Question 1: What is Reproduction? What are different types of reproduction?
Answer: REPRODUCTION: Reproduction is defined as the production of individuals of the same species i.e. the next generation of species is called reproduction.
Types of reproduction: Reproduction is of two types.
1) A-Sexual Reproduction: The type of reproduction in which there is no fusion of the male and female gametes is called A-Sexual Reproduction.
2) Sexual Reproduction: The type of reproduction in which there is fusion of the male and female gametes is called Sexual Reproduction.
|An individual can live without reproducing, but a species cannot survive without reproduction.|
Question 2: Outline the methods of asexual reproduction in animals. What are the different ways by which prokaryotes, protozoans and fungi reproduce asexually?
METHODS Or types OF ASEXUAL REPRODUCTION:
A sexual reproduction does not involve the fusion of gametes. There are many types of asexual reproduction, all producing individuals that are genetically identical to each other and to the parent.
1) Binary Fission:
Binary fission means “division into two”. In this type of reproduction an organism simply divide into two individuals at the same time. Both the daughter organisms are identical to each other and their parents. In this process simple cell division takes place. First karyokinesis or duplication of DNA takes place and then cytokinesis occurs to divide the cell into two. Prokaryotes, some unicellular eukaryotes and some invertebrates like echinoderms and planaria reproduce by this process.
- a) Binary fission In Bacteria:In Bacteria first the DNA duplicates and then cell membrane invaginates to divide cytoplasm into two and thus two daughter organisms produce at the same time.
- b) Binary fission in amoeba: In amoeba the binary fission completes in two steps. First karyokinesis occurs which divide the nucleus into two and finally cytokinesis occurs by the invagination of cell membrane which divide the cell into two.
Figure: Binary fission in a bacterium (left) and in an Amoeba (right)
- c) Binary fission in planaria:The body of planaria divides into two pieces and each piece form a complete organism.
2) Multiple fission: Some unicellular organisms (e.g. Amoebae) form hard walls called cysts around them, under unfavourable conditions. When favourable conditions return, the nucleus of parent divides into many daughter nuclei by repeated divisions. This is followed by the division of cytoplasm into several parts. Each new part of cytoplasm encloses one nucleus. So a number of daughter cells are formed from a single parent at the same time. After sometime the cyst bursts and many cells releases. This kind of fission is known as multiple fission. Examples: Amoeba, Bacteria, Plasmodium, etc.
Fragmentation: The division of an organism to many pieces or fragments at a same time is called fragmentation. Certain worms grow to full size, they spontaneously break up into 8 or 9 pieces. Each piece (fragment) develops into a mature worm, and the process is repeated. If a planarian breaks into many pieces instead of two, it will also be called as fragmentation. Examples: worms, planaria, etc.
Figure : Fragmentation in a planarian
In this type of asexual reproduction, a bud develops as a small outgrowth on parent’s body. In case of yeast (a unicellular fungus) a small bud is formed on one side of cell. The nucleus of cell divides and one of the daughter nuclei is passed into the bud. Parent cell may form more than one bud at a time. Each bud enlarges and develops the characteristics of parent organism. The bud may separate from parent body. In some cases, the buds never separate and as a result, colonies of individuals are formed.
Animals such as sponges, Hydra and corals also reproduce by means of budding. In them, a small bud is formed on the side of body, by mitosis. This bud enlarges by the formation of more cells. It then detaches from the parent body and grows into new organism.
In corals, the buds do not detach from the parent body. Corals form big colonies, because the buds grow into new organisms by remaining attached to the parent body.
|Figure: Budding in yeast|
|Figure : Budding in Hydra|
Spore Formation: Spores are haploid reproductive structures produced by lower plants, fungi, etc. fungi form thick wall spore sacs called sporangia.Iside sporangia a cell produces many daughter cells called spores The sporangia then burst and releases spores The spores then germinate and produce new organisms. Under unfavorable conditions, some bacteria also produce spores inside their body and so bacterial spores are called endospores. Examples: Fungi like rhizopus and bacteria like Clostridium and Bacillus species reproduce through this process.
Figure : Spore formation in Rhizopus
Mature sporangium (left), sporangium bursts (right)
Figure : Spore formation in a bacterium
Parthenogenesis: A type of asexual reproduction in which an egg develops without fertilization into an embryo (Offspring). It is the development of an unfertilized egg into an embryo and finally into an organism. Example: Some fishes, drones ( male honey bees) and frogs reproduce by this process.
Question3: What is vegetative propagation? Explain the different parts of the plant that help in natural vegetative propagation and artificial vegetative propagation?
Vegetative Propagation or vegetative reproduction: The type of propagation that occurs through vegetatve parts of the plants is called vegetative propagation. In this type of reproduction vegetative parts of plants i.e. roots, stems or leaves give rise to new plants. It occurs naturally as well as artificially.
Natural Vegetative Propagation: Vegetative propagation occurs naturally by following ways.
