Q27 of 30 Page 1

Explain mutualism with the help of any two examples. How is it different from commensalism?

• Both the interacting species are benefited in mutualism interaction.


• Examples of mutualism are given below:


1. Association between fungi and plant:The mutualistic relationship showed by Mycorrhizae is associations between fungi and the roots of higher plants.For the absorption of essential nutrients from the soil, the fungi help the plant while in turn, the plant provides the fungi with energy-yielding carbohydrates.


2. Pollination:The pollen and nectar for pollinators and juicy and nutritious fruits for seed dispersers as a reward provided by the flower of plants for the getting benefit for pollinating their flowers and dispersing their seeds. The plant-pollinator’ pair often goes co-evolution to safeguard against the use of the nectar by other non-important organisms.


• Mutualism is different from commensalism in that the latter gives benefit to just one of the participating species, the benefitted species being called a commensal.


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25

(a) Why are transgenic animals so called?

(b) Explain the role of transgenic animals in (i) Vaccine safety and (ii) Biological products with the help of an example each.


 26

How have human activities caused desertification? Explain.

OR


How does algal bloom destroy the quality of a fresh water body? Explain.


 28

(a) Draw a diagrammatic sectional view of a mature anatropous

ovule and label the following parts in it:


(i) that develops into seed coat.


(ii) that develops into an embryo after fertilization.


(iii) that develops into an endosperm in an albuminous seed.


(iv) through which the pollen tube gains entry into the embryo sac.


(v) that attaches the ovule to the placenta.


(b) Describe the characteristic features of wind pollinated flowers.


OR


(a) Draw a diagrammatic sectional view of the female reproductive system of human and label the parts


(i) where the secondary oocytes develop


(ii) which helps in collection of ovum after ovulation


(iii) where fertilization occurs


(iv) where implantation of embryo occurs.


(b) Explain the role of pituitary and the ovarian hormones in menstrual cycle in human females.


 29

Describe the asexual and sexual phases of life cycle of Plasmodium that causes malaria in humans.

OR


(a) What is plant breeding? List the two steps the classical plant breeding involves.


(b) How has the mutation breeding helped in improving crop varieties? Give one example where this technique has helped.


(c) How has the breeding programmed helped in improving the public nutritional health? State two examples in support of your answer.