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Organism And Population Class 12 Important Questions And Answers MCQ PDF

Organism And Population Class 12

Organism And Population Class 12:- The ecology is the study of the relationship of the living organisms with the abiotic and biotic components of their environment.This is concerned with the four levels of biological organisation and the organism.

Organism And Population Class 12
Organism And Population Class 12

Organism And Population Class 12 – Very Short Answer Type Questions

Q.1. Write the name of the species which can withstand a close range of temperature

A.1. Stenothermal Entities can withstand a close range of temperature.

Q.2. Define Eurythermal organisms.

A.2. They are the organisms which exhibit a wide range of the temperature tolerance.

Q.3. What do we call the species which can endure the wide extent of salinity?

A.3. Euryhaline species can endure the wide extent of salinity.

Q.4. Interaction between the two species is called as?

A.4. Interaction between the two species called as Interspecies interaction

Q.5. Define stenohaline species.

A.5. They are the species which exhibit the narrow range of the salinity tolerance.

Q.6. Define commensalism.

A.6. This is a type of the interaction where the one species is benefitted while the other one remains unaffected.

Q.7. Write the relationship where the species generates the poisonous particles which harm the other species.

A.7. In Parasitism 

Q.8. What is Mycorrhiza?

A.8. This is a symbiotic interaction between the root of the higher plants and the fungus that gets its nourishment from its symbiont that in turn assists in the absorption process of the higher plants.

Q.9. Write the name of the emergent land plants which can sustain the salinities of the sea.

A.9. The Halophytes

Q.10. The Higher or the raised altitude areas have the blazing sunlight and the lower temperatures as opposed to the plains. Why give the reason?

A.10. This is due to the being less distant from the particle free air and the sun. Likewise, the lower atmospheric pressure causes the low temperatures that are increased in the plains.

Q.11. What is homeostasis?

A.11. Maintaining the constant internal temperature despite the differing external environmental state is called as the homeostasis.

Organism And Population Class 12 Quiz

Q.12. Define aestivation.

A.12. To avoid the excessive desiccation and heat in the summer, some of the organisms switch to a behavioural adjustment that causes them to slow down their metabolic activities. It is called as the aestivation or the summer sleep.

Q.13. What is diapause? Write its significance.

A.13. The Diapause is the phase of the pendulous growth that is adopted by the certain entities in the ponds and the lakes to sustain and survive unfriendly conditions.

Q.14. How will be the growth rate pattern be affected by the infinite resources?

A.14. It will be the exponential.

Q.15. Write the name of the living organisms that sustains parts of the plant and plant sap.

A.15. Phytophagous sustains part of the plant and plant sap.

Q.16. Explain the high altitude sickness. What are their symptoms?

A.16. This is caused when the people visit to high altitude regions, which have less oxygen concentration so that he reacts by showing the symptoms like headache, nausea, palpitations etc.

Q.17. Make a list as an example for the commensalism.

A.17. The Barnacle growing on the back of the blue whale is an example of commensalism.

Q.18. Describe with the suitable examples of the ectoparasites and the endoparasites.

A.18. The Ectoparasites nourishes the external surface of the host . For example, The ticks on dogs whereas the endoparasites dwell in the body of the host at the various locations such as the lungs, kidney etc, for example, the gut parasites such as tapeworm.

Q.19. Describe about the brood parasitism with an example.

A.19. It is when the parasites lay eggs on the nest of host. For example, The Cuckoo lays its eggs in the cell of the host .

Q.20. Why do the plants in the arid regions have sunken stomata?

A.20. The Sunken stomata minimize the water loss by transpiration. That is why, the plants in the arid regions have the sunken stomata.

Organism And Population Class 12 – Short Answer Type Questions

Q.1. Why the coral reefs found on the eastern coast of the India and the Tamil Nadu and not found in the Andhra Pradesh and the West Bengal?

A.1. The Conditions such as the optimal temperatures, along with the less siltation condition and the high salinity favour the growth of the coral reefs.

Q.2. Will a fish replaced from the freshwater source to an aquarium with the sea water be able to survive? Give the reasons.

A.2. No, as the body is adapted to survive in a close range of the salinity and cannot survive in the high salinity of the seawater.

Organism And Population Class 12

Q.3. Why do the marine entities lack the contractile vacuoles as compared to the freshwater entities?

A.3. The Contractile vacuoles aid in the osmoregulation since the fresh water entities are the hypertonic allowing water to diffuse in the cell constantly resulting in the accumulation in the contractile vacuoles which propels the extra water out of the cell frequently thereby maintaining the constancy in the internal environment. In the marine entities, due to the high salinity, the contractile vacuoles are not required.

Q.4. Define heliophytes and sciophytes. Write an example for each of them.

A.4. The Heliophytes are the plants which grow well in the bright sunlight whereas the plants which require the low intensity of the light are the sciophytes or the shade loving plants.

Q.5. The Submerged plants receive the lesser illumination as compared to the exposed floating plants in the lake. Give its reasons.

A.5. This is due to all colours of the apparent segments of the spectrum of the light not seep in the depths of the water.

