NCERT Solutions for Class 12 Biology Chapter 13 Organisms and Populations to Study Online or download FREE in PDF form. NCERT Solutions based on latest NCERT Books are also given to download in PDF format. Explore Your Knowledge with the others.
|Chapter 13:||Organisms and Populations|
NCERT Solutions for class 12 Biology Chapter 13
Go back to Class 12 Biology main Page
Solutions for 12 Biology Chapter 13
- View Online NCERT Sols
- Download NCERT Solutions
- NCERT Book Chapter 13
- Revision Notes with Practice Questions for 2019-20 Exams
- NCERT Exemplar Problems for Class 12 Biology
Class 12 Biology Chapter 13 Question Answers
Important Terms on 12 Biology Chapter 13
- Organisms: Organisms form the basic unit of study in ecology.
- Species: Organisms with similar features and the potential to interbreed among themselves and produce fertile offspring, constitute a species.
- Populations: Population is a group of individuals of the same species, inhabiting in a given area. Interspecific competition for basic needs operate among the individuals of population.
- Biological Community: Biological community is constituted by an assemblage of the populations of all different species that live in an area and interact with each other. A biotic community has a distinct species composition and structure.
A branch of science that studies interactions among organisms and their physical environment. Ecology is basically concerned with four levels of biological organisation – Organisms, population, communities and biomes. Ramdeo Mishra is called as the Father of Ecology in India.
- Ecosystem: Is a biological system in nature and composed of a biotic community integrated with its physical (abiotic) environment through the exchange of energy and recycling of the nutrients.
- Biomes: Biomes is a very large unit, constituting of a major vegetation type and associate fauna found is a specified zone. Annual Variations is the intensity, duration of temperature and precipitation account for the formation of major biomes like desert, rain, forest and Tundra.
- Habitat: Habitat is the place where an organism lives.
Major Biomes of India: Tropical rain forest, deciduous forest, desert, sea coast. Regional and local variations within each biome lead to formation of a wide variety of habitats.
- The ecological niche of an organism represents the range of conditions that it can tolerate the resources it utilises and its functional role in the ecological system. Each species occupies a distinct niche and no two species occupy the same niche.
- Biosphere: It is the sum total of all the biomes on the earth.
- Environment: Environment is a sum total of all biotic and abiotic factors that surround and potentially influence an organism. Temperature, water, light and soil are the major abiotic factors.
Most living organisms cannot survive at temperature above 45°C°. How are some microbes able to live in habitats with temperatures exceeding 100°C?
How is diapause different from hibernation?
Hibernation or winter sleep is a resting stage where in animals escape winters (cold) by hiding themselves in their shelters. They escape the winter season by entering a state of inactivity by slowing their metabolism. The phenomenon of hibernation is exhibited by bats, squirrels, and other rodents.
Define phenotypic adaptation. Give one example.
If a marine fish is placed in a fresh water aquarium, will the fish be able to survive? Why or why not?
Name important defence mechanisms in plants against herbivory.
Morphological defence mechanisms:
Cactus leaves (Opuntia) are modified into sharp spines (thorns) to deter herbivores from feeding on them.
Sharp thorns along with leaves are present in Acacia to deter herbivores.
In some plants, the margins of their leaves are spiny or have sharp edges that prevent herbivores from feeding on them.
Chemical defence mechanisms:
All parts of Calotropis weeds contain toxic cardiac glycosides, which can prove to be fatal if ingested by herbivores.
Chemical substances such as nicotine, caffeine, quinine, and opium are produced in plants as a part of self-defence.
What is the ecological principle behind the biological control method of managing with pest insects?
An orchid plant is growing on the branch of mango tree. How do you describe this interaction between the orchid and the mango tree?
Give an example for an endothermic animal.
Define population and community.
A population can be defined as a group of individuals of the same species residing in a particular geographical area at a particular time and functioning as a unit. For example, all human beings living at a particular place at a particular time constitute the population of humans.
A community is defined as a group of individuals of different species, living within a certain geographical area. Such individuals can be similar or dissimilar, but cannot reproduce with the members of other species.
List any three important characteristics of a population and explain
Three important characteristics of a population are:
Birth rate (Natality): It is the ratio of live births in an area to the population of an area. It is expressed as the number of individuals added to the population with respect to the members of the population.
Death rate (Mortality): It is the ratio of deaths in an area to the population of an area. It is expressed as the loss of individuals with respect to the members of the population.
Age Distribution: It is the percentage of individuals of different ages in a given population. At any given time, a population is composed of individuals that are present in various age groups. The age distribution pattern is commonly represented through age pyramids.