NEET Practice Questions (MCQs) with Answers & Solutions

(d) Bacteria, fungi and lower plants survive in adverse conditions through formation of thick-walled spores. Algae form resting spore or akinetes which are thick-walled spores and store food material. In fungi, thick-walled perennating spores called chlamydospores are formed. Bacteria form endospores which is probably the most resistant living thing known. They may remain alive in boiling water for more than 2 hours.

(b) Monarch butterfly escapes from predators because of its bitter taste. Viceroy butterfly (Basilarchia archippus) mimics monarch butterfly to escape from predators.

(b) Immigration is the entry of individuals into a region for permanent or temporary settlement thereby increasing the population density of that particular region due to addition of individuals. Food shortage, disease and famine are the factors that would limit the growth of a population. 

(a) The population growth curve will be S-shaped or sigmoid or logistic. The growth cure has five phases - lag phase, positive acceleration phase, exponential phase, negative acceleration phase and stationary phase. Most of the organisms including human population shows S-shaped curve.

(b) Circadian rhythm or diurnal rhythm is any 24 hour periodicity in the behaviour or physiology of animals or plants. Examples are the sleep/activity cycle in many animals and the growth movements of plants. Circadian rhythms are generally controlled by biological clocks.

Population increases due to increase in birth rate and immigration while population decreases due to increase in death rate and emigration.

A. Population is stable when B+I = D+E

B. Population is increasing when B+I > D+E

C. Population is decreasing when B+I < D+E.

Some organisms are tolerant of a wide range of salinities (euryhaline) but others are restricted to a narrow range (stenohaline). Many freshwater animals cannot live for long in sea water and vice versa because of the osmotic problems, they would face.

(page-222)

The property of an organism to maintain the constancy of its internal environment despite varying external environmental conditions is called as homeostasis.

(page-223)

Homeostasis can be achieved in humans by both physical and physiological means.

Physiologically: temperature regulation by sweating and shivering.

Physically: By sitting at home or in car to avoid cold temperature.

(page-223)

The osmoconformers change their temperature and osmotic concentration with respect to the external environment. It does not remain constant.

(page-224)