermeable to water but allows for the transport of electrolytes.
• Function: The Loop of Henle plays a crucial role in creating a concentration gradient in the kidney. It allows for the reabsorption of water in the descending limb, concentrating the filtrate, while the ascending limb actively transports sodium, chloride, and other ions out of the tubule. This establishes a concentration gradient necessary for water reabsorption in the collecting duct.

1. Distal Convoluted Tubule (DCT):

• Structure: The DCT is a tubule located after the Loop of Henle.
• Function: The DCT is responsible for further reabsorption and secretion. It selectively reabsorbs water and electrolytes, depending on the body’s needs, and participates in the regulation of acid-base balance through the secretion of hydrogen and bicarbonate ions.

1. Collecting Duct:

• Structure: The collecting duct receives filtrate from multiple nephrons and runs through the medulla towards the renal pelvis.
• Function: The collecting duct plays a crucial role in the final concentration of urine. It allows for the reabsorption of water under the influence of antidiuretic hormone (ADH), thereby concentrating the urine. It also participates in the regulation of electrolyte balance and pH.

58. What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration

Aquatic organisms use oxygen dissolved in surrounding water. Since air dissolved in water has fairly low concentration of oxygen, the aquatic organisms have much faster rate of breathing.

Terrestrial organisms take oxygen from the oxygen-rich atmosphere through respiratory organs. Hence, they have much less breathing rate than aquatic organisms.

59. What are the different ways in which glucose is oxidised to provide energy in various organisms ?

First step of breakdown of glucose (6 carbon molecules) takes place in the cytoplasm of cells of all organisms. This process yields a three carbon molecule compound called pyruvate.
Further break down of pyruvate takes place in different ways in different organisms.

Anaerobic respiration : The anaerobic respiration in plants (like yeast) produces ethanol and carbon dioxide as end products.
(ii) Aerobic respiration : In aerobic respiration break down of pyruvate takes place in presence of oxygen to give rise three molecules of carbon dioxide and water. The release of energy in aerobic respiration is much more than in anaerobic respiration.
(iii) Lack of oxygen : Sometimes, when there is lack of oxygen especially during physical exercise, in our muscles, pyruvate is converted into lactic acid (3 carbon molecule compound). Formation of lactic acid in muscles causes cramp.

60. How are fats digested in our bodies ? Where does this process take place ?

Digestion of fats takes place in the small intestine.
Bile juice secreted by the liver poured in the intestine along with pancreatic juice. The bile salts present in the bile juice emulsify fhe large globules of fats. Therefore, by enulsification large globules break down into fine globules to provide larger surface area to act upon by the enzymes.
Lipase enzyme present in the pancreatic juice causes break down of emulsified fats. Glands present in the wall of small intestine secrete intestinal juice which contains lipase enzyme that converts fats into fatty acids and glycerol.

61.  What is the role of saliva in the digestion of food ?
Saliva contains salivary amylase enzyme that breaks down starch into sugars like maltose.

Saliva keeps the mouth cavity clean and moistens the food that help in chewing and breaking down the big pieces of food into smaller ones.

61. explain why pregnancy may continue if the ovary of an expectant mother  is removed  after the fourth month

It secretes human chorionic gonadotropin that ensures persistence of the corpus luteum. The later serves to secrete ovarian hormone estrogen, progesterone, and relaxin that are required to maintain pregnancy. Hence, removal of ovaries after 4th month would not affect the pregnancy.

62. State the role of testes  in the mammalian reproductive system

The Testis has following three functions. First, it produces spermatozoa, the male gametes. Second, it synthesizes testosterone, the principal male sex hormone. Third, it participates with the hypothalamus-pituitary unit in regulating reproductive function.

63. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.

The food material taken in during the process of nutrition is used in cells to provide energy for various life processes. Diverse organisms do this in different ways – some use oxygen to breakdown glucose completely into carbon dioxide and water; some use other pathways that do not involve oxygen. In all cases, the first step is the breakdown of glucose, a six-carbon molecule, into a three-carbon molecule called pyruvate. This process takes place in the cytoplasm. Further, the pyruvate may be converted into ethanol and carbon dioxide. This process takes place in yeast during fermentation. Since this process takes place in the absence of air (oxygen), it is called anaerobic respiration. Breakdown of pyruvate using oxygen takes place in the mitochondria. This process breaks up the three-carbon pyruvate molecule to give three molecules of carbon dioxide. The other product is water. Since this process takes place in the presence of air (oxygen), it is called aerobic respiration. The release of energy in this aerobic process is a lot greater than in the anaerobic process.

