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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


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


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


Geometric representation  of age structure is a characteristic of

  • Biotic community

  • Population

  • Landscape

  • Landscape


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