How do organism reproduce
1. On what factors does the type of reproduction adopted by an organism depend on?[NCERT Exemplar]
Answer: The organism’s habitat, physiology and genetic make-up determines the type of reproduction adopted by it.
2. What is asexual mode of reproduction?
The mode of reproduction in which formation and fusion of gametes does not take place is called asexual reproduction. Only somatic part is involved in such reproduction.
Define clone.
Clone is a group of individuals of the same species that are morphologically and genetically similar.
Name the type of fission with examples.
Binary fission — Amoeba
Transverse fission — Paramecium
Multiple fission — Plasmodium
What is budding?
It is a mode of asexual reproduction in which one or more outgrowths (buds) protrude out, which later get detached from the parent body to grow into a new individual, e.g., yeast.
Name one organism where chain budding is found.
Yeast
Mention two inherent characteristics of Amoeba and yeast that enable them to reproduce asexually.
[NCERT Exemplar]
They are unicellular organisms.
They have a very simple body structure.
Name the type of asexual reproduction where the parent cell ceases to exist.
Fission/Binary fission/Longitudinal fission/Multiple fission.
What is conidia?
The asexual, non-motile spores produced externally/exogenously in some fungi are called conidia, e.g., Penicillium.
Define gemmules.
Internal asexual reproductive units or buds in sponges are called gemmules.
Name one plant which propagates by the means of its leaf.
Bryophyllum
How does potato multiply?
[HOTS]
Potato multiplies by buds (eyes) of the tuber (vegetative propagation).
Why do vegetative propagules in sugarcane and ginger appear from the nodes?
[NCERT Exemplar] [HOTS]
This is because the nodes have meristematic cells.
Define sexual reproduction.
Sexual reproduction is the mode of reproduction in which male and female gametes fuse together to form a diploid zygote that grows into new individual.
What is zygote?
Zygote is a single diploid cell formed by fusion of male and female gametes.
What are the terms used for similar gametes and dissimilar gametes?
Similar gametes — Homogametes/Isogametes Dissimilar gametes — Heterogametes/Anisogametes.
What are antherozoids?
The male gamete or male reproductive unit is called antherozoid or spermatozoa.
What are the technical terms used for a bisexual condition?
Homothallic and monoecious.
What are the technical terms used to denote unisexual condition?
Heterothallic and dioecious.
What do you mean by staminate?
The unisexual male flower bearing stamens is called staminate.
What is meant by pistillate?
The female flower bearing pistil is called pistillate.
Name two dioecious plants.
Papaya and date palm.
What do you understand by oestrus cycle?
The reproductive cycle in non-primates is called oestrus cycle, e.g., cow, sheep.
What is menstrual cycle?
The reproductive cycle in primates is called menstrual cycle, e.g., monkeys, apes.
What do you mean by seasonal breeders?
Some mammals exhibit reproductive cycle only during favourable season. They are called seasonal breeders, e.g., frog, many birds and deer.
Define continuous breeders.
Some mammals are reproductively active throughout their reproductive phase. Such animals are called continuous breeders, e.g., cattle and rabbit.
What marks the end of reproductive phase?
Senescence marks the end of reproductive phase.
Write the two pre-fertilisation events from the list given below:
Syngamy, Gametogenesis, Embryogenesis, Pollination
[HOTS]
Gametogenesis, Pollination.
Which is the most critical event in sexual reproduction?
[HOTS]
Fertilisation of gametes is the most critical event in sexual reproduction.
What is a gamete?
Gamete is the sexual reproductive unit. They are usually haploid cells.
What is gametogenesis?
The process of formation of gamete in male and female sex organs is called gametogenesis.
What are hermaphrodites?
The animal bearing both male and female sex organs are called hermaphrodites. Example, earthworms, sponge and tapeworm.
Name one bisexual and one unisexual animal.
Bisexual animal — Earthworm
Unisexual animal — Cockroach
Name two plants having haploid body.
Algae and fungi.
Name two plants having diploid body.