64. Distinguish between tendon  and ligament

A tendon serves to move the bone or structure. A ligament is a fibrous connective tissue that attaches bone to bone, and usually serves to hold structures together and keep them stable.

65. List the structures in the skin  that plays the role of thermoregulation

The skin, being the largest organ of the body, plays a crucial role in thermoregulation, helping to maintain a stable body temperature. Several structures within the skin contribute to this thermoregulatory function. These structures work together in a coordinated manner to regulate body temperature. When the body temperature rises, sweat glands produce sweat, blood vessels dilate to increase blood flow to the skin, and evaporation of sweat cools the body down. Conversely, in cold temperatures, blood vessels constrict to reduce heat loss, and the hair follicles can help trap heat close to the skin’s surface. This include:

1. Sweat Glands: Sweat glands are distributed throughout the skin and are responsible for producing sweat. When the body temperature rises, the sweat glands secrete sweat onto the skin’s surface. As the sweat evaporates, it absorbs heat from the body, cooling it down. This process is known as evaporative cooling and helps regulate body temperature.
2. Blood Vessels: Blood vessels, including arteries, veins, and capillaries, are present throughout the skin. They play a vital role in thermoregulation by controlling blood flow. When the body temperature rises, blood vessels near the skin’s surface dilate, allowing increased blood flow to the skin. This process is called vasodilation and helps dissipate heat from the body. Conversely, in cold temperatures, blood vessels constrict (vasoconstriction), reducing blood flow to the skin and minimizing heat loss.
3. Hair Follicles: Hair follicles, although not directly involved in thermoregulation, contribute to the overall insulation of the skin. When the body is cold, tiny muscles at the base of hair follicles contract, causing the hairs to stand up (known as piloerection). This action creates a layer of trapped air around the skin, providing additional insulation and helping to retain heat.
4. Sebaceous Glands: Sebaceous glands are associated with hair follicles and produce an oily substance called sebum. Sebum helps lubricate and moisturize the skin and hair. While sebaceous glands are not directly involved in thermoregulation, they help in maintaining the skin’s integrity, preventing excessive water loss through the skin, and protecting it from environmental factors that could disrupt thermoregulation.
5. State two distinctive features of cervical vertebrae

Within the lungs, the passage divides into smaller and smaller tubes, which finally terminate in balloon-like structures, which are called alveoli. The alveoli provide a surface where the exchange of gases can take place. The walls of the alveoli contain an extensive network of blood vessels. As we have seen in earlier years, when we breathe in, we lift our ribs and flatten our diaphragm, and the chest cavity becomes larger as a result. Because of this, air is sucked into the lungs and fills the expanded alveoli. The blood brings carbon dioxide from the rest of the body for release into the alveoli, and the oxygen in the alveolar air is taken up by blood in the alveolar blood vessels to be transported to all the cells in the body. During the breathing cycle, when air is taken in and let out, the lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released.

67. State four characteristics of arteries  in relation to the transport system
    1. Arteries have a thick middle layer of involuntary muscle to increase or decrease diameter
    2. The inner layer of endothelium which reduces friction

• situated deeper in the tissue to maintain body temperature

1. arteries have no valves except in the base of the aorta and the pulmonary arteries
2. In the arteries , blood is  always under high pressure

68. What would be the consequences of a deficiency of haemoglobin in our bodies?

Due to the deficiency of haemoglobin in blood, its oxygen carrying capacity decreases. As a result the production of energy by oxidation will become slower. Therefore, one would fall sick and would feel fatigue most of the time.

69. How is oxygen and carbon dioxide transported in human beings ?
    • Transport of oxygen : Haemoglobin present in the blood takes up the oxygen from the air in the lungs. It carries the oxygen to tissues which are deficient in oxygen before releasing it.
      (ii) Transport of carbon dioxide : Carbon dioxide is more soluble in water. Therefore, it is mostly transported from body tissues in the dissolved form in our blood plasma to lungs. Here it diffuses from blood to air in the lungs.

70. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds ?

Separation of oxygenated and deoxygenated blood allows good supply of oxygen to the body. This system is useful in animals that have high energy requirement. Mammals and birds constantly need oxygen to get energy to maintain their body temperature constant.

