Ecology & Ecosystems

Introduction to Ecology

Ecology is the study of interactions between organisms and their environment. It includes both living (biotic) and non-living (abiotic) factors.

• Biotic factors: plants, animals, microbes.
• Abiotic factors: sunlight, temperature, water, soil, pH, oxygen.

Types of Ecosystems

• Terrestrial ecosystems: forests, grasslands, deserts.
• Aquatic ecosystems: freshwater (lakes, rivers), marine (oceans, coral reefs).
• Artificial ecosystems: gardens, farms, aquariums.

Food Chains & Food Webs

Food chains show the flow of energy from one organism to another. Food webs show interconnected food chains.

• Producers: make their own food (plants, algae).
• Primary consumers: herbivores.
• Secondary consumers: carnivores that eat herbivores.
• Tertiary consumers: top predators.
• Decomposers: break down dead matter and recycle nutrients (fungi, bacteria).

Energy Flow & Nutrient Cycles

• Energy Flow: Energy enters as sunlight, is captured by producers, passed through consumers, and lost as heat.
• Carbon Cycle: Photosynthesis, respiration, decomposition, combustion.
• Nitrogen Cycle: Nitrogen fixation, nitrification, denitrification.
• Water Cycle: Evaporation, condensation, precipitation, infiltration.

Adaptations

• Structural: cactus spines, thick bark.
• Behavioral: migration of birds, nocturnal activity.
• Physiological: salt excretion in mangroves, hibernation in bears.

Practice Questions

• Define ecology and distinguish between biotic and abiotic factors. (4 marks)
• Explain the difference between a food chain and a food web. (4 marks)
• Draw a simple food chain with at least 4 trophic levels. (3 marks)
• Describe the carbon and nitrogen cycles. (6 marks)
• Explain structural, behavioral, and physiological adaptations with examples. (5 marks)