Geometric representation  of age structure is a characteristic of

  • Biotic community

  • Population

  • Landscape

  • Landscape


B.

Population

Geometric representation of age structure is a characteristic of population. In most-populations, individuals are of different ages. The proportion of individual in each age group is called age structure of that population.

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Consider the following statements concerning food chains
A) removal of 80% tigers from an area resulted in greatly increased growth of vegetation
B) removal of most of the carnivores resulted in an increased population of deers
C) length of food chains is generally limited to 3-4 trophic levels due to energy loss
D) the length of food chains may vary from 2 to 8 trophic level
Which two of the above statements are correct? 

  • B and C

  • C and D

  • A and D

  • A and D


A.

B and C

The series of organisms eating one and being eaten by other is called food chain. A simple food chain consists of producers, herbivores and carnivores. The length of the food chain is generally limited to 3-4 trophic levels due to energy loss. In grazing food chain the producers (ie, plants) are eaten by herbivores are eaten by carnivores. Therefore, the removal of most of the carnivores resulted in an increased population of deer.

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What is true about the isolated small tribal populations? 

  • There is a decline in population as boys marry girls only from their own tribe

  • Hereditary diseases like colour blindness do not spread in the isolated population

  • Wrestlers who develop strong body muscles in their lifetime pass this character on their progeny

  • Wrestlers who develop strong body muscles in their lifetime pass this character on their progeny


B.

Hereditary diseases like colour blindness do not spread in the isolated population

The population can be defined as a group or assemblage of organisms of the same species that live at a given time in a particular area. In human beings a dominant X- linked gene is necessary for the formation of colour sensitive cells the cones, in the retina of the eye. The recessive form of this gene is incapable of producing the colour sensitive cones and homozygous recessive female and hemizygous recessive males are unable to distinguish between these two colours. As the isolated population do not have any hereditary diseases like colour blindness, so they do not spread accordingly.

According to the theory of inheritance of acquired characters of Lamarck the Wrestlers, who develop strong body muscles in their lifetime, must pass this character onto their progeny, but this is not found true.
Gene pool is defined as the sum total of genes present in a Mendelian population. The study of gene pools tells us the total number of genes, their kinds and variety present in the population.

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The table below gives the populations (in thousand) of ten species (A-J) in four areas (a-d) consisting of the number of habitats given within  brackets aginst each. study the table and answer the question which follows: 

Area and number of habitats

Species and their populations (in thousands) in the area

A

B

C

D

E

F

G

H

I

J

a(11)

b(11)

c(13)

d(12)

23

1.2

0.52

6.0

-

3.1

1.1

9.0

-

10.3

10.2

-

0.62

-

1.5

3.0

-

8.2

1.1

11.2

11.3

0.9

0.48

2.4

1.4

4.2

0.8

8.4

2.2

4.1

3.2

10.2

11.1

4.8

0.4

3.3

0.8

7.3

11.3

2.1

 Which area out of a to d shows maximum species diversity?

  • b

  • c

  • d

  • d


C.

d

Habitat is the place where an organism live. The population has been defined as a collective group of organisms of the same species occupying a particular place at a particular time. In the given table area d has maximum species diversity, as there are 10 species (A-J) reside in 12 habitats, while in area c the 10 species reside in 13 habitats so, exhibit less diversity than area d.

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The population of an insect species shows an explosive increase in numbers during rainy season followed by its disappearance at the end of the season. What does this show?

  • S-shaped or sigmoid growth of this insect

  • The food plants mature and die at the end of the rainy season

  • Its population growth curve is of J-type

  • Its population growth curve is of J-type


C.

Its population growth curve is of J-type

Its population growth curve is J-shaped in which density increases rapidly in exponential fashion and then stops abruptly as environmental resistance or another limiting factor becomes effective more or less suddenly.

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