Organisms & Its Environment

1 Mark Questions

1. Give an example of an organism that enters 'diapause' and why? [Delhi 2014]

Ans. Many zooplanktons in lakes and ponds enter diapause. They enter diapause to escape unfavourable environmental conditions and to delay the overall development.

2.Mention how do bears escape from stressful time in winter. [Delhi 2013c] Ans. Bears escape from stressful time in winter by going into hibernation

1. Write the basis on which an organism occupies a space in its community/natural surroundings.[All India 2013]

Ans. An organism occupies individual or species level in its community. This level is occupied on the basis of ecological level of organisation or ecological hierarchy. Individual-> Population - > Biotic community -> Biome

4. Why are some organisms called as eurythermals and some other as stenohaline? [Foreign 2011]

Ans. Organisms, which can tolerate and thrive in a wide range of temperatures are called as eurythermal while organisms, which can tolerate and thrive in a narrow range of salinities are stenohaline

1. Why are green plants not found beyond a certain depth in the ocean? [HOTS; Delhi 2011]

Ans. Beyond a certain depth, green plants are not found, because light is unavailable in that zone.

6.Mention any two activities of animals, which get cues from diurnal and seasonal variations in light intensity, [Delhi 2011 c]

Ans. The two activities of animals which get cues from diurnal and seasonal variations in light intensity are:

1. Timing their foraging
2. Migratory activities
3. Reproduction (any two)

1. How do animals like fishs and snails avoid summer related unfavourable conditions? [Delhi 2010]

Ans. Fish migrate and snails go into aestivation or summer sleep to avoid summer-related problems.

1. How do prickles help cactus survive in desert? Give two methods. [All India 2010 C]

Ans. The two methods by which prickles help cactus survive in desert are:

1. By reducing and altering outer surface to reduce evaporation of water.
2. By providing defense against grazing animals.

9. Which one of the two, stenothermals or eurythermals shows wide range of distribution on earth and why?[HOTS; Delhi 2008]

Ans. Eurythermals show a wide range of distribution on earth, as they can tolerate and thrive in a wide range of temperatures

10. When and why do some animals like snails go into aestivation? [All India 2008]

Ans. During stressful conditions of the habitat and inability to migrate, animals like snails undergo aestivation and protect themselves

11. Why is the polar region not a suitable habitat for tiny humming birds? [HOTS; All India 2008]

Ans. Humming birds have a larger surface area compared to body volume. They tend to lose body heat very fast, when it is cold outside. Due to this, they need to spend more energy to generate body heat. Hence, polar region being a cold habitat is not suitable for tiny hummingbirds

12. When and why do some animals go into hibernation? [Foreign 2008]

Ans. When unfavourable conditions are for a short time and if the animals could not migrate, they undergo hibernation to avoid stressful winter conditions.

13.List any two physiological responses that help you to gradually get acclimatised to high altitudes when you go from the plains. [Delhi 2008 C]

Ans. The physiological condition or responses in order to get accl imatised to high attitudes are:

1. To compensate low oxygen, the production of red blood cells is increased.
2. High haemoglobin content and its decreased binding capacity.
3. Faster breathing rate (any two).

14.Define homeostasis. [All India 2008 C]

Ans. The process to maintain the constancy of internal environment of the body, despite varying external environmental conditions is called homeostasis

15. When and why do some animals like frogs hibernate? [Delhi 2008]

Ans. When unfavourable conditions are for a short time period and animals are unable to migrate, they hibernate to avoid the stres winter.

16.Between amphibians and birds, which will be stable to cope with global warming? Give reason.[HOTS; All India 2008]

Ans. Birds will be stable to cope with global warming because they can tolerate a wide range of temperatures (eurythermals).