Pteridophytes and gymnosperms.
What is meant by meiocytes?
In diploid organisms, gamete mother cell which undergoes meiosis to produce gamete is called meiocytes.
Name two organisms where both male and female gametes are motile.
What is syngamy?
The fusion of male and female gametes to form a zygote is called syngamy.
Name one plant and animal in which external fertilisation takes place.
Plant — Algae; Animal — Fish.
Mention any two conditions that enhance the chances of syngamy in organisms exhibiting external fertilisation.
Organisms exhibiting external fertilisation show great synchrony between the sexes, release a large number of gametes into the surrounding medium.
Name one plant and animal in which internal fertilisation take place.
Plant — Gymnosperms;
Animal — Mammals.
In which type of life cycle does a zygote undergoes
Mitosis
Mitosis — Diplontic life cycle
Meiosis
Meiosis — Haplontic life cycle.
Name one oviparous and viviparous animal.
Oviparous animal — Reptile
Viviparous animal — Mammals
Write two advantages of vivipary.
Two advantages of vivipary are:
Proper embryonic care and protection of the young one.
The chances of survival of young one is greater.
Rearrange the following events of sexual reproduction in the sequence in which they occur in a flowering plant: embryogenesis, fertilisation, gametogenesis, pollination.
[NCERT Exemplar] [HOTS]
Gametogenesis, pollination, fertilisation, embryogenesis.
From which part does fruit, seed and embryo develop?
[HOTS]
Fruit — ripened ovary
Seed — ripened ovule
Embryo — mature zygote.
Suggest a possible explanation why the seeds in a pea are arranged in a row, whereas those in tomato are scattered in the juicy pulp.
[NCERT Exemplar] [HOTS]
The ovary of pea plant is monocarpellary and the ovules are arranged along one margin whereas in tomato the ovary is tricarpellary with axile placentation.
Is Marchantia monoecious or dioecious? Where are the sex organs borne in this plant?
[HOTS]
Marchantia is dioecious. The male sex organs, antheridia, are borne on the antheridiophores and female sex organs called archegonia are borne on archegoniophores.
On what factors does the type of reproduction adopted by an organism depend on?
[NCERT Exemplar]
The organism’s habitat, physiology and genetic make-up determines the type of reproduction adopted by it.
What is asexual mode of reproduction?
The mode of reproduction in which formation and fusion of gametes does not take place is called asexual reproduction. Only somatic part is involved in such reproduction.
Define clone.
Clone is a group of individuals of the same species that are morphologically and genetically similar.
Name the type of fission with examples.
Binary fission — Amoeba
Transverse fission — Paramecium
Multiple fission — Plasmodium
What is budding?
It is a mode of asexual reproduction in which one or more outgrowths (buds) protrude out, which later get detached from the parent body to grow into a new individual, e.g., yeast.
Name one organism where chain budding is found.
Yeast
Mention two inherent characteristics of Amoeba and yeast that enable them to reproduce asexually.
[NCERT Exemplar]
They are unicellular organisms.
They have a very simple body structure.
Name the type of asexual reproduction where the parent cell ceases to exist.
Fission/Binary fission/Longitudinal fission/Multiple fission.
What is conidia?
The asexual, non-motile spores produced externally/exogenously in some fungi are called conidia, e.g., Penicillium.
Define gemmules.
Internal asexual reproductive units or buds in sponges are called gemmules.
Name one plant which propagates by the means of its leaf.
Bryophyllum
How does potato multiply?
[HOTS]
Potato multiplies by buds (eyes) of the tuber (vegetative propagation).
Why do vegetative propagules in sugarcane and ginger appear from the nodes?
[NCERT Exemplar] [HOTS]
This is because the nodes have meristematic cells.
Define sexual reproduction.
Sexual reproduction is the mode of reproduction in which male and female gametes fuse together to form a diploid zygote that grows into new individual.
What is zygote?
Zygote is a single diploid cell formed by fusion of male and female gametes.
What are the terms used for similar gametes and dissimilar gametes?