71. Describe the mmmalian double circulatory system

The mammalian double circulatory system refers to the circulation of blood through two separate circuits in the body: the pulmonary circulation and the systemic circulation. This system allows for efficient oxygenation of blood and delivery of oxygenated blood to the body’s tissues.

1. Pulmonary Circulation:

Pathway: The pulmonary circulation begins in the right atrium of the heart, where deoxygenated blood from the body enters through the superior and inferior vena cava. From the right atrium, the blood flows into the right ventricle. The right ventricle then pumps the deoxygenated blood to the lungs through the pulmonary artery. In the lungs, the blood undergoes oxygenation and gets rid of carbon dioxide through the process of gas exchange. Oxygenated blood returns to the heart through the pulmonary veins, entering the left atrium.

Function: The primary function of the pulmonary circulation is to transport deoxygenated blood from the body to the lungs, where it picks up oxygen and releases carbon dioxide. This oxygenation of blood occurs in the alveoli of the lungs, where oxygen diffuses into the bloodstream, and carbon dioxide diffuses out of the bloodstream to be exhaled. Once oxygenated, the blood returns to the heart to be pumped out to the rest of the body.

1. Systemic Circulation:

Pathway: The systemic circulation starts in the left atrium, where oxygenated blood from the lungs enters the heart. From the left atrium, the blood flows into the left ventricle, which is the strongest chamber of the heart. The left ventricle pumps the oxygenated blood out of the heart through the aorta, the largest artery in the body. The oxygenated blood then travels through various arteries, arterioles, and capillaries to reach the body’s organs, tissues, and cells. In the capillaries, oxygen and nutrients are delivered to the cells, while waste products, such as carbon dioxide and metabolic byproducts, are picked up. The deoxygenated blood returns to the heart through veins and enters the right atrium to start the pulmonary circulation again.

Function: The systemic circulation supplies oxygenated blood to all the organs, tissues, and cells of the body. It delivers oxygen and nutrients necessary for cellular metabolism and removes waste products generated by cellular respiration. The exchange of substances between the bloodstream and tissues occurs in the capillaries, where nutrients and oxygen diffuse out of the blood, while waste products and carbon dioxide diffuse into the blood for eventual removal.

72. Describe double circulation in human beings. Why is it necessary?
    The double circulatory system of blood flow refers to the separate systems of pulmonary circulation and the systemic circulation.The adult human heart consists of two separated pumps, the right side with the right atrium and ventricle which pumps deoxygenated blood into the pulmonary circulation.
    The oxygenated blood re-enters the left side of the heart through the pulmonary vein into the left atrium and passes to the left ventricle where it is pumped to the rest of the body. This part of the circulation is called as systemic circulation. This type of circulation is called double circulation. The advantage of a double circulatory system is that blood can be pumped to the rest of the body at a higher pressure.
73. Describe the flow of blood through the mammalian heart

The mammalian circulatory system is divided into three circuits: the systemic circuit, the pulmonary circuit, and the coronary circuit. Blood is pumped from veins of the systemic circuit into the right atrium of the heart, then into the right ventricle. Blood then enters the pulmonary circuit, and is oxygenated by the lungs. From the pulmonary circuit, blood re-enters the heart through the left atrium. From the left ventricle, blood re-enters the systemic circuit through the aorta and is distributed to the rest of the body.

Blood flows through the heart in the following order: 1) body –> 2) inferior/superior vena cava –> 3) right atrium –> 4) tricuspid valve –> 5) right ventricle –> 6) pulmonary arteries –> 7) lungs –> 8) pulmonary veins –> 9) left atrium –> 10) mitral or bicuspid valve –> 11) left ventricle –> 12) aortic valve –> 13) aorta –> 14) body.

74. Distinguish between plasma and serum

Serum and plasma both come from the liquid portion of the blood that remains once the cells are removed, but that’s where the similarities end. Serum is the liquid that remains after the blood has clotted. Plasma is the liquid that remains when clotting is prevented with the addition of an anticoagulant.

75. Outline  the series of events in human cardiac circle

The human heart consists of four chambers, comprising left and right halves. Two upper chambers include left and right atria; lower two chambers include right and left ventricles.  The key function of the right ventricle is to pump deoxygenated blood through the pulmonary arteries and pulmonary trunk to the lungs. While the left ventricle is responsible for pumping newly oxygenated blood to the body through the aorta.

