Chapter 8. How do Organisms Reproduce?

Reproduction: Reproduction is the process by which living organisms produce new individuals similar to themselves to ensures continuity of life on earth.

Importance of D.N.A Copying in Reproduction: 

A basic event in reproduction is the creation of a DNA copy. Cells use chemical reactions to build copies of their DNA. This creates two copies of the DNA in a reproducing cell, and they will need to be separated from each other. The following importances of D.N.A copying are as in reproduction:

(i) The consistency of DNA copying during reproduction is important for the maintenance of body design features that allow the organism to use that particular niche.

(ii) Organisms look similar because their body designs are similar. If body designs are to be similar, the blueprints for these designs should be similar.

(iii) There come variations in the copy of D.N.A that couse ability for organisms to survive in unlike conditions. 

(iv) The DNA in the cell nucleus is the information source for making proteins. If the information is changed, different proteins will be made. Different proteins will eventually lead to altered body designs.

The Cause of variations in Body Design: 

In the reproductive cells organisms prepare blueprints of reproductive body designs to be similar body designs. But there comes some changes or variations in body designs due to some errors. As the chromosomes in the nucleus of a cell contain information for inheritance of features from parents to next generation in the form of DNA (Deoxyribo Nucleic Acid) molecules. The DNA in the cell nucleus is the information source for making proteins. If the information is changed, different proteins will be made. Different proteins will eventually lead to altered body designs. These errors are main cause of variations in organisms during the protien synthesis. 

How do variations comes in organisms? 

There form two copies of D.N.A in the reproductive cells during the reproductions as well as others cellular structures generate and when these copies detach to each other then one cell divides itself to form to newer cells. Hence In the nucleus of cell D.N.A have the difference informations for the protien synthesis so this causes variations in reproductive cells. As DNA copying mechanisms cannot be absolutely accurate and resultant errors taken place. These errors are a source of varitions in populations of organisms.  

The Importance of Variations in Organisms:  

(i) Variations cause difference features in organisms that allow their species to take habbitates in ecosystems or use particular niche. 

(ii) Variations are also useful for species to survive in the environment. 

(iii) 

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Q1.What are the significances of reproduction?
Q2.Why do we find variations in the offspring of parents although they have taken birth from the same parents?
Q3.Why variations are considered extremely important?
Q4.Differentiate between regeneration and fragmentation?
Q5.Why is regeneration not same as reproduction?
Q6.How will an organism be benefited if it reproduces through spores?
Q7.Which part of plant is considered as the reproductive part? Draw the L.S of labeled diagram of reproductive part showing the male and female reproductive organ.
Q8.Distinguish between self and cross pollination.
Q9.Differentiate pollination and fertilization.
Q10.Explain the post fertilization changes in flower.
Q11.What are the advantages of seed formation?
Q12.Give the labeled diagram of
a. Germination of pollen on stigma.
b. Seed Germination.
c. Structure of seed.
Q13.What are the similar changes observed in boys and girls at puberty?
Q14.What are the different changes that occur in boys and girls during puberty?
Q15.Define Puberty?
Q16.Distinguish between primary and secondary sex organs?
Q17.What are two important functions of testes and ovary?
Q18.Why are human testes extra abdominal?
Q19.What are the functions of testosterone and estrogen?
Q20.Distinguish between male and female germ cell.
Q21.Where fertilization does takes place in case of human oviduct or fallopian tube?
Q22.What is placenta? What is its function?
Q23.What happens when egg is not fertilized?
Q24.The marriageable are of male and female is 21 years and 18 years respectively, the rule is made by government, although the sexual maturation take place in them earlier. Why?
Q25.What are the adverse effects of early marriage?
Q26.What is reproductive health?
Q27.What are the various types of contraception?