Reproduction In Animals - Class 8 Biology - Extra Questions

Give any two differences between a zygote and a foetus.

  • Zygote- Zygote is the result of fertilization, it is the fusion of male and female gamete. It is unicellular in nature.  
  • Fetus- Zygote undergoing multiple cellular division and reaching a stage where it starts resembling a human structure, it is called a foetus. It is multicellular in nature.


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

Clone refers to a group of genetically identical organisms. Crossing over during meiosis and random fertilization of male and female gametes add genetic diversity to sexually reproducing organisms. Asexual reproduction skips meiosis and fertilization of male and female gametes and therefore, produces genetically identical progeny i.e. clone by single parent cell.


What is metamorphosis? Give an example.

Explanation:

  • Metamorphosis is the process of transformation from an immature form to an adult form in two or more distinct stages.
  • Metamorphosis generally takes place in insects or amphibians and some molluscs, crustaceans, cnidarians, echinoderms, and tunicates. 
  • An example of metamorphosis is the change that takes place from the tadpole to form a frog.


Indicate whether the following statements are true (T) or false (F).
(a) Oviparous animals give birth to young ones. ( )
(b) Each sperm is a single cell. ( )
(c) External fertilization takes place in frog. ( )
(d) A new human individual develops from a cell called gamete. ( )
(e) Egg laid after fertilization is made up of a single cell. ( )
(f) Amoeba reproduces by budding. ( )
(g) Fertilization is necessary even in asexual reproduction. ( )
(h) Binary fission is a method of asexual reproduction. ( )
(i) A zygote is formed as a result of fertilization. ( )
(j) An embryo is made up of a single cell. ( )

a) Oviparous animals give birth to young ones - (F)
No, viviparous animals give birth to young ones.

(b) Each sperm is a single cell - (T)
Sperm cells are gametes, and thus, they are unicellular

(c) External fertilization takes place in frog - (T)
The female frog releases many egg cells in the water. As the egg cells come out of the female, the male frog releases sperm cells over them. Fertilization takes place. Fertilization in frogs takes place outside the body of the female frog in the water.
 
(d) A new human individual develops from a cell called as gamete - (F)
No, a new human individual develops from combination of two gametes called as zygote.

(e) Egg laid after fertilization is made up of a single cell - (T)
After fertilization zygote is formed which is single cell.

(f) Amoeba reproduces by budding - (F)
 No, amoeba reproduces by binary fission.

(g) Fertilization is necessary even in asexual reproduction - (F)
In asexual reproduction, a single organism or cell makes a copy of itself without fertilization.

(h) Binary fission is a result of asexual reproduction - (T)
Binary fission is the process of splitting of a parent cell into two daughter cell without fertilization.

(i) A zygote is formed as a result of fertilization - (T)
Zygote is formed by fertilization of male and female gamete.

(j) An embryo is made up of a single cell - (F)
No, an embryo is now made up of three layers ectoderm, mesoderm, and endoderm. 


Define the term metamorphosis. Briefly describe the various stages occurring in the life-cycle of a butterfly.

Metamorphosis is a  process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. 
There are four stages in the metamorphosis of butterflies and moths: egg, larva, pupa, and adult.
  • Stage 1 - Eggs: In the first stage, a female butterfly lays eggs. The eggs are really small and round. About five days after the eggs are laid, tiny worm-like creatures hatch out from the eggs.
  • Stage 2 - Caterpillar (Larva): The second stage is the caterpillar. A caterpillar is sometimes called larva. A caterpillar is a long creature. It looks like a worm. This is the eating and growing stage. A caterpillar grows really fast. Caterpillars shed their skin four or more times while they are growing. A caterpillar shedding its outgrown skin is called moulting.
  • Stage 3 - Chrysalis (Pupa): Stage three is the chrysalis. This is when the caterpillar is done growing. The caterpillar makes a chrysalis. Another name for a chrysalis is a pupa. It is mostly brown or green. It is the same colour as that of the things around it. This is so that other animals cannot see it. This protects them.
  • Stage 4 - Butterly (Adult)): In stage four, the chrysalis opens. Soon, a butterfly comes out.


How was the of cloning  sheep Dolly achieved ? What was the purpose of cloning this sheep?

Dolly was the sheep which was the first cloned mammal through somatic cells using the process of nuclear transfer. It was introduced on 5 July 1996. It was one of the biggest achievements in the field of biotechnology. This achievement demonstrated that the DNA of adult cells has one type of cells still this cell can be used to make an entire organism through nuclear transfer. The genes were taken from Finn Dorset white sheep and are transported to another Scottish blackface ewe. The progeny was found to be having a white face. This project was named as the dolly. The purpose of cloning this sheep was to increase the affinity and effect of cloning technology. This cloning was at the Roslin research institute to produce medicines in the milk of farm animals. This technique was simply to increase the production of medicines.


What are clones?

Clones are identical copies of an organism produced by biotechnological methods


Differentiate between the 'Budding of Hydra' and 'Binary fission of Amoeba.'

 Budding in Hydra   Binary fission in Amoeba 
Asexual reproduction in which a new organism develops from a bud in the parent.It is the type of asexual reproduction in which the parent divides to give rise to two daughter organisms.
This bud is simply an outgrowth of cells at one particular site.The parent replicates its genetic material and divides it equally between the two daughters.
The bud or the new organism remains attached to the parent and gets detached on maturation.Both the cytoplasm and the nucleus of the parent divide into two.


Is 'Dolly' living now-a-days?

'Dolly' is a cloned sheep from the somatic cell of an adult sheep and survived for around 8-9 year and is no more now-a-days.


Show budding in Hydra diagrammatically.

This diagram shows the budding in Hydra. Budding is a type of asexual reproduction in which a new organism is formed from a bud of an existing organism. The new organism remains attached to the parent organism till it gets matured.
1380052_1245591_ans_b1e0e227c9364f88a98a57889536680b.png


Define regeneration.

Regeneration is the development of a complete organism from the parts of the body of the organism which are accidentally cut during an injury. For example, Planaria undergoes regeneration.


What does figure represent? 
1811262_bbef61f02a5c42288b0178c784de6555.png

In this figure binary fission of Amoeba is taking place with dividing nucleus. 


What is fertilization? Name the cell formed as product of fertilization.

The process of fusion of male gamete and female gamete is called fertilization. Fertilization results in the formation of diploid zygote. 


Differentiate between gametogenesis in human males and females on the basis of
i) time of initiation of the process.
ii) products formed at the end of the process.

Explanation:

  • Gametogenesis is the process of formation of haploid gamete from germ cells in both human males and females respectively.

  •  During this process, the germ cell will undergo meiosis which produces the haploid cells that will directly develop into gametes. 

The difference between the gametogenesis on the basis of time of initiation –


s.no Gametogenesis on the basis of males females
 1 The time of initiation of the processStarts at puberty  embryonic development
 2 Products formed at the end of the process One primary spermatocyte produces four spermatozoa One primary oocyte produces one ovum and two polar nuclei.


A child observed a permanent slide fixed under a microscope. He concluded that the slide shows binary fission in amoeba. Draw the four stages.

The 4 stages of binary fission in amoeba are shown through the given diagram.
1380902_1191589_ans_a756720c582842a3b143f2901ad98f2f.png


Class 8 Biology Extra Questions