Please refer to VBQs for Class 12 Biology Reproduction in Organisms. All value based questions for Biology Class 12 have been provided with solutions. We have provided below important values questions and answers. Students should learn these solved VBQs for Class 12 Biology as these will help them to gain more marks and help improve understanding of important topics.
Reproduction in Organisms VBQs Class 12 Biology with Answers
Very Short Answer Type Questions
Question. Write the two pre-fertilization events from the list given below :
Syngamy, gametogenesis, embryogenesis, pollination.
Answer : Gametogenesis and pollination.
Question. Mention any two conditions that enhance the chances of syngamy in organisms exhibiting external fertilization.
Answer : Organisms exhibiting external fertilisation show great synchrony between the sexes, release a large number of gametes into the surrounding medium.
Question. Name the common phenomenon with reference to reproduction in rotifers, honey bees and turkey.
Answer : The common phenomenon with reference to reproduction in rotifers, honey bees and turkey is parthenogenesis. It is the process in which the female gamete undergoes development to form new organism without fertilization.
Question. Cucurbits and papaya plants bear staminate and pistillate flowers. Mention the categories they are put under separately on the basis of type of flowers they bear.
Answer : Cucurbits are monoecious plants because they bear both staminate and pistillate flowers on the same plant.
Papaya plants are dioecious because staminate and pistillate flowers are borne on different plants.
Question. Name the type of cell division that takes place in the zygote of an organism exhibiting haplontic life cycle.
Answer : Meiotic division.
Question. Which of the following statements is true for cucurbits ?
(i) It is monoecious producing both staminate and pistillate flowers in the same plant.
(ii) It is monoecious producing staminate and pistillate flowers in two different plants.
(iii) It is dioecious producing staminate flowers in one plant and pistillate flowers in another.
Answer : (i) Statement (i) is correct. i.e., The plants are monoecious because both male and female flowers are borne on the same plants.
Question. Identify the picture and mention the vegetative part that helps it to propagate.
Answer : The given figure represents rhizome of ginger.A rhizome is an underground stem with stored food and bud. These buds form new aerial shoot during favourable conditions. Rhizome takes part in vegetative propagation due to these buds.
Question. Which ones of the following organisms exhibit binary fission?
Bacillus, Penicillium, Yeast, Amoeba
Answer : Bacillus and Amoeba reproduce by binary fission. In this process, the parent organism divides into two equal halves each forming an independent daughter organism.
Question. Give one example each of the plant that reproduces by
(a) runner
(b) offset
Answer : (a) Lawn grass reproduces by runner.
(b) Eichhornia reproduces by o set.
Question. Name an organism where cell division in itself is a mode of reproduction.
Answer : In Amoeba asexual reproduction takes place by division of parent body.
Question. Which one of the following statements is true of yeast?
(i) The cell divides by binary fission. One of them develops into a bud.
(ii) The cell divides unequally. The smaller cell develops into a bud.
(iii) The cell produces conidia which develop into a bud.
Answer : (ii) Yeast reproduce by budding. The cell divides unequally. The smaller cells develop into a bud.
Question. Which of the following statements is true of Hydra?
(i) It produces asexual gemmules.
(ii) It produces unicellular bud.
(iii) It produces multicellular bud.
Answer : (iii) Hydra produces multicellular bud.
Question. Name the vegetative propagules in the following:
(a) Agave
(b) Bryophyllum
Answer : (a) In Agave, bulbils are the vegetative propagules.
(b) In Bryophyllum, vegetative propagation is carried out by adventitious buds that arise from notches present at margins of leaves.
Question. Which one of the following statements is true of ginger?
(i) Germinating bud appears from the eye of the stem tuber.
(ii) Germinating bud appears from the node of rhizome.
(iii) Germinating bud appears from the notch of the leaf margin.
Answer : (ii) Germinating bud appears from the node of rhizome of ginger.
Question. Give one example each of the fungus which reproduces by :
(a) budding
(b) conidia
Answer : (a) Yeast reproduces asexually by budding.
