Science (Single Award) | Ecology and the environment

Welcome to Ecology: Your Place in the Planet!

Hello future scientists! This chapter, Ecology and the Environment, is incredibly relevant because it helps us understand how all living things – including you – interact with each other and with the world around them. It’s essentially the study of life’s interconnected relationships!

Don't worry if some of the terms seem new; we will break them down piece by piece. By the end of this section, you will understand energy flow, natural cycles, and the significant impact humans have on the Earth. Let's get started!

Section 1: The Basics of Ecology and Ecosystems

What is Ecology?

Ecology is simply the study of how organisms (living things) relate to each other and to their environment (non-living things).

To study ecology, we need specific terms to describe the different levels of organization:

• Habitat: This is the natural place where an organism lives. (Example: A pond is the habitat of a frog.)
• Population: A group of organisms of the same species living in the same area. (Example: All the water lilies in one pond.)
• Community: All the different populations (plants, animals, fungi, bacteria) living and interacting in one area. (Example: All the frogs, fish, lilies, and bacteria in the pond.)
• Ecosystem: The community (all living things) plus the physical environment (non-living things like water, rocks, temperature, and sunlight).

Analogy for Understanding Levels

Imagine your school:
A student is an Organism.
All the students in Year 10 are a Population.
All students, teachers, and staff together are the Community.
The community, plus the building, the air conditioning, and the light (the non-living parts), make up the school Ecosystem.

Measuring Distribution and Abundance

How do scientists figure out how many organisms live somewhere? They often use techniques like quadrats and transects.

• Quadrat: A square frame used to outline a specific area (e.g., 0.5m x 0.5m). Scientists place these randomly to estimate the number or percentage cover of a species.
• Transect: A line (often a tape measure) stretched across an area to show how distribution changes, especially when moving from one habitat type to another (e.g., from the edge of a forest into an open field).

Quick Review: An ecosystem includes both biotic (living) factors like communities and abiotic (non-living) factors like water and temperature.

Section 2: Feeding Relationships and Energy Flow

Producers, Consumers, and Decomposers

All living things need energy. Energy flows through an ecosystem in one direction, starting with the sun.

1. Producers (The Energy Makers):

• These organisms, mainly plants and algae, make their own food using photosynthesis.
• They capture light energy from the sun.
• They are always at the start of any food chain.

2. Consumers (The Eaters):

• These organisms get energy by eating other organisms.
• Primary Consumers (Herbivores): Eat producers (e.g., cows, rabbits).
• Secondary Consumers (Carnivores/Omnivores): Eat primary consumers (e.g., foxes, small fish).
• Tertiary Consumers: Eat secondary consumers.

3. Decomposers (The Clean-Up Crew):

• Organisms like bacteria and fungi that break down dead plants, animals, and waste products.
• This process returns vital nutrients back into the soil, ready for producers to use again.

Food Chains and Food Webs

Food Chains

A food chain shows the transfer of energy from one organism to the next.
Crucial Rule: The arrows show the direction of energy flow, meaning they point from the organism being eaten to the organism that is doing the eating.

Example:
Grass \(\to\) Rabbit \(\to\) Fox

(Energy flows from the grass, which is eaten by the rabbit, which is eaten by the fox.)

Food Webs

In reality, organisms rarely eat just one type of food. A food web is a network of interconnected food chains, showing the complex feeding relationships in a community.

Did you know? If one species in a food web disappears (like a key predator), it can throw the whole ecosystem out of balance!

Energy Loss and Pyramids of Biomass

When one organism eats another, not all the energy is transferred. Energy is lost at every step (trophic level).

Where does the energy go?

• Most (around 90%) is lost as heat during respiration.
• Some is lost in waste products (faeces/urine).
• Some is used for movement and growth.

Because so much energy is lost, the total mass of living material (biomass) decreases at each higher level. This is why we represent feeding relationships using a Pyramid of Biomass:

• The producer level (the base) is always the widest.
• Each level above is smaller, showing less total biomass can be supported.

Key Takeaway: Energy flow is inefficient. This loss is why there are usually only 4 or 5 levels in any food chain – there simply isn't enough energy left to support more!

Section 3: Cycles in Nature

In an ecosystem, materials like water and carbon are constantly recycled. This means the total amount of these substances on Earth stays roughly the same.

The Water Cycle

Water moves constantly between the land, the air, and living organisms.

