Class 12 Biology Chapter 1 Reproduction in Organisms

Class 12 Biology Chapter 1 Reproduction in Organisms Solutions to each chapter is provided in the list so that you can easily browse through different chapters Assam Board HS 2nd Year Biology Chapter 1 Reproduction in Organisms Question Answer.

Class 12 Biology Chapter 1 Reproduction in Organisms

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Also, you can read the AHSEC book online in these sections Solutions by Expert Teachers as per AHSEC (CBSE) Book guidelines. These solutions are part of AHSEC All Subject Solutions. Here we have given Assam Board Class 12 Biology Chapter 1 Reproduction in Organisms Solutions for All Subjects, You can practice these here.

Reproduction in Organisms

Chapter – 1

REPRODUCTIONS

Very Short Answer Type Questions

Q.1. What do you mean by life span? 

Ans : The period from birth to the natural death of an organism represents its life span. Every organism has a specific average life span. 

Q.2. What kind of organisms are called immortal? 

Ans : The organism undergoing binary fissions are called immortal as after binary fission nothing is left with the parental body so there is no natural death. 

Q.3. What are called vegetative propagules? 

Ans : Vegetative organ such as roots, stems and leaves bear adventitious buds and bring about the formation of new plants. These structures are called as vegetative propagules. 

Q.4. How does Hydra reproduces asexually? 

Ans : Hydra reproduces asexually by means of budding. 

Q.5. What are prefertilization events? 

Ans : The prefertilization events are : 

(a) Gametogenesis i.e. formation of gametes (egg and sperms) 

(b) Transfer of Gamete (from male to female)

Q.6. Define juvenile phase of life. What is the other term used to denote juvenile phase of life? 

Ans : All organisms have to reach a certain stage of growth and maturity in their life, before they can reproduce sexually. This period of growth is called juvenile phase of life. 

The other term used to devote juvenile phase in case of plants is vegetative phase or juvenility. 

Q.7. What are polycarpic plants? 

Ans : The plants which flower every year after attaining certain maturity are called as polycarpic plants. When gynoecium contains more carpel then it is called polycarpic. 

Q.8. What is gametogenesis? 

Ans : Formation of haploid gametes from diploid gametogonia by means of reduction cell division is called Gametogenesis. It may be either spermatogenesis or oogenesis. 

Q.9. Oestrous cycle is confined to what types of organisms? 

Ans : Oestrous cycle is confined to non-primates like cows, sheep, rats, deer, dog, tigers etc. 

Q.10. How we can differentiate external fertilization from internal type of fertilization? 

Ans : When the fertilization i.e. the union of male and female gametes takes place outside the body of organism i.e. the medium is called the external fertilization and the fertilization which is taking place inside the body of organism is called internal fertilization. 

Q.11. Define embryogenesis? 

Ans : Embryogenesis is the development of an organism from the fusion of sexual reproductive gametes to death and involves the formation of an embryo. 

Q.12. What do you mean by homogametes? 

Ans : When two fusing gametes are morphologically as well as physiologically similar to each other, then it is called as homogametes isogametes e.g. Alga and Monocystis. 

Q.13. Define the term Parthenogenesis. 

Ans : Parthenogenesis can be defined as the development of an unfertilized ovum into a fully formed haploid organism and hence it is called as virgin birth or monoparental. 

Q.14. What type of organism is called ‘Terror of Bengal’. 

Ans : Water hyacinth (Eichhornia) is called the ‘Terror of Bengal’. 

Q.15. Why is the offspring formed by asexual reproduction referred to as clone?

Ans : In asexual reproduction, the offsprings produced are morphologically as well as genetically identical and exact copies of their parent. Hence called as clones. 

Q.16. What is sexual dimorphism? 

Ans : The animals where male and females are different in their morphology, are called sexual dimorphism. 

Q.17. How is the continuity of species is maintained in the living world? 

Ans : By the process of reproduction, the species is maintaining continuity. 

Q.18. which type of organisms cell division is itself a mode of reproduction? 

Ans : In protozoa like amoeba, Paramoecium, Euglena etc. The cell division itself is a mode of reproduction. 