(b) Penicillium reproduces asexually by conidia formation.
Question. Name an alga that reproduces asexually through zoospores. Why are these reproductive units so called?
Answer : Chlamydomonas (an algae) reproduces asexually through zoospore formation. These spores are unicellular, naked (without cell wall), motile and flagellated and hence named zoospores
Question. How does Penicillium reproduce asexually?
Answer : Penicillium reproduces asexually by conidia formation. These are non-motile spores produced singly or in chains by constriction at the tip or lateral side of special hyphal branches called conidiophores.These are produced exogenously, dispersed by wind and germinate directly by giving out germ tubes.
Question. Cut-pieces of a Bryophyllum leaf when put into wet soil produce new plants. How?
Answer :Cut pieces of Bryophyllum leaf when put in wet soil produce new plant due to presence of adventitious buds. Buds present on the marginal notches of leaves of Bryophyllum help in vegetative propagation.
Question. Offspring derived by asexual reproduction are called clones. Justify giving two reasons.
Answer : In asexual reproduction, offspring are produced by a single parent with or without the involvement of gamete. The offspring are produced are similar to one another and, are also exact copies of their parents. Thus, these offspring are morphologically and genetically similar and hence called as clone.
Question. Identify this reproductive structure and name the organism they are being released from.
Answer : The reproductive structures represented by the given figure are zoospores. Zoospores are special kind of motile and flagellated spores produced inside zoosporangia. Organism represented by the given figure is Chlamydomonas, that reproduces asexually by zoospore formation.
Question. Name the organism and the mode of reproduction represented in the diagram given below.
Answer : The given figure represents budding in yeast.
Short Answer Type Questions
Question. Why do algae and fungi shift to sexual mode of reproduction just before the onset of adverse conditions?
Answer : Organisms, such as fungi and algae, switch to sexual mode of reproduction just before the onset of adverse conditions because sexual reproduction brings variation into the individuals, some of which might help the individuals to adapt to the changed environmental conditions and survive. This ensures the continuity of species.
Question. Coconut palm is monoecious, while date palm is dioecious. Why are they so called?
Answer : Coconut palm is monoecious because it bears both male and female flowers on the same plant, whereas date palm is said to be dioecious as it bears male and female flowers on separate plants.
Question. Give one example of an animal which exhibits oestrous cycle.
Answer : Cows exhibits oestrous cycle.
Question. Which of the following statements is true of date-plam?
(i) It is monoecious producing both staminate flowers and pistillate flowers in the same plant.
(ii) It is monoecious producing staminate
flowers in one tree and pistillate flowers in another tree.
(iii) It is dioecious producing staminate flowers in one tree and pistillate flowers in another tree.
Answer : (iii) Date palm is a dioecious plant producing staminate flower in one tree and pistillate flower in another tree.
Question. Cucurbits and papaya plants bear staminate and pistillate flowers. Mention the categories they are put under separately on the basis of the type of flowers they bear.
Answer : Cucurbits are monoecious plants i.e., they bear both male and female flower on the same plant. On the otherhand, papaya plants are dioecious i.e., both male and female flowers are present on separate plant.
Question. A list of three flowering plants is given below.
List – Datepalm, cucurbits and pea.
Which ones out them are (a) monoecious and
(b) bearing pistillate flowers?
Answer : (a) Cucurbits and pea plants are monoecious bearing both staminate and pistillate flowers on the same plant.
(b) Date palm, cucurbits and pea, all three bear pistillate flowers.
Question. Mention the unique flowering phenomenon exhibited by Strobilanthus kunthiana (neelakuranji).
Answer : Strobilanthus kunthiana produce flowers once in twelve years.
Question. Name the mode of reproduction that ensures the creation of new variants.
Answer : Sexual reproduction ensures creation of new variants. It involves, fusion of gametes from different parents which results in genetic recombination that cause variations.
Question. Name the phase all organisms have to pass through before they can reproduce sexually.
