Lecture Notes: Biomes, Biospheres, and Ecosystems

Introduction

• Understanding biosphere: part of Earth's surface where living organisms reside.
• Goals: Define biosphere, biomes in South Africa, and ecosystems.

Biosphere

Definition

• Bio: Living organisms.
• Sphere: Globe.
• The biosphere: Supports various life forms, extends ~7-8km above sea level and ~6-8km below sea level.

Components

• Hydrosphere: Water bodies (oceans, rivers, lakes).
• Lithosphere: Soil and rocks.
• Atmosphere: Air and gases.

Atmosphere

• Gases: Nitrogen (71%), Oxygen (21%), Carbon dioxide (small %), Water vapor.
• Importance: Supports respiration, photosynthesis, protects from harmful UV radiation.
• Layers:
  • Troposphere: Closest, ~10km above sea level, supports life.
  • Stratosphere: ~50km above sea level.
  • Mesosphere: ~85km above sea level.
  • Thermosphere: ~500km above sea level.

Hydrosphere

• Water Bodies: Oceans (97%), Freshwater (3%).
• Importance: Provides water needed for survival, habitat for aquatic organisms.

Lithosphere

• Composition: Topsoil supports plant life, underlayer rocks and sand.
• Importance: Source of nutrients, habitat for microorganisms.

Key Interconnections

• Air, water, and soil are essential for sustaining life forms.
• Ecologists break down the biosphere into smaller units for study: Biomes → Ecosystems → Communities → Populations → Organisms.

Biomes in South Africa

Definition

• Large areas characterized by specific climate, plants, and animals.
• Divided into terrestrial and aquatic biomes.

Components

• Terrestrial Biomes: Specific types of vegetation and climate conditions.
• Aquatic Biomes: Fresh and saltwater ecosystems (dams, lakes, rivers, seas).

South African Terrestrial Biomes

1. Savanna: Largest biome.
2. Grassland: Central highveld and coastal regions.
3. Nama Karoo: Dry and arid regions.
4. Succulent Karoo: Cold, dry regions, west coast.
5. Fynbos: Southwestern region, endemic species.
6. Thicket: Eastern coastal region.
7. Forest: Scattered along coasts.

Aquatic Biomes

• Types: Freshwater (dams, lakes, rivers, wetlands) and Marine (sandy shores, rocky shores, coral reefs, mangrove swamps, estuaries).

Ecosystems

Definition and Characteristics

• Specific areas within biomes with characteristic vegetation and organism interactions (biotic and abiotic components).
• Examples: Freshwater ponds, rotten logs, rock pools.

Components

• Abiotic Factors: Non-living (temperature, soil, light, water, atmospheric gases, wind).
• Biotic Factors: Living organisms (producers, consumers, decomposers).

Categories of Abiotic Factors

1. Climatic Factors: Light, temperature, water type and amount, wind velocity.
2. Adaphic Factors: Soil composition, water content, air, minerals, pH.
3. Physiographic Factors: Landform, slope, altitude.

Importance

• Abiotic factors affect the distribution and types of organisms.

Biotic Components

1. Producers (Autotrophs): Plants, algae, and some bacteria that perform photosynthesis.
2. Consumers (Heterotrophs): Organisms that consume other organisms.
   • Primary Consumers: Herbivores (e.g., buffalo, springbok).
   • Secondary Consumers: Carnivores (e.g., lions, leopards).
   • Tertiary Consumers: Larger predators (e.g., apex predators).
   • Omnivores: Consume both plants and animals.
3. Decomposers (Saprophytes): Bacteria, fungi that break down dead organic matter.

Energy Flow and Food Chains

1. Food Chains: Show the flow of energy from producers to consumers.
2. Food Webs: Interconnected food chains showing a more complex interaction.

Trophic Levels

• Producers → Primary Consumers → Secondary Consumers → Tertiary Consumers.
• Energy flows from one trophic level to the next.

Summary

• Abiotic Components: Climatic, edaphic, and physiographic factors.
• Biotic Components: Producers, consumers, decomposers.
• Interactions between biotic and abiotic components define ecosystems and contribute to the biosphere's complexity.