Organisms and Populations Class 12 Notes

Ecology is the branch of biology which mainly involves the study about the interactions among organisms and their environment. Basically, there are four levels of biological organization.

  • Organisms.
  • Populations.
  • Communities.
  • Biomes.

What is Organism?

An Organism refers to a contiguous living system that lives in an environment and has the capability to adapt and retain certain structure and behavior. It includes fungus, bacteria, plants, animals, and humans.

Major abiotic factors which lead to variation in the physical and chemical conditions of different habitat are temperature, water, light, and soil.

What is Population?

The word Population is defined as a group of individuals or organisms of any species living in a well–defined geographical area, at a specific time with the capability of interbreeding. For example -A population of a deer in a forest.

The attributes of a population are:

  • Birth rate- Total number of young ones born in a period of time.
  • Death rates- Total number of deaths in a period of time.
  • Sex Ratio- Total number of females and males per 1000 individuals.
  • Age pyramid: A plot of age distribution.

Few Important Questions

  • What is adaptation?
  • What is hibernation?
  • List out the Importance of light to plants?
  • Distinguish between Hibernation and Aestivation?
  • What are Biotic and Abiotic Factors of Living Organisms?

Learn more about organisms and populations from the topics given below:


Practise This Question

Regarding assertion and reason, choose the correct statement
Assertion [A]: Plant breeding is now increasingly being carried out by using molecular genetic tools.
Reason [R]: Advancements in genetics, molecular biology and tissue culture are being used today for crop improvement.