Chapter 13 - Biodiversity and Conservation

Biodiversity and Conservation explains the variety of life at genetic, species and ecosystem levels, the patterns in which biodiversity is distributed, the causes and consequences of biodiversity loss and the methods used to conserve it. NCERT Class 12 Biology Chapter 13 connects ecological science with one of the central challenges of the modern world: preventing irreversible biological loss.

Teachoo’s category includes detailed notes, NCERT solutions, graph explanations, conservation comparisons, important questions, MCQs and case-based practice for CBSE and NEET.

Levels of biodiversity

Biodiversity exists at several levels:

• Genetic diversity – variation within a species

• Species diversity – variety of species in a region

• Ecological diversity – variety of ecosystems and habitats

Genetic diversity allows populations to contain different alleles and biological characteristics. Species diversity considers the number and relative variety of species. Ecological diversity includes forests, deserts, wetlands, coral reefs, grasslands and other systems.

Students should use the correct level when interpreting examples. Rice strains demonstrate genetic diversity, differences in amphibian richness may demonstrate species diversity, and the variety of Indian habitats demonstrates ecological diversity.

How many species exist?

Only a portion of Earth’s species has been formally described. Estimating total richness is difficult because many organisms occur in poorly studied habitats, many microbes cannot be cultured through conventional methods and tropical regions remain incompletely catalogued.

Animals form a large proportion of recorded species, and insects are extraordinarily diverse. India occupies a relatively small part of global land area but contains a substantial share of recorded species diversity, making it a megadiverse country.

Numerical estimates in NCERT should be treated as textbook figures for examination use, while students should understand that scientific inventories continue to change.

Patterns of biodiversity

Species diversity is not distributed uniformly.

Latitudinal gradient

Species richness generally decreases from tropical regions towards the poles. Proposed explanations include greater evolutionary time in less-disturbed tropical environments, greater climatic stability, greater niche specialisation and higher solar-energy availability.

Species–area relationship

Within a region, species richness increases with the area explored, up to a limit. The relationship can be represented as:

log S = log C + Z log A

S represents species richness, A represents area, Z is the regression slope and C is the intercept. The relationship becomes linear on a logarithmic scale.

Students should interpret what a steeper slope means and distinguish normal regional relationships from comparisons across very large areas.

Importance of biodiversity

Species-rich communities may show greater productivity, stability and resistance to certain disturbances or invasions. Long-term ecological experiments have helped investigate these relationships.

The rivet-popper analogy compares species in an ecosystem to rivets holding an aircraft together. The loss of a few components may not cause immediate collapse, but continued loss weakens the system, and the loss of critical species may have especially large effects.

Biodiversity supports food, fibre, medicines, pollination, nutrient cycling, soil protection, climate regulation, cultural value and scientific knowledge.

Loss of biodiversity

The current rate of species extinction is strongly influenced by human activity. Biodiversity loss may reduce productivity, weaken resistance to environmental change and increase variability in ecosystem processes.

The four major causes are often described as the evil quartet:

• Habitat loss and fragmentation

• Overexploitation

• Alien species invasion

• Co-extinction

Habitat destruction removes living space, while fragmentation divides large habitats into isolated patches. Overexploitation removes organisms faster than populations can recover. Invasive alien species may outcompete, consume or alter native species. Co-extinction occurs when the loss of one species causes the loss of another species that depends on it.

Students should connect each cause with the specific NCERT examples because these are common examination targets.

Why should biodiversity be conserved?

Arguments for conservation can be grouped as:

• Narrowly utilitarian – direct products such as food, fibre and medicines

• Broadly utilitarian – ecosystem services such as pollination and climate regulation

• Ethical – the intrinsic value of other species and responsibility to future generations

These arguments complement one another. Conservation is not only about protecting visibly attractive animals; it also preserves ecological functions, genetic resources and species that may not yet have known economic uses.

In situ conservation

In situ conservation protects species within their natural ecosystems. It can conserve interacting communities, evolutionary processes and multiple levels of biodiversity together.

Methods and areas include:

• Biosphere reserves

• National parks

• Wildlife sanctuaries

• Biodiversity hotspots

• Sacred groves

Biodiversity hotspots combine high endemism with severe habitat threat and are priority regions for conservation.

Ex situ conservation

Ex situ conservation protects threatened organisms or genetic material outside natural habitats. Methods include:

• Zoological parks

• Botanical gardens

• Seed banks

• Tissue culture

• Cryopreservation

• In vitro fertilisation and managed breeding

Ex situ conservation can provide urgent protection, but it does not replace the ecological relationships maintained by a complete natural habitat.

Important diagrams, graphs and examples

• Levels of biodiversity

• Global distribution of recorded taxa

• Latitudinal-diversity pattern

• Species–area graph

• Evil-quartet example table

• In situ versus ex situ conservation

• Indian hotspots, protected areas and sacred-grove examples

Why is this chapter important?

CBSE frequently asks conservation reasoning, cause–effect questions and case-based environmental problems. NEET tests definitions, graphs, equations, extinction examples, hotspots, sacred groves and differences between conservation strategies.

How should students study this chapter?

Use four linked questions: What biodiversity exists? How is it distributed? Why is it being lost? How can it be conserved? Memorise examples only after placing them under the correct concept. Practise the species–area equation and log graph separately.

Frequently Asked Questions

What are the three principal levels of biodiversity?

They are genetic diversity, species diversity and ecological or ecosystem diversity.

Why do tropical regions generally contain more species?

They have had greater evolutionary time, relatively stable conditions, opportunities for niche specialisation and high solar-energy availability.

What does Z represent in the species–area relationship?

Z is the slope of the regression line when species richness and area are plotted on logarithmic scales.

What are the four causes in the evil quartet?

Habitat loss and fragmentation, overexploitation, alien species invasion and co-extinction.

What is the difference between in situ and ex situ conservation?

In situ conservation protects species in their natural ecosystems. Ex situ conservation protects organisms or genetic material outside their natural habitats.

Are zoos sufficient for conserving biodiversity?

No. They can protect selected threatened species, but they cannot preserve complete ecosystems, natural interactions and all evolutionary processes.

Why are sacred groves important?

Traditional protection can preserve habitat fragments and provide refuges for rare, endemic and threatened species.

Is biodiversity valuable only when humans can use it directly?

No. Biodiversity has ecological, cultural, scientific and intrinsic value in addition to direct economic uses.