Ecosystems and Environmental Factors

Introduction and Environment

• Environment: The surroundings or conditions where an organism lives or operates.
• Natural Environment: Features existing without human interference (e.g., oceans, forests).
• Built Environment: Man-made surroundings (e.g., buildings, infrastructure).

Ecosystem Overview

• Definition: A dynamic unit consisting of a community of living organisms (biotic factors) interacting with their non-living physical environment (abiotic factors).
• Function: Driven by energy flow and nutrient cycling.

Biotic Factors: Producers, Consumers, and Decomposers

• Producers (Autotrophs): Organisms that manufacture food (glucose) using sunlight, $CO_2$, and $H_2O$ via photosynthesis. Types include:   - Xerophytes: Adapted to drought.   - Hydrophytes: Grow in water/swamps.   - Mesophytes: Adapted to average water conditions.
• Consumers (Heterotrophs): Cannot produce food.   - Primary: Herbivores (feed on plants).   - Secondary: Carnivores (feed on primary consumers).   - Tertiary: Feed on other carnivores.   - Omnivores: Eat both plants and animals.
• Decomposers: Break down dead tissue and waste, returning nutrients to the soil.

Abiotic Factors: Physiographic Factors

• Physiography: The study of Earth's physical features and landscapes.
• Slope (Gradient): The inclination of land surface, calculated as the ratio of "rise" over "run."   - Types: Steep, Gentle, Convex, Concave, and Uniform.   - Impact: Affects drainage, erosion, and soil moisture (steep slopes increase runoff).
• Aspect: Position relative to the sun.   - Northern Hemisphere: South-facing is warmer/drier; North-facing is cooler with luxurient growth.   - Southern Hemisphere: North-facing is warmer/drier; South-facing is cooler/wetter.
• Altitude: Height above sea level. Higher altitudes experience lower temperatures, higher wind speeds, and higher rainfall, leading to stunted vegetation.

Abiotic Factors: Edaphic (Soil) Factors

• Components: Minerals, organisms, humus, air, and water.
• pH Level: Degree of acidity or alkalinity.
• Humus: Decaying organic matter that provides nutrients and improves water retention.
• Soil Texture: Determined by particle size (Sand, Clay, or Loam). Sand has large air spaces; Clay has small air spaces.

Abiotic Factors: Light and Temperature

• Radiant Energy: The sun is the primary energy source, converted to chemical potential energy via photosynthesis.
• Photoperiodism: An organism's response to the length of day and night (Short-day vs. Long-day plants; Nocturnal vs. Diurnal animals).
• Temperature Adaptations:   - Estivation: "Summer sleep" to escape hot, dry conditions.   - Hibernation: "Winter sleep" to survive extreme cold and food shortages.