- Bulbs:Bulbs are short underground stems surrounded by thick, fleshy leaves that contain stored food. Adventitious roots emerge under the base of bulb or basal bud or axillary bud while shoots emerge from the top of the base or apical bud. Tulips, onions and lilies reproduce by bulbs.
- Corms:Corms means trunk. Trunk is short and swollen underground stems containing stored food. Buds are present at the top of corm. From a bud, shoot grows and forms a new plant. Dasheen (Clocacia) and garlic reproduce by corms.
- Rhizomes:Rhizomes are horizontal underground stems with scale leaves. There are enlarged portions called nodes on rhizome. Buds are produced at nodes. The buds present on the upper surface of rhizome give rise to shoot. The lower surface of rhizome produces adventitious roots. Ginger, ferns and water lilies reproduce by rhizomes.
Figure 14.8: Some types of natural vegetative propagation
- Stem Tubers:Stem Tubers are the enlarged portions of an underground stem (rhizome). There are aggregations of tiny buds in the form of “eyes” along the surface of tuber. Each bud develops into shoot that grows upward and also produces roots. Potatoes and yams reproduce by tubers.
- Suckers:Suckers are lateral stems close to ground level. A sucker grows underground from some distance and then turns up, producing the new plant. Mint and Chrysanthemum reproduce in this way.
- Vegetative propagation through leaves:Vegetative propagation by leaves is not common and is seen in plants such as Bryophyllum (Pather chut). This plant has fleshy leaves and adventitious buds are present at the margins of leaves. When leaf falls on ground, the buds grow into new plants.
Artificial Vegetative Propagation: Gardeners and farmers use artificial methods of vegetative propagation to increase the stock of a plant. The following two are the most common methods of artificial vegetative propagation.
|Figure : A Bryophyllum leaf with buds|
- Cuttings:In this type of vegetative propagation a small part of stem that have meristematic region is cut from the plant and then placed in the soil having right conditions. They form roots and shoots and produce new plants. Examples: Roses, ivy and grapes.
- Grafting: In grafting, a piece of stem is cut from the plant and is attached with another plant with established root system. After a while, the vascular bundles of the attached stem piece and the host plant are connected to each other. The stem piece and the plant begin to grow together. Examples: This method is used to propagate many roses, peach trees, plum trees and various seedless fruits (including grapes).
Figure : Artificial vegetative propagation: Cutting (left) and Grafting (right)
Advantages and Disadvantages of Vegetative Propagation OR Vegetative reproduction or micro propagation of Plants:
- Offspring are genetically identical so useful traits can be preserved.
- Only one parent organism is required.
- It is very faster process and produce large number of individuals in very less time.
- It is useful to produce seedless fruits.
- It uses only a small part of plant so this method of propagation is also called micro-propagation.
- Young plant uses the food resources from parent plant during development.
- The new plant matures more quickly.
Disadvantages of vegetative propagation:
- No genetic variation, so species specific diseases can attack and this can result in the destruction of entire crop.
- Over crowding causes severe competition for survival among them.
Question 4: What is cloning? Why cloning is a type of a-sexual reproduction?
Answer: Cloning: The process of producing identical individuals from a single cell or tissue of an organism is called cloning. The technique used in cloning is called tissue culture. In tissue culturing a tissue is taken from any part of the plant and put in a suitable nutrient medium. By mitosis the tissue produce large number of cells and is called callus. These tissues are transferred to medium containing hormones. Calluses grow and produce new plant. The small plant is then planted in fields. Cloning is a type of asexual reproduction because it does not involve the fusion of male and female gametes.
Question 5: Write a brief note on sexual reproduction in plants?
Answer: SEXUAL REPRODUCTION IN PLANTS: Sexual reproduction involves the production of gametes (sperms and egg cells) and their fusion i.e. fertilization. These gametes are produced by different plants by different processes. Sperms of mosses are motile and can swim to egg cells so requires water for pollination. Angiosperms sperms are non motile so they are pollinated by insects or winds. In life cycle of plants sexual and asexual generation alternate with each other. This process is called alternation of generation. In this process gametophytic generation alternate with sporophytic generation.
Question 6: Discuss alternation of generation in angiospermic plants?
Answer: Alternation of generation: In the life cycle of plants, two different generations alternate with each other. One generation is diploid and produces spores. It is called sporophyte generation. The other generation is haploid and produces gametes. It is called gametophyte generation. The phenomenon in which two different generations alternate with each other during life cycle is known as alternation of generations.
In most plants, sporophyte generation is dominant. It means that it is big in size and is independent. Sporophyte produces haploid spores by meiosis. The spores develop into gametophyte. It is small in size and depends upon sporophyte. It produces gametes by mitosis. The male and female gametes fuse and form diploid zygote. The zygote undergoes repeated mitosis and develops into a new diploid sporophyte.
Figure: An overview of alternation of generations in plants
Question 7: Draw a labeled structure of a typical flower and describe functions of each part?
Answer: Structure of a typical flower: A typical flower consists of four whorls.
Calyx: Calyx is the outermost whorl in a flower. It is usually green in colour. It protects the inner parts during bud stage. Its individual unit is called sepal.
Corolla: It is the second whorl. Its individual unit is called petal. These are mostly brightly colored and attract the insects for pollination.
Androecium: It is the third part and is the male reproductive part of the flower. Its individual unit is called stamen. Each stamen has thread like filament. At the free end of which filament is attached. Anthers has sacs in which haploid microspores or pollen grains are produced through meiosis. Each microspore germinates into the male gametophyte generation. During it, the nucleus of microspore undergoes mitosis and produces two nuclei i.e. a tube nucleus and a generative nucleus. The generative nucleus again undergoes mitosis and produces two sperms. So, a germinated microspore has a tube nucleus and two sperms. All these structures are the male gametophyte generation of plant.
Gynoecium: It is the fourth whorl and is the female reproductive part of flower. Its individual unit is called carpel (or pistil). Each carpel is made up of the basal ovary,middle style and upper stigma. Inside ovary, there are one to many ovules. Inside each ovule, one haploid macrospore is produced through meiosis. Macrospore germinates into the female gametophyte generation. During it, macrospore undergoes mitosis and produces an egg cell and some associated structures (e.g. fusion nucleus). Egg cell and associated structures are the female gametophyte generation of plant.
Figure: Structure of a flower
Question 8: How Pollen grains are produced? Is pollen grain is a gamete?
Answer: Pollen grains are special structures that carry the male gametes. A pollen grain is not a gamete but it only carries the male gametes. It is binucleate. It means that it contains two male gametes or sperms as a gamete has only one nucleus. Microspore mother cell is the anther undergoes meiosis, each producing four haploid microspores. The microspore nucleus undergoes mitosis form a binucleate haploid cell. This binucleate nucleus develops into a polen grain. The mature anther opens and allow the polen grains to carry out process of pollination.
Question 9: Write a short note on development of embryo sac?
- In the ovule a diploid megaspore mother cell undergoes meiosis.
- Four haploid megaspores are produced.
- Three of the megaspores disintegrate.
- Only one megaspore survives in each ovule.
- The haploid nucleus of the surviving megaspore undergoes three mitotic divisions.
- Eight haploid nuclei are now present.
- Within the swollen “megaspore cell” six haploid cell and two polar nuclei are formed. The entire structure is called embryo sac.
- One of the cell near to the micropyle end of the ovule is the haploid female gamete (egg cell).
Question10: What is pollination? What are the different agents of pollination? What are the properties of wind and insect pollinated plants?
Answer: Pollination: The transfer of pollen grains from flower’s anther to stigma is called pollination.
Types of pollination: There are two types of pollination.
Self pollination: The transfer of pollen grains from the anther to the stigma of the same flower or other flower of the same plant is called self pollination. Example: Pea, Sunflower.
Cross pollination: Cross pollination is the transfer of pollen grains from the flower on one plant to the flower on other plant of the same species.. Examples: Apple, grapes, etc.
Agents of cross pollination: Cross pollination is brought about by various agencies like wind, water, bees, birds, bats and other animals including man. Examples of insect pollinated flowers are buttercup, rose, wallflower, sunflower, orchid etc. Examples of wind pollinated flowers are grasses, hazel, willow, corn etc.
|Table: Adaptations in insect-pollinated and wind-pollinated flowers
Question 11: What is meant by fertilization and double fertilization? Which group of plants shows double fertilization?
Answer: Fertilization: The fusion of male and female gametes is called fertilization.
Double fertilization: Double fertilization is the fusion of a sperm to an egg and the other sperm to polar nuclei. The polen grain germinates forming a pollen tube that inter to the ovule. The one sperm fuses with haploid egg cell forming a zygote. While the other sperm fuses with two polar nuclei forming triploid endosperm.
Figure: Life cycle of a flowering plant
|For your information:
· The flower is actually a condensed shoot with the nodes present very close to each other. The different parts of the flower are attached to the nodes. All the structures present at one node are collectively called the whorl.
· Different flowers have one to many carpels. These may either be fused or free.
· Theophrastus (the successor of Aristotle) was a Greek philosopher. He laid a solid foundation of botany including the morphology and functions of the flowers. He recognized the male and female sex parts of the flowers and described the pollination and fertilization in flowers.
|This is self pollination because the polen grains transfers fron the anther to the stigma of flower present on the same plant.|
|Initiating and Planning:
Hypothesize why Mendel used Pea plants for his experiments.
Answer: Mendel used pea plants in his experiments because it shows self as well as cross pollination.
|For your information: The evolution of seed has been proved as an important step in the success and spread of flowering plants, as compared to the seed-less plants like mosses and ferns.|
|For your information:
In some plants, ovaries develop into fruit without the fertilization inside their ovules. This process is known as parthenocarpy and it results in seedless fruits e.g. bananas and seedless varieties of grapes.
Question 12: Write a short note on development of seed?
Answer: The zygote formed by fusion of sperm and egg undergoes mitotic divisions and forms embryo. The store food or endosperm remains outside the embryo in the form of single cotyledons or two cotyledons. The wall of the ovule converted into seed coat. The ovary becomes fruit.
Question 13: Explain the structure of seed. Also draw diagram.
Answer: Seed: A mature ovule is called a seed. A typical seed consists of following parts.
Seed coat: Seed coat or testa is the outermost covering of seed. Beneath this is a thin layer called tegmen. Protection of inner parts is the function of seed coat.
Hilum: Place of attachment of seed to fruit is called hilum.
Micropyle: Minute pore on the seed is called micropyle. Function of absorption of water during germination.
Embryo: Beneath tegmen embryo is present. Embryo consists of axis and cotyledons (seed leaves).
Axis: Axis is mainly the central part consists of following.
Radicle: It lies towards pointed end of the seed. Roots arise from this part.
Plumule: Minute bud on the upper side of hypocotyls. Stem arise from this part.
Hypocotyl: The part of plant emryo below cotyledon is hypocotyls.
Cotyledon: Cotyledons are leaves like structures in seed.
Endosperm: It is the stored food functions during germination.
Figure: The structure of a dicot seed
Question 14: What is hypocotyl and epicotyl stem?
Answer: The embryonic stem above the point of attachment of cotyledon(s) is called epicotyl. The embryonic stem below the point of attachment of cotyledon is called hypocotyl.
Question 15: What is seed germination? What are different types of seed germination? What conditions are necessary for the germination of seeds? Explain, how the epigeal and hypogeal germinations are different?
Answer: Germination of Seed: The process by which inactive seed becomes active and develop seedling is called germination.
Types of germination: There are two main types of the germination.
Epigeal germination: The type of germination in which cotyledon forced above the ground is called epigeal germination. In this type of germination hypocotyls elongates. Examples: Beans, cotton and papaya, etc.
Hypogeal germination: In this type of germination cotyledons remains below the ground and epicotyls elongates. Pea, maize, wheat and coconut.
Figure: Types of seed germination; epigeal (left) and hypogeal (right)
|For your information:
· The form of the stored nutrients in seeds varies depending on the kind of plant.
· Most seeds go through a period, during which there is no growth. This period is called the dormancy of the seed. Dormant seeds are ripe seeds but do not germinate. Under favourable conditions, the seeds break dormancy and begin to germinate.
Conditions for Seed Germination:
Seed germination depends on both internal and external conditions. The internal conditions include a live embryo and sufficient food storage. The most important external conditions include water, oxygen and favourable temperatures.
Water (moisture): Seeds of most plants have low water content, and germination cannot occur until seed coat or other tissues have imbibed (taken in) water. The absorbed water is used in the digestion of the stored food and it also helps in the elongation of hypocotyl and epicotyl.
Oxygen: Oxygen is essential for the respiration in the cells of embryo.
Temperature: Seeds differ greatly in their temperature requirements for germination.The optimum temperature for the germination of the seeds of most plants ranges from 25-30OC.
- Germination of seeds of many plants is also favoured by light. In others, germination is retarded by light.
Difference between epigeal and hypogeal germination:
|Epigeal germination||Hypogeal germination|
|1) Germination in which the cotyledons are forced above the ground.||1) Germination in which the cotyledons remains in the seed below the ground.|
|2) The hypocotyl elongates.||2) The epicotyl elongates.|
|3) Cotyledons become photosynthetic. The first leaves formed from cotyledons.||3) Cotyledons do not become photosynthetic.|
|4) Seed coat emerges from soil.||4) Seed coat remains in soil.|
|5) Examples: Pea, bean.||5) Examples: Wheat, Mango.|
Question 16: Give a comparison of asexual and sexual reproduction?
Answer: A-Sexual Reproduction: 1) Only one parent plant is involved.
2) No meiosis takes place.
3) No gametes formation.
4) No fertilization takes place.
5) No variations, offsprings are identical to their parents.
6) Rapid production of large number of offsprings.
Sexual reproduction: 1) Two parents takes part in reproduction.
2) Meiosis takes place in reproduction.
3) Gametes are formed.
4) Fertilization takes place.
5) Genetic recombination occurs that leads to variations and production of varieties.
6) Less rapid increase in number.
Question 17: Write a detailed note on sexual reproduction in animals? Also describe the processes of spermatogenesis and oogenesis in detail.
Answer: Sexual reproduction: The type of reproduction that involves the fusion of male and female gametes is called sexual reproduction.
Sexual reproduction in animals: Most animals reproduce sexually. Sexual reproduction consists of two main components.
Formation of Gametes (Gametogenesis): The formation of gametes is called gametogenesis. In this process, diploid (2N) gamete mother cells undergo meiosis and form haploid (1N) gametes. The male and female gametes (sperms and egg cells or ova) are produced in specialized organs called gonads. Male gonads are called testes (Singular: testis) while female gonads are called ovaries.
A) Spermatogenesis:The production of sperms in testes is called spermatogenesis. This process completes in following steps.
Multiplication phase: In semineferous tubules of testes large number of spermatogonia are produced by mitosis from some cells. These are diploid cells.
