Write the full form of DNA. Name the part of the cell where it is located. Explain its role in the process of reproduction of the cell.
The full form of DNA is deoxyribonucleic acid. It is the genetic material found in the chromosomes, which are present in the nucleus of a cell.
Role of DNA in the process of repro ¬duction of the cell:
DNA plays an important role in the reproduction of a cell. The reproducing cell produces an identical copy of DNA through some cellular mechanism. Since the newly formed copy of DNA lacks an organised cellular structure, the cell gets divided to provide cell cover to the newly formed DNA. Thus, two daughter cells are formed from the single cell as a result of the copying of DNA.
How are the modes for reproduction different in unicellular and multicellular organisms ?
State one genetically different feature between sperms and eggs of humans. What is its consequence?
What is the effect of DNA copying which is not perfectly accurate on the reproduction process?
List two advantages of practising vegetative propagation in plants. Select two plants raised by this method from the list given below:
Banana, Gram, Pea, Rose, Tomato, Wheat.
What is AIDS? Which microbe is responsible for AIDS infection? State one mode of transmission of this disease. Explain in brief one measure for the prevention of AIDS.
What is reproduction? What are its two types? Which one of the two confers new characteristics on the offsprings and how?
Name the two types of germ-cells present in human beings. How do they structurally differ from each other? Give two differences.
Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?
Draw a diagram of a human female reproductive system and label the part
(i) that produces egg
(ii) where fusion of egg and sperm take place
(iii) where zygote is implanted
What happens to human egg when it is not fertilised?
Differentiate between ‘self-pollination’ and ‘cross-pollination’. Describe double fertilisation in plants.
What are sexually transmitted diseases?
Name four such diseases. Which one of them damages the immune system of human body?
Explain the following methods of contraception giving one example of each:
(i) Barrier method
(ii) Hormonal imbalance method
(iii) Surgical method.
List the parts of human male reproductive system which contribute fluid to the semen. State two advantages semen offers to the sperms.
If a woman is using a copper-T will it help in protecting her from sexually transmitted diseases?
(a) In the human body what is the role of
(i) seminal vesicles, and (ii) prostate gland?
(b) List two functions performed by testis in human beings.
Name the information source of making proteins in the cell. State two basic events in reproduction.
(a) Explain the terms:
(i) Implantation (ii) Placenta
(b) What is the average duration of human pregnancy?
(a) What is fragmentation in organism?
Name a multicell-ular organism which reproduces by this method.
(b) What is regeneration in organism? Describe regeneration in Planaria with the help of a suitable diagram.
State in brief the changes that take place in a fertilised egg (zygote) till birth of the child in the human female reproductive system. What happens to the egg when it is not fertilised?
Which of the following is not a pan Of the female reproductive system in human beings ?
(a) Ovary
(b) Uterus
(c) Vas deferens
(d) Fallopian tube
“Variations that confer an advantage to an individual organism only will survive in a population.” Justify.