Exploring Ecosystems & Biomes

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• Geography
• Upper Secondary (Key Stage 4)
• GCSE

Exploring Ecosystems & Biomes

Learning Objectives

At the end of the lesson you will be able to define ecosystems, identify key global biomes, describe food chains and nutrient cycles, and explain why ecosystems are important.

What is an Ecosystem?

An ecosystem is a natural environment and includes the flora (plants) and fauna (animals) that live and interact within that environment. Flora, fauna and bacteria are the biotic or living components of the ecosystem. Ecosystems are dependent on the following abiotic or non-living components:

• climate - the temperature and amount of rainfall are very important for determining what species can survive in the ecosystem

• soil - the soil type is important as this provides nutrients that will support different plants

• water - the amount of water available in an ecosystem will determine what plants and animals can be supported

The biotic parts of the ecosystem, which include bacteria, flora and fauna, have a complex relationship with the abiotic components - changing one will lead to a change in the other.

Changes to ecosystems

Ecosystems are very sensitive to change. The living and non-living components of the ecosystem can be altered by either natural factors or human management.

Changes to the ecosystem caused by natural factors include:

• drought

• flood

• fire

• disease

Changes to the ecosystem caused by human management include:

• introducing more fish (fish stocking)

• altering the drainage of the land which may influence the amount of water

• changing the pH level of the water

• altering the nutrient levels of the water if fertilisers are leached into the water resulting in eutrophication

Any of these changes can have a negative impact on the ecosystem and could result in the collapse of a food chain.

Ecosystem Examples

Examples include forests, ponds, and grasslands—each with unique living things and conditions.

Key Parts of Ecosystems

Ecosystems have biotic (living) parts like plants and animals, and abiotic (non-living) parts like sunlight, water, and soil.

🌿 Biotic (Living) Components

These are all the living organisms in an ecosystem. They depend on each other for food, shelter, and survival.

Main groups:

• Producers – Plants and algae that make their own food using sunlight (photosynthesis)

• Consumers – Animals that eat plants or other animals

• Decomposers – Fungi and bacteria that break down dead matter and return nutrients to the soil

Examples

• Trees, grasses, flowers

• Fish, birds, insects, mammals

• Mushrooms, microbes in soil and water

Role in the ecosystem
Biotic components create food chains and food webs, transfer energy, and recycle nutrients through feeding and decomposition.

☀️ Abiotic (Non-Living) Components

These are the physical and chemical factors that shape the environment and determine what can live there.

Key factors:

• Sunlight (main energy source)

• Water (rivers, rain, humidity)

• Air (oxygen, carbon dioxide)

• Soil and minerals

• Temperature, rainfall, wind, and climate

Role in the ecosystem
Abiotic factors control where organisms can live, how they grow, and how the ecosystem functions.

How They Work Together

• Plants use sunlight, water, air, and soil to grow.

• Animals eat plants or other animals for energy.

• Decomposers break down waste and dead organisms, returning nutrients to the soil.

• Those nutrients help plants grow again.

In short:
Abiotic parts provide the conditions and resources.
Biotic parts use those resources to create a living, connected system.

What is a Biome?

A biome is a very large geographical region defined by its climate (temperature and rainfall) and the typical plants and animals that live there.

Key idea: Biomes are bigger than ecosystems.
A biome contains many ecosystems that share similar climate and living conditions.

How climate shapes a biome

• Temperature and rainfall decide what plants can grow.

• Plants determine what animals can survive there.

• This creates a recognisable pattern of life across a huge area.

Major Global Biomes

Global biomes include tropical rainforests, deserts, tundra, grasslands, temperate forests, and savannas. These are vast regions of the Earth that are defined mainly by their climate, especially patterns of temperature and rainfall. The climate in each biome determines the type of vegetation that can grow there, and this in turn affects the animals that can survive. For example, hot and wet conditions in tropical rainforests support dense tree growth and very high biodiversity, while extremely dry deserts can only support drought-resistant plants and specially adapted animals. In cold tundra regions, low temperatures and frozen ground limit plant growth to mosses and grasses, whereas grasslands and savannas are dominated by grasses due to seasonal rainfall and grazing animals. Temperate forests, with moderate rainfall and seasonal changes, support deciduous trees and a wide variety of wildlife. Although these biomes occur in different parts of the world, each one shows a clear relationship between climate, plants, and animals across a very large area.

Tropical Rainforest

Key traits

• Hot and wet all year; very high rainfall

• Layered structure: canopy, understory, forest floor

• Thin soils; nutrients recycled rapidly

Living things

• Tall evergreen trees, vines, epiphytes

• Monkeys, parrots, insects, frogs, big cats, microbes

Cool interactions

• Intense competition for light → tall trees and climbing plants

• Fast decomposition → nutrients quickly reused by plants

Desert Biome

Key traits

• Very low rainfall; extreme temperatures

• Sandy or rocky soils with little organic matter

• Water is the main limiting factor

Living things

• Cacti, shrubs, drought-resistant plants

• Lizards, snakes, camels, insects, small mammals

Cool interactions

• Plants store water; animals are often nocturnal to avoid heat

• Food chains are short due to low plant growth

Tundra Biome

Key traits

• Very cold; little rainfall

• Permafrost (permanently frozen ground)

• Very short growing season

Living things

• Mosses, lichens, grasses, small shrubs

• Arctic foxes, reindeer, birds, insects

Cool interactions

• Plants grow low to resist wind and cold

• Migratory animals arrive in summer to breed

Grassland Ecosystem (Temperate)

Key traits

• Moderate rainfall; not enough for many trees

• Frequent fires and grazing

• Deep, fertile soils

Living things

• Grasses, wildflowers

• Grazers, burrowing animals, insects, predators

Cool interactions

• Fire and grazing prevent tree growth

• Deep roots hold soil and store nutrients

🌿 Savanna Ecosystem (Tropical Grassland)

Key traits

• Hot with distinct wet and dry seasons

• Grasses with scattered trees (e.g., acacia)

• Seasonal drought and fires

Living things

• Grasses, acacia trees

• Elephants, zebras, lions, insects, birds

Cool interactions

• Large herbivores shape vegetation by grazing

• Fires and drought control tree density

🍂 Temperate Forest Ecosystem

Key traits

• Moderate rainfall; four seasons

• Deciduous trees that lose leaves in autumn

• Rich soils from leaf litter

Living things

• Oak, beech, maple trees; shrubs; fungi

• Deer, birds, foxes, insects, microbes

Cool interactions

• Leaf fall → decomposition → nutrient-rich soil

• Seasonal changes affect animal behaviour and plant growth

Food Chains Explained

A food chain shows how energy flows from one organism to another. It starts with a producer (a plant or algae that makes food using sunlight) and passes through a series of consumers up to a top predator.

The order in a food chain

1. Producer – makes its own food (photosynthesis)

2. Primary consumer – eats the producer (herbivore)

3. Secondary consumer – eats the herbivore (carnivore/omnivore)

4. Tertiary consumer / top predator – eats other consumers

Example Food Chain

Grass → Rabbit → Fox → Hawk

• Grass (producer) captures energy from the Sun

• Rabbit gets energy by eating grass

• Fox gets energy by eating the rabbit

• Hawk, as top predator, gets energy by eating the fox

Key GCSE points

• Arrows show the direction of energy transfer (who is eaten by whom)

• Energy decreases at each step because some is lost as heat and movement

• Most food chains have 3–5 organisms before the energy runs too low

What is a Nutrient Cycle?

A nutrient cycle is a natural process that recycles essential elements (such as carbon and nitrogen) through living organisms and the non-living environment in an ecosystem.

Instead of being used once, these nutrients move in a loop between:

• Plants

• Animals

• Decomposers (fungi and bacteria)

• Soil, water, and air

What is a Nutrient Cycle?

How the cycle works (general pattern)

1. Plants take nutrients from the soil/air to grow.

2. Animals get those nutrients by eating plants (or other animals).

3. When organisms excrete waste or die, decomposers break them down.

4. Nutrients are returned to the soil or air.

5. Plants reuse them — and the cycle continues.

Two key examples you should know

• Carbon cycle – carbon moves through photosynthesis, feeding, respiration, and decomposition.

• Nitrogen cycle – nitrogen is fixed from the air into the soil, used by plants, passed to animals, and returned by decomposers.

Why nutrient cycles matter

• Prevent nutrients from running out

• Keep soil fertile for plant growth

• Support food chains and whole ecosystems

Nutrient Cycles in Action

The water, carbon, and nitrogen cycles move essential materials for life between the air, land, water, and living organisms. These cycles constantly recycle resources so they can be used again and again in ecosystems.

Nutrient Cycles in Action

💧 Water cycle — Water cycle

• Evaporation from seas, lakes, and rivers

• Condensation forms clouds

• Precipitation falls as rain/snow

• Collection in rivers, soil, and oceans

• Plants return water to the air by transpiration

Why it matters: supplies fresh water for plants, animals, and habitats.

🌿 Carbon cycle

• Plants remove carbon dioxide by photosynthesis

• Carbon passes through food chains by feeding

• Respiration and decomposition return CO₂ to the air

• Combustion (burning fuels) also releases CO₂

Why it matters: carbon is the building block of all living cells.

🌱 Nitrogen cycle

• Nitrogen gas is fixed into the soil by bacteria or lightning

• Plants absorb nitrates to make proteins

• Animals get nitrogen by feeding

• Decomposers return nitrogen to the soil

• Denitrification returns nitrogen to the air

Why it matters: nitrogen is needed to make proteins for growth and repair.

Why Are Ecosystems Important?

Ecosystems are vital because they provide the basic resources that all living things need to survive. They supply food, medicine, clean air, and clean water, and they create the conditions that make life on Earth possible for humans, animals, and plants.

Key benefits (ecosystem services)

• Food
  Crops, fish, fruits, and livestock all depend on healthy soils, pollination, and water.

• Medicine
  Many medicines come from plants and microorganisms found in forests, oceans, and soils.

• Clean air
  Plants remove carbon dioxide and release oxygen through photosynthesis.

• Clean water
  Forests, soils, and wetlands filter and store water, reducing pollution and floods.

• Pollination
  Insects like bees pollinate crops and wild plants.

• Climate control
  Forests and oceans store carbon and help regulate global temperatures.

Human Impact on Ecosystems

Human activities can seriously damage ecosystems. Deforestation, pollution, and climate change alter habitats, reduce biodiversity, and disrupt the balance between living organisms and their environment. Protecting ecosystems is vital to secure resources and stability for the future.

Major human impacts

• Deforestation
  Cutting down forests for farming, fuel, or building removes habitats and reduces carbon storage.

• Pollution
  Plastics, chemicals, and waste contaminate water, soil, and air, harming plants and animals.

• Climate change
  Rising temperatures, droughts, floods, and wildfires shift or destroy habitats.

• Overexploitation
  Overfishing, hunting, and resource extraction reduce populations faster than they can recover.

Why protection matters

Damaged ecosystems provide fewer ecosystem services like clean water, fertile soil, food, and climate regulation. Conservation, sustainable resource use, reforestation, and reducing pollution all help ecosystems recover and continue supporting life on Earth.

Quick Quiz: Multiple-choice

Which of these is NOT an example of a biome?

a) Desert

b) Lake

c) Tundra

Answer

b) Lake

A lake is an ecosystem (a specific habitat), not a large climate-defined region.

Desert and tundra are biomes because they are vast areas defined by climate, with characteristic plants and animals.

Short Definitions Practice

Define the following in your own words:

ecosystem

producer

consumer

nutrient cycle

Biome

Foods cycle

Reflection

Why is it important for humans to understand and protect ecosystems and biomes?