CBSE Guess > Papers > Question Papers > Class X > 2009 > Science > Science

Q. 21. State two problems caused by biodegradable waste that we generate in our daily life. 2

Ans. Problems caused by biodegradable waste in our daily life.
(i) When biodegradable wastes are collected in the form of garbage, these provide a lot of organic matter for the decomposers. During decomposition of these wastes, foul smell and some harmful gases are given out in the environment.
(ii) Organic matter of biodegradable substances cause the growth of mosquitoes and flies which act as vectors for the disease causing microbes.

Q. 22. State two problems caused by the non-biodegradable waste that we generate in our daily life. 2

Ans. Problems caused by the non-biodegradable waste:
(i) Non-biodegradable wastes cannot be made less toxic easily and hence they are major pollutants of the environment.
(ii) Non-biodegradable waste can be passed along the food chain from crops to man and other animals and harm them.

Q. 23. What is regeneration? State a reason why a more complex organism cannot give rise to new individuals through this method. 2

Ans. Regeneration. The process of getting back a full organism from its body parts is called regeneration. The simple animals like hydra and planaria show regeneration.

In complex multicellular organisms, specialised cells make up tissues; tissues make up organs; organs make up organ system; and finally organ system make up organisms. Since complex multicellular organisms have a very high degree of organisation in their body, they cannot be reproduced from their cut body parts by the process of regeneration.

Q.24. What are plant hormones? Write two important functions of auxin. 2

Ans. Plant hormones are special type of chemicals secreted by the plants to control and coordinate plant growth, development and responses to the environment.

Functions of Auxins:
(i) It promotes cell enlargement and cell differentiation.
(ii) It promotes fruit growth.

Q. 25. The human beings who look so different from each other in terms of colour, size and looks are said to belong to the same species. Why? Justify your answer. 3

Ans. The human beings who look so different from each other in terms of colour, size and looks are said to belong to the same species because the process of reproduction can occur between them. These differences are known as variations, i.e. the occurrence of differences among the individuals of a species. Although all human beings look different, they have the same number of chromosomes. A large number of variations occur in sexual reproduction because two parents are involved in the process and result in the birth of human beings of different colour, size and looks.

Science 2009 Question Papers Class X
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