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Organisms And Populations

Question
CBSEENBI12001835
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(a) List the different attributes that a population has and not an individual organism.

(b) What is population density ? Explain any three different ways the population density can be measured, with the help of an example each.

Solution

(a) Following are the attributes that a population has but an individual organism does not have:

  • Birth rate: per capita births. It represents the increase in number with respect to the population.
  • Death rate: per capita deaths. It represents the decrease in number with respect to the population.
  • Sex ratio: Ratio of number of males to females in a given  population.
  • Age distribution: A population at any given time is composed of individuals of different ages.

(b) Population density means number of individuals present per unit area. Population density can be measured by determining the population size. The different methods to study population size are as follows:

(1) Indirect method:  In this method the population density is measured without actually counting or seeing the organism. For examples – the tiger consensus in our national park and tiger reserves are often based on the pug marks and fecal pellets of the tiger.
Example: The number of Parthenium plants in a given area can be measured using the quadrat method.

(2) Direct observation: It involves the counting of organisms in the given area.
Example: In order to determine the number of bacteria growing in a Petri dish, their colonies are counted.

(3)Relative densities: When the population is too large to be counted then relative density is taken into account . For example: The number of fishes caught per trap gives the measure of their total density in a given water body.

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........................ 

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