This set of Class 12 Biology Chapter 13 Multiple Choice Questions & Answers (MCQs) focuses on “Organisms and Populations – Responses to Abiotic Factors – 1”.
1. What is 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 called?
a) Regulators
b) Conformers
c) Migratory
d) Hibernating
View Answer
Explanation: Conformers are the poikilotherms that are the organisms in which body temperature changes with the ambient temperature and in aquatic animals, the osmotic concentration of the body fluid change with that of the ambient water osmotic concentration. Some examples are Insects, lizards, fishes, etc.
2. What organisms are able to maintain homeostasis which ensures a constant body temperature, constant osmotic concentration, etc., are called?
a) Regulators
b) Conformers
c) Migratory
d) Hibernating
View Answer
Explanation: The warm-blooded animals are those who are able to maintain homeostasis by physiological (sometimes behavioral also) means which ensure constant body temperature, constant osmotic concentration, etc. They are also called as regulators. Some examples are mammals, birds, etc.
3. Which of the following organisms are capable of osmoregulation as well as thermoregulation?
a) Cactus
b) All mammals
c) Bryophytes
d) Angiosperms
View Answer
Explanation: All mammals are capable of thermoregulation and osmoregulation. Thermoregulation is the ability to maintain constant body temperature under changing environmental temperatures while osmoregulation is the ability to maintain a constant osmotic concentration of body fluids under high solute concentrations.
4. According to evolutionary biologists why mammals are successful?
a) Expression of thoughts
b) Constant osmotic concentration
c) Right of speech
d) Constant body temperature
View Answer
Explanation: According to evolutionary biologists mammals are successful because they have the ability to maintain constant body temperature. They are warm-blooded animals and also called as endotherms or regulators.
5. For which of the following organisms thermoregulation is energetically expensive?
a) Large animals
b) Elephants
c) Humming birds
d) Man
View Answer
Explanation: Thermoregulation is energetically expensive to humming birds because of their small size. The smaller is the animals; more is the heat loss from the body. Thermoregulation is energetically expensive for small animals and shrews.
6. In which of the following organisms various kinds of thick-walled spores which help them survive unfavorable conditions and germinate on the availability of suitable environment found?
a) Humans
b) Fungi
c) Banyan
d) Mango
View Answer
Explanation: Fungi produce various kinds of thick-walled spores that help to survive unfavorable conditions and germinate on the availability of a suitable environment. Along with these such spores are also produced by bacteria, lower plants, and algae.
7. Which structure in higher plants serves as a means to overcome a period of dormancy, stress and then helps in dispersal?
a) Spores
b) Petals
c) Sepals
d) Seed
View Answer
Explanation: Seeds in higher plants serve as a means to tide over a period of stress and also helping in dispersal. A seed is an embryonic plant, a viable offspring that is enclosed in the protective outer covering.
8. In which state do zooplankton species in lakes and ponds enter under unfavorable conditions?
a) Diapause
b) Aestivation
c) Hibernation
d) Speciation
View Answer
Explanation: The zooplankton species in lakes and ponds enter diapause stage under unfavorable conditions. 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.
9. In which case, annual migration does not occur?
a) Arc Tern
b) Salamander
c) Salmon
d) Siberian Crane
View Answer
Explanation: Migration is the movement of organisms from one geographical location to another. It can be temporary or permanent. The annual migration is a yearly cycle. Among the above-given options, the annual migration is not seen in salamanders.
10. In what form does hibernation occur in animals?
a) Occasional
b) Rhythmic
c) Periodic
d) Intermittent
View Answer
Explanation: Hibernation is a stage of suspended development seen in higher organisms. It occurs in winters. It is mostly seen in endotherms in which all the metabolic activities are slowed down. It is a periodic cycle.
11. Heat loss or heat gain is the function of which area?
a) Body volume
b) Surface area
c) Bodyweight
d) Body size
View Answer
Explanation: The gain or loss of heat occurs through the surface area of the body. It is important for maintaining homeostasis of an organism. It is easily done by mammals as they are thermoregulators.
12. Which alternative do the organisms have, if the stressful external conditions are localized or remain only for a short duration?
a) Conform
b) Regulate
c) Migrate
d) Speciate
View Answer
Explanation: The organisms have an alternative to migrate if the stressful external conditions are localized or remain only for a short duration. Migration is the movement of organisms from one geographical location to another. It can be temporary or permanent.
13. In which state do seeds enter under unfavorable conditions?
a) Diapause
b) Dormancy
c) Hibernation
d) Aestivation
View Answer
Explanation: The seeds enter dormancy under unfavorable conditions. It is an adaptive mechanism of plants which prevents seed from germinating. It helps in delayed germination under favorable conditions.
14. In the below figure what does (B) line indicates?
a) Regulators
b) Partial conformers
c) Scavengers
d) Herbivores
View Answer
Explanation: In the above figure the (B) line indicates regulators. Regulators are the organisms that can maintain constant internal environment with changing outer environmental conditions. Examples of regulators are endotherms such as mammals, birds and few invertebrates.
15. In which state do snails enter under unfavorable conditions?
a) Diapause
b) Hibernation
c) Dormancy
d) Aestivation
View Answer
Explanation: Some snails and fishes enter in aestivation during summers. 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 earthworms, bees, tortoise, crocodile, etc.
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