Biology Today — December 2017

Total Marks : 160 Time Taken : 40 Min.

T

his specially designed column enables students to self analyse their

extent of understanding of specified chapters. Give yourself four

marks for correct answer and deduct one mark for wrong answer.

Self check table given at the end will help you to check your

readiness.

-8 Practice Problems

Class XII

• Ecosystem

1. Which of the following help in maintaining homeostasis or
   balance of nature?
   (a) Carrying capacity of the environment
   (b) Capacity of the ecosystem for recycling of wastes
   (c) Feedback system (d) All of these


2. Amount of living biomass present in a unit area of an
   ecosystem at a given time is referred to as
   (a) standing state (b) standing crop
   (c) trophic structure (d) net primary productivity.


3. The species that colonise newly distributed habitats and
   coexist with superiorly more competitive species are called
   (a) fugitive species (b) pioneer species
   (c) guild (d) climax species.


4. Match column I with column II and select the correct option.
   Column I Column II
   A. Reducers (i) Heterotrophs
   B. Phagotrophs (ii) Herbivores
   C. Key industry animals (iii) Autotrophs
   D. Transducers (iv) Microconsumers
   (a) A-(iv); B-(i); C-(ii); D-(iii)
   (b) A-(iii); B-(ii); C-(i); D-(iv)
   (c) A-(iv); B-(i); C-(iii); D-(ii)
   (d) A-(i); B-(iii); C-(iv); D-(ii)


5. Select the correct difference between standing crop and
   standing state.
   Standing crop Standing state
   (a) It is the amount of inorganic
   nutrients present in an ecosystem.

It is the amount of biomass

present in an ecosystem.

(b) It represents part of non-living

matter.

It represents entire living

matter.

(c) It cannot be circulated

between living and non-living

components.

It can be circulated.

(d) It is regularly depleted and

replenished.

It is continuously synthe-

sised and consumed.

6. Select the wrong statement regarding energy flow in an
   ecosystem.
   (a) Energy flows in one direction only.
   (b) About 1-5% of the energy reaching the ground is
   converted by the green plants into chemical energy.
   (c) Energy requirement for maintenance of body gradually
   decreases in successive trophic levels.
   (d) Only 10% of the gross productivity of producers is
   entrapped by herbivores for their body building.


7. Which of the following is correctly matched?
   (a) Frog – Primary consumer
   (b) Productivity – Kcal/m^2 /yr
   (c) Tertiary consumers – Slime moulds
   (d) Temperate ecosystem – Ocean


8. The rate of synthesis of organic matter by consumers is
   (a) net primary productivity
   (b) gross primary productivity
   (c) standing state
   (d) secondary productivity.


9. Pyramid of biomass in a pond ecosystem is
   (a) always upright
   (b) inverted
   (c) spindle shaped
   (d) sometimes inverted and sometimes upright.


10. Refer to the given figure showing pyramid of number in a
    certain habitat. Identify the habitat and select the correct
    option.

A

B

C

(a) A-Grass; B-Rabbit; C-Fox

(b) A-Phytoplankton; B-Small fish; C-Large fish

(c) A-Tree; B-Birds; C-Hawk

(d) A-Tree; B-Birds; C-Parasites