Growth phase: Some spermatogonia inter the growth phase and are now called primary spermatocytes (2n).
Division phase: Each primary spermatocyte (2n) undergoes meiosis-I and produce two haploid secondary spermatocytes (1n). These cells undergoes meiosis-II and produce four haploid spermatids.
Maturation phase: Spermatids are non motile, so many changes occurs in them to convert them into motile sperms. Their nuclei shrink, acrosome is formed, a tail and a mitochondrial ring also form. After these changes spermatids are called sperms.
B) Oogenesis:The production of egg cells in ovaries is called oogenesis.
Some cells of ovary prepare structures called follicles, in which many diploid oogonia are present. Some oogonia produce diploid primary oocytes. One of the primary oocytes completes meiosis-I and produces two haploid cells. The smaller cell is called first polar body and the larger one is called secondary oocyte. The secondary oocyte completes meiosis-II and produces two haploid cells i.e. a second polar body and an egg cell. The first polar body also divide and produce two other polar bodies. So at the end of this process three polar bodies and one egg cell are present.
2) Fertilization: The fusion of male and female gametes to form zygote is called fertilization. Zygote is the first formed cell in the life of a living organism. It is the first diploid cell that divides mitotically form embryo. Embryo by further development changes to new individual.
Types or mechanisms of fertilization: There are two types or mechanisms of fertilization.
1) External fertilization: The type of fertilization in which egg cell fertilized outside the body of mother is called external fertilization. External fertilization occurs mostly in aquatic environment. It requires both the male and the female animals to release their gametes into their surroundings at almost the same time.
Examples: External fertilization occurs in many invertebrates and the first two groups of vertebrates i.e. fishes and amphibians.
Advantage: Production of large number of gametes and offsprings.
Disadvantages: Predators eat most of eggs or water current reduce the chances of fertilization.
|Figure: External fertilization in fish|
Internal fertilization: In internal fertilization, fusion of gametes occurs inside body of female organism. In this type of fertilization sperms are released in reproductive tract of female.
Examples: It occurs in reptiles, birds and mammals. Such animals provide protection to the developing embryo.
- a) Reptiles and birds:After fertilization, reptiles and birds make protective shells around their egg cells and then lay them. The shell is resistant to water loss and damage.
- b) Mammals:In mammals (with the exception of egg-laying mammals) the development of fertilized egg into new baby takes place within mother body. In this case, there is extra protection to the embryo and mother also supplies everything that embryo needs.
Figure: Reptiles and Bird’s egg provides protection and food to embryo
Question 18: Write a note on the male and female reproductive systems of rabbit?
Answer: Reproduction in Rabbit: Rabbits are small mammals found in several parts of the world. They are used in research as experimental animals.
- A) Male Reproductive System: The male reproductive system of rabbit consists of a pair of testes that produce sperms, the associated ducts that transport sperm to external genitalia and glands that add secretions to sperms.
(i) Testes: Testes are located in a bag of skin called the scrotum that hangs below the body. Each testis consists of a mass of coiled tubes called the seminiferous tubules. In these tubules, the sperms are formed. Testes are attached to the walls of the walls of the scrotum by a small cord called scrotal cord.
(ii) Associated ducts: Associated ducts involve following ducts.
- a) Collecting ducts:These ducts collect the mature sperms.
- b) Epididymus:Mature sperms moves from collecting duct to epididymus.
- c) Vas deferens:This is a slender tube through which sperms moves from epididymus.
- d) Urethra (duct in the penis):Both sperm ducts join at urethra below urinary bladder. It is the passage way for both sperms and urine.
- e) Genital aperture:The opening of penis is called genital aperture. It is the pore in the penis.
(iii) Associated glands: As the sperms pass down the ducts from testes to urethra. The associated glands adds various secretions. Semen is the material containing sperm in a fluid. It contain 10% sperms and 90% fluid. Following are the important associated glands.
- a) Seminal vesicles:The efferent duct that located dorsal to neck of urinary bladder. Its secretions provide nutrients to the sperms.
- b) Prostate glands:Its secretion neutralizes the acidity of the fluid.
- c) Cowper’s glands:Cowper’s glands produce secretions that lubricate the ducts.
Figure: Male reproductive system of rabbit
|Rabbits re-ingest their own pallet-like faeces to digest their food further and extract sufficient nutrients.|
- B) Female Reproductive System of rabbit:The female reproductive system of rabbit consists of ovaries and associated ducts.
1) Ovaries (Singular ovary): ovaries are small oval organs situated in abdominal cavity just ventral to kidneys. Like most animals, female rabbits have a pair of ovaries. The outer region of ovary produces egg cells. A cluster of specialized cells called follicle surrounds and nourishes each egg cell. The surface of ovary is rough due to these follicles.
2) Fallopian funnel: It is funnel shaped opening of the fallopian tube.
3) Fallopian tube (Oviduct): The narrow convoluted portion near to fallopian funnel is called fallopian tube. The ovary releases its egg to fallopian tube. Since the opening of fallopian tube lies closer to the ovary. Fertilization occurs in fallopian tubes and the fertilized egg (zygote) is carried to uterus.
