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Unlock This CourseAn ecosystem is basically a community of living things all interacting with each other AND with their non-living surroundings. Think of it like a giant web pull one thread and everything else is affected. Ecosystems can be tiny (like a rock pool) or enormous (like the Amazon rainforest). What makes something an ecosystem is that all the parts are connected and dependent on each other.
Key Definitions:
The iGCSE loves asking you to identify biotic and abiotic factors in a given ecosystem, or explain how a change in one component affects others. Master this topic and you'll find the rest of Environmental Management much easier it all builds from here!
Biotic components are everything that is alive, or was once alive, in an ecosystem. They are split into groups based on how they get their energy. Understanding these groups helps you explain how energy and nutrients flow through an ecosystem.
Producers make their own food using sunlight through photosynthesis. They are the foundation of almost every food chain on Earth. Without producers, nothing else could survive.
Example: In a tropical rainforest, giant trees like the Brazil nut tree are producers, capturing sunlight in the canopy layer.
Consumers cannot make their own food they have to eat other organisms. They are split into different levels depending on what they eat.
Decomposers are one of the most important biotic components, but they often get forgotten! They break down dead organic matter dead plants, dead animals and animal waste and return the nutrients back into the soil. Without decomposers, nutrients would be locked up in dead material forever and producers would run out of the minerals they need to grow.
Microscopic decomposers found in soil, water and even inside other organisms. They are incredibly efficient at breaking down organic matter into simple minerals.
Mushrooms and moulds are fungi. They release enzymes that break down tough materials like wood and leaves. Fungi are especially important in forest ecosystems.
Slightly larger decomposers like earthworms, woodlice and millipedes. They physically break up dead material into smaller pieces, making it easier for bacteria and fungi to finish the job.
The Amazon rainforest in South America is the world's largest tropical rainforest, covering around 5.5 million km². Its biotic components include over 40,000 plant species (producers), 1,300 bird species, 3,000 fish species and millions of insect species (consumers at various levels). The forest floor is teeming with decomposers fungi and bacteria that rapidly break down fallen leaves and dead animals in the warm, humid conditions. This rapid decomposition is why the soil in rainforests is actually quite thin and nutrient-poor nutrients are quickly taken back up by plant roots!
Light, water and temperature are abiotic factors
Abiotic components are the physical and chemical features of an environment. They might not be alive, but they completely control which organisms can survive in an ecosystem. Change one abiotic factor and you can wipe out entire species or allow new ones to move in. This is why abiotic factors are so important in Environmental Management.
The main abiotic components to know:
The Sahara Desert in North Africa is the world's largest hot desert, covering about 9 million km². Its abiotic conditions are extreme: temperatures can reach 50°C during the day and drop below freezing at night. Annual rainfall is less than 25mm in most areas. The soil is sandy or rocky with very few nutrients. These harsh abiotic conditions mean biotic components are limited only highly adapted organisms like camels, fennec foxes, date palms and cacti-like succulents can survive. This shows perfectly how abiotic factors control which biotic components exist in an ecosystem.
The real magic of ecosystems is in how biotic and abiotic components constantly affect each other. This is not a one-way street living things also change their non-living environment. Here are some key interactions to understand:
Tree roots break up rock and add organic matter when leaves decompose, improving soil quality. Legume plants (like clover) add nitrogen to soil through nitrogen-fixing bacteria in their roots a biotic process changing an abiotic factor.
A change in rainfall patterns can completely change which species dominate an area. The gradual drying of the Sahel region in Africa has reduced vegetation cover, which then reduces rainfall further a feedback loop between abiotic and biotic components.
Elephants knock down trees, creating open grassland. Beavers build dams, creating wetland habitats. Earthworms improve soil drainage and nutrient content. Biotic components actively reshape abiotic conditions.
The Serengeti in East Africa is one of the world's most famous ecosystems. Abiotic factors include a distinct wet season (November–May) and dry season, with annual rainfall of 500–1,200mm and temperatures averaging 20–25°C. These abiotic conditions support vast grasslands (biotic producers), which in turn support huge herds of wildebeest (around 1.5 million), zebras and gazelles (primary consumers). Lions, cheetahs and hyenas (secondary/tertiary consumers) feed on these herds. Decomposers like vultures and bacteria return nutrients to the soil. The annual wildebeest migration is directly triggered by abiotic changes the movement of rainfall across the ecosystem.
Different ecosystems have very different combinations of biotic and abiotic components. Here's a quick comparison of three major ecosystem types to help you see the patterns:
Abiotic: High rainfall (2,000mm+/year), high temperatures (25–30°C), high humidity, nutrient-poor soils
Biotic: Extremely high biodiversity thousands of plant, animal and insect species. Dense canopy, shrub layer and forest floor communities.
Abiotic: Very low temperatures (-20°C in winter), low rainfall (less than 250mm/year), permafrost (permanently frozen ground), strong winds
Biotic: Low biodiversity mosses, lichens, sedges, Arctic foxes, reindeer, lemmings, migratory birds in summer only.
Abiotic: Warm, clear, shallow saltwater (26–29°C), high salinity, high light penetration, low nutrient levels
Biotic: Extremely high biodiversity coral polyps (producers via symbiotic algae), thousands of fish species, sea turtles, sharks, crustaceans.
❌ Don't say soil is biotic soil itself is abiotic, but the organisms living IN the soil (bacteria, worms) are biotic.
❌ Don't confuse habitat and ecosystem a habitat is where an organism lives; an ecosystem includes all the interactions too.
❌ Don't forget decomposers they are biotic components and are absolutely essential for nutrient cycling.
✅ Do remember: if it's alive (or was alive), it's biotic. If it was never alive, it's abiotic.
Let's pull everything together before your quiz. Make sure you can confidently explain each of these points: