This set of Biology Exam Questions and Answers for Class 12 focuses on “Organisms and Populations – Responses to Abiotic Factors – 2”.
1. What is diapause?
a) Shedding of leaves
b) Stage of suspended development
c) Aging in mammals
d) Programmed cell death
Explanation: Diapause is a stage of suspended development. It is like hibernation in higher animals except it is used to avoid hot, dry summers in tropical areas. It is done by the zooplankton species in lakes and ponds under unfavorable conditions.
2. What is the suspension of metabolic activities during summer called?
Explanation: The suspension of metabolic activities during summer is called aestivation. It is prolonged dormancy and is also known as summer sleep. It helps in maintaining body temperature and avoids water loss in mostly cold-blooded animals such as snails, bees, tortoise, crocodile, etc.
3. What is maintaining the constancy of the internal environment called?
Explanation: Homeostasis is maintaining the constancy of the internal environment according to changing the external environment. It is a self-regulating process done by all organisms.
4. What are birds and mammals?
a) Thermoconfirmers and osmoconfirmers
b) Thermoconfirmers and osmoregulators
c) Thermoregulators and cold-blooded animals
d) Thermoregulators and osmoregulators
Explanation: All mammals and birds are thermoregulators and osmoregulators. These are the organisms the organism in which body temperature and the osmotic concentration of the body fluid changes with the ambient temperature and change with that of the ambient water osmotic concentration respectively.
5. What are most of the invertebrates?
Explanation: Thermoconformers are the organisms whose body temperature changes according to changing environmental temperatures. They do not carry out thermoregulation. They are usually cold-blooded animals.
6. Why small animals are rarely found in polar regions?
a) Less loss of heat
b) Their surface area and body mass ratio is high
c) Their surface area and body mass ratio is low
d) Their surface area is small
Explanation: The small animals are rarely found in polar regions because they have a high surface area and body mass ratio. This is to more loss of heat and thus regulating their body temperature becomes difficult.
7. The Siberian cranes migrate to which National Park in India?
a) Kaziranga National Park, Assam
b) Silent Valley National Park, Kerala
c) Chikla Lake Bird Sanctuary, Orissa
d) Keoladeo National Park, Rajasthan
Explanation: Many birds from Siberia migrate to Keoladeo National Park, Bharatpur, Rajasthan. These Siberian cranes usually migrate during the onset of the autumn season and then return to arctic tundra for breeding around the end of April and the beginning of May.
8. Which rule states that in a cold climate, mammals possess shorter ears and limbs to minimize the heat loss?
a) Bergman’s rule
b) Blackman’s rule
c) Allen’s rule
d) Lindeman’s rule
Explanation: Allen’s rule is an eco-geographical rule which states that in a cold climate, mammals possess shorter ears and limbs to minimize heat loss. It was stated by Joel Asaph Allen in 1877. It is a form of an adaptation done for survival in colder regions.
9. What do the desert lizards do when their body temperature drops?
a) They burrow in the sand
b) They hide in the soil
c) They move in a shady place
d) They bask in the sun
Explanation: The desert lizards are cold-blooded animals that cannot regulate their body temperature. They bask in the sun when their body temperature drops to regulate their temperature to perform various metabolic activities.
10. Which process do some snails and fishes undergo to prevent themselves from desiccation?
11. For which of the following organisms thermoregulation is energetically expensive?
a) Large-sized aquatic animals
b) Small-sized terrestrial animals
c) Large-sized terrestrial animals
d) Medium-sized terrestrial animals
Explanation: Thermoregulation is energetically expensive for small-sized terrestrial animals because of their small size. The smaller is the animals; more is the heat loss from the body. The examples of small animals are humming birds, shrews, etc.
12. In which of the following, organisms completely stop their metabolic activities?
Explanation: The organisms stop their metabolic activities completely after death. In all others such as hibernation, aestivation, diapause the metabolic activities of organisms are slowed temporarily to avoid the loss of energy.
Sanfoundry Global Education & Learning Series – Biology – Class 12.
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