Answer : All organisms have to pass through the period of growth known as juvenile or vegetative phase before they start reproducing sexually. The period of growth is between the birth of an individual upto reproductive maturity.
Question. Meiosis is an essential event in the sexual life cycle of any organism. Give two reasons.
Answer : Meiosis is an essential event in the life cycle of a sexually reproducing organism because:-
(i) It helps to restore diploid chromosome number during fertilisation.
(ii) It is a source of variation. Random segregation of chromosomes and exchange of genetic material between homologous chromosomes increases the genetic diversity.
Question. Name the phenomenon and the cell responsible for the development of a new individual without fertilisation as seen in honey bees.
Answer : Female gamete undergoes development to form new individual without fertilisation. This phenomenon is known as parthenogenesis.
Question. Write the two pre-fertilisation events from the list given below:
Syngamy, Gametogenesis, Embryogenesis, Pollination
Answer : Two pre-fertilisation events are gametogenesis and pollination.
Question. Mention the site where syngamy occurs in amphibians and reptiles respectively.
Answer : In amphibians, syngamy takes place outside the body of the organism in water and in reptiles syngamy takes place inside the body of the female organism. Thus, in amphibians external fertilisation takes place and in reptiles internal fertilisation takes place.
Question. Name any two organisms and the phenomenon involved where the female gamete undergoes development to form new organisms without fertilisation.
Answer : The phenomenon where female gamete undergoes development to form new organism without fertilisation is called parthenogenesis. It occurs in honeybees and rotifers.
Question. Write the difference between staminate and pistillate.
Answer : In flowering plants, staminate is a unisexual male flower which bears stamens only while pistillate is a female flower which bears pistils only.
Question. The cell division involved in gamete formation is not of the same type in different organisms. Justify.
Answer : Gametes in all heterogametic species are of two types, male and female. Gametes are haploid though the parent body from which they arise may be either haploid or diploid. Several organisms belonging to monera, fungi, algae and bryophytes have haploid plant body, but organisms belonging to pteridophytes, gymnosperms, angiosperms and most of the animals including human beings, have diploid parental body. Meiosis will take place, if the diploid body has to produce haploid gametes. In diploid organisms, specialised cells called meiocytes undergo meiosis, at the end only one set of chromosome gets incorporated into each gamete.
Question. Unicellular organisms are immortal, whereas multicellular organisms are not. Justify.
Answer : Most unicellular organisms specially those which undergoes binary fission are immortal because they reproduce by cell division. The parent body as a whole constitutes the reproductive unit and disappears when its division into daughter individuals is completed. There is no remains of parent body cell and thus, parent cannot be said to have died. Infact, after binary fission, the parent continues living as two daughter individuals.
In multicellular organisms reproduction occurs in specialised organs involving specialised cells.
The whole body of parent dies due to ageing and senescence.
Question. (a) Name the organisms that reproduce through the following reproductive structures.
(i) Conidia (ii) Zoospores
(b) Mention similarity and one difference between these two reproductive units.
Answer :
(a) (i) Penicillium reproduces through conidia formation.
(ii) Chlamydomonas reproduces through zoospores formation.
(b) Similarity – Conidia and zoospores, both are asexual reproductive structures.
Difference : Conidia are non-motile spores whereas zoospores are motile and flagellated spores.
Question. (a) Why do organisms like algae and fungi shift from asexual mode of reproduction to sexual mode ?
(b) What is a juvenile phase in organisms ?
Answer : (a) To tide over adverse conditions.
(b) A phase of growth and maturity, before organisms can reproduce sexually.
Question. Explain the importance of syngamy and meiosis in sexual life cycle of an organism.
Answer : Syngamy : Restoration of (2n) chromosome number/diploidy/zygote formation/variations (due to syngamy).
Meiosis : Gamete formation/reduction of (n) chromosome number/haploidy/variation (due to crossing over)
Detailed Answer :
Meiosis and syngamy maintain the fixed chromosome number of the species. In a sexual life cycle of an organism, meiosis leads to formation of gametes which are haploid.
