2nd PUC Biology Important Questions Chapter 1 Reproduction in Organisms

Karnataka 2nd PUC Biology Important Questions Chapter 1 Reproduction in Organisms

Question 1.
Define Lifespan?
Answer:
The period from birth to the natural death of an organism.
Note: The life span of an organism varies greatly.
Ex: Crow – 15 Years, Tortoise – 100-150 Years.

Question 2.
Why unicellular organisms are considered as immortal?
Answer:
In single celled organisms, the parent continues to live as daughter cells.

Question 3.
Define Reproduction?
Answer:
It is a biological process in which organism gives rise to young ones similar to itself.

Question 4.
Write the Significance of reproduction or Why is reproduction essential for organisms? (2M)
Answer:

• The offspring grow mature and in turn produce new offspring.
• It is a process of species maintenance.
• If reproduction is absent, a species may soon get extinct.

Question 5.
Define asexual reproduction?
Answer:
It is a mode of reproduction in which a single parent produces young ones without the formation and fusion of gametes.

Question 6.
Mention the features of asexual reproduction?
Answer:

• It is uniparental.
• Occurs in unicellular organisms, plants and animals with simple organisation.
• It involves mitotic cell division.
• Offsprings are identical to one another and exact copies of their parents.

Question 7.
Why is the offspring formed by asexual reproduction referred to as clones? or Define clone.
Answer:
Morphologically and genetically similar off springs identical to their parents are known as clones.

Question 8.
Explain the different methods of asexual reproduction with examples?
Answer:
(a) Binary Fission: The body of a matured parent cell divides into two halves, each half grows into an adult.
Eg: Bacteria, Amoeba, Paramoecium.

(b) Cell division: The parent cell divides into two give rise to new individuals.
Eg: Protists, Monera.

(c) Budding: A new individual develops as a small outgrowth on the surface of the parent, later gets separated and matures into a new organism.
Ex: Yeast, Hydra. Sponges → Gemmules [internal buds or Internal asexual reproductive units]

(d) Spores: Specialised microscopic unicellular asexual reproductive structures to overcome unfavourable climatic conditions.
Ex: Zoospores (motile spores) – Chlamydomonas.Conidia – Penicillium.

Question 9.
Mention the asexual reproductive structures of Penicillium?
Answer:
Conidia.

Question 10.
Define vegetative reproduction?
Answer:
It is a process of formation of new plants from vegetative parts of the plant body.

Question 11.
What are vegetative propagules?
Answer:
Vegetative reproductive structures, having the capacity of giving rise to new offspring.

Question 12.
Name the vegetative propagules of the following? or Mention the units of vegetative propagation in plants, or Name the types of vegetation in propagules in the following plants (a) Potato (b) Ginger (c) Bryophyllum
Answer:

1. By Roots: Root tubers of sweet potato, Dahlia etc.
2. By Stem:
   (a) Tuber of Potato.
   (b) Rhizome of Ginger, Banana.
   (c) Sucker of Mint and Chrysanthemum.
   (d) Runner of Oxalis.
   (e) Offset of Eichhomia (Water Hyacinth).
   (f) Bulb of Onion.
3. By Leaves: Bryophyllum – leaf buds.
4. Inflorescence: Bulbils part of the inflorescence of plant Agave.

Question 13.
Name asexual reproductive structures in
(i) Hydra
Answer:
Budding

(ii) Chlamydomonas
Answer:
Zoospores

(iii) Pencillium.
Answer:
Conidia

Question 14.
Name the vegetative propagules of the following plant?
(a) Agave
Answer:
Bulbil

(b) Ginger
Answer:
Rhizome

(c) Bryophyllum.
Answer:
(c) Leaf buds

Question 15.
Why Eichhornia is known as Terror of Bengal?
Answer:
Eichhomia is an aquatic invasive weed,found growing in standing water. It drains oxygen from the water which leads to death of fishes and other aquatic organisms.

Question 16.
Write the importance of asexual reproduction in plant propagation?
Answer:
Asexual reproduction ability of plants is fully exploited for commercial propagation of economically important plants. Methods: Cutting, Grafting, Tissue Culture (Artificial Vegetative Reproduction).

Question 17.
Define sextjal reproduction?
Answer:
It is a mode of reproduction in which young ones are produced through formation and fusion of gametes by the same individual or by two different individuals of different sex.

Question 18.
Write any four differences between sexual and Asexual reproduction? (2M)
Answer:

Asexual Reproduction	Sexual Reproduction
1. Occurs in lower organisms.	1. Lower and Higher organisms.
2. Uniparental.	2. Generally biparental.
3. No formation of gametes.	3. Involves formation of gametes
4. Mitotic cell division.	4. Meiotic cell division.
5. Variations absent	5. Variations are produced.
6. Offspring genetically similar to parents	6. Offspring genetically dissimilar to parents.

