Respiration
Respiration is the process by which organisms convert organic matter into carbon dioxide (CO₂) and water (H₂O), releasing energy. It occurs in all living organisms. Aerobic respiration requires oxygen and releases significant energy. The Energy released is used for maintaining the organization of organisms, while excess energy is dissipated as heat, increasing entropy in the ecosystem.
glucose + oxygen → carbon dioxide + water
Photosynthesis
Photosynthesis is the process by which primary producers convert light energy into chemical energy stored in glucose. It is carried out by autotrophs (e.g., plants, algae) and provides the raw materials for biomass production.
carbon dioxide + water → glucose + oxygen
Feeding Relationships and Trophic Levels
Trophic Levels
Trophic levels are the position an organism occupies in a food chain or web.
Key Groups:
- Producers (Autotrophs):
- Make their own food through photosynthesis (e.g., plants, algae).
- Form the first trophic level.
- Some chemosynthetic organisms (e.g., deep-sea bacteria) produce food without sunlight.
- Consumers:
- Depend on other organisms for energy.
- Examples: Herbivores (primary consumers), and carnivores (secondary/tertiary consumers).
- Decomposers:
- Break down dead organic matter, recycling nutrients in the ecosystem.
- Examples: Fungi, bacteria.
Feeding Models
- Food Chains: Show direct feeding relationships (linear flow of energy).
- Food Webs: Complex networks of feeding relationships showing energy flow across multiple organisms.
- Ecological Pyramids:
- Quantitative models that represent feeding relationships for a given area and time.
- Types:
- Pyramid of Numbers: Number of organisms at each trophic level.
- Pyramid of Biomass: Total mass of living matter at each level.
- Pyramid of Productivity: Energy flows through each level over time.
In accordance with the second law of thermodynamics, there is a tendency for numbers and quantities of biomass and energy to decrease along food chains; therefore, the pyramids become narrower towards the apex.
Biomagnification and bioaccumulation
Bioaccumulation is the build-up of persistent or non-biodegradable pollutants within an organism or trophic level because they cannot be broken down. Biomagnification is the increase in concentration of persistent or nonbiodegradable pollutants along a food chain. Toxins such as DDT and mercury accumulate along food chains due to the decrease of biomass and energy.
