Question 1

Question 6Why does menstruation occur?

Accepted Answer

In females, the ovary releases one egg every month, the uterus also prepares itself every month to receive a fertilised egg. Thus its lining becomes thick and spongy. This would be required for nourishing the embryo if fertilisation had taken place. In absence of fertilised eggs this lining is not needed any longer. So, the lining slowly breaks and comes out through the vagina as blood and mucous. This cycle takes place roughly every month and is known as menstruation.

Question 2

Question 7Draw a labelled diagram of the longitudinal section of a flower.

Accepted Answer

Below labelled diagram shows the longitudinal section of a flower:

Question 3

Question 8What are the different methods of contraception?

Accepted Answer

The different methods of contraception are:Barrier method (condom)Intrauterine Devices like copper -TBirth control pillsSurgical methods: Vasectomy, Tubectomy

Question 4

Question 9How are the modes for reproduction different in unicellular and multicellular organisms?

Accepted Answer

Unicellular organisms generally reproduce by asexual methods like budding, binary fission, multiple fission, fragmentation, spore formation. Variation is not common in their progeny.On other hand, multicellular organisms can divide by sexual as well as asexual methods. For example, vegetative propagation in plants is a means of asexual reproduction while all higher animals reproduce sexually. Variation is seen in sexually reproducing organisms.

Question 5

Question 10How does reproduction help in providing stability to populations of species?

Accepted Answer

Reproduction helps in providing stability to populations of species in following ways:It maintains population by replacing the number of individuals lost due to death.It helps the species population to survive by creating variations.It helps in evolution of species due to selective adaptation.

Question 6

Question 11What could be the reasons for adopting contraceptive methods?

Accepted Answer

The reasons for adopting contraceptive methods are:To avoid unwanted pregnancies.To control population rise or birth rate.To safeguard oneself against sexually transmitted diseases.

Question 7

Question 2How will an organism be benefited if it reproduces through spores?

Accepted Answer

Some of the advantages of reproduction through spores formation are:Spores are often small, lightweight, and easily dispersed by wind, water, or other external factors. This helps them to travel far distances to avoid competition for essential resources required for growth.The spores are covered by thick walls that protect them until they come into contact with another moist surface and can begin to grow.It helps the parent organism to conserve energy compared to the resources required for more complex reproductive structures (such as seeds or offspring).

Question 8

Question 3Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?

Accepted Answer

More complex organisms have high level of tissue differentiation and these tissues are highly specialized in their functions. The body has organ-system level of organisation. They can regenerate few damaged tissues but cannot regenerate organ or organ sysytem. Therefore, more complex organisms cannot give rise to new individuals through regeneration. Regeneration is only possible in lower and simple organisms that do not show complex cellular differentiation.

Question 9

Question 4Why is vegetative propagation practised for growing some types of plants?

Accepted Answer

Vegetative propagation is practised for growing some types of plants because:Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from seeds.Such methods also make possible the propagation of plants such as banana, navel orange, rose and jasmine that have lost the capacity to produce seeds.All plants produced are genetically similar enough to the parent plant to have all its characteristics. This result in uniformity in produce.

Question 10

Question 5Why is DNA copying an essential part of the process of reproduction?

Accepted Answer

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. Therefore, the creation of a DNA copy is an essential part of the process of reproduction.

Question 11

Question 1How is the process of pollination different from fertilisation?

Accepted Answer

PollinationFertilisationPollination is the transfer of pollen grains from anther of a flower to stigma of the same or a different flower.Fertilisation is the fusion of male and female gametes resulting in the formation of a zygote.Pollination is a physical process.Fertilisation is a biochemical process.External agents like wind, water, animals are required.No external agent is required.It occurs in flowering plants only.It occurs in almost all plants and animals also.

How do Organisms Reproduce?

Exercises

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