Question 19.
Explain the different stages in the life cycle of living organisms?
(a) Define Juvenile Phase?
Answer:

1. Juvenile Phase: It is a period of growth of an organisms before reproductive maturity. It is called as a vegetative phase in plants.
2. Reproduction Phase: It is a period of growth of an organism where they start reproducing sexually.

(b) Define Senescent Phase?
Answer:
Senescent Phase (Ageing Process): It is the end of reproductive phase, which gradually results in slowing of physiological functions leading towards death of an organism.

Question 20.
What are Annuals/Biennials/Perennial plants give examples?
Answer:

Question 21.
Name the plant which flowers once in its lifetime?
Answer:
Bamboo [50-100 years].

Question 22.
Name the plant that flowers once in 12 years?
Answer:
Strobilanthus Kunthiana (Neelakuranji).
[Plants reproductive phase is marked by flowering, based on flowering capacity, they care classified into Mono and Polycarpic plants.]

Question 23.
Difference between Monocarpic plants and Polycarpic plants?
Answer:

Monocarpic Plants	Polycarpic Plants
1. These plants flower only once in their lifetime.	1. These plants flower many times a year throughout their life cycle.
2. After flowering and fruiting they die. Ex: Bamboo, Rice, Wheat, Carrot etc.	2. Flowering and Fruiting continues till the completion of their life span. Ex: Mango, Apple, Orange, Jackfruit etc.
3. Strobilanthes Kunthiana.

Question 24.
Differentiate between seasonal and continuous breeders?
Answer:

Seasonal Breeders	Continuous Breeders
These animals are reproductively active during favourable seasons. Ex: Frog, Lizards, Birds etc.	These animals are reproductively active throughout their reproductive phase. Ex: Rabbit, Primates etc.

Question 25.
What is reproduction cycle?
Answer:
Reproductive cycles are the cyclic changes that occur in the female reproductive systems of Mammals.

Question 26.
Differentiate between the Menstrual and Oestrus cycles.
Answer:

Menstrual Cycle	Oestrus Cycle
1. Females of placental mammals exhibit cyclical changes in the activities of ovaries during the reproductive phase of Primate mammals. Ex: Monkeys, Humans.	1. Females of placental mammals exhibit cyclical changes in the activities of ovaries during Apes and reproductive phase of Non-Primate mammals. Ex: Cow, Dog, Sheep.
2. Heat period is absent.	2. Heat period at the time of ovulation.
3. Breeding occurs during any season and any part of the reproductive cycle.	3. Non-breeding season, [anaestrous period]

Question 27.
Write 3 Phases of sexual reproduction?
Answer:

1. Pre fertilisation Events – (a) Gametogenesis, (b) Gamete transfer.
2. Fertilisation – Fusion of male and female gametes.
3. Post fertilisation Events – Zygote formation, Embryogenesis.

Question 28.
Define gametogenesis?
Answer:
The process of formation of gametes or sex cells within the sex organs or gonads.

Question 29.
Differentiate between isogamy and anisogamy? or Distinguish between homogametes and heterogametes?
Answer:

Homogametes (Isogametes)	Heterogametes (Anisogametes)
Male and female gametes which are morphologically similar Ex: Algae, Protozoa.	Male and Female gametes are morphologically dissimilar. Ex: Fucus, Human.

Question 30.
Defferentiate between Monoecious and Dioecious plants? Give examples.
Answer:
(a) Bisexual or Monoecious /Homothallic plants are the plants with both male and female reproductive structures on same plant. Ex: Cucurbit, coconut, Maize, Chara (Algae).
(b) Unisexual or Dioecious/Heterothallic plants are the plants with male and female reproductive structure on different plants. Ex: Papaya, Marchantia (Bryophyte), Date Palm, Cycas etc.

Question 31.
Why papaya is considered as dioecious plants?
Answer:
It bears male and female reproductive structures on different plants.

Question 32.
‘Papaya plants exhibit xenogamy only, why?
Answer:
Papaya plants are dioecious in nature, thus they exhibit xenogamy.

Question 33.
What is heterothallic condition? Differentiate between staminate and pistillate flowers.
Answer:

• If plant possess male and female reproductive structures on different plants is termed as heterothallic condition,
• If a flowering plant possess unisexual male flowers with only androecium it is called as staminate flower.
• If a flowering plant possess unisexual female flower with only gynoecium it is called as Pistillate flower. (Cell division during gamete formation
• All gametes are haploids, but parent body may be diploid or haploid. The type of cell division differs during gamete formation).

