CIE iGCSE Biology-20.2 Habitat destruction- Study Notes- New Syllabus
CIE iGCSE Biology-20.2 Habitat destruction- Study Notes – New syllabus
CIE iGCSE Biology-20.2 Habitat destruction- Study Notes -CIE iGCSE Biology – per latest Syllabus.
Key Concepts:
Core
- Describe biodiversity as the number of different species that live in an area
- Describe the reasons for habitat destruction, including:
(a) increased area for housing, crop plant production and livestock production
(b) extraction of natural resources
(c) freshwater and marine pollution - State that through altering food webs and food chains, humans can have a negative impact on habitats
- Explain the undesirable effects of deforestation as an example of habitat destruction, to include: reducing biodiversity, extinction, loss of soil, flooding and increase of carbon dioxide in the atmosphere
What Is Biodiversity?
Definition:
Biodiversity refers to the number and variety of different species of living organisms that exist in a particular area or on Earth as a whole.
📌 Key Points:
- It includes all types of life – plants, animals, fungi, and microorganisms.
- A habitat with high biodiversity has many different species.
- A habitat with low biodiversity has few species, or mainly one dominant species.
🧠 Example:
A rainforest has high biodiversity – with thousands of plant, animal, and insect species.
A monoculture farm (like a field of only wheat) has low biodiversity – mostly just one species.
🌍 Why It Matters:
Biodiversity helps maintain balanced ecosystems. It provides essential services like:
- Food and medicine supply
- Oxygen production
- Pollination and seed dispersal
- Natural recycling through decomposition
Reasons for Habitat Destruction
Habitat destruction is the process by which natural environments are damaged or removed, making them unsuitable for the species that live there. This is one of the main causes of biodiversity loss.
1. Increased Area for Housing, Crops, and Livestock
✅ What happens: As the human population grows, more land is needed for:
- Urban development (houses, roads, cities)
- Crop farming (to grow food)
- Livestock farming (to raise animals for meat, milk, and eggs)
🌿 Impact: Forests, wetlands, and grasslands are cleared, destroying natural habitats and displacing or killing wildlife.
2. Extraction of Natural Resources
✅ What happens: Humans clear habitats to access:
- Timber (for building and fuel)
- Minerals and fossil fuels (coal, oil, gas)
- Metals (for industry and technology)
🌿 Impact: Mining, logging, and drilling operations destroy habitats, pollute soil and water, and disrupt animal populations.
3. Freshwater and Marine Pollution
✅ What happens: Wastewater, chemicals, and plastics from industries, farms, and households pollute:
- Rivers and lakes (freshwater)
- Seas and oceans (marine ecosystems)
🌿 Impact: Pollution can kill aquatic life, damage coral reefs, and poison food chains. It also makes the habitat uninhabitable for many species.
🧠 Summary Table:
| Reason | How It Destroys Habitats |
|---|---|
| Housing, crops, livestock expansion | Land clearing removes natural vegetation and wildlife |
| Extraction of natural resources | Logging, mining, and drilling disrupt or remove ecosystems |
| Freshwater and marine pollution | Chemicals and waste harm aquatic organisms and water quality |
Human Impact on Food Webs and Habitats
Key Statement:
Humans can have a negative impact on habitats by altering food chains and food webs.
📌 Explanation:
Human activities such as:
- Overfishing
- Deforestation
- Pollution
- Introducing foreign (invasive) species
can lead to the following consequences:
- Removal or drastic reduction of certain species
- Disruption of natural feeding relationships
- Imbalance and collapse of ecosystems
🌿 When a species is removed or drastically reduced, the entire food web is affected, often resulting in habitat collapse and biodiversity loss.
🧠 Example:
If humans overfish large predatory fish:
- Prey species may increase uncontrollably.
- This can lead to overgrazing or overconsumption (e.g. algae overgrowth).
- The whole food web becomes unstable and may collapse.
Undesirable Effects of Deforestation
Deforestation is the large-scale removal of forests, often to make space for farming, urban development, or logging. While it may offer short-term gains, it causes significant long-term environmental damage.
1. Reduced Biodiversity
- Explanation: Forests support a wide variety of species. Tree removal destroys habitats, food sources, and breeding areas.
- Result: Many species can no longer survive → biodiversity declines.
2. Extinction of Species
- Explanation: Some species are endemic and cannot live outside their forest habitat. Once lost, they may go extinct.
- Result: Permanent loss of unique plants and animals.
3. Loss of Soil (Soil Erosion)
- Explanation: Tree roots bind soil together. Without trees, soil is washed away by rain and blown away by wind.
- Result: Less fertile land and disrupted ecosystems.
4. Increased Risk of Flooding
- Explanation: Trees slow down rainwater absorption. Without them, water flows rapidly into rivers.
- Result: Higher risk of floods and damage to land and homes.
5. Increased Carbon Dioxide in the Atmosphere
- Explanation: Trees absorb CO₂ during photosynthesis. When cut or burned, CO₂ is released back into the atmosphere.
- Result: Contributes to the greenhouse effect and climate change.
🧠 Summary Table:
| Effect | Explanation |
|---|---|
| Reduced biodiversity | Loss of species due to habitat destruction |
| Extinction | Endemic species may die out completely |
| Loss of soil | Tree roots no longer protect soil → erosion |
| Flooding | Less absorption → increased surface runoff |
| More CO₂ in the atmosphere | Fewer trees to absorb CO₂, more is released → climate impact |