NCERT Exemplar solutions for Biology [English] Class 12 chapter 13 - Organisms and Populations [Latest edition]

Autecology is ______.

Ecotone is ______.

Biosphere is ______.

Ecological niche is ______.

According to Allen’s Rule, the mammals from colder climates have ______.

Salt concentration (Salinity) of the sea measured in parts per thousand is ______.

Formation of tropical forests needs mean annual temperature and mean annual precipitation as ______.

Which of the following forest plants controls the light conditions at the ground?

What will happen to a well-growing herbaceous plant in the forest if it is transplanted outside the forest in a park?

If a population of 50 Paramoecium present in a pool increases to 150 after an hour, what would be the growth rate of population?

What would be the per cent growth or birth rate per individual per hour for the same population mentioned in the previous question (Question 10)?

A population has more young individuals compared to the older individuals. What would be the status of the population after some years?

What parameters are used for tiger census in our country’s national parks and sanctuaries?

Which of the following would necessarily decrease the density of a population in a given habitat?

A protozoan reproduces by binary fission. What will be the number of protozoans in its population after six generations?

In 2005, for each of the 14 million people present in a country, 0.028 were born and 0.008 died during the year. Using exponential equation, the number of people present in 2015 is predicted as ______.

Amensalism is an association between two species where ______.

Lichens are association of ______.

Which of the following is a partial root parasite?

Which one of the following organisms reproduces sexually only once in its lifetime?

Species that can tolerate narrow range of temperature are called ______.

What are Eurythermic species?

Species that can tolerate wide range of salinity are called ______.

Define stenohaline species.

What is the interaction between two species called?

What is commensalism?

Name the association in which one species produces poisonous substance or a change in environmental conditions that is harmful to another species.

What is mycorrhiza?

Emergent land plants that can tolerate the salinities of the sea are called.

Why do high altitude areas have brighter sunlight and lower temperatures as compared to the plains?

What is homeostasis?

Define aestivation.

What is diapause and its significance?

What would be the growth rate pattern, when the resources are unlimited?

What are the organisms that feed on plant sap and other plant parts called?

What is high altitude sickness? Write its symptoms.

What is Commensalism? Explain it with suitable example.

Define ectoparasite and endoparasite and give suitable examples.

What is brood parasitism? Explain with the help of an example.

Why are coral reefs not found in the regions from west Bengal to Andhra Pradesh but are found in Tamil Nadu and on the east coast of India?

If a fresh water fish is placed in an aquarium containing sea water, will the fish be able to survive? Explain giving reasons.

Why do all the fresh water organisms have contractile vacuoles whereas majority of marine organisms lack them?

Define heliophytes and sciophytes. Name a plant from your locality that is either heliophyte or sciophyte.

Why do submerged plants receive weaker illumination than exposed floating plants in a lake?

In a sea shore, the benthic animals live in sandy, muddy and rocky substrata and accordingly developed the following adaptations.

Burrowing

Find the suitable substratum against adaptation.

In a sea shore, the benthic animals live in sandy, muddy and rocky substrata and accordingly developed the following adaptations.

Building cubes

Find the suitable substratum against adaptation.

In a sea shore, the benthic animals live in sandy, muddy and rocky substrata and accordingly developed the following adaptations.

Holdfasts/peduncle

Find the suitable substratum against adaptation.

Categorise the following plants into hydrophytes, halophytes, mesophytes and xerophytes. Give reasons for your answers.

Salvinia

Categorise the following plants into hydrophytes, halophytes, mesophytes and xerophytes. Give reasons for your answers.

Opuntia

Categorise the following plants into hydrophytes, halophytes, mesophytes and xerophytes. Give reasons for your answers.

Rhizophora

Categorise the following plants into hydrophytes, halophytes, mesophytes and xerophytes. Give reasons for your answers.

Mangifera

In a pond, we see plants which are free-floating; rooted–submerged; rooted emergent; rooted with floating leaves; Write the type of plant against the following examples.

The density of a population in a habitat per unit area is measured in different units. Write the unit of measurement against the following:

Bacteria

The density of a population in a habitat per unit area is measured in different units. Write the unit of measurement against the following:

Banyan

The density of a population in a habitat per unit area is measured in different units. Write the unit of measurement against the following:

Deer

The density of a population in a habitat per unit area is measured in different units. Write the unit of measurement against the following:

Fish

Label the three tiers 1, 2, 3 given in the above age pyramid.

What type of population growth is represented by the above age pyramid?

In an association of two animal species, one is a termite which feeds on wood and the other is a protozoan Trichonympha present in the gut of the termite. What type of association they establish?

Lianas are vascular plants rooted in the ground and maintain erectness of their stem by making use of other trees for support. They do not maintain direct relation with those trees. Discuss the type of association the lianas have with the trees.

Give the scientific names of any two microorganisms inhabiting the human intestine.

What is a tree line?

Define ‘zero population growth rate’. Draw a age pyramid for the same.

List any four characters that are employed in human population census.

Give one example for the following type.

Migratory animal

Give one example for the following type.

Camouflaged animal

Give one example for the following type.

Predator animal

Give one example for the following type.

Biological control agent

Give one example for the following type.

Phytophagous animal

Give one example for the following type.

Chemical defense agent

Fill in the blanks

Observe the set of 4 figures A, B, C and D and, answer the following questions

1. Which one of the figures shows mutualism?
2. What kind of association is shown in D?
3. Name the organisms and the association in C.
4. What role is the insect performing in B?

Fig. (A)	Fig. (B)
Fig. (C)	Fig. (D)

Comment on the following figures: 1, 2 and 3:

A, B, C. D, G, P, Q, R, S are species

An individual and a population has certain characteristics. Name these attributes with definitions.

The following diagrams are the age pyramids of different populations. Comment on the status of these populations.

Comment on the growth curve given below.

A population of Paramoecium caudatum was grown in a culture medium. After 5 days the culture medium became overcrowed with Paramoeium and had depleted nutrients. What will happen to the population and what type of growth curve will the population attain? Draw the growth curve.

Discuss the various types of positive interactions between species.

In an aquarium two herbivorous species of fish are living together and feeding on phytoplanktons. As per the Gause’s Principle, one of the species is to be eliminated in due course of time, but both are surviving well in the aquarium. Give possible reasons.

While living in and on the host species, the animal parasite has evolved certain adaptations. Describe these adaptations with examples.

Do you agree that regional and local variations exist within each biome? Substantiate your answer with suitable example.

Which element is responsible for causing soil salinity? At what concentration does the soil become saline?

Does light factor affect the distribution of organisms? Write a brief note giving suitable examples of either plants or animals.

Give one example for the following:

Eurythermal plant species

Give one example for the following:

A hot water spring organism

Give one example for the following:

An organism seen in deep ocean trenches

Give one example for the following:

An organism seen in compost pit

Give one example for the following:

A parasitic angiosperm

Give one example for the following:

A stenothermal plant species

Give one example for the following:

Soil organism

Give one example for the following:

A benthic animal

Give one example for the following:

Antifreeze compound seen in antarctic fish

Give one example for the following:

An organism which can conform