Cardiac cycle events can be divided into diastole and systole. Diastole represents ventricular filling, and systole represents ventricular contraction/ejection. Systole and diastole occur in both the right and left heart, though with very different pressures

Cardiac Cycle Phases

Following are the different phases that occur in a cardiac cycle:

Atrial Diastole: In this stage, chambers of the heart are calmed. That is when the aortic valve and pulmonary artery closes and atrioventricular valves open, thus causing chambers of the heart to relax.

Atrial Systole: At this phase, blood cells flow from atrium to ventricle and at this period, atrium contracts.

Isovolumic Contraction: At this stage, ventricles begin to contract. The atrioventricular valves, valve, and pulmonary artery valves close, but there won’t be any transformation in volume.

Ventricular Ejection: Here ventricles contract and emptying. Pulmonary artery and aortic valve close.

Isovolumic Relaxation: In this phase, no blood enters the ventricles and consequently, pressure decreases, ventricles stop contracting and begin to relax. Now due to the pressure in the aorta – pulmonary artery and aortic valve close.

Ventricular Filling Stage: In this stage, blood flows from atria into the ventricles. It is altogether known as one stage (first and second stage). After that, they are three phases that involve the flow of blood to the pulmonary artery from ventricles.

76. Name the structure through which red blood cells  flow from superior vena cava  to the dorsal aorta

Both the superior vena cava and inferior vena cava empty blood into the right atrium. Blood flows through the tricuspid valve into the right ventricle. It then flows through the pulmonic valve into the pulmonary artery before being delivered to the lungs.

77. Describe the structure and working of the human heart.

• Structure :Heart is a muscular pumping organ that pumps out the blood into the blood vessels. Contraction of the heart is called systole and relaxation is called diastole.
• When the auricles are filled with blood they are in diastole. The tricuspid and bicuspid valves remain closed. This is called atrial diastole.
• When the auricles are full they contract. This leads to opening of tricuspid and bicuspid valves. Blood from right and left auricles is pushed into right and left ventricles respectively. This is called atrial systole.
• Following this the valves are closed the ventricles contract. The deoxygenated blood from right ventricle enters the pulmonary artery and oxygenated blood from left ventricle enters the aorta. This is called ventricular systole.
• During this time the auricles are in diastole the atrial systole (0.1 sec), ventricular systole (0.3 sec) and ventricular diastole (0.4 sec) constitute a cardiac cycle.

78. Describe the production of heart sounds

The rhythmic closure and opening of the valves cause the sound of the heart.

The first sound LUBB is of longer duration and is produced by the closure of the tricuspid and bicuspid valves after the beginning of ventricular systole.

The second sound DUPP is of a shorter duration and produced by the closure of semilunar valves “at the end of ventricular systole.

79. Why is the Sinoatrial node called the pacemaker of heart?

(i) The human heart is myogenic in nature. The contraction of the heart is initiated by a specialised portion of the heart muscle called sinoatrial node.

(ii) This is situated in the wall of the right atrium near the opening of the superior venacava.

(iii) It is made up of thin fibres.

(iv) This is called the pacemaker of the heart because it is capable of initiating impulse which can stimulate the heart muscle to contract.

80. (a) List four components of lymphatic system

The lymphatic system consists of

• lymphatic vessels,
• a fluid called lymph,
• lymph nodes,
• the thymus,
• and the spleen.

80. Describe the formation of lymph

Lymph is a fluid similar in composition to blood plasma. It is derived from blood plasma as fluids pass through capillary walls at the arterial end. As the interstitial fluid begins to accumulate, it is picked up and removed by tiny lymphatic vessels and returned to the blood. As soon as the interstitial fluid enters the lymph capillaries, it is called lymph. Returning the fluid to the blood prevents edema and helps to maintain normal blood volume and pressure.

81. Functions of the lymphatic system

ü Drains excess fluids and proteins from tissues all around the body and returns them back into the bloodstream.

ü Removes waste products produced by cells.

ü Fights infections.

ü Absorbs fats and fat-soluble vitamins from the digestive system and transports these into the bloodstream.

82. Name the functions of mammalian blood

• Blood has many different functions, including:
• transporting oxygen and nutrients to the lungs and tissues.
• forming blood clots to prevent excess blood loss.
• carrying cells and antibodies that fight infection.
• bringing waste products to the kidneys and liver, which filter and clean the blood.
• regulating body temperature.