Q.19. Define syngamy. 

Ans : Syngamy can be defined as the complete and permanent fusion of reproductive gamete i.e. ovum and sperm which is also called as fertilization. 

Q.20. What kind of speciality is found in the following behaviour of Bamboo plants and Strobilanthes kunthiana (Neelakuranjii). 

Ans : Bamboo plants produces flower once is their life time that too after 50-100 years. Hence it is called as Monocarpic. 

Q.21. What do you mean by regeneration? 

Ans : Regeneration is the capacity of formation of a complete organism from a body fragment i.e. Hydra.

Q.22. Why is the apple referred to as a false fruit? 

Ans : Apple is formed by the modification of thalamus but not from the ovary, hence it is called as false fruit. 

Q.23. Why grafting is not possible in monocots of angiosperms? 

Ans : Monocot doesn’t show the secondary growth, hence grafting is not possible in case of these plants. 

Q.24. Between an annual and a perennial plant which one has a shorter juvenile phase and why? 

Ans : Annual plants have shorter juvenile phase while the perennials have longer because annual plants have to complete its life cycle within a year.

Q.25. ‘Although potato tuber is an underground part, it is a stem’, – state reason in support of the statement. 

Ans : Tuber of Potato is a swollen apical underground part which is actually a stem because it bears number of nodes or eyes. New plant can produced from the buds. 

Q.26. Give two names of monoecious animals present in the biological world. 

Ans : (i) Earthworm (pheretima posthuma) 

         (ii) Leech (Hirudinaria granulosa) 

Q.27. Why are gametes produced in large number in organisms that exhibit external fertilization? 

Ans : To make sure the process of fertilization. 

Q.28. What is the technique of obtaining large number of plantlets by invitro? 

Ars : Tissue culture is the only technique by which we can get large number of plantlets by invitro. 

Q.29. ‘Reproduction is essential and important of organisms’. Why? 

Ans : Reproduction is essential and important by which living organism give rise to young ones similar to self. To maintain the continuity of diversity of living organisms, reproduction is essential. 

Q.30. New banana plants are developed from which part of the parent? 

Ans : Rhizome. 

Q.31. Name an unicellular fungi which reproduces asexually by budding. 

Ans : Yeast.

Q.32. What is clone? 

Ans : Clone is a group of genetically similar cells or organisms produced by asexual method from the same parent. 

Q.33. With which type of reproduction do we associate the reduction division? 

Ans : Reduction all division is associated with sexual reproduction. 

Q.34. what type of germination the germinating seeds are attached to the parent plant. 

Ans : Intlypocoty/germination, germinating seeds are attached to the parent body. 

Q.35. Why single celled organisms like Amoeba and Bacteria do not have natural death. 

Ans : Because they multiply by binary cell division where single cell or organism is divided into two and hence there is no natural death. 

(B). Fill up the blanks : 

Q.1. The process of fusion of haploid cells is called_____.

Ans : Fertilization (Syngamy) 

Q.2. _____ is the fusion of male gamete with a female gamete. 

Ans : Fertilization. 

Q.3. _____  is the common propagules for vegetative propagation of mint plant. 

Ans : Runner. 

Q.4. In terms of sexuality earthworm is _____ but Cockroach is _____ animal. 

Ans : Monoecious, dioecious.

Q.5. In an angiosperm flower after fertilization ovary and ovules develops into ____ and ____ respectively.

Ans : Fruit, seed.

Q.6. The offsprings produced by asexual reproduction is termed as _____

Ans : Clone. 

Q.7. Bryophyllum ___ buds  reproduces asexually by formation of ___ buds ____.

Ans: daigremontianum, adventitious, of leaf.

Q.8. A piece of potato tuber will form a new plant if it possesses ____.

Ans : eye or bud. 

Q.9. The offspring produced through the process of ____ reproduction are not exactly similar to their parents. 

Ans : Sexual. 

Q.10. When male differs from female in morphology it is called _____

Ans : Sexual dimorphism. 

Q.11. If a plant fails to develop viable seeds, these could best be grown by _____ method.

Ans : Vegetative propagation. 

