In a lake that undergoes thermal stratification, blooms of phytoplankton tend to occur

1. before thermal stratification 

2. after thermal stratification 

3. at the onset of thermal stratification 

4. at the mid-phase of thermal stratification 

Commensalism is an association of two species in which

1. one lives, attached to the other, without harming it

2. both organisms derive benefits from each other

3. one derives its nutrition from the other

4. none of the above

Some students, during a study, caught, marked and released 80 fishes in a pond. Later

100 fishes were caught at random. Among these 40 were found to be marked. What is

the approximate number of fishes in the pond?

1. 50                   

2. 100

3. 200                 

4.  4000

The sphere of living matter together with water, air and soil on the surface of earth is

called

1. atmosphere                       

2. hydrosphere

3. lithosphere                       

4. biosphere

Mutualism is found in 

1. Hermit crab and sea anemone

2. Ox pecker and rhinoceros

3. Zoochlorellae and Hydra

4. E.coli and man.

July 11 is observed as:

1. World population day

2. No tobacco day

3. World environment day

4. World health day

Which one of the following is a matching pair of certain organism(s) and the kind of

association?

1. Shark and sucker fish - predation

2. Algae and fungi in lichens - mutualism

3. Orchids growing on trees - parasitism

4. Cuscuta (dodder) growing in other flowering plants - epiphytism 

The Great Barrier Reef along the east coast of Australia can be categorised as

1. population       

2. community

3. ecosystem       

4. biome

If the Bengal Tiger becomes extinct

1. Hyenas and wolves will become scars

2. The wild areas will be safe for man and domestic animals

3. Its gene pool will be lost forever

4. The population of beautiful animals like deers will get stabilized. 

Which one of the following correctly represents an organism and its ecological niche?

(1) Vallisneria and pond

(2) Desert locust (Schistocerca) and desert

(3) Plant lice (aphids) and leaf

(4) Vultures and dense forest