CBSE Class 12 Biology Organisms and Populations Key Points

CBSE Class 12 Biology Organisms and Populations Key Points. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

ORGANISMS AND POPULATIONS

(KEY POINTS)

Important Questions for NCERT Class 12 Biology Organisms and Populations

Ques. Certain characteristic demographic features of developing countries are
(a) high fertility, low or rapidly falling mortality rate, rapid population growth and a very young age distribution
(b) high fertility, high density, rapidly rising mortality rate and a very young age distribution
(c) high infant mortality, low fertility, uneven population growth and a very young age distribution
(d) high mortality, high density, uneven population growth and a very old age distribution. 

Answer: A

Ques. What is a keystone species?
(a) A species which makes up only a small proportion of the total biomass of a community, yet has a huge impact on the community’s organization and survival.
(b) A common species that has plenty of biomass, yet has a fairly low impact on the community’s organization.
(c) A rare species that has minimal impact on the biomass and on other species in the community
(d) A dominant species that constitutes a large proportion of the biomass and which affects many other species. 

Answer: A

Ques. The maximum growth rate occurs in
(a) stationary phase
(b) senescent phase
(c) lag phase
(d) exponential phase. 

Answer: D

Ques. Mycorrhiza is an example of
(a) symbiotic relationship
(b) ectoparasitism
(c) endoparasitism
(d) decomposers. 

Answer: A

Ques. Two opposite forces operate in the growth and development of every population. One of them is related to the ability to reproduce at a given rate. The force opposite to it is called
(a) fecundity
(b) environmental resistances
(c) biotic control
(d) mortality. 

Answer: B

Ques. Which type of association is found in between entomophilous flower and pollinating agent?
(a) Mutualism (b) Commensalism
(c) Co-operation (d) Co-evolution 

Answer: D

Ques. Two different species cannot live for long duration in the same niche or habitat. This law is
(a) Allen’s law
(b) Gause’s hypothesis
(c) Dollo’s rule
(d) Weismann’s theory. 

Answer: B

Ques. In a population, unrestricted reproductive capacity is called as
(a) biotic potential (b) fertility rate
(c) carrying capacity (d) birth rate. 

Answer: A

Ques. In which of the following plant sunken stomata are found?
(a) Nerium (b) Hydrilla
(c) Mango (d) Guava 

Answer: A

Ques. An interesting modification of flower shape for insect pollination occurs in some orchids in which a male insect mistakes the pattern on the orchid flower for the female species and tries to copulate with it, thereby pollinating the flower. This phenomenon is called
(a) pseudopollination (b) pseudoparthenocarpy
(c) mimicry (d) pseudocopulation.

Answer: D

Ques. The abundance of a species population, within its habitat, is called
(a) relative density (b) regional density
(c) absolute density (d) niche density. 

Answer: D

Ques. Which one of the following pairs is correctly matched?
(a) Parasitism - intraspecific relationship
(b) Uricotelism - aquatic habitat
(c) Excessive perspiration - xeric adaptation
(d) Streamlined body - aquatic adaptation 

Answer: D

Ques. Mycorrhiza exhibits the phenomenon of
(a) parasitism (b) symbiosis
(c) antagonism (d) endemism. 

Answer: B

Ques. Association of animals when both partners are benefitted
(a) colony (b) mutualism
(c) commensalism (d) ammensalism. 

Answer: B

Ques. Which one is true?
(a) Commensalism when none of the interacting populations affect each other.
(b) Symbiosis when the interaction is useful to both the populations.
(c) Symbiosis when neither populations affects each other.
(d) Commensalism when the interaction is useful to both the populations. 

Answer: B

Ques. The relation between algae and fungi in a lichen is
(a) symbiosis (b) parasitism
(c) commenalism (d) protocooperation.

Answer: A

Ques. A mutually beneficial association necessary for survival of both partners is
(a) mutualism/symbiosis
(b) commensalism
(c) amensalism
(d) both (a) and (b). 

Answer: A

Ques. Competition for light, nutrients and space is most severe between
(a) closely related organism growing in different niches
(b) closely related organisms growing in the same area/niche
(c) distantly related organisms growing in the same habitat
(d) distantly related organisms growing in different niches.

Answer: B

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