4) Uterus: Oviduct or fallopian tube widens posteriorly to form uterus. Uterus is divided into two separate parts called horns, which joins and opens into vagina or birth canal.
5) Vagina: The two horns (utri) joins to form vagina.
6) Cervix: Cervix is the portion of uterus which separates the uterus from vagina where sperms are deposited.
7) Urinogenital aperture or urethra: Birth canal opens in urethra.
Figure: Female reproductive system of rabbit
Question 19: Write a short note on fertilization and development in rabbit?
Answer: Fertilization and Development in Rabbit: Rabbits can breed throughout the year but male rabbits are commonly sterile during the summer months. Male rabbit deposits its sperms in the vagina (birth canal) of female. Sperms swim through cervix and uterus to fallopian tubes where they fertilize the egg cells, released from ovary. After fertilization, zygote is carried to uterus. By this time, the zygote has started dividing and is now called embryo. The embryo is implanted in uterus walls. A connection, called placenta, is established between embryo and uterus wall. Embryo develops into new offspring (rabbit kit) in 30–32 days, after which it is born.
Question 20: Growth in human population increases day by day. Explain what are the main causes of overpopulation? Why do we consider that overpopulation is a global problem?
Answer: Growth in Human Population or overpopulation: When population growth exceeds the carrying capacity of an area or environment, it results in overpopulation. At the time of independence population of Pakistan was 32.5 million. In 2007-2008 this population was 163,775,000. By the end of this decade, our population is expected to exceed 176 million. Pakistan’s population had a relatively high growth rate in past.
Problems with overpopulation: 1) Shortage of water.
3) Loss of ecosystem.
4) Loss of natural resources.
5) Global warming.
6) High mortality rate due to poverty.
7) Environmental changes.
Causes and factors affecting overpopulation: 1) Better living conditions.
2) Lack of education and family planning.
3) Medical treatment that increase life span.
4) Increase birth rate by advancement in fertility treatment.
5) Low death rate due to better care.
6) Immigration (Local overpopulation problem).
Overpopulation is a global problem: Overpopulation is a global problem because there will be a struggle for food in the near future if the world gets too populated. This is because as the world gets more populated, the food supply must increase to support the newborns. Once the world gets more populated and the developing countries will fail to support their people with food. Secondly this causes fewer jobs to be available around the globe in near future. Peace is also impossible in near future in overpopulated areas.
Overpopulation is a global problem: Overpopulation is a global problem nowadays. Today human beings are considered the new dinosaurs of the world. Due to very high population growth rate various problems occur. Some are as follows.
1) Food and water shortage: In many areas of the world there is simply not enough food to feed the growing populations. Each day 40,000 children die due to malnutrition, shortage of food and food related diseases. The supply of fresh water also decreases due to overpopulation.
2) Environmental problems: Overpopulation also leads to environmental problems like global warming, deforestation, desertification, Pollution, etc.
3) Other problems: Overpopulation is also responsible for social problems, economic problems, traffic problems, less availability of jobs, etc.
Question 21: What is the need of population planning in Pakistan?
Answer: Need of population planning in Pakistan: Pakistan is one of the developing country and population increases day by day, by a rapid rate. If population increases at this speed we will be unable to meet the needs of people. Due to increase population, resources become insufficient like hospitals, schools and roads, etc… It exerts a great pressure on economic conditions as well, so we need plan programs to reduce fertility and improve social behaviors and living standards of people.
|For your information:
The United Nations Population Fund:
UNFPA began operations in 1969. It is the largest international organization funding for population and health programmes. The UNFPA works in over 140 countries, for awareness about the consequences of overpopulation.
Question 22: What are sexually transmitted diseases? Give an introduction of Pakistan’s National AIDS Control Program (NACP).
Answer: Sexually transmitted diseases (STD): The diseases that are transmitted through sexual act are called sexually transmitted diseases. Example: AIDS (Acquired immune deficiency syndrome).
AIDS: AIDS stands for Acquired Immuno Deficiency Syndrome. It is a type of sexually transmitted diseases and is caused by human immuno deficiency virus (HIV).
Effects: This virus destroys white blood cells, which results in loss of resistance against infections. It is a fatal disease.
Mode of transmissions:
- Spreads through transfer of body fluids such as blood and semen.
- Unprotected sexual activities such as immoral sexual behaviors and homosexuality.
- Sharing drug needles with an infected person.
- Sharing razors with infected persons.
- Through infected mother milk or during pregnancy.
****Important note: Saliva and tears do not transmit HIV.
Symptoms: Primary symptoms include flu and fever, prolong headache, muscle pain, fatigue. Some people do not show HIV symptoms. It mostly affects those people easily who have weak immune system.
Treatment: No proper treatment. Antiviral drugs are used but they have no serious effects on virus.
National AIDS Control Program (NACP): Pakistan’s Federal Ministry of Health established NACP in 1987. The main objectives of this program are as follows.
