Overview
This lecture covers human influences on ecosystems, focusing on pollution (water, land, air), conservation strategies, and endangered species management from the Cambridge IGCSE syllabus.
Pollution and Human Impact
- Pollution means harmful substances enter the environment, making it unsafe for living things.
- Water pollution is caused by untreated sewage, pesticides, and fertilizers entering aquatic ecosystems.
- Eutrophication occurs when excess nutrients lead to algae overgrowth, oxygen depletion, and death of aquatic organisms.
- Plastics are non-biodegradable; they persist in the environment and harm aquatic and terrestrial life.
- In water, plastic causes habitat destruction, animal injuries, contamination, and toxin release.
- On land, plastic pollution affects soils, plant growth, wildlife, and spreads microplastics in the ecosystem.
- Air pollution from methane (mainly livestock and landfills) and carbon dioxide (burning fossil fuels) intensifies the greenhouse effect.
- Increased greenhouse gases result in climate change, leading to altered weather, rising sea levels, and extreme events.
Conservation and Sustainable Resources
- Conservation is the management of natural resources to ensure their long-term use.
- A sustainable resource is produced as fast as it is removed, preventing depletion.
- Forests can be managed by education, protected areas, quotas, and replanting.
- Fish stocks are conserved through education, closed seasons, quotas, and using nets that avoid catching young fish.
Endangered and Extinct Species
- An endangered species has very few individuals left and is at risk of extinction.
- Extinct species have no living individuals remaining.
- Causes include climate change, habitat destruction, hunting, overharvesting, pollution, and introduced species.
- Conservation measures include monitoring/protection, education, captive breeding, and seed banks.
- Programs maintain biodiversity, reduce extinction, protect ecosystems, and ensure ecosystem functions.
Captive Breeding and Genetic Diversity
- Captive breeding uses artificial insemination and in vitro fertilization (IVF) to help endangered species reproduce.
- IVF increases genetic diversity, helping populations resist disease and adapt to change.
- Small populations have less genetic variety, increasing vulnerability and extinction risk.
Key Terms & Definitions
- Pollution — Introduction of harmful substances into the environment.
- Eutrophication — Nutrient overload causing algae bloom and oxygen loss in water.
- Non-biodegradable — Unable to decompose naturally (e.g., plastics).
- Greenhouse Effect — Trapping of heat by gases in Earth’s atmosphere.
- Conservation — Protection and sustainable management of natural resources.
- Sustainable Resource — Resource maintained at a rate that prevents depletion.
- Endangered Species — Species at high risk of extinction.
- Extinct Species — Species with no surviving individuals.
- Captive Breeding — Helping species reproduce in controlled environments.
- In Vitro Fertilization (IVF) — Fertilizing eggs outside the body and re-implanting.
Action Items / Next Steps
- Revise the key causes and effects of pollution on ecosystems.
- Study conservation methods for forests and fish stocks.
- Review definitions and examples of endangered/extinct species.
- Understand captive breeding and its role in biodiversity.