Ecosystems and Interactions
1. What Is an Ecosystem?
Learning outcomes
- I can define an ecosystem and describe its components.
- I can identify living and non-living parts of an ecosystem.
- I can explain how organisms interact with their environment.
- I can compare different types of ecosystems.
- I can describe how ecosystems function as interconnected systems.
Introduction
Every living thing on Earth depends on its surroundings to survive. Plants need sunlight, water, and nutrients, while animals require food, water, shelter, and suitable environmental conditions. Together, organisms and their physical surroundings form ecosystems.
An ecosystem can be as small as a puddle or as large as an ocean. Regardless of size, every ecosystem is made up of living organisms interacting with each other and with the non-living world around them.
What Is an Ecosystem?
An ecosystem is a community of living organisms interacting with each other and with their non-living environment.
It includes everything found within a particular area:
- Plants
- Animals
- Fungi
- Microorganisms
- Water
- Air
- Soil
- Rocks
- Sunlight
- Climate
Figure 1. An ecosystem contains both living (biotic) and non-living (abiotic) components that constantly interact.
Biotic and Abiotic Components
Every ecosystem has two main types of components.
Biotic Factors (Living)
Biotic factors are the living or once-living parts of an ecosystem.
Examples include:
- Trees
- Birds
- Fish
- Insects
- Fungi
- Bacteria
Abiotic Factors (Non-Living)
Abiotic factors are the physical and chemical parts of the environment.
Examples include:
- Sunlight
- Water
- Air
- Rocks
- Soil
- Temperature
- Rainfall
These conditions determine which organisms can survive.
Figure 2. Living organisms depend on abiotic factors such as sunlight, water, air, and soil for survival.
Organisms Interact with Their Environment
Living things constantly interact with one another and with the environment.
Examples include:
- Plants absorb sunlight to make food.
- Bees pollinate flowers.
- Birds build nests in trees.
- Fish obtain oxygen from water.
- Earthworms improve soil quality.
- Predators hunt prey.
These interactions help ecosystems remain balanced.
Ecosystems Are Interconnected Systems
Nothing in nature exists completely on its own.
For example:
Plants → Herbivores → Carnivores → Decomposers → Nutrients → Plants
This continuous cycling of energy and nutrients keeps ecosystems functioning.
Types of Ecosystems
Major ecosystem types include:
- Forests
- Grasslands
- Deserts
- Freshwater
- Marine
Each has different climates, organisms, and environmental conditions.
Figure 3. Earth contains many different ecosystems, each supporting unique communities of organisms.
Example: A Pond Ecosystem
Biotic:
- Fish
- Frogs
- Insects
- Algae
- Ducks
- Bacteria
Abiotic:
- Water
- Rocks
- Mud
- Sunlight
- Oxygen
- Temperature
If pollution enters the pond, nearly every organism may be affected because all parts of the ecosystem are connected.
Worked Example
Question
Identify whether each of the following is biotic or abiotic.
| Item | Biotic or Abiotic? |
|---|---|
| Oak tree | Biotic |
| Soil | Abiotic |
| Rabbit | Biotic |
| Sunlight | Abiotic |
| Mushroom. | Biotic |
| Rainfall | Abiotic |
| Bacteria | Biotic |
| Air | Abiotic |
Real-World Connection
Healthy ecosystems provide many ecosystem services that humans rely on every day, including:
- Producing oxygen
- Purifying water
- Pollinating crops
- Recycling nutrients
- Controlling pests
- Regulating climate
- Providing food, medicines, and raw materials
Protecting ecosystems helps protect our own quality of life.
Did You Know?
Many coral reefs occupy less than 1% of the ocean floor, yet they support about 25% of all known marine species. Because of this incredible biodiversity, coral reefs are often called the "rainforests of the sea."
Key Terms
Abiotic factor – A non-living part of an ecosystem.
Biotic factor – A living or once-living part of an ecosystem.
Community – All the populations of different species living in an area.
Ecosystem – A community of organisms interacting with one another and with their physical environment.
Environment – The surroundings in which an organism lives.
Habitat – The natural place where an organism lives.
Interaction – The way organisms affect one another or their environment.
Key Takeaways
- An ecosystem is made up of living organisms and their non-living environment.
- Living (biotic) and non-living (abiotic) components interact continuously.
- Organisms depend on one another and on their physical surroundings for survival.
- Ecosystems exist in many forms, including forests, deserts, grasslands, freshwater, and marine environments.
- Changes to one part of an ecosystem can affect the entire interconnected system.