- To help the public for the prevention of HIV.
- Safe blood transfusion.
- Reduction of STDs (Sexually transmitted diseases).
Prevention of HIV by NACP in Pakistan: frequency of HIV infection is very slow in Pakistan. But the country is at risk of epidemics due to various risk factors. For the prevention of AIDS, NACP started programmes on TV and radio channels in 2005. Objective of this program are as follows.
1) To change public attitude for safe sexual activities.
2) Created demand for information on HIV and AIDS.
3) Improve attitude and behaviors among health care workers.
Role of Non-Governmental Organizations (NGOs): According to the latest data by the World Bank, at least 54 NGOs are working in Pakistan for HIV/AIDS public awareness and for the care and support of persons living with HIV/AIDS. These NGOs also work on AIDS education and prevention for sex workers and other high-risk groups. NGOs serve as members of the Provincial consortium on HIV/AIDS, which has been set up in all the provinces of Pakistan.
|For your information:
· Pakistan has a multicultural and multiethnic society and hosts the largest refugee population in the world.
· According to the United nations Programme on AIDS i.e. UNAIDS estimates, some 70,000 to 80,000 persons, or 0.1 percent of the adult population in Pakistan, are infected with HIV.
· The number of drug addicts in Pakistan is currently estimated to be about 500,000, of whom 60,000 inject drugs.
· Although NGOs are very busy in HIV/AIDS prevention activities, it is believed that they are reaching less than 5 percent of the vulnerable population.
Question1. How are the natural and artificial vegetative propagations the methods of asexual reproduction in plants?
Answer: Natural and vegetative propagations considered asexual methods because it does not involve the fusion of male and female gametes.
- Why do gardeners use the methods of cutting and grafting?
Answer: Gardeners use cutting process to produce very large number of plants in less time. They also use grafting process to produce best varieties of fruits and other plants.
- “Parthenogenesis is a type of asexual reproduction”. Give comments on this statement.
Answer: In parthenogenesis an unfertilized egg develops into new offsprings without fusion with male gametes, so it is a type of asexual reproduction.
- Outline the life cycle of a flowering plant.
Answer: Life cycle of a flowering plant: There are two types of generations in flowering plants.
Sporophytic Generation: It is dominant, multicellular diploid generation which is formed from zygote or fertilized egg. Sporophyte produces spores by meiosis.
It is small multicellular haploid generation which is formed form spores. Male gametophyte develops from microspore or pollen grain and produce male gametes called sperms. The female gametophyte develops from megaspore which produces eggs by meiosis.
- What structural adaptations will you find in a wind-pollinated flower?
Answer: 1) These flowers are generally small.
2) Petals are green or dull in color.
3) They do not produce nectar.
4) Flowers hang down for easy shaking.
5) Stamens and stigmas hang out of ring of petals.
6) Pollen grains produced in large number/light with smooth surface.
7) Stigma has feathery branches for catching pollen.
Question 6. Give an introduction of Pakistan national AIDS control program?
Answer: Related to question no.22.
UNDERSTANDING THE CONCEPT
- What are the different ways by which prokaryotes, protozoans and fungi reproduce asexually?
Answer: Please see answer of question no.2.
- Explain the different parts of the plant that help in natural vegetative propagation.
Answer: Please see answer of question no.3.
- Explain, how the epigeal and hypogeal germinations are different?
Answer: Related to question no.15.
- What conditions are necessary for the germination of seeds?
Answer: Related to question no.15.
- Outline the methods of asexual reproduction in animals.
Answer: Please see answer of question no.2.
- Write a note on the male and female reproductive systems of rabbit.
Answer: Please see answer of question no.18.
- Describe the processes of spermatogenesis and oogenesis.
Answer: Please see answer of question no.7.
- Why do we consider that overpopulation is a global problem?
Answer: Please see answer of question no.20.
The terms to know.
Acrosome: Cap-like head of sperm cell which helps it in penetrating the egg cell is called acrosome.
Alternation of generations: In plants, the phenomenon in which the sporophyte and gametophyte generations alternate with each other is called alternation of generation.
Anther: The sac-like structure of a stamen in which pollen grains are produced is called anther.
Binary fission: Division into two; the simplest method of asexual reproduction in prokaryotes and many unicellular eukaryotes in which an organism simply divides into two.
Budding: A type of asexual reproduction in which a bud develops as a small outgrowth on parent’s body and forms the new individual.
Bulb: Underground vertical shoots which have modified leaves are called bulbs.
Calyx: The outermost whorl of flowers; consists of sepals is known as calyx.
Carpel: Part of the gynoecium or female reproductive part of the flower; consists of stigma, style and ovary is called carpel or pistil.
Cervix: In female reproductive system, the part which separates uterus from the vagina is called cervix.
Cloning: Cloning is a method of asexual reproduction in which identical offsprings are produced from a vegetative tissue or cell of the parent.
Corm: Corm is a Short, swollen underground stem; has bud(s) at the top; gives rise to new plants by vegetative propagation.