Syngamy is the process that leads to fusion of haploid gametes and formation of diploid zygote.
Question. Why do algae and fungi shift to sexual mode of reproductions just before the onset of adverse conditions ?
Answer : Most of the algae and fungi are unable to survive under adverse environmental conditions.
Therefore, in order to tide over these unfavourable conditions, these organisms shift to the sexual mode of reproduction during which they produce male/female gametes that fuse to form the zygote. The zygote secretes a thick wall around itself and undergoes a period of rest for passing the unfavourable conditions. Gradually, on the approach of favourable conditions, the zygote germinates to produce the new thalli of algae and mycelium of fungi.
Question. (i) Why is a whiptail lizard referred to as parthenogenetic ?
(ii) State the difference between meiocyte and gamete with respect to chromosome number.
Answer : (i) Whiptail lizards are referred to as parthenogenetic because they develop from unfertilized egg i.e, the egg produces the new individual without fertilization.
(ii) Meiocytes have diploid number (2n) of chromosomes whereas gametes contain haploid number (n) of chromosomes.
Question. Out of many papaya plants growing in your garden, only a few bear fruits. Give reasons.
Answer : Unisexual/Dioecious/male and female flowers are borne on separate plants, only plants bearing female flowers will bear fruits. Monoecious (hermophrodite) Papaya plants bear fruit too.
Detailed Answer :
Papaya has both dioecious and monoecious plants bearing unisexual or bisexual flowers. They can occur in three sexual forms-male, female and hermaphrodites. A fruit is formed when fertilization occurs in the ovary of the female flower. So, if a male or a female plant is growing alone, it will produce flowers but not fruits as both male and female is required for fruit formation. However, hermaphrodite papaya plant will always bear fruits, as their flowers contain both male and female parts.
Question.
(i) State the type of gametes shown in the diagram above.
(ii) Identify the process taking place and the resultant structure.
(iii) Name an organism that reproduces in this manner.
Answer : (i) Isogametes
(ii) Syngamy or fertilization and zygote
(iii) Cladophora/Chlamydomonas.
Question. A moss plant is unable to complete its life cycle in dry environment. State two reasons.
Answer : A moss plant can not complete its life cycle in dry condition because of following two main reasons :
(i) It requires water for the dehiscence of antheridium-the male sex organ and the opening of the archegonium-the female sex organ.
(ii) It requires the presence of water for the flagellated antherozoids (the male gametes) to swim and reach the female gamete (egg or ovum) situated deep in the archegonium under the influence of a chemical (maleic acid), accomplishing fertilization.
Question. Differentiate between parthenocarpy and parthenogenesis. Give one example of each.
Or
How is parthenocarpy different from parthenogenesis ? Give an example of each.
Answer :
| Parthenogenesis | Parthenocrapy |
| New organism develops without fertilization. =1 | Formation of fruit without fertilization. =1 |
| e.g. Drones / male honey bee / turkey / rotifers / some lizards / any other correct example. =½ | e.g. banana / grapes / any other correct example. = |
Detailed Answer:
The phenomenon of development of fruit from the ovary in the flowering plants without the stimulus of fertilization is called parthenocarpy and the fruits so formed are called parthenocarpic fruits.
e.g., banana. Whereas the phenomenon in which the egg or ovum develops into an embryo and then into a new organism without the act of fertilization is called parthenogenesies e.g., male honeybee, rotifers and green algae like Ulothrix.
Question. Some animals like honey bees are called parthenogenetic animals. Why?
Answer : Male honey bees are formed from unfertilised egg. Therefore, these animals are called as parthenogenetic animals.
Question. Write two major adaptations in animals exhibiting external fertilization.
Answer : (i) There is a great tendency of synchronization between male and female sexes i.e, they release the mature gamete simultaneously in water.
(ii) They release a large number of gametes in the surrounding medium (water) so that there may be greater chances of syngamy i.e., the fusion of male and female gametes.