83. (a)Name two blood plasma components

Two important components of blood plasma are:

1. Water: Water makes up the largest portion of blood plasma, accounting for about 90-92% of its composition. It serves as the fluid medium that carries various substances, such as nutrients, hormones, gases, and waste products, throughout the body.
2. Proteins: Blood plasma contains a variety of proteins that perform crucial functions. Some of the important plasma proteins include:

• Albumin: Albumin helps maintain the osmotic pressure of the blood, which is essential for regulating fluid balance between the blood and surrounding tissues. It also acts as a carrier for certain hormones, drugs, and fatty acids.
• Globulins: Globulins are a diverse group of proteins that have multiple functions, including transport of ions, hormones, and lipids, as well as playing a role in immune responses.
• Fibrinogen: Fibrinogen is involved in blood clotting. It gets converted into fibrin during the clotting process, which forms a mesh-like structure to aid in the clot formation and repair damaged blood vessels.

These components, along with other dissolved substances like electrolytes, hormones, gases, and waste products, make up the composition of blood plasma. They collectively contribute to the proper functioning of the circulatory system and support various physiological processes in the body.

84. What is the importance of valves in the heart?
    • Regulate the flow of blood in a single direction. 
    • Prevent back flow of blood.
85. How are arteries and veins structurally different from one another?

·	· : ARTERY :	· VEIN
· 1.	Distributing vessel	: Collecting vessel
· 2.	Pink in colour :	Red in colour
· 3.	Deep location :	Superficial in location
· 4.	Blood flow with high pressure	: Blood flow with low pressure
· 5.	Wall of artery is strong, thick and elastic :	Wall of vein is weak, thin and non-elastic
· 6.	All arteries carry oxygenated blood except pulmonary arteries :	All veins carry deoxygenated blood except pulmonary veins
· 7.	Internal valves are absent :	Internal valves are present
·

86. Differentiate between systemic circulation and pulmonary circulation.

· S.No	Systemic circulation	:Pulmonary circulation
· 1.	It starts from left ventricle and circulates oxygenated blood to various parts of the body.	It starts from the right ventricle to lungs with deoxygenated blood.
· 2	Ends in a right atrium with deoxygenated blood	Ends in a left atrium with oxygenated blood.

 

87. Explain why the walls of the right ventricle are thicker than the right auricles.

The right ventricles have thicker walls to pump out blood with force away from the heart.

The right auricle is only receiving blood from the Pre caval and Post caval veins. Hence it is thin walled than the ventricle.

88. Give reasons why Mature RBC in mammals do not have cell organelles.

Mammalian RBC lack nucleus and makes the cells biconcave which increase the surface area for oxygen binding.

Lack of mitochondria allows the RBC to transport all the oxygen to tissues, and loss of endoplasmic reticulum allows more flexibility for RBC to move through the narrow capillaries.

89. Why are leucocytes classified as granulocytes and agranulocytes? Name each cell and mention its functions.

Granulocytes  because They contain granules in their cytoplasm. Hence they are called as granulocytes. The granulocytes are of three types.

            Neutrophils, ii. Eosinophils, iii. Basophils

Neutrophils and its function : These corpuscles form 60% – 65% of the total leucocytes. Their number in increased during infection and inflammation.

Eosinophils and its function : Their number increases during conditions of allergy and parasitic infections. It brings about detoxification of toxins.

Basophils and its function : They form 0.5 – 1.0 % of the total leucocytes. They release chemicals during the process of inflammation.

Agranulocytes  because Granules are not found in the cytoplasm of these cells.

They are of two types.

Lymphocytes : They form 20 – 25% of the total leucocytes. They produce antibodies during bacterial and viral infections.

Monocytes : These cells form 5 – 6 % of the total leucocytes. They are phagocytic and can engulf bacteria.

90. Differentiate between systole and diastole.

Systole : Contraction phase of the heart

Diastole : Relaxation phase of the heart

91. Explain the conduction of heart beat.

• Human heart is myogenic in nature. Contraction is initiated by a specialized muscle, the Sino-Atrial (SA) node which is situatedin the wall of the right atrium near the opening of the superior vena cava.
• The SA node is broader at the top and tapering below. It is made up of thin fibres.
• SA node acts as the ‘pacemaker’of the heart because it is capable of initiating impulse which can stimulate the heart muscles to contract.
• Impulse from the SA node spreads as a wave of contraction over the right and left atrial wall pushing the blood through the atrioventricular valves into the ventricles.
• The wave of contraction from SA node reaches the AtrioVentricular (AV) node which is stimulated to emit an impulse of contraction spreading to the ventricular muscle via the atrioventricular bundle and the Purkinje fibres.