Corolla: The second whorl of flower, consisting of petals is called corolla.
Cotyledon: A modified leaf present in seeds; often gives nourishment to the developing seedling is called cotyledon.
Cowper’s gland: An accessory gland in rabbits male reproductive system; provides lubrication to the ducts is known as Cowper’s gland.
Endosperm nucleus: In the female gametophyte, the triploid nucleus formed by the fusion of sperm and the fusion nucleus.
Endosperm tissue: The tissues that develops from endosperm nucleus; often serves as a food supply for developing embryo.
Endospores: The spores formed inside the bacterial cell are called endospores.
Epicotyl: The embryonic stem above the point of attachment of the cotyledon(s) is called epicotyls.
Epididimys: A storage area for sperms on the upper part of the testes is called epididymus.
Epigeal germination:Epigeal germination is a type of seed germination in which the hypocotyl elongates and forms a hook, pulling the cotyledons above the ground.
Fallopian tube: A part of the female reproductive system; receives egg cell discharged from the ovary
Follicle: A structure in the ovary in which the mature egg develops is called follicle.
Fragmentation: Fragmentation is a type of asexual reproduction in which the animal breaks up into many pieces and each piece develops into a mature animal.
Fusion nucleus: A part of the female gametophyte in plants; formed by the fusion of two nuclei; gives rise to endosperm nucleus when fertilized by a sperm is called fusion nucleus.
Gametogenesis: The process of the formation of gametes is called gametogenesis.
Gametophyte: The haploid generation in plant life cycle; produces gametes is called gametophyte.
Grafting: A type of artificial vegetative propagation in which a piece of stem is cut from the plant and is inserted into another plant with established root system to produce best variety.
Gynoecium: The central female reproductive whorl in the flower; consists of carpels is called gynoecium.
Hilum: A scar on the seed coat; the point where the seed is attached to the ovary wall is called hilum.
Hypocotyl: Hypocotyl is the embryonic stem below the point of attachment of cotyledon.
Hypogeal germination: A type of seed germination in which the epicotyl elongates and forms the hook while the cotyledons stay underground.
Micropyle: Minute pore on the seed is called micropyle functions in the absorption of water during germination. “OR” The opening of the ovule through which the pollen tube enters is called mycropyle. Seed uses it for the absorption of water.
Microspore: The haploid cells produced in the polen sacs that divides mitotically and produce male gametophyte is called microspore.
Multiple fission: Multiple fission means division into many. A type of asexual reproduction in which a unicellular organism divides into many at the same time.
Oogenesis: The formation of ovum (egg cell) is called oogenesis.
Oogonium (Plural Oogonia): The diplod cells in the follicles of the ovary; produce diploid primary oocytes during oogenesis.
Ovary: The female gonad; produces egg cells and female sex hormones is called ovary.
Ovule: In seed plants, a structure present in the ovary; contains macrospore that develops into female gametophyte; ovule develops into seed after fertilization.
Plumule: The part of the plant embryo that develops into new shoot is called plumule.
Pollen grain or microspores: The haploid cells produced in the polen sacs that divides mitotically and produce male gametophyte is called microspore.
Pollen tube: A tube formed by the tube nucleus of the pollen grain; carries sperms to the ovule.
Prostate gland: An accessory gland in the male reproductive system; produces a secretion that neutralizes the acidity.
Radicle: The part of the plant embryo that develops into new root.
Rhizomes: Horizontal underground stems; have scale leaves with buds; shoots of the new plant develop and grow form buds.
Seed dormancy: A period, during which there is no growth in the seed; seeds in dormancy are ripe seeds but do not germinate; under favourable conditions, the seeds break dormancy and begin to germinate
Semen: The material containing sperms in a fluid is called semen.
Seminal vesicle: The associated gland in male reproductive system; produces secretions having nutrients for the sperms.
Seminiferous tubule: The coiled tubes present in testes; sperms are formed in these tubules
Sperm: : The male gametes are called sperms.
Spermatid: The immature non-motile forms of sperms; are converted into sperms after many changes.
Spermatogenesis: The process of formation of sperms is called spermatogenesis.
Spermatogonium (Plural: spermatogonia): The diploid cells in semineferous tubules of the testes; divide mitotically and produce primary spermatocytes.
Sporophyte: The diploid generation in plant life cycle; produces spores is called sporophyte.
Stamen: The individual part of the androcium; consists of anther and filament.
Stigma: The upper part of the carpel is called stigma.
Style: The middle portion of the carpel above the ovary is called style.
Testa: The upper protective covering of the seed is called testa or seed coat.
Testis: The male gonads ; produces sperms and male sex hormones.
Tuber: The swollen ends of slender rhizomes (underground stem); new plants develop from buds on the stem tubers.
Uterus horn: The two separate parts of the uterus in the female are called uterus horns.
Vas deferens: The tubes that carry sperms from each testis to the urethra.
Vegetative propagation: A type of asexual reproduction in which the vegetative parts of the plants i.e. roots, stems or leaves produce new generation.