Ecosystem Dynamics: Energy Flow, Nutrient Cycles, and Population Growth

Food Relations

Producers

Autotrophs: Organisms that produce organic matter from inorganic matter.

Consumers

Heterotrophic organisms:

• Herbivores: Primary consumers (plant eaters).
• Carnivores: Secondary consumers (eat herbivores).
• Omnivores: Consume both plants and animals.

Decomposers

Heterotrophs: Organisms that consume detritus and transform it into inorganic materials (e.g., fungi, bacteria).

• Detritivores: Organisms like earthworms and slugs that partially transform inorganic matter.

Trophic Chains and Webs

• Food Chain: A linear series of organisms where each is consumed by the next.
• Food Web: A complex network of interconnected food chains within an ecosystem.

Energy Transfer

• Respiration: Energy used to sustain the organism, with some released as heat.
• Debris: Dead matter that serves as food for decomposers.
• Biomass: Organic matter that provides energy to the next consumer in the chain.

Carbon Cycle

Producers perform photosynthesis to create organic carbon, which is passed to consumers through the food chain. Through respiration, carbon is returned to the atmosphere as CO₂. Dead matter buried by sediments can eventually become oil or coal. Note: Volcanoes and cars also contribute to carbon emissions, while many sea creatures use dissolved carbon to form their shells.

Nitrogen Cycle

Producers utilize nitrogen from water and transform it into organic matter via photosynthesis. Bacteria fix atmospheric nitrogen into a usable form for producers. Nitrogen compounds pass to consumers through the food chain. Upon death or excretion, nitrogen returns to the environment. Decomposing bacteria transform nitrogen in detritus into nitrates, while other bacteria convert nitrates back into atmospheric nitrogen. Additionally, atmospheric nitrogen is used artificially to manufacture inorganic fertilizers.

Reproductive Strategies

• High birth rate and high pup mortality: Common in species like fish.
• Low birth rate and low pup mortality: Common in mammals that provide care and protection for their offspring.

Population Growth

• J-shaped growth: Occurs with unlimited resources, leading to exponential population increases (population explosion).
• S-shaped growth: Occurs with limited resources, where population growth stabilizes.
• Carrying Capacity: The maximum population size a habitat can sustain without degradation over time.

Pest Management

Definitions

• Pest: Any organism that interferes with human activity.
• Pesticide: Chemical systems used to remove unwanted organisms. An ideal pesticide targets only the pest, saves money, and does not harm other living things.

Integrated Pest Control

• Introduce natural predators, parasites, and pathogens.
• Sterilize male insects of the pest species to create competition against fertile males.
• Construct traps to attract and eliminate the target pest.