Wildlife: Animal Species and Their Role in Ecosystems

The animals of the ecosystem are the consumers that keep nature working. They pollinate flowers, spread seeds, control prey numbers, clean up dead matter and even build new habitats. Without animals, food chains would break and plants, soil and water would all suffer. This guide explains each role with examples.

This page is the main guide to wildlife on this site. It covers the roles animals play, keystone species, the IUCN Red List, rare animals of India and the world, and how wildlife is protected. Each section links to a detailed article for deeper study.

What are the animals of the ecosystem?

An ecosystem is a community of living things linked to each other and to their non-living surroundings. NCERT’s earlier Class 8 book, Resources and Development, calls this web of interdependent life a life-supporting system. Plants, animals and microbes all depend on one another inside it.

Wildlife means the wild animals of an area. That chapter says wildlife includes animals, birds and insects, and also the life forms that live in water. Fish, frogs, snakes, butterflies, eagles and elephants all count.

Animals are consumers. A consumer is a living thing that gets its energy by eating other organisms. Plants are producers, because they make food from sunlight. Energy passes from plants to plant-eaters and then to meat-eaters. This chain of feeding is called a food chain. Many linked food chains form a food web.

NCERT’s Class 12 Biology chapter “Ecosystem” adds two useful terms. Animals that feed on plants are primary consumers. Animals that eat those plant-eaters are secondary consumers. Its simple example of a grazing food chain runs from grass to goat to man. A second kind, the detritus food chain, starts with dead organic matter instead of living plants.

Scientists usually sort consumers by what they eat:

• Herbivores eat plants. Deer, elephants, grasshoppers and rabbits are herbivores.
• Carnivores eat other animals. Tigers, owls and sharks are carnivores.
• Omnivores eat both plants and animals. Bears and many crows do this.
• Scavengers eat animals that are already dead. In India, vultures are the classic scavengers.
• Detritivores eat dead plant and animal matter. Earthworms, millipedes and termites belong here.

What roles do animals play in an ecosystem?

Every animal has a job, often called its ecological role. The earlier Class 8 textbook makes this point clearly. It notes that animals big or small are all integral to keeping the ecosystem in balance. The main roles are explained below.

Pollinators

Pollination is the transfer of pollen from one flower to another so that seeds can form. Bees, butterflies, moths, some birds and some bats carry pollen as they feed on nectar. National Geographic describes bees as mutualists. Both partners gain: the bee gets food, and the flower gets fertilised. Many fruits and crops depend on these visits.

Seed dispersers

Seed dispersal means carrying seeds away from the parent plant. Birds, monkeys, bats and elephants eat fruit and drop the seeds elsewhere in their dung. Squirrels bury nuts and forget some of them. Seeds carried in this way can sprout far from the parent tree. This helps forests spread and regrow after damage.

Predators

A predator is an animal that hunts and eats other animals, called its prey. Predators stop prey from becoming too many. National Geographic gives the example of tiger sharks in Australia. Where the sharks patrolled, sea turtles grazed more widely and did not wipe out the sea grass beds. Predators also tend to remove old or sick animals, leaving healthier prey.

Herbivores and grazers

Grazing animals eat grass and leaves. They keep plants from growing too thick, and their dung returns nutrients to the soil. Large herbivores also open up paths and clearings in forests. They form a major food supply for predators.

Scavengers, detritivores and decomposers

Three different groups handle dead matter, and students often mix them up.

Scavengers are animals that eat the bodies of animals that are already dead. The vulture is India’s best example. NCERT’s earlier Class 8 book calls it a scavenger and a vital cleanser of the environment, because it feeds on dead livestock. Without scavengers, carcasses would lie rotting for much longer.

Detritivores are animals that eat detritus, the dead leaves, bark, flowers, dead animal remains and dung lying on the ground. Earthworms, millipedes, termites and some other insects are detritivores. NCERT’s Class 12 Biology book explains that detritivores such as the earthworm break detritus into smaller pieces. This first step is called fragmentation.

Decomposers finish the job. NCERT’s Class 12 book says they are mainly fungi and bacteria. They release enzymes that break dead material into simple inorganic substances, such as carbon dioxide, water and nutrients. Plants then take up these nutrients again. So decomposers are microbes and fungi, not birds or large animals.

The same chapter lists the steps of decomposition: fragmentation, leaching, catabolism, humification and mineralisation. Humus, a dark substance formed on the way, rots very slowly and stores nutrients in the soil. Warm, moist conditions speed decomposition, while cold and a lack of oxygen slow it down.

India’s vultures show how easily a scavenger can be lost. The old Class 8 book explains that they died of kidney failure soon after feeding on livestock treated with diclofenac, a painkiller. A Rajya Sabha reply reported by PIB in December 2024 records that the Drugs Controller General of India banned the use, sale and manufacture of veterinary diclofenac in August 2006. The same reply says two drugs found safe to vultures, meloxicam and tolfenamic acid, are now widely used.

Ecosystem engineers

An ecosystem engineer is an organism that creates, changes or destroys a habitat. The beaver of North America is the classic example. National Geographic explains that beaver dams change river flow and create wetlands. Many other plants and animals then live in those wetlands.

Animals and people

Wildlife also serves people directly. The Class 8 chapter lists milk, meat, hides and wool, along with honey from bees. Bees also help in the pollination of flowers, so one insect feeds both people and plants.

Roles of animals at a glance

What is a keystone species?

A keystone species is one that has a large effect on its ecosystem compared with its numbers, or abundance. National Geographic’s glossary puts it simply: an organism with a major influence on the way its ecosystem works. The name comes from the keystone at the top of a stone arch. Remove that one stone and the arch falls down.

National Geographic notes that ecologist Robert Paine coined the term in the 1960s. He studied starfish on the rocky Pacific coast of Washington state. The starfish ate mussels and kept their numbers down. When Paine removed the starfish, the mussels spread and crowded out other species. The variety of life there dropped sharply.

Keystone species can be predators, ecosystem engineers or mutualists. Even plants can play the role. Mangroves hold coastlines together and shelter young fish among their roots. Scientists still debate which species deserve the label, since it is not a formal category.

Keystone species: meaning and examples

Our full article on keystone species and their examples covers predators, engineers and mutualists with cases from India and abroad. It also explains what happens when a keystone animal disappears.

Which groups of animals are studied most in school?

School syllabuses often begin with birds and with animals of extreme climates. Birds are easy to watch, and polar animals show clearly how bodies adapt to a habitat.

Characteristics of birds

Birds are warm-blooded animals with feathers, a beak without teeth and wings. They lay hard-shelled eggs. Light, hollow bones help most of them fly. Read the full list of features that make a bird for exam-ready points.

Famous bird species around the world

Some birds are famous for their size, colour or skills. Examples include the ostrich, the bald eagle, the peacock and the emperor penguin. Our article on famous bird species around the world introduces many of them.

Migratory birds

Migration is the regular seasonal journey of animals between two places. Many birds fly to warmer areas in winter to find food, then return to cooler regions to breed. India’s wetlands receive many winter visitors. Learn why and how they travel in migratory birds: meaning and examples.

Birds of the Amazon rainforest

The Amazon rainforest of South America is one of the richest places for birds on Earth. Macaws, toucans, harpy eagles and hoatzins live in its warm, wet forests. Explore them in our guide to the birds of the Amazon rainforest.

Arctic animals

Arctic animals survive long, freezing winters. Many have thick fur, a layer of fat called blubber, or white coats that blend with snow. The polar bear, Arctic fox and walrus are common examples. See Arctic animals and their adaptations for a full list.

What are the IUCN Red List categories?

The IUCN Red List is a global record of how close species are to extinction. IUCN stands for the International Union for Conservation of Nature. Its current rules are the IUCN Red List Categories and Criteria, Version 3.1 (approved 2000; second edition 2012). The IUCN Council gave that approval on 9 February 2000.

The system has nine categories. Three of them, Critically Endangered, Endangered and Vulnerable, are grouped together as threatened. A species is placed in one of these three when it meets any of five criteria, labelled A to E.

Note that Data Deficient is not a category of threat. It simply means more study is needed. A species listed as Data Deficient may still turn out to be threatened later.

IUCN Red List categories in detail

Each category has its own rules and examples. Our article on the IUCN Red List categories from Extinct to Least Concern explains the five criteria in simple language.

Vulnerable species

A vulnerable species faces a high risk of dying out in the wild. It is the lowest of the three threatened levels. See vulnerable species: meaning and examples for animals in this group.

Endangered animals

Endangered animals face a very high risk of extinction. Habitat loss and hunting are the usual causes. Browse names and facts in endangered animals: pictures, names and facts.

Critically endangered animals

This is the highest threat level before extinction in the wild. Species here often survive in tiny, scattered groups. Our list of critically endangered animals explains what pushed each one to the edge.

Extinct animals

Extinction means a species has vanished for ever. The dodo is a famous example from the past. Learn about recently lost species and the reasons in extinct animals and why they disappeared.

Which rare animals of India should students know?

India is rich in wildlife, and several of its animals are now rare. Our guide to biodiversity in India explains how many species the country holds.

Endangered animals in India

Many Indian animals are under pressure from shrinking habitats and poaching. Tigers, rhinos, elephants and many birds need protection. See our list of endangered animals in India for a state-by-state guide.

Great Indian Bustard

The Great Indian Bustard is a large, heavy bird of dry, open grasslands. NCERT’s earlier Class 8 book names it among the animals that it is illegal to kill in India. Read about its habitat and sanctuaries in Great Indian Bustard: habitat and conservation.

Forest owlet

The forest owlet is a small owl of the dry forests of central India. It was once believed lost and was later found again. Learn about its habitat in forest owlet: India’s rare owl.

Nicobar megapode

The Nicobar megapode lives only on the Nicobar Islands. Instead of sitting on its eggs, it buries them in large mounds of soil and leaves. Heat from the mound warms the eggs. Find out more in Nicobar megapode: habitat and nesting.

Snow leopard

The snow leopard is a big cat of the high Himalaya and other Asian mountains. Its thick, grey coat and long tail suit cold, rocky slopes. The same Class 8 chapter lists it among animals poached for illegal trade. Read snow leopard: habitat and range in India.

Which rare animals of other countries are well known?

Some rare animals outside India are famous because of strong recovery efforts. Their stories show both the danger and the hope in conservation.

California condor

The California condor is a huge vulture of western North America. Like India’s vultures, it is a scavenger that feeds on carcasses. It came close to dying out in the last century. Captive breeding and careful releases have brought birds back to the wild. See California condor: habitat, diet and recovery.

Northern bald ibis

The northern bald ibis is a dark, bald-headed bird that nests on cliffs in dry, open country. Its wild range has shrunk a great deal over the centuries. Read northern bald ibis: habitat and conservation for its story.

Mountain lion

The mountain lion, also called the cougar or puma, is a large wild cat of the Americas. It is a top predator that hunts mainly deer. Learn more in mountain lion facts: habitat and diet.

There is also a wider lesson in these stories. When one species disappears, others feel the effect. Fewer pollinators mean fewer seeds. Fewer predators can let grazers multiply. Fewer scavengers leave carcasses rotting for longer.

How is wildlife in India threatened and protected?

The earlier Class 8 book names poaching for hides, skins, horns and feathers as a major concern, along with habitat loss. India’s main wildlife law is the Wild Life (Protection) Act, 1972. PIB reports that the Wild Life (Protection) Amendment Act, 2022 came into force on 1 April 2023. Trade across borders falls under CITES, which, according to NCERT, protects roughly 5,000 animal and 28,000 plant species. Threats, laws and protected areas are covered in full in our guide to biodiversity: meaning, types and threats.

Sources

• IUCN — IUCN Red List Categories and Criteria: Version 3.1, Second edition (2012)
• National Geographic Education — Keystone Species
• NCERT (earlier Class 8 book) — Resources and Development, Ch. 2 on land, soil, water, vegetation and wildlife
• NCERT Class 12 — Biology, Chapter 12: Ecosystem
• PIB — Rajya Sabha reply on vulture conservation and diclofenac (5 December 2024)
• PIB — Wild Life (Protection) Amendment Act, 2022: commencement and captive-breeding licences