Sunlight and ecosystems
- Most ecosystems rely on a supply of energy from sunlight
- Autotrophs are directly dependent on sunlight, heterotrophs are indirectly dependent on it.
Producers
3 types of autotrophs that carry out photosynthesis:
- Plants
- Eukaryotic algae including seaweeds that grow on rocky shores
- Cyanobacteria
Heterotrophs in ecosystems
- Consumers
- Detritivores
- Saprotrophs
Use carbon compounds in their food as a source of energy
Energy conversion
Light energy is converted into chemical energy in carbon compounds by photosynthesis
Food chain
A sequence of organisms, each feeding on the previous one
- Producers are always the first organisms in a food chain
1. Producers
2. Primary consumers
3. Secondary consumers
4. Tertiary consumers
etc.
Grass --> insect --> mouse --> fox
Energy in food chains
Chemical energy in carbon compounds flows through food chains by means of feeding
Grass --> insect --> mouse --> fox
(arrows indicate the direction of energy flow)
Respiration and energy release
Living organisms need energy for the following:
- Synthesizing large molecules like DNA, RNA and proteins
- Pumping molecules or ions across membranes by active transport
- Moving things around inside the cell, such as chromosomes, or vesicles, or in musc
Exothermic reaction
A reaction where energy is released
Heat energy in ecosystems
Energy conversions made by living organisms:
- Light energy to chemical energy in photosynthesis
- Chemical energy to kinetic energy in muscle contraction
- Chemical energy to electrical energy in nerve cells
- Chemical energy to heat energy in heat-gener
Heat losses from ecosystems
Ecologists assume that all energy released by respiration for use in cell activities will ultimately be lost from an ecosystem
Biomass
The total mass of a group of organisms. Consists of the cells and tissues of those organisms, including the carbohydrates and other carbon compounds they contain (measured in grams).
Energy losses and ecosystems
- The only energy left to the next trophic level is the chemical energy stored in carbohydrates and other carbon compounds that have not been lost in cell respiration.
- Energy in uneaten material passes to saprotrophs and detritivores rather than passing