2.1 Energy Flow in Ecosystems

1. 2.1 Energy Flow in Ecosystems • Biomass is the total mass of all living things in a given area. (measured in g/m2 or kg/m2) • Organisms interact with the ecosystem by: • Obtaining food from the ecosystem • Contributing energy to the ecosystem

2. Energy Flow in Ecosystems • Plants are called producers because they make carbohydrates during photosynthesis. CO2 + H2O + sunlight  C6H12O6 + O2 • Consumers get their energy by feeding on producers or other consumers. - Decomposers break-down wastes & dead organisms, through the process of biodegradation.

3. Energy Flow & Energy Loss in Ecosystems • Methods to represent energy moving through ecosystems. • Food chains: show the flow of energy in an ecosystem. • Food webs: represent interconnected food chains. They model the feeding relationships in an ecosystem • Food pyramids: show the changes in available energy from one trophic level to another in a food chain. They’re also called ecological pyramids

4. Terrestrial & aquatic food chains Food Chains • Each step is a trophic level • Producers = 1st trophic level • Primary consumers = 2nd trophic level • Secondary consumers = 3rd trophic level • Tertiary consumers = 4th trophic level

5. Consumers in a food chain can be classified as: • Detrivores (decomposers) - obtain energy & nutrients from dead organisms & waste matter. • they have their own, separate food chains & they feed on every trophic level. • Eg. small insects, earthworms, bacteria & fungi • Herbivores- primary consumers • eat plants (producers) only • Ex. Horse eating hay This dung beetle is a detrivore.

6. 3. Carnivores- secondary or tertiary consumers • Secondary consumers eat non-producers (herbivores) • Eg. Frog eating a grasshopper • Tertiary consumers eat secondary consumers • also called top predators, top carnivores or top consumers • Eg. Lions eating humans 4. Omnivores- consumers that eat both • plants & animals • Eg. include humans and bears

7. Food Webs • Most organisms are part of many food chains. • Arrows in a food web represent the flow of energy and nutrients. • Following the arrows leads to the top carnivore(s). This