Q.12. Male gametes in angiosperms are formed by the division of _____ cell. 

Ans : meiocyte cells. 

Q.13. The egg apparatus of an angiosperms embryo sac comprises of _____ and ____ Cell. 

Ans : ovary and ovule. 

Q.14. Fungi reproduces asexually by forming ____ and____.

Ans : zoospores, buds (conidia) 

Q.15. The gametes which are similar in structure in both sexes are _____.

Ans : Isogametes (Homogametes) 

Q.16. The period from birth to the natural death of an organism is called____.

Ans : Life. span. 

Q.17. When scion is grafted to a stock the quality of fruits produced will be determined by the genotype of _____.

Ans : Scion.

Q.18. Conidia asexual reproductive structure found in______.

Ans : Penicillium. 

(C) Select the True or False Statements : 

Q.1. No individual is immortal, except sponge. 

Ans : False.

Q.2. Syngamy means fusion of cytoplasm. 

Ans : False. 

Q.3.Seeds are called products of sexual reproduction because they are formed by fusion or gametes. 

Ans : True. 

Q.4. In animals juvenile phase of life cycle is followed by reproductive phase. 

Ans : True. 

Q.5. In the life cycle of organisms, Gametogenesis → Syngany → Embryogenesis → Żygote represent correct sequence of events. 

Ans : False. 

Q.6. The term monoceious and homothallic are used to denote bisexual condition. 

Ans : True. 

Q.7. Individuals of a clone have same genome. 

Ans : True. 

Q.8. The ovary ripens to form ovules. 

Ans: False. 

Q.9. Papaya is a dioecious plant. 

Ans : True. 

Q.10. Condia are unisexual reproductive structures in Algae. 

Ans : False. 

Q.11. Dioecious organisms are seen in both plants and animals. 

Ans : True.

Q.12 . Zoospores are always sexual reproductive structure. 

Ans : False 

II. QUESTIONS FOR (2 MARKS) 

Q.1. What is life span? Name the different stages of life span of an organisms. 

Ans : The period from birth to the natural death of an organism represents its life span. Every organism has a specific life span. 

The different stages of life span are : 

(i) Juvenility : It represents the stage when organisms develops the capacity to reproduce. 

(ii) Maturity : In this stage reproduction starts.

(iii) Ageing and Senescence : The progressive deterioration in body of an organism is called ageing and the terminal irreversible stage of ageing is called senescence. 

(iv) Death : It is the permanent cessation of all vital activities. 

Q.2. Write down the differences between ovipary and vivipary nature of organisms. 

Ans : The egg laying animals are called the oviparity and the animals which gives birth of young ones all called vivipary. 

Q.3. Offspring formed due to sexual reproduction have better chances of survival, Why? 

Ans : (i) Sexual reproduction introduces variations in offspring, hence of evolutionary significance. 

(ii) It helps the offsprings to adjust according to changes in the 3. environment. 

(iii) As a result of new character combination, better offsprings are produced, thus result is better varieties. 

Q.4. Differentiate between oestrus and menstrual cycles. 

Ans:       

Q.5. Differentiate syngamy from fertilization. 

Ans : Syngamy is the union of two haploid gametes producing a diploid zygote. But in fertilization different events takes place which finally lead to syngamy. 

Q.6. What are hermaphrodite organisms? Give the common names of one hermaphrodite organism each from both plants and animals. 

Ans : The organisms bearing both the sexes are called hermaphrodite or monoecious. The common hermaphrodite plant is – Maize and common hermaphrodite animal is earthworm. 

Q.7. Describe the significance of vegetative propagation. 

Ans : Significance of vegetative propagation are : 

(i) Character of the parent plants are preserved. 

(ii) It is a quicker method. 

(iii) It is a cheaper method of propagation. 

(iv) It is the only method of reproduction in plants which don’t produces seeds. 

(v) It is less expensive method of multiplying plants. 

Q.8. Which type of plants shows successful grafting and why it is so?

Ans : Grafting is generally done between the related varieties of species. This method has been practiced for many economically useful plants, such as rose, mango, apple, pear, citrus, rubber etc. It is successfully done because the grafting mostly depends upon the union of the cambium of scion and stock which results the organic connection between them. 

Q.9. Why a plant of lower cryptogams produces large number of antherozoids but relatively only few egg cells? 

Ans : Large number of antherozoids are produced to make the fertilization as a sure shot process. 

Q.10. Why papaya is said to be dioecious where as coconut is monoecious, inspite of both of them bears unisexual flowers? 

Ans : Papaya is called dioecious because male and female flowers are present on different plant. But in case of coconut, it is called monoecious because a plant may have both male and female flowers. Moreover both the plants may have unisexual flowers. 

Q.11. Why do internodal segments of Sugarcane faiis to propagate vegetatively even when they are in contact with damp soil?

Ans : Because the internodal parts of the sugarcane do not have the capacity to produce a new plant. 

Q.12. Reduction division or meiosis can be associated with what type of reproduction and how? 

Ans : Reduction division or Meiosis is associated with sexual reproduction. In sexual reproduction gametes are to form where chromosome number should be reduced to half. Hence in reproductive cells by meiosis, the chromosome number reduced to half which again maintain the number after fertilization i.e. by formation of zygote. 

Q.13. Match the items in column ‘A’ with items in column ‘B’ 

Ans: 

Q.14. Match the items in column ‘A’ with items in column ‘B’ 

Ans: 

Q.15. Draw the sketches of a zoospore and a conidium. Mention a dissimilar and a common feature found between them. 

Ans :              

The main difference between the zoospore and the conidia that zoospores are motile and can move freely but the conidia are non motile.The common feature between the zoospore and conidia that both are the mode of asexual way of reproduction. 

Q.16. How many kinds of natural vegetative reproduction takes place in flowering plants? 

Ans : The natural vegetative propagation that takes place in flowering plants may be of following types :

(a) Vegetative propagation by roots : Sweet potato propagates by adventitious tuberan notes while in Goman, Sisso plants can multiply by the roots. 

(b) Vegetative propagation by stem : It is found in case of Rhizome (e.g.. Ginger), stem tuber (sweet potato) and runner (wood sord) where the stem helps in multiplication of the plant. 

(c) Vegetative propagation by leaf: Bryophyllum is the best example to multiply vegetatively by the leaf. 

Q.17. In angiosperms pollen tube of germinated pollen carries two male gametes. What is the purpose of carrying two gametes when single gamete can fertilize the egg? 

Ans : In angiosperms pollen tube of germinated pollen carries two male gametes. Out of these two male gametes,one is united with the egg all nucleus to form zygote and finally to form seed while the other male gamete united with secondary nucleus to form the endosperm. 

Q.18. How does the progeny formed from asexual reproduction differ from that formed the sexual reproduction? 

Ans : The progeny formed by asexual reproduction having the same genetic make up and the progeny formed by sexual reproduction are with different genetic characters because here mixing of maternal and paternal characters takes place. 

Q.19. Differentiate between Parthenocarpy and Parthenogenesis. 

Ans : Parthenogenesis is the formation of embryo directly from egg cell or a male gamete. It is a type of apogamy. 

Sometimes fruits may be formed without the act of fertilization and then it is called as parthenocarpy. Normally they do not have the seed. 

III. QUESTIONS FOR – 3 MARKS. 

Q.1. Explain with suitable examples why meiosis and gametogenesis are always interlinked. 

Ans : The process of gametogenesis and meiosis has the linked because the gametes are formed only by the meiosis cell division. Generally meiosis cell division takes place in body cells where chromosome number always maintained as in. In gametogenesis the gametes are formed which are haploid in number and as a result of fertilization the chromosome number is, maintained. Hence, meiosis or reduction cell division is an essential process at the time of gametogenesis. 

Q.2. Honeybees produce their young ones only by sexual reproduction. In Spite of this in a colony of bees we find both haploid and diploid individuals in the colony state the reasons behind their formation. 

Ans : Honey bee reproduces sexual and by parthenogenesis only. In a hive 3 castes are found : 

(a) Fertile female called queen. 

(b) Fertile male called drone. 

(c) Sterile female called worker. 

