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Organisms and Populations

Q1. What are euryhaline and stenohaline organisms?

Ans: The organism tolerating the high range of temperature is called eurythermal and the organism which can tolerate narrow range of temperature is called stenothermal.


Q2. What is homeostasis?

Ans: The ability of an organism to maintain the constancy of its internal environment despite varying external environmental conditions.


Q3. Mention any four major abiotic factors.

Ans: Temperature, water, light and soil.


Q4. State Allen's rule.

Ans: Mammals have shorter ears and limbs to minimize heat loss. This is called Allen's rule.


Q5. How humans are adapted to live in high altitude? Explain.

Ans:

  • The people living in high altitudes compensate low oxygen by increasing production of red blood cells (RBCs).

  • The binding capacity of haemoglobin decreases and breathing rate increases.

  • People living at high altitudes of Himalayas have higher RBC count or total Hb than people living in plains.


Q6. Explain the factors that fluctuates the population growth / population density.

Ans:

The population density can fluctuate due to the following reasons;

  1. Natality: It is the number of births during a given period of time. It increases the population density.

  2. Mortality: It is the number of deaths in a given time period. It decreases the population density.

  3. Immigration: It is the number of individuals of same species added to a habitat in a given time period. It increases the population density.

  4. Emigration: It is the number of individuals of same species that move to a different habitat in a given time period. It decreases the population density.


Q7. Explain the logistic growth model.

Ans:

  • The logistic growth model can be seen when the resources become limited at certain point of time, so no population can grow exponentially.

  • This growth model is more realistic.

  • Every ecosystem or environment or habitat has limited resources to support a particular maximum number of individuals called its carrying capacity (K).


Q8. What are ectoparasites and endoparasites? List any three parasitic adaptations in animals.

Ans:

Ectoparasites are the parasites which feed on the external surface of the host organism for food and shelter.

E.g., lice on humans, ticks on dogs, copepods, Cuscuta.


Endoparasites are the parasites which live inside the host's body at different sites like liver, kidney, lungs, etc., for food and shelter.

E.g., tapeworm, liver fluke, Plasmodium.


Adaptations of parasitic animals:

  • Loss of unnecessary sense organs.

  • Presence of adhesive organs or suckers.

  • Loss of digestive system.

  • High reproductive capacity.


Q9. What is commensalism? Explain by giving