Similar gametes — Homogametes/Isogametes Dissimilar gametes — Heterogametes/Anisogametes.
What are antherozoids?
The male gamete or male reproductive unit is called antherozoid or spermatozoa.
What are the technical terms used for a bisexual condition?
Homothallic and monoecious.
What are the technical terms used to denote unisexual condition?
Heterothallic and dioecious.
What do you mean by staminate?
The unisexual male flower bearing stamens is called staminate.
What is meant by pistillate?
The female flower bearing pistil is called pistillate.
Name two dioecious plants.
Papaya and date palm.
What do you understand by oestrus cycle?
The reproductive cycle in non-primates is called oestrus cycle, e.g., cow, sheep.
What is menstrual cycle?
The reproductive cycle in primates is called menstrual cycle, e.g., monkeys, apes.
What do you mean by seasonal breeders?
Some mammals exhibit reproductive cycle only during favourable season. They are called seasonal breeders, e.g., frog, many birds and deer.
Define continuous breeders.
Some mammals are reproductively active throughout their reproductive phase. Such animals are called continuous breeders, e.g., cattle and rabbit.
What marks the end of reproductive phase?
Senescence marks the end of reproductive phase.
Write the two pre-fertilisation events from the list given below:
Syngamy, Gametogenesis, Embryogenesis, Pollination
[HOTS]
Gametogenesis, Pollination.
Which is the most critical event in sexual reproduction?
[HOTS]
Fertilisation of gametes is the most critical event in sexual reproduction.
What is a gamete?
Gamete is the sexual reproductive unit. They are usually haploid cells.
What is gametogenesis?
The process of formation of gamete in male and female sex organs is called gametogenesis.
What are hermaphrodites?
The animal bearing both male and female sex organs are called hermaphrodites. Example, earthworms, sponge and tapeworm.
Name one bisexual and one unisexual animal.
Bisexual animal — Earthworm
Unisexual animal — Cockroach
Name two plants having haploid body.
Algae and fungi.
Name two plants having diploid body.
Pteridophytes and gymnosperms.
What is meant by meiocytes?
In diploid organisms, gamete mother cell which undergoes meiosis to produce gamete is called meiocytes.
Name two organisms where both male and female gametes are motile.
What is syngamy?
The fusion of male and female gametes to form a zygote is called syngamy.
Name one plant and animal in which external fertilisation takes place.
Plant — Algae; Animal — Fish.
Mention any two conditions that enhance the chances of syngamy in organisms exhibiting external fertilisation.
Organisms exhibiting external fertilisation show great synchrony between the sexes, release a large number of gametes into the surrounding medium.
Name one plant and animal in which internal fertilisation take place.
Plant — Gymnosperms;
Animal — Mammals.
In which type of life cycle does a zygote undergoes
Mitosis
Mitosis — Diplontic life cycle
Meiosis
Meiosis — Haplontic life cycle.
Name one oviparous and viviparous animal.
Oviparous animal — Reptile
Viviparous animal — Mammals
Write two advantages of vivipary.
Two advantages of vivipary are:
Proper embryonic care and protection of the young one.
The chances of survival of young one is greater.
Rearrange the following events of sexual reproduction in the sequence in which they occur in a flowering plant: embryogenesis, fertilisation, gametogenesis, pollination.
[NCERT Exemplar] [HOTS]
Gametogenesis, pollination, fertilisation, embryogenesis.
From which part does fruit, seed and embryo develop?
[HOTS]
Fruit — ripened ovary
Seed — ripened ovule
Embryo — mature zygote.
Suggest a possible explanation why the seeds in a pea are arranged in a row, whereas those in tomato are scattered in the juicy pulp.
[NCERT Exemplar] [HOTS]
The ovary of pea plant is monocarpellary and the ovules are arranged along one margin whereas in tomato the ovary is tricarpellary with axile placentation.
Is Marchantia monoecious or dioecious? Where are the sex organs borne in this plant?