Generally Queen lays two types of eggs- fertilized and unfertilized eggs. From the fertilized eggs either the queen (fertile female) or the worker (sterile female) can formed while from the unfertilized eggs only males are developed. Queen develops eggs by meiosis or reduction cell division while the haploid male develops gametes only by mitosis process. As a result of union of male and female gametes queen or worker may developed. The males are formed by a process of parthenogenesis.

Q.3. Briefly discuss, mentioning all the changes held in an angiosperm flower subsequent to pollination and fertilization with necessary diagrams. 

Ans : In angiosperms, the pollen grain is transferred from another to the stigma where the pollen grain germinate and forms a pollen tube which leads the male gamete to meet the ovum is the ovary. Finally in the ovary, fertilization takes place.

Again in dioecious animals, male and females are found in different individuals where male gametes are to transfer to the female body. In side the female body fertilization takes place. It is done by the means of sexual reproduction. For this purposes the male gametes are produced in nature. 

But in plants, for the transfer of pollen grains, they become sticky so that they can easily do the pollination.

Q.4. In the plants like Bryophyllum, Potato, Ginger, Mint etc. is it possible to consider vegetative propagation as a type of asexual reproduction. If it is so justify the statement with reasons. 

Ans : In Bryophyllum, potato, ginger, mint etc. vegetative propagation is a mode of reproduction where new plant is developed from any part of the plant body. For example, in Bryophyllum, the leaf bud is developing a new plant body, in potato the eye can form a new plant, in ginger the rhizome can develop the new plant and in mint the new plant develops from the bud of each node. So, we can say that only by vegetative propagation these can multiply i.e. by asexual mode of reproduction. 

Q.4. “Fertilization is not an obligatory event for fruit formation in certain plants.” Explain the statement with of examples. 

Ans : We know that for the formation of fruit, fertilization is essential specially in angiosperms. After the fertilization the ovary is transformed into fruit and the ovule is transformed into seed. But in some plants fruit may develop without the fertilization process from the ovary and then this type of fruit is called parthenocarpic fruit as it is formed by parthenogenesis process only. It is also called as false fruit. It is found in Apple. Here actually the thalamus is modified into fruit in place of ovary. 

Q.5. Explain why internal fertilization is found to be more successful than the external fertilization in the living bodies? 

Ans : When the fertilization takes place inside the female body then it is called as internal fertilization and when it is taking place in the external medium i.e. water then it is called as external fertilization.

In the animals/organisms where internal fertilization is taking place there the male gametes are released in the female body and make sure to fertilization. But in the animals where external fertilization is taking place, there the male gametes are released in the medium and females also releases their gametes in that medium. 

In case of internal fertilization, it is a sure short process but in external fertilization there is no certainty. Hence males gametes number should be several times more than the animals/organisms which fertilize internally. Hence internal fertilization is called more successful than the external fertilization. 

Q.7. Mention atleast three points of differences found between asexual and sexual reproduction of living organisms. 

Ans : Difference between Asexual and Sexual Reproduction :

Q.8. Why higher organisms have resorted to sexual reproduction in spite of their complexity in all respect. 

Ans : Sexual reproduction is a complex but slow process as compared to the asexual reproduction. Because, here fusion of male and female gametes takes place. Due to the fusion of male and female gametes, non identical offsprings are formed. In case of higher organism they can multiply when they attain the maturity. The sexuality develops along with the maturity. Thus these animals go for reproduction. But the reproduction in higher animals where sexual method is followed there the process is more complicated and very slow process. Although it is elaborate, complex and slow but the animals follow for the continuation of their life. Moreover very less number of offsprings are produced and after a long interval which have large life span also. 

Q.9 . Give the definition of Juvenile phase, Reproductive phase and Senescence phase of an organism? 

Ans : (i) Juvenile Phase : All organisms have to reach a certain stage of growth and maturity in their life, before they can reproduce sexually. These period of growth is called juvenile phase or vegetative phase. 

(ii) Reproductive Phase : Reproductive stage in plants is represented by appearance of flowers. In animals the end of juvenile phase is indicated by many of them showing morphological and physiological changes prior to active reproductive behaviour. 

(iii) Senescence Phase : The end of reproductive phase is one of the parameters of senescence or old stage. At this stage, body metabolism is slowed down and ultimately this stage leads to death. 

Q.10. What do you mean by external and internal fertilization? Mention the disadvantages of external fertilization. 

Ans : External Fertilization: The fertilization i.e. union of male gamete and female gamete when takes place in the external medium like water is called the external fertilization. It is found in fish, frog etc. 

Internal Fertilization : When the fertilization takes place in side the female body i.e. mothers womb then it is called internal fertilization it is found in all mammals. 

Disadvantages of External fertilization: 

(i) It is not a sure shot process because it is dependent on the medium. 

(ii) Here rate of production of male gametes should be several times more than these where internal fertilization takes place. 

(iii) It is a wasteful process. 

(iv) It is always found only in aquatic animals. 

(v) After fertilization also the role of survivility not is very less. 

(vi) The medium may not support the gametes for the fertilization process. 

Q.11. What is meant by vegetative propagation? Discuss the importance of vegetative propagation in agriculture. 

Ans : The vegetative like roots, stems and leaves can form a new plant body and it is called as vegetative propagation. 

Vegetative propagation is important for the following reasons: 

(a) Vegetative propagation has great survival value in nature. 

(b) The plants raised through vegetative propagation can attain maturity within a short period. 

(c) In agricultural field it plays two major role-firstly multiply the plants in rapid way and secondly it maintains the genetic qualities of the plant. 

(d) During unfavourable condition also we can multiply the plant by vegetative way of multiplication. 

Q.12. Explain how the meiotic process of cell division can be interlinked with the process of gametogenesis? 

Ans : Meiosis cell division is the division where chromosome number is reduced to half and hence it is called as reduction cell division. 

Generally the gametes are haploid but develops from the diploid cells in the reproductive organs. The cells undergoes a series of cell division which is called meiosis to reduce the chromosome number to half. 

The process of formation of gametic from the diploid (2n) cells is called gametogenesis. The gametogenesis involves the process meiosis cell division by which from the diploid gamete mother cell (2n), haploid gametes (n) are formed. Hence we can conclude that meiotic process of cell division and gametogenesis has interlink. 

Q.13. Explain that Embryonal protection and care comparatively better in Viviparous than Oviparous organisms. 

Ans : In oviparous animals, the eggs are laid outside and whole of the period of embryonic development is exposed to harmful environment and biological factors, So chances of death are high in such cases. But in viviparous, the embryo is cared by the mother a female animal inside her body where the embryo has better chance of survival. 

IV. QUES TION FOR (5 MARKS) (EXPLANATORY) 

Q.1. What are the different events takes place in the process of sexual reproduction of an angiosperm plants. Describe briefly all the events with all necessary diagrams’. 

Ans : In angiosperms, the different events that takes place in the process of fertilization can be divided into 3 parts-pre-fertilization, fertilization and post fertilization events. 

(i) Pre-fertilization event: The pre fertilization events can be divided into two parts. 

(ii) Gametogenesis : It involves the formation of gametes which are haploid and formed from diploid gametogonia by the process of meiosis. The gametogenesis may be of spermatogenesis or oogenesis. 

Gamete Transfer: For fertilization both the gamete should unite together and here the motile male gamete coine to female gamete by any means. The transfer of male gamete a pollen grains from other to the stigma is done by self a with the help of other agents- which is called as pollination. 

The pollination may be of two types self pollination and cross pollination. Cross pollination is done by agents like air, water, insects, other animals like man etc. 

(i) Fertilization : Fusion of male and female gamete is called the syngamy and the mechanism of union of male and female gamete is called the fertilization. The haploid cells (n) combine together to form the diploid (2n) animal or organism. 

(ii) Post Fertilization Events : Post Fertilization events include the formation of zygote and embryogenesis. 

(a) Zygote : As a result of union of male and female gametes together, a diploid zygote is formed. It is, the first resultant of sexual reproduction. 

(b) Embryogenesis : under goes a number of division which is called the cleavage and finally form a ball like structure called morula. Then it divides and form the embryo of the organism. 

In angiosperm they develop seed. It is formed from the ovule and whole zygote is modified to embryo. 

Q.2. What is post fertilization phase. Describe briefly with of diagrams the post fertilization changes held in an angiosperm flower. 

Ans : In flowering plants zygote is formed inside the ovule. After fertilization, sepals, petals and stamens of the flower wither and fall off.

The Pistil remains attached to the flower. Zygote formes and the embryo and ovule having embryo forms the seed. Ovary wall develop into fruit wall (pericarp). Ovary develops into fruit. Pericarp is protective in function. After dispersal of fruits and seeds, seed germinate to form new plants in suitable germinating conditions. 

Q.3. Although sexual reproduction is a long, energy – intensive complex form of reproduction, many groups of organisms prefers this mode. Why this is sco gives the reasons. 

Ans : Sexual reproduction is found in most of the organisms. Even the organisms which depend upon asexual reproduction for their multiplication like algae and fungi, shift on to sexual mode of reproduction before the onset of adverse conditions. It is probably that gametes appeared from asexual spores under unfavourable conditions. Fusion of gametes had resulted in pooling of resources and combination of genetic potentialities of two. At the time of origin of sex benefits of this accidental fusion came to stay in life cycle. It is called a hunger theory of sex. These fusing gametes got specialized with evolution in higher organisms and gave rise to different types of heterogametes. 

Q.4. Some plants like Rose produces large attractive bisexual flowers but they seldom produce fruits. Give the reasons for failure of fruit formation in this type of plants. 

Ans : Rose is a neked seeded plant and so its seed is not found in side the fruit. Here the zygotes develops into embryo and ovules develops into seeds. But the ovary is unable to develop the fruit. So there is no fruit in some flowering plants like rose, but seldom they produce the fruit after fertilization. 

Q.5. Define the different forms of sexuality found in Angiospermic plants. Explain the each type citing examples mentioning their common and scientific names. 

Ans : On the basis of sexuality, the angiosperm plants are classified into : 

(a) Unisexual Plant : The individual plant bears only one sex, either male or female. For e.g.. Papaya, cucurbita. 

(b) Bisexual Plant : The plants which contains both the sexes in the single individual is called bisexual plant. Here the flower contains both male and female reproductive port together. For eg. coconut. 

Q.6. Although Rose plants produce large, attractive bisexual flowers but they seldom produce fruits. Discuss the reasons for failure of fruits formation in Rose. 

Ans : Rose is naked seeded plant and so its seed is not found inside the fruit. Here the zygotes develops into embryo and ovules develops into seeds. But the ovary is unable to develop fruit. So there is no fruit in some ring plants like rose, but seldom they produce the fruits after fertilization. Generally the multiply buy vegetative methods or asexual methods only. 

Q.7. Describe with suitable examples the different modes of asexual reproduction found in Animals. 

Ans : The development of female gametes into new individuals without the fertilization process is known as asexual reproduction. Sometimes it is also called as somatogenic reproduction. 

Asexual reproduction may be of following types : 

(i) Binary fission : It is the simplest division where cell is divided into two equal parts. It is generally found in lower group of organisms or animals. The binary fission may be of transverse binary fission which is found in Amoeba or may be longitudinal fission which is found in euglena and in some corals.

(ii) Multiple fission : It is very common among amoeba where the cell is divided by binary fission but tal:ing place in rapid way, producing numerous daughter amoeba. It is also called as sporogony. 

(iii) Budding : Here a small bud develops and from it they can multiply. When getting mature, the buds get detached from the parent body an perform and independent life eg. Hydro, Sycon, Planaria etc. 

(iv) Plasmotomy: Here cytoplasm divides two or more parts but without the nuclear division and hence each daughter cell has a few nuclei. 

(v) Gemmule formation: Asexual reproduction occurs in fresh mater sponges by the formation of gemmules. Gemmules are composed of undifferentiated cells which contain some reserved food materials. When favourable conditions come again, gemmules hatch into the adult. 

(vi) Regeneration: Several organisms have the power of regeneration. The organisms can regenerate a part of the body or the whole body. It is found sponge and planaria along with coelenterata and echinodermata.

Dev Kirtonia

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