Q10 of 26 Page 1

How do the following organisms overcome the stressful external conditions?

(i) Bacteria


(ii) Snail


(iii) Bear


(iv) Zooplankton in lakes.


Adaptation in stressful external conditions in the following organisms are:

(i) Bacteria: bacterias slow down their metabolic rate and form thick walled spores to overcome stressful conditions. These spores germinate when the conditions become suitable.


(ii) Snail: they undergo aestivation to avoid summer related problems.


* Aestivation: it is the state of reduced activity in an organism to escape desiccation due to heat in summer.They stay in cool or shady places.


(iii) Bear: bears undergo hibernation during winters.


* Hibernation- is a state of reduced activity in an organism to escape winter conditions.Animal ret in warm places.


(iv) Zooplankton in lakes: under unfavourable conditions zooplankton species in lakes and ponds enter diapause, which is a stage of suspended/ delayed development.


More from this chapter

All 26 →
8

(i) Write the scientific name of the vector that is responsible for the spread of dengue.

(ii) Write any two precautions that must be taken to check the spread of this disease.


OR


(i) Write the causes of AIDS.


(ii) How does the transmission of the disease causing agent occur?


 9

Write two high yielding varieties of wheat along with their characteristic features.

 11

Name the following that form the parts of a typical angiosperms ovule:

(i) The stalk that attaches it to the placenta in the ovary.


(ii) The layers that protect it. The mass of tissue enclosed by these layers.


(iii) The different types of cells present in its mature embryo sac.


OR


List the different parts of a typical dicotyledonous embryo along with their functions.


 12

(a) Why are some seeds called albuminous and others non-albuminous?

(b) Which one of the following are albuminous or exalbuminous


(i) Pea


(ii) Wheat


(iii) Groundnut


(iv) Maize