[HOTS]
Marchantia is dioecious. The male sex organs, antheridia, are borne on the antheridiophores and female sex organs called archegonia are borne on archegoniophores.
What is the effect of DNA copying which is not perfectly accurate in the reproduction process?
The DNA copying which is not perfectly accurate in the reproduction process results in variations in populations for better survival of the species.
What methods will you use for growing jasmine and rose plants?
For growing jasmine plants, layering method will be used and for growing rose plants, cutting and grafting methods will be used.
Name the part of Bryophyllum where the buds are produced for vegetative propagation.
[CBSE Delhi 2016]
In Bryophyllum, the buds are produced in leaf notches.
Which parts of plants can grow vegetatively?
Modified stems like onion bulbs, runners of doob grass, ginger rhizomes, potato tubers, root tubers of sweet potato and dahlia, stem cutting of plants like rose and leaves of plants like Bryophyllum can be grown vegetatively.
Can you consider cell division as a type of reproduction in unicellular organism? Give one reason.
[NCERT Exemplar]
Yes, because it results in the formation of two daughter cells, i.e., it results in the production of more individuals of the organism.
What is the function of pollen grains in flowers?
Pollen grains are the male gametes which fertilise the egg cell present in the ovule of a flower.
Write the various methods of cross-pollination.
Various methods of cross-pollination are entomophily (insect pollination), anemophily (wind pollination), hydrophily (water pollination) and zoophily (animal pollination).
Why cannot fertilisation take place in flowers if pollination does not occur?
[NCERT Exemplar]
OR
Why is fertilisation not possible without pollination?
[CBSE (F) 2016]
In a flower, fertilisation requires both male and female gametes. If pollination does not occur, male gametes will not be available hence fertilisation cannot take place.
Explain the role of cotyledon and plumule in germination.
Cotyledon stores food and the plumule acts as future shoot.
Is the chromosome number of zygote, embryonal cells and adult of a particular organism always constant? How is the constancy maintained in these three stages?
[NCERT Exemplar]
Yes, the constancy is maintained because cells in all these three structures undergo only mitotic divisions.
In a bisexual flower inspite of the young stamens being removed artificially, the flower produces fruit. How is it possible?
[NCERT Exemplar]
This is because the pistil is intact due to which cross-pollination takes place leading to fertilisation and formation of fruit.
Formation of sperms in testes and ova in ovary is called gametogenesis.
In tobacco plant, the male gametes have twenty four chromosomes. What is the number of chromosomes in the female gamete? What is the number of chromosomes in the zygote?
[NCERT Exemplar]
Number of chromosomes in female gamete is 24 and in zygote it is 48.
How is the sperm genetically different from the egg?
Sperms contain either X or Y chromosome whereas an egg will always have an X chromosome.
What would be the ratio of chromosome number between an egg and its zygote? How is the sperm genetically different from the egg?
[NCERT Exemplar]
The ratio is 1 : 2. Sperms contain either X or Y chromosome whereas an egg will always have an X chromosome.
List two functions performed by the testis in human beings.
[CBSE Delhi 2015]
Functions of testis:
(i) To produce sperms.
(ii) To produce male sex hormone/testosterone.
List two functions of ovary of human female reproductive system.
[CBSE (AI) 2016]
(i) To produce female gamete.
(ii) To secrete female hormones.
Name the life process of an organism that helps in the growth of its population.
[CBSE (AI) 2015]
Reproduction helps in the growth of the population.
What happens when a mature Spirogyra filament attains considerable length?
[CBSE (AI) 2016]
When a mature Spirogyra filament attains considerable length its filament breaks up into smaller fragments and each fragment grows into a new filament or individual.
Name two simple organisms having the ability of regeneration.
[CBSE (AI) 2015]
Planaria/Hydra/Earthworm (Any two)
What happens when a Planaria gets cut into two pieces?
[CBSE Delhi 2016]
Each piece regenerates into a new Planaria.
Name the method by which Hydra reproduces. Is this method sexual or asexual?