Q.6. Make a list of these plants based on the different types – free-floating, rooted-submerged, rooted-emergent, rooted with floating leaves.

Plant name Type







Plant name Type

Hydrilla Submerged

Nymphaea rooted with floating leaves

Lemna free-floating

Vallisneria rooted-submerged

Typha rooted-emergent

Q.7. Make a list of the unit of the density of population in a habitat per unit area.

a) Bacteria b) Banyan c)Deer d)Fish

A.7. a) Bacteria – Volume/number unit b) Banyan – Biomass/area/region c) Deer – Number/area d) Fish – Weight/area

Q.8.Write the name of the kind of the interaction built by a termite feeding on the wood and the other is a protozoan Trichonympha residing in the gut of the termite.

A.8.The termite nourishes and they accommodates for the Trichonympha to exist. This is present in the gut and they digests the wood ingested by the termite. The termite dies if the protozoan is absent as it would be unable for the termite to digest it. Therefore it is mutualism.

Q.9. Make a list of the scientific names of the 2 microbes harbouring in the human intestine.

A.9. The Lactobacillus and the Escherichia Coli.

Organism And Population Class 12

Q.11. What is a tree line?

A.11. This is the point of the habitat where the trees are fit for the growing. Due to the various environmental conditions such as the higher altitudes, the colder temperatures or the deficiency of the moisture, trees are not found beyond this line, even if it is found, display stunted the growth.

Q.12. Define a zero population growth rate.

A.12. This is when the pre-reproductive age group entities are correspondingly fewer and the post-reproductive and the reproductive phases are in an equivalent stage.

Q.13. Write the four attributes applied in the human population census.

A.13. They are following:

The Sex ratio

The Age distribution

The Natality and mortality

The Population growth.

Q.14. Write the difference between the ectotherms and the endotherms.

A.14. The difference between the ectotherms and the endotherms is as follows:


The Endotherms are the

The Cold-blooded animals.

The Warm-blooded animals

The Temperature varies with respect to the surrounding temperature.

It Maintains a constant body temperature.

For eg., Fish, amphibian, reptiles.

For eg., mammals and birds

Organism And Population Class 12 – Long Answer Type Questions

Q.1. Make the list of an individual and the population and explain the characteristics of an individual and the population.

A.1. Following are the characteristics:

The Gene pool

The Dispersal biotic potential

The Distribution pattern

The dispersion or intra-distribution patterns is called as the process of the division of the individuals of the population within the boundaries of the geography. Due to the emigration or the immigration, an individual tends to get dispersed at the some point in their life in the population. The Emigration is when the group of the individuals in a population switch to the another habitat during the a particular period of the time. The Immigration, on the other hand, is the totality of the same species which have entered the habitat from elsewhere during  the particular interval of time. The Biotic potential, under the ideal environmental conditions, is the inherent potential of the population to the increase in its size. In a the reproducing population, the gene pool is called  as, all the genotypes of all the individuals.

Organism And Population Class 12

Q.2. Explain the following growth curve


A.2. This is a logistic growth curve that is presumed to be more realistic as an the ecosystem does not provide the infinite resources in a habitat (‘r’ denotes carrying capacity). Where the ‘N’ represents the population density that is the number of the species of  the population per unit area is for the expected increase of the intrinsic rate.

Q.3.Explain the different kinds of the positive interactions which  take place in between different species.

A.3. Following are the three types of interspecific interactions:

The Positive or beneficial interaction:

The Negative interaction

The Neutral interaction

Q.4. Explain the adaptations of the animal parasites while the living in and on the host species with the suitable examples.

A.4. Listed below are the adaptations:

The lack of the unwanted sense organs as the seen in mites, fleas and lice. (Absence of wings)

They possess the  suckers to stick onto the host as observed in leeches and tapeworms

The absence of the digestive system as seen in the tapeworm.

The Increased reproductive capacity. For Example: Roundworms reproduces massive progeny

Organism And Population Class 12

Q.6.Write the name of the element which causes salinity in the soil. Describe the state at which the soil turns saline.

A.6. The salt content in the soil because of the improper irrigation that causes the soil salinity. The Salination is the process which refers to enhancing the salt content. Following are the causes of soil salinity:

The Improper irrigation procedures from a the salt-laden water table cause salt concentration to the increase. Due to the evaporation, this gets stored.

The Fertilization of crop. The Fertilizers contain the potassium which forms a the salt-sylvite that occurs naturally.

This salinity the degenerates vegetation and the soil. The normal pH value ranges from the 2.2-9.7, anything above this range causes the soil to get the deteriorated by the salinity.

Organism And Population Class 12

Q.7. The distribution of organisms affected by light? Describe briefly with the suitable examples of the animals or plants.

A.7. For the photosynthesis, of plants require the sunlight. Therefore the light affects the plant distribution. For Example: Many shrubs and the herbs grow in the forests vegetation and they are adapted to undertake the photosynthesis under low light states, hence they are observed in the shady areas under canopied, the tall trees. The Areas having adequate sunlight the generally have big sized trees. To the procure maximum the sunlight, several the plants grow vertically. These can be the characterized by the presence of small leaves compared to the same species of the same age with the better exposure to sunlight. 

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