Organisms and Populations

Explain the exponential and logistic models of population growth with the help of their equations and graphs. What does the carrying capacity (K) represent?

How do desert plants such as Opuntia adapt to conserve water? State any two adaptations.

Explain the following population attributes with an example each: (i) birth rate, (ii) sex ratio, (iii) age pyramid.

Distinguish between commensalism, mutualism and parasitism, giving one example of each.

Explain the following interspecific interactions with one example each: (i) predation, (ii) competition, (iii) mutualism, (iv) parasitism, (v) amensalism. Indicate the (+/−/0) effect on each species.

What is meant by 'allen's rule'? How does it help mammals in cold climates conserve heat?

State the competitive exclusion principle proposed by Gause. Explain resource partitioning as a mechanism that allows competing species to coexist.

Why is percent cover or biomass a more meaningful measure of population density than the number of individuals for a plant like a banyan tree?

How many marks is Organisms and Populations worth in the Class 12 board exam?

Around 6 marks of the 70-mark CBSE Biology theory paper, based on the official unit-wise weightage. Population growth curves + species interactions table.

Is Organisms and Populations easy or hard?

It's rated medium — a moderate-difficulty chapter in Class 12 Biology. Most students need about 3 hours to cover it well.

What should I focus on in Organisms and Populations?

Going by the board papers themselves, the recurring areas are Population Growth, Adaptations, Population Attributes, Population Interactions, Species Interactions — that's where the marks actually sit.

What questions come from Organisms and Populations in board exams?

Between 2019–2024, CBSE board papers asked questions from this chapter on Population Growth, Adaptations, Population Attributes, Population Interactions — 1- to 5-mark questions.