[CBSE (F) 2016]
Hydra reproduces by budding or regeneration.
It is a method of asexual reproduction.
Name the method by which Spirogyra reproduces under favourable conditions. Is this method sexual or asexual?
[CBSE Delhi 2017]
Spirogyra reproduces by fragmentation. It is an asexual method.
How does Planaria reproduce? Is this method sexual or asexual?
[CBSE Delhi 2017]
Planaria reproduces by regeneration. This method is asexual.
How does Plasmodium reproduce? Is this method sexual or asexual?
[CBSE Delhi 2017]
Plasmodium reproduces by multiple fission. This method is an asexual means of reproduction.
Name the male and female gametes in animals.
In animals, male gametes are called sperms while female gametes are called eggs or ova.
Why are testes placed outside the abdominal cavity in the scrotal sac?
Testes are placed outside the body cavity in the scrotal sac because it requires a temperature 2°C lower than the normal body temperature for production of sperms.
What is hymen?
It is a thin fold of membrane which surrounds or partly closes the external vaginal opening.
What is funeral of unfertilised egg?
Menstruation is also called funeral of egg since it is not fertilised.
What is gestation?
The period of development of foetus in the uterus till birth is called gestation. It is of 9 months duration (i.e., 280 days or 40 weeks from the first day of the last menstrual cycle) in human beings.
Define parturition.
The birth of the fully developed foetus (childbirth) is called parturition.
Name the causative agent of the disease ‘Kala-azar’ and its mode of asexual reproduction.
[CBSE (F) 2015]
The causative agent of Kala-azar is Leishmania and the mode of asexual reproduction is binary fission.
Name the parts of a bisexual flower that are not directly involved in reproduction.
[CBSE (F) 2015]
(i) Sepals/calyx
(ii) Petals/Corolla
(iii) Thalamus
List two unisexual flowers.
[CBSE (F) 2016]
Water melon and papaya are unisexual flowers.
What is DNA?
[CBSE (F) 2015]
DNA is the carrier of hereditary information from parents to the next generation.
Write names of one male and one female sex hormone.
Male sex hormone is testosterone and female sex hormone is oestrogen.
Write whether true (T) or false (F):
Duration of menstrual cycle in human female is 20 days.
F
Onset of menstruation is termed menopause.
In human beings, male attains puberty little later than females.
T
One male gamete fuses with one female gamete or egg. This process of fusion of male and female nuclei is called syngamy.
What are those organisms called which bear both the sex organs in the same individiual? Give one example of such organism.
[CBSE (AI) 2016]
Organisms bearing both the sex organs in the same individual are called bisexual. Example, Hydra, Mustard.
Give an example of a unisexual and bisexual flower.
[CBSE (AI) 2014]
Cucumber is a unisexual flower and hibiscus is a bisexual flower.
Where is the zygote located in the flower after fertilisation?
[NCERT Exemplar]
Zygote is located inside the ovule which is present in the ovary.
Where do the following functions occur?
Production of an egg
In ovary
Fertilisation
In fallopian tube
Implantation of zygote.
In uterus (uterine wall).
What changes are observed in the uterus if fertilisation does not occur?
[NCERT Exemplar]
If fertilisation does not occur, the thick and spongy lining of the uterus slowly breaks and comes out through the vagina as blood and mucus.
Give reason for the statement- Since the ovary releases one egg every month, the uterus also prepares itself every month by making its lining thick and spongy.
[CBSE Sample Paper 2016]
The lining of uterus becomes thick for nourishing the embryo if fertilisation takes place and egg reaches the uterus.
What is menopause?
The period of permanent cessation of menstruation in females, usually occurring between the age of 45 and 50 is called as menopause.
Name the organs producing sperms and ova respectively in humans.
[CBSE (F) 2017]
Testis produces sperms and ovary produces ova in humans.
What is fertilisation? Where does it occur in a human female?
[CBSE (F) 2017]
Fertilisation is the fusion of sperm or male gamete and female gamete. It takes place in oviduct or fallopian tube of human female.
