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Organisms And Populations

Question
CBSEENBI12002095

(a) Compare, giving reasons, the J-shaped and S-shaped models of population growth of a species.
(b) Explain ‘fitness of a species’’ as mentioned by Darwin.

Solution

(a) There are 2 models of population growth : (i) The exponential growth (ii) Logistic growth (i) Exponential growth : This growth occurs where the resources (food + space) are unlimited. The equation can be represented as dt dN = (b – d) × N Let (b – d) = r rN dt dN = or rt t 0 N = N e N = population size Nt = population density after time t. N0 = population density at time zero r = growth rate b = birth rate d = death rate In this growth, when N in relation to time is plotted on graph, the curve becomes J-shaped.


(a) J-shaped curve ⇒ exponential growth
(b) S-shaped curve ⇒ logistics growth
Every ecosystem has limited resources to support a particular maximum carrying capacity (K). When N is plotted in relation to time t, a sigmoid-S-shaped curve is obtained & is also called as VERHULST-PEARL logistic growth. The equation is : dt dN = rN K (K − N) N = population density at time t. r = growth rate K = carrying capacity.

Some More Questions From Organisms and Populations Chapter

In which interaction only one species is benefitted while the other species is neither harmed nor benefitted ?

Which of the following interaction both species suffer ?

In which of the following interaction both species are benefitted ?

Fill in the blanks with suitable words :

1. The optimal capacity of the organism to produce offspring is called........................

2. Rapid increase in human population is called........................

3. Mathematical expression of the growth of population is called........................

4. Yeast cells grown in a culture medium show........................growth curve.

5. Main cause of population explosion is........................

State true or false :

Coin one word for the following statements :

1.Organism that can tolerate only a narrow range of salinity.

2. Plants that can survive a wide range of temperature.

3. Interaction of two species in which one is benefited while other is neither benefited nor harmed.

4. Number of births during a given period in the population that are added to the initial density.

5. the process of maintaing a constant body temperature.

A few organisms can tolerate and thrive in a wide range of temperature, they are called........................

Majority of organisms are restricted to a narrow range of temperature, such organisms are called ........................ 

The organisms ideally try to maintain the constancy of its internal environment by the process called........................

Mammals from colder climates have shorter ears and limbs to minimize heat loss. This rule is called........................