Question 34.
What are Diploids and Haploids? Give examples.
Answer:

1. Diploids: In these organisms, diploid parents produces haploid gametes by meiosis [gamete mother cells
   = Meiocytes],
   Eg: Pteridophytes, Gymnosperms, Angiosperms, Animals including human beings.
2. Haploids: In these organisms, Haploid parents produces Haploid gametes by mitosis (meiosis occurs during zygote formation). Eg: Algae, Fungi.

Question 35.
Define gamete transfer?
Answer:
It is the transfer of male gamete towards female gametes for the purpose of fertilisation.

Question 36.
Define fertilisation?
Answer:
“The process of fusion of haploid sperm with haploid egg to produce diploid Zygote” (syngamy).

Question 37.
Differentiate between external and internal fertilisation?
Answer:

External Fertilisation	Internal Fertilisation
1. Syngamy occurs outside the body of the parents in an external medium.	1. Syngamy occurs within the female body in the genital tract.
2. Copulatory organs are absent.	2. Males are provided with copulatory organs
3. Ex: Fishes, Amphibians, Algae.	3. Ex: Reptiles, Mammals, Gymnosperms, Angiosperms.

Question 38.
Define parthenogenesis with any 2 Examples? or Define parthenogenesis.
Answer:
Parthenogenesis: The female gamete develops into Embryo to form a new organism without fertilisation.
Ex: Rotifers, Insects, Drones, Lizards, Turkey etc.

Question 39.
Define Zygote?
Answer:
Fusion of male and female haploid gametes results in formation of zygote.
[Note: Development of zygote varies with organisms and environment.

• In External fertilisation it is formed in External medium (water) and formed inside the body of the organism in Internal fertilisation.
• In fungi and Algae Zygote develops thick wall and undergoes dormancy before germination to overcome unfavourable conditions.

Question 40.
What are haplontic and diplontic life cycles?
Answer:

• Haplontic life cycle – Zygote divides by meiosis to form haploid spores and form haploid individuals.
• Diplontic life cycle – Zygote divides mitotically to form diploid individuals.

Question 41.
Define Embryogenesis?
Answer:
“Development of Embryo from the zygote”.

Question 42.
Define organogenesis?
Answer:
The zygote grows by repeated mitotic division form cells and undergo cell differentiation to become tissues and organs to form an organism. This is known as organogenesis.
[Note: 1. In flowering plants, Zygote is formed inside the ovule and developes into Embryo. Ovary developes into fruit and Ovule developes into seed.]

Question 43.
Define Pericarp?
Answer:
The ovary wall or fruit wall develops into ‘Pericarp’.
[Note: 2. In Animals, based on the development of zygote, they are classified into Oviparous, Viviparous, animals.]

Question 44.
Define Ovipary? Give any two examples.
Answer:
Egg-laying animals. Eg. Reptiles, Birds.

Question 45.
Differentiate between Oviparous and Viviparous animals?
Answer:

Oviparous	Viviparous
1. These animals lay fertilised eggs, and the development of the embryo takes place outside the body of the female.	1. These animals give birth to young ones, and the development of the embryo takes place inside the body of the female.
2. After a period of incubation the young ones hatch out. Ex: Reptiles, birds.	2. After a period of growth young ones are delivered out. Ex: Mammals.

Question 46.
How Vivipary is advantageous to young ones.
Answer:
Because of proper embryonic care and protection,the chances of survival is greater in viviparous animals,than oviparous animals.

Question 47.
(a) What are hermaphrodites? Mention two example.
Answer:
Animals which possess both male and female reproductive organs are termed as hermaphrodites.
Ex: Leech, tapeworm, earthworm.

(b) Offsprings of asexual reproduction are called clones. Why?
Answer:
Morphologically and genetically similar offspring identical to their parents are known as clones.

Question 48.
Mention the asexual reproductive unit in sponges.
Answer:
Gemmules.

→ Introduction:
Reproduction is the production of new individuals, physically independent of their parents. It is one of the important characteristics of living organisms.

→ Types of Reproduction:

1. Asexual Reproduction.
2. Sexual Reproduction.

→ Phases in Sexually Reproducing Organisms:
All organisms have to reach a certain stage of growth and maturity in their life before they attain capable of sexual reproduction.

→ Gamete Transfer Types:

1. Male and female gametes are motile. Ex: lower Algae and fungi
2. Male Motile and female gamete stationary Ex: higher organisms.
3. In Angiospcms pollens are transferred to the stigmatic surface by pollination, which leads to fertilisation.
4. In invertebrates swimming movement of sperm enables it to reach egg.
5. In vertebrates sperms are transported from the region of deposition to the region of fertilisation.

2nd PUC Biology Important Questions with Answers