1. Evaporation: The Sun heats liquid water (from lakes, oceans, leaves) and turns it into water vapour (a gas).
2. Condensation: As the water vapour rises and cools, it turns back into tiny liquid droplets, forming clouds.
3. Precipitation: When the clouds get heavy, water falls back to Earth as rain, snow, or hail.
4. Transpiration: Water vapour released into the atmosphere from the leaves of plants.

Simple Trick: Remember the three main states: Liquid \(\to\) Gas \(\to\) Liquid.

The Carbon Cycle

Carbon is the basis of all life (found in carbohydrates, proteins, fats). The carbon cycle describes how carbon moves through the air, land, and living things.

Carbon Movement: Taking it OUT of the Atmosphere (CO\(_2\))

• Photosynthesis: Producers (plants/algae) take carbon dioxide (CO\(_2\)) from the atmosphere and use the carbon to make glucose (food/biomass). This transfers carbon to the plant.

Carbon Movement: Putting it BACK INTO the Atmosphere (CO\(_2\))

• Respiration: All living organisms (plants, animals, microbes) release CO\(_2\) into the atmosphere as a waste product when they use glucose for energy.
• Decomposition: When organisms die, decomposers break them down, releasing carbon back into the soil and atmosphere (as CO\(_2\) from their respiration).
• Combustion (Burning): Burning wood, fossil fuels (coal, oil, gas) releases stored carbon back into the atmosphere as CO\(_2\). (This process is upsetting the natural balance!)

Section 4: Humans and the Environment (Impact)

Threats to the Environment

Human activity has dramatically increased the speed at which substances cycle, often leading to negative environmental changes.

1. Pollution

Air Pollution:

• Acid Rain: Burning fossil fuels releases gases like sulfur dioxide. These gases dissolve in rainwater, making it acidic. Acid rain damages trees, kills fish in lakes, and erodes buildings.
• Enhanced Greenhouse Effect: See below.

Water Pollution:

• Sewage and Fertilizers: Waste and agricultural runoff introduce large amounts of nutrients (nitrates and phosphates) into rivers and lakes.
• Eutrophication: This nutrient overload causes rapid growth of algae (an "algal bloom"). When the algae die, decomposers use up all the oxygen in the water during respiration, causing fish and other aquatic life to suffocate and die.

Land Pollution:

• Non-biodegradable waste (plastics) builds up in landfills, taking hundreds of years to break down, contaminating soil and harming wildlife.

2. Deforestation (Cutting Down Forests)

Large-scale removal of trees is carried out for timber, farming, and housing. This has three major ecological consequences:

• Loss of Biodiversity: Forests contain millions of species. Removing trees destroys habitats, leading to the extinction of plants and animals.
• Soil Erosion: Tree roots hold the soil together. Without trees, heavy rain washes the fertile topsoil away, making the land barren.
• Increased CO\(_2\) Levels: Living trees absorb CO\(_2\). When trees are cut down and burned or left to decompose, the stored carbon is released back into the atmosphere.

3. Climate Change (The Enhanced Greenhouse Effect)

The Greenhouse Effect is natural and essential: gases like CO\(_2\) and water vapour trap some heat from the Earth, keeping the planet warm enough for life.

The Enhanced Greenhouse Effect (often called Global Warming or Climate Change) is caused by humans releasing excessive amounts of greenhouse gases (mainly CO\(_2\) from burning fossil fuels, and methane from cattle farming and waste).

This extra blanket of gases traps too much heat, leading to:

• Rising global temperatures.
• Melting polar ice caps and rising sea levels.
• Changes in weather patterns (more extreme droughts, floods).
• Loss of habitat (especially coastal areas).

Conservation and Sustainability

Conservation means protecting and managing natural resources and environments. Sustainability means meeting the needs of the current generation without compromising the ability of future generations to meet their own needs.

Ways we can promote sustainability:

• Recycling: Reduces landfill waste and the need to extract new raw materials.
• Sustainable Energy: Switching from fossil fuels to renewable energy sources (wind, solar) to reduce CO\(_2\) emissions.
• Protecting Habitats: Creating national parks and marine reserves to safeguard biodiversity.
• Reforestation: Planting new trees to absorb CO\(_2\) and restore habitats.

You’ve covered a huge amount of material! Remember that studying ecology isn't just theory—it’s about understanding the world you live in and how you can help protect it. Keep up the great work!