92. Enumerate the functions of blood.
    • Transport of respiratory gases.
    • Transport of digested food materials to the different body cells.
    • Transport of hormones.
    • Transport of nitrogenous excretory productslike ammonia, urea and uric acid.
    • It is involved in protection of the body and defense against diseases.
    • Blood acts as bufferand helps in regulation of pH and body temperature.
    • It maintainsproper water balance in the body.
93. What causes the opening and closing of guard cells of stomata during transpiration?

Stomata are open in the day and closed at night. The opening and closing of the stomata is due to the change in turgidity of the guard cells.

When water enters into the guard cells, they become turgid and the stoma open. When the guard cells lose water, it becomes flaccid and the stoma closes.

94. What are the necessary conditions (or autotrophic nutrition and what are its by-products ?

Necessary conditions for autotrophic nutrition :
(i) Presence of chlorophyll in the living cells.
(if) Provision of supply of water to green plants or cells of the plant.
(iii) Sufficient sunlight.

• Sufficient supply of carbon dioxide.
• By-product of auto tropic nutrition is oxygen.

95. State four  process involved in holozoic nutrition

Holozoic Nutrition is a process in which complex food is taken into a specialist digestive system and broken down into small pieces to be absorbed. This consists of 5 stages, ingestion, digestion, absorption, assimilation, and egestion.
96.  What are the differences between the transport of materials in xylem and phloem ?

Xylem	Phloem
Xylem conducts water and dissolved minerals from roots to leaves and other parts.	Phloem conducts prepared food material from leaves to other parts of plant in dissolved form.
In xylem, the transport of material takes place through vessels and tracheids which are dead tissues.	In phloem, transport of material takes place through sieve tubes with the help of companion cells, which are living cells.
In xylem upward movement of water and dissolved minerals is mainly achieved by transpiration pull. It is caused due to suction created by evaporation of water molecules from the cells of a leaf.	In translocation, material is transferred into phloem tissue using energy from ATP. This increases the osmotic pressure that moves the material in the phloem to tissues which have less pressure

96. What are the necessary conditions for autotrophic nutrition and what are its byproducts?

• Carbon and energy requirements of the autotrophic organism are fulfilled by photosynthesis. It is the process by which autotrophs take in substances from the outside and convert them into stored forms of energy. This material is taken in the form of carbon dioxide and water, which is converted into carbohydrates in the presence of sunlight and chlorophyll. Carbohydrates are utilised for providing energy to the plant. The carbohydrates, which are not used immediately, are stored in the form of starch, which serves as the internal energy reserve to be used as and when required by the plant.
  differentiate between light dependent  and light independent reaction in photosynthesis

Light-dependent photosynthesis	Light-independent photosynthesis
It is called light-dependent photosynthesis because it needs light or depends on light to produce organic energy molecules ATP and NADPH.	It is called light-independent photosynthesis because no light is required here to reduce carbon dioxide and glucose by the use of ATP and NADPH.
It occurs in the grana or thylakoid of the chloroplast.	It occurs in the stroma of the chloroplast.
During light-dependent photosynthesis photolysis or splitting of molecules of water take place into hydrogen and oxygen.	During light-independent photosynthesis reduction of carbon dioxide into glucose, molecules take place through a series of reactions constituting the Calvin cycle.
Here chlorophyll absorbs light energy and loses one electron during this process. The chlorophyll molecule gets back its lost electron from the electron released during photolysis of water.	The carbon dioxide is taken up at night and an intermediate product in the form of malic acid is produced. This acted upon by the energy absorbed through chlorophyll and the ATP produced will reduce malic acid into carbohydrates.
It is also called the photochemical phase of photosynthesis.	It is also called the biochemical phase of photosynthesis.
Photolysis occurs in light-dependent photosynthesis.	Photolysis does not occur in light-independent photosynthesis.
The end product of this reaction is ATP and NADPH.	The end product of this reaction is glucose.

 

100. Explain the role of water  in the light dependent reaction of photosynthesis

When water is split, it produces oxygen, hydrogen, and electrons. These electrons move through chloroplast structures and produce ATP via chemiosmosis. The hydrogen is converted to NADPH, which is then utilized in light-independent reactions. As a waste product, oxygen gas diffuses out of the organism.

101. Outline Transpiration process in plants

Transpiration is the evaporation of water in plants through stomata in the leaves.

Water evaporates from mesophyll cells of leaves through the open stomata, this lowers water concentration in mesophyll cells.

As a result, more water is drawn into these cells from the xylem present in the veins through the process of osmosis.

As water is lost from the leaves, pressure is created at the top to pull more water from the xylem to the mesophyll cells, this process is called transpiration pull.

This extends up to the roots causing the roots to absorb more water from the soil to ensure continuous flow of water from the roots to the leaves

102. What would happen to the leaves of a plant that transpires more water than its absorption in the roots?

If the leaves of a plant transpire more water than its absorption in the roots, it can lead to the following:

Absorption of water will increase since the cells will require more water to compensate the loss by transpiration.

The plants may also start wilting. If they are unable to absorb more water from the soil. This can happen in deserts where temperature is high and rate of transpiration will be more but soil will not be rich in water.

103. Explain why Minerals cannot be passively absorbed by the roots.
     • All minerals cannot be passively absorbed by the roots because minerals are present in the soil as charged particles (ions) that cannot move across cell membranes.
     • The concentration of minerals in the soil is usually lower than the concentration of minerals in the root. Hence most minerals enter the root by active absorption requiring energy. Hence minerals cannot be passively absorbed by the roots.
104. Guard cells are responsible for opening and closing of stomata.

Stomata are open in the day and closed at night. The opening and closing of the stomata is due to the change in turgidity of the guard cells.

When water enters into the guard cells, they become turgid and the stoma open. When the guard cells lose water, it becomes flaccid and the stoma closes.

105. The movement of substances in the phloem can be in any direction. Explain

Phloem transports food (sucrose) from a source to a sink. The source is part of the plant that synthesize food, i.e., the leaf, and sink, is the part that needs or stores the food.

But, the source and sink may be reversed depending on the season, or the plants need.

The direction of movement in the phloem can be upwards or downwards, i.e., bidirectional.

106. Describe the process by which plants absorb water

There are millions of root hairs on the tip of the root which absorb water and minerals by diffusion. Root hairs are thin walled, slender extension of epidermal cell that increase the surface area of absorption.

Root Tip with Root Hairs

Pathway of Water Absorbed by Roots :

1. Once the water enters the root hairs, the concentration of water molecules in the root hair cells become more than that of the cortex.
2. Thus water from the root hair moves to the cortical cells by osmosis and then reaches the xylem.
3. From there the water is transported to the stem and leaves.

1. S. of the root showing movement of water from soil to xylem

Types of Movement of Water into the Root Cells : Once water is absorbed by the root hairs, it can move deeper into root layers by two distinct pathways:

1. Apoplast pathway
2. Symplast pathway

Apoplast Pathway :

The apoplastic movement of water occurs exclusively through the intercellular spaces and the walls of the cells.

Apoplastic movement does not involve crossing the cell membrane. This movement is dependent on the gradient.

Symplast Pathway :

In symplastic movement, the water travels through the cells i.e. their cytoplasm; intercellular movement is through the plasmodesmata.

Water enter the cells through the cell membrane, hence the movement is relatively slower. Movement is again down a potential gradient.

107. Describe transpiration and give its importance  

Transpiration is the evaporation of water in plants through stomata in the leaves.

Importance of Transpiration :

• Creates transpirationpull for transport of water.
• Supplies water for photosynthesis.
• Transports minerals from soil to all parts of the plant.
• Cools the surface of the leaves by evaporation.
• Keeps the cells turgid; hence, maintains their shape.

108. Identify the forces that hold colum of water in xylem of a tree

In the case of xylem, adhesion occurs between water molecules and the molecules of the xylem cell walls. Cohesion, which is molecular attraction between “like” molecules. In water, cohesion occurs due to hydrogen bonding between water molecules.

109. State the function of a plant stem

The primary functions of the stem are to support the leaves; to conduct water and minerals to the leaves, where they can be converted into usable products by photosynthesis; and to transport these products from the leaves to other parts of the plant, including the roots.

110. Explain the role  of environmental factors  on the rate of transpiration

The number and size of leaves, the thickness of their cuticles and the number of stomata are all adaptations that affect the rate of transpiration in plants.

Besides, any condition that affects the rate of evaporation or photosynthesis will affect the rate of transpiration and therefore the environment plays a large role.  The light intensity, temperature, humidity, wind and water supply will all affect the transpiration rate.