Q26 of 30 Page 1

How have human activities caused desertification? Explain.

OR


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


Deforestation is the conversion of forested areas to the non-forested areas. A number of human activities that contribute to deforestation.


• To construct the road, buildings, new city, etc. the trees are being cut down that result in desertification.


• The major reason is the conversion of forest to agricultural land so as to feed the growing human population.


• Soil erosion by deforestation due to the induserialization and construction of house.


• Due to the increasing population and repeated cultivation affects the soil quality which results in deforestation.


OR


• Algal bloom growth is promoted by the presence of a high quantity of nutrients in waters, which results in a layer that finally covers the whole surface of the water bodies.


• Algal blooms result in deterioration of water quality and fish mortality.


• Some bloom-forming algae are very toxic to human beings and animals.


• Due to high respiratory rate the biological oxygen demand (BOD) of the water body increases which causes the death of a number of aquatic organisms.


More from this chapter

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24

(a) Why are the fruit juices bought from market clearer as compared to those made at home?

(b) Name the bioactive molecule produced by Trichodermapolysporum and Monascuspurpureus.


 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.


 27

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

 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.