Edexcel iGCSE Biology-5.1 Population, Community, Habitat & Ecosystem- Study Notes- New Syllabus

Population, Community, Habitat and Ecosystem

📝 Introduction

• Living organisms do not exist alone. They interact with other organisms and their surroundings.
• To study these interactions, biologists use terms such as population, community, habitat and ecosystem.
• These terms describe different levels of organisation in nature.
• Understanding these terms helps explain how living things survive, reproduce and depend on each other.
• These concepts form the foundation of ecology.

🌱 Levels of Ecological Organisation

• Living organisms are organised in different levels, from a single species to a complete ecosystem.

Individual Organism → Population → Community → Ecosystem

• Each level includes the one before it and becomes more complex.

👥 Population

Definition

A population is all the organisms of the same species living in the same area at the same time.

Key Features

• All members belong to one species.
• They live in the same habitat or area.
• They can breed with each other and produce fertile offspring.
• The size of a population can increase or decrease over time.

Examples

• All the deer living in a forest.
• All the mango trees in an orchard.
• All the frogs living in a pond.
• All the rabbits in a grassland.

Important Point

• If different species live together, they do not form a population.

🌳 Community

Definition

A community is all the populations of different species living and interacting in the same habitat.

Key Features

• Consists of many different populations.
• Includes plants, animals, fungi and microorganisms.
• Organisms interact in many ways, such as:
  • Feeding relationships.
  • Competition.
  • Pollination.
  • Predation.
  • Decomposition.

Examples

A pond community may include:

• Fish
• Frogs
• Algae
• Water plants
• Insects
• Bacteria
• Snails

Together, these different populations form one community.

Important Point

• A community contains only living organisms.
• It does not include non-living factors like water, soil or sunlight.

🏞️ Habitat

Definition

A habitat is the natural place where an organism lives. It provides everything an organism needs to survive.

A Habitat Provides

• Food
• Water
• Shelter
• Space
• Suitable temperature
• Places to reproduce

Examples

Important Point

• Different species can live in the same habitat if enough resources are available.

🌍 Ecosystem

Definition

• An ecosystem is a community of living organisms together with the non-living (abiotic) environment in which they live and interact.
• An ecosystem includes both biotic and abiotic components.

Biotic Components

• Biotic components are the living parts of an ecosystem.
• They include:
  • Plants
  • Animals
  • Fungi
  • Bacteria
  • Protists
• These organisms interact with one another in many ways.

Abiotic Components

• Abiotic components are the non-living parts of an ecosystem.
• Examples include:
  • Sunlight
  • Water
  • Air
  • Soil
  • Temperature
  • Minerals
  • Humidity
  • pH
• These factors affect how organisms survive and grow.

Examples of Ecosystems

• Pond ecosystem
• Forest ecosystem
• Grassland ecosystem
• Desert ecosystem
• Marine ecosystem
• Coral reef ecosystem

Each ecosystem has its own living organisms and environmental conditions.

Relationship Between the Four Terms

• These four terms are connected and represent increasing levels of organisation.

Example: Pond

• Population → All frogs living in the pond.
• Community → Frogs, fish, insects, algae, plants and bacteria living together.
• Habitat → The pond, which provides water, food and shelter.
• Ecosystem → The pond community together with water, sunlight, dissolved oxygen, soil and other non-living factors.

Why are Ecosystems Important?

• Ecosystems help to:
  • Support different forms of life.
  • Provide food and shelter for organisms.
  • Maintain nutrient cycles.
  • Balance populations through interactions.
  • Keep the natural environment stable.

📊 Comparison of Population, Community, Habitat and Ecosystem

📝 Key Points

• A population is made up of organisms of the same species living in one area.
• A community consists of different populations living and interacting together.
• A habitat is the natural place where an organism lives.
• An ecosystem includes all living organisms and the non-living environment interacting with each other.
• Population → Community → Ecosystem represents increasing levels of ecological organisation.
• Habitat is the place where organisms live, while an ecosystem includes both the habitat and all the interactions between living and non-living components.

📝 Quick Recap
Population → one species in an area
Community → all species in an area
Habitat → home of an organism
Ecosystem → community + environment (living + non-living)