Class 9 Social Science · Chapter 11 NotesLife on Earth

A biome is a large natural region of the world where similar climatic conditions support particular types of plants and animals. The word comes from bios, meaning life, and the suffix -ome, which denotes a group of biological constituents. Icy tundras, hot deserts, green forests and vast grasslands are all biomes. A useful comparison is that a biome is like a broad environmental region, while an ecosystem is like a neighbourhood within it, where plants, animals and non-living things interact closely. Temperature, precipitation patterns, dominant plant species and the growth forms of vegetation decide which biome develops in a place. Together, the world's biomes form the living world of the planet and help maintain the balance of nature.

• Biomea large region with similar climate and characteristic plant and animal life
• Ecosystema smaller unit within a biome where living and non-living things interact
• Key controlstemperature, precipitation, dominant plants and vegetation growth forms

Land-based biomes are grouped into forests, grasslands, deserts and tundra according to climate. Forest biomes are warm, wet and rich in life at every level. Tropical rainforests lie near the Equator, between 23.5° N and 23.5° S, and are found in the Amazon Basin, the Congo Basin, parts of Southeast Asia, Central America, India's Andaman & Nicobar Islands and the North-Eastern states. They are called a gene bank because they preserve unique genetic material. Grasslands are open areas with mainly grass and few trees; temperate grasslands such as the prairies and steppes have fertile soil, while tropical savannas have scattered trees and large animals. Deserts are the driest biomes, hot like the Sahara or cold like the Gobi, and the Rann of Kutch is one of the world's largest salt deserts. The tundra is the coldest biome, with permafrost, mosses, lichens, small shrubs and animals such as reindeer, arctic foxes and polar bears.

• Rainforest layersemergent layer, upper canopy, understory or lower canopy, forest floor
• Temperate grasslandsprairies (North America) and steppes (Asia)
• Tropical grasslandssavannas, as in Africa
• Permafrostsoil frozen almost year-round, which prevents tree growth

Aquatic biomes cover about three-fourths of the Earth's surface and are divided into freshwater and marine biomes. Freshwater biomes include rivers, lakes, ponds and wetlands, which are crucial for agriculture, drinking water and species such as fish, frogs and insects. Marine biomes include oceans, seas and coral reefs; they are rich in biodiversity, influence climate by storing and distributing heat, and support whales, dolphins, fish and plankton as well as the livelihoods of millions of people. A biome pyramid is a graphical representation of the relationship between organisms in a biome in terms of energy, number or biomass. Producers such as plants and algae form the base and capture solar energy through photosynthesis. Above them come herbivores, then carnivores, then top predators. As we move up, the number of organisms, biomass and available energy decrease because energy is lost as heat at each trophic level during metabolic processes.

• Freshwater biomerivers, lakes, ponds, wetlands
• Marine biomeoceans, seas, coral reefs
• Biome pyramid orderproducers → herbivores (primary consumers) → carnivores (secondary consumers) → top predators (tertiary consumers)

Biodiversity is the variety of life on Earth, including plants, animals, microorganisms and the ecosystems they inhabit. It covers not only the number of species but also genetic differences within species and the variety of habitats and ecological processes that sustain life. Biodiversity is unevenly distributed, so geography matters for conservation. In India, the Himalaya, the Western Ghats, North-East India and the Andaman & Nicobar Islands are hotspots rich in unique species found nowhere else. Conservation strategies must suit the geographical setting: mangrove protection along coasts, afforestation in mountains, protected areas such as national parks, wildlife sanctuaries, biosphere reserves and World Heritage Sites, and wildlife corridors that allow animal movement and gene flow. Human-environment interaction also matters, since sustainable practices differ by region, such as terrace farming in hills and agroforestry in plains.

• Biodiversityvariety of species, genetic differences within species, and variety of habitats and ecological processes
• Indian hotspotsHimalaya, Western Ghats, North-East India, Andaman & Nicobar Islands
• Protected areasnational parks, wildlife sanctuaries, biosphere reserves, World Heritage Sites

Forests support rural and tribal communities with food, fuel, fodder, medicine, shelter, timber, bamboo and firewood. Non-timber forest products such as honey, fruits, nuts, resins and medicinal plants meet daily needs and earn income. Communities including the Gonds and Bhils perform rituals to honour forest deities before collecting resources, reflecting respect for nature. Ecotourism means responsible travel to forested areas where tourists enjoy nature while contributing to its conservation; it stresses minimal environmental impact, respect for local communities and learning about ecosystems. Thenmala in Kollam district, Keralam, is India's first planned ecotourism destination, developed jointly by the Tourism, Forest and Irrigation Departments; its name means Honey Hill and it lies within the Western Ghats, a UNESCO World Heritage Site. A Geographical Indication (GI) tag identifies a product as originating from a specific place whose quality or reputation is linked to that origin. Examples include Ramban Sulai Honey, Tezpur Litchi, Channapatna Toys, Kandhamal Haldi, Erode Manjal, Nilgiri Tea, Tripura Queen Pineapple and Khasi Mandarin.

• NTFP examplestendu leaves, mahua flowers, honey, lac, bamboo
• Ecotourismresponsible travel with minimal impact that supports conservation and local people
• GI tagan intellectual property right linking a product's quality or reputation to its geographic origin

Forest dwellers depend on forests for household needs, culture and livelihood. Women play a vital role in collecting and managing forest resources and in passing on traditional knowledge. Forest communities act as knowledge holders, income earners, guardians of cultural traditions and protectors of forests; the Bishnoi Movement in Rajasthan led by Amrita Devi influenced the Chipko Movement in Uttarakhand, where village women hugged trees to prevent deforestation. Yet forest dwellers face difficulties: poor access to healthcare, education and clean water; health problems for women from fuelwood fumes; restrictions on forest use; deforestation; human-wildlife conflict with elephants, monkeys and wild boars; natural disasters such as floods and landslides; and discrimination. The Scheduled Tribes and Other Traditional Forest Dwellers (Recognition of Forest Rights) Act, 2006, or Forest Rights Act, recognises rights over forest land and resources, allows collection of minor forest produce and grants ownership of small cultivated patches. Other measures include tribal welfare schemes, Joint Forest Management, PESA, DAJGUA and PM JANMAN. Mendha Lekha in Gadchiroli, Maharashtra, inhabited mainly by the Gond tribe, became the first village in India to gain rights over its forest under the Act; it follows Mawa Nate Mawa Raj (our village, our rule) and protects about 1,800 hectares of forest through Gram Sabha decisions.

• Forest Rights Act, 2006recognises traditional rights over forest land and resources
• JFMJoint Forest Management, where local communities help protect forests and share produce
• Mendha Lekhacommunity forest management through collective Gram Sabha decisions

Ecological commons are natural resources such as forests, rivers, lakes, grazing lands, air and biodiversity that are shared by a community and used collectively for its survival and well-being. Unlike private property, they are not owned by any single individual but belong to the community and are often managed through traditional rules. People have depended on commons for food, water, fuel, fodder and medicinal plants, but population growth, industrial use and privatisation are shrinking or degrading many of them. In Bihar, the Bihar Fish Jalkar Management Act, 2006, introduced community-led management of water bodies after large landowners had marginalised fishing communities. For centuries, regions with seasonal rainfall managed water collectively: the Chandella and Bundela kings built around 8,000 tanks in Bundelkhand between 800 and 1200 CE; keres were built in Karnataka, eri tanks in Tamil Nadu, chevuru tanks in Andhra Pradesh and Odisha, ahar pynes in Bihar, and the Gond kings funded katas, three-sided reservoirs, in the Gondwana region. Official estimates place more than 15 lakh functional tanks in India today.

• Ecological commonsshared natural resources managed collectively
• Kataa three-sided reservoir funded by the Gond kings
• Bihar Fish Jalkar Management Act, 2006legal support for community-led fishery management