Ecosystems: Key Terms (Cambridge (CIE) IGCSE Geography): Revision Note

Ecosystems: Key terms

What are ecosystems?

Abiotic – Non-living parts of an ecosystem, like temperature, sunlight, water, and soil, which affect how organisms live.

Biotic – Living components of an ecosystem, such as animals, plants, fungi, and microorganisms.

Community – Different species living together in the same area and interacting with each other.

Decomposition – The process by which dead organisms are broken down by fungi and bacteria, returning nutrients to the environment.

Ecosystem – A natural system where living organisms interact with each other and with non-living elements in their environment.

Interdependence – When species rely on each other for things like food, shelter, pollination, or seed dispersal.

Organisation levels – The way ecosystems are structured: individual → population → community → ecosystem.

Population – A group of the same species living in a specific area.

Recycling (in ecosystems) – Natural processes like photosynthesis and respiration that move nutrients and gases (like carbon and water) around.

Characteristics of the Antarctic ecosystem

Albedo – A measure of how much sunlight is reflected by a surface. Ice has a high albedo, helping to cool the Earth.

Antarctic Circle – The imaginary line of latitude around the Earth at about 66.5° south of the Equator; marks the region containing Antarctica.

High pressure – A weather condition over Antarctica where cold air sinks, leading to dry and cold conditions with little precipitation.

Insolation – Solar energy received by the Earth. Due to the angle, Antarctica receives less insolation than the equator.

Katabatic winds – Cold, dense air that flows down from the Antarctic interior, often creating strong, unpredictable winds.

Polar desert – A dry, cold desert found in polar regions like Antarctica, where precipitation is very low.

Precipitation – Rain, snow, sleet, or hail. In Antarctica, nearly all precipitation falls as snow.

UV radiation – Ultraviolet rays from the sun. Because the ozone layer is thinner over Antarctica, more UV reaches the surface and can harm living organisms.

Threats to the Antarctic ecosystem

Climate change – Long-term changes in Earth’s climate; in Antarctica, this causes ice melt and warming seas.

Fishing (overfishing) – Removing too many fish (like krill or toothfish), which can harm the food chain and marine biodiversity.

Food web collapse – When key species like krill are removed, leading to population crashes of animals that rely on them, like whales and penguins.

Illegal, Unreported, and Unregulated (IUU) fishing – Fishing that does not follow the rules, making it hard to protect ecosystems.

Invasive species – Plants or animals brought by humans that outcompete or harm native species.

Krill – Tiny shrimp-like creatures that are a keystone species in the Antarctic marine food web.

Microplastics – Tiny plastic particles that can enter food chains and harm organisms.

Ozone layer depletion – The thinning of the ozone layer (caused by CFCs), allowing more UV rays to reach Earth, especially over Antarctica.

Trophic cascade – A chain reaction in a food web caused by changes in one part, usually starting from the bottom or top of the chain.

Managing threats to the Antarctic

Antarctic Treaty System (ATS) – An agreement between countries to protect Antarctica for peace and science, banning military activity and mining.

CCAMLR (Commission for the Conservation of Antarctic Marine Living Resources) – An international body that manages fishing and protects marine life.

IAATO (International Association of Antarctica Tour Operators) – An organisation that sets rules for tourists in Antarctica to reduce environmental damage.

Madrid Protocol (1991) – A law that protects Antarctica’s environment, bans mining, and requires Environmental Impact Assessments (EIAs).

Marine Protected Areas (MPAs) – Special ocean areas where fishing and other human activities are restricted to protect wildlife and ecosystems.

Sustainable management – Using natural resources in a way that meets current needs without damaging the environment for future generations.

Territorial claims – Some countries claim parts of Antarctica, but under the treaty, no nation owns it officially.

Characteristics of the tropical rainforest

Biodiversity – The huge variety of living things in the rainforest. It’s one of the most biodiverse ecosystems on Earth.

Buttress roots – Big roots that stick out from tree trunks to support tall trees in shallow soil.

Canopy – The upper layer of trees that forms a thick roof and blocks sunlight from reaching lower layers.

Diurnal range – The difference in temperature between day and night. In rainforests, it’s small (around 7°C).

Drip tips – Pointed tips on leaves that let rainwater quickly run off to prevent mould or damage.

Emergents – The tallest trees that rise above the canopy, reaching heights of 45–55 metres.

Epiphytes – Plants that grow on tree trunks and branches instead of in soil, absorbing water from the air and rain.

Humidity – The amount of water vapour in the air. In rainforests, it’s always high—usually over 75%.

Insolation – The amount of sunlight reaching the Earth’s surface. Rainforests near the equator receive a lot.

Lianas – Climbing vines that use tree trunks to reach sunlight higher up in the forest.

Nutrient cycle – How nutrients move quickly between plants, soil, and decomposers due to the warm, wet climate.

Precipitation – Rainfall. Rainforests get over 2,000 mm of rain each year.

Shrub layer – The lower forest layer made up of small bushes and plants that grow up to 3–4 metres tall.

Trade winds – Winds that blow into the equator region, bringing warm, moist air and causing rainfall.

Threats to the tropical rainforest

Agriculture – Farming is a major cause of deforestation. It includes commercial crops (like palm oil) and small-scale slash-and-burn farming.

Biodiversity loss – When deforestation destroys habitats, many plants and animals die out or disappear.

Climate change – Cutting trees adds more carbon dioxide to the air, which worsens global warming.

Deforestation – Clearing forests by cutting down trees. Often done for farming, logging, roads, or mining.

Evapotranspiration – Water lost to the air through evaporation and from plants. Deforestation reduces this, affecting rainfall.

Illegal logging – Cutting down trees without permission, especially in protected forests.

Leaching – Rain washes nutrients out of the soil when tree cover is removed, making soil infertile.

Mining – Extracting minerals like tin or iron ore from the forest. It often causes large-scale forest loss.

Monoculture – Growing only one type of crop, like palm oil, which reduces biodiversity and soil quality.

Palm oil plantations – Huge farms that grow palm trees. These often replace biodiverse forests.

Slash and burn – A method where trees are cut and burned to clear land for farming. It’s damaging and risky.

Soil erosion – The loss of soil due to wind and rain, made worse when trees are gone and roots no longer hold the soil in place.

Subsistence farming – Small-scale farming for local needs, which still contributes to forest loss when land is cleared.

Rainforest case study: Malaysian rainforest

Batek and Orang Asli – Indigenous groups in Malaysia whose homes and way of life are at risk due to rainforest destruction.

Bakun Dam – A huge dam built in Malaysia that flooded rainforest areas to make hydroelectric power.

Biosphere Reserve – Protected areas that balance conservation with human activity. Penang Hill is a good example.

CITES – An international agreement that protects endangered plants and animals from being traded.

Debt-for-nature swap – When countries agree to protect the rainforest in exchange for some of their national debt being cancelled.

Ecotourism – Low-impact tourism that helps protect the environment and supports local communities.

Gombizau and Bavanggazo – Villages involved in rainforest-friendly activities like honey farming and tourism.

MTCC (Malaysian Timber Certification Council) – Certifies that timber companies are using sustainable practices.

Reforestation – Planting new trees to replace those that have been cut down.

Selective logging – Only cutting certain trees to reduce harm to the forest.

Sustainable management – Using rainforest resources in a way that keeps them available for the future.

Temiar – Another Indigenous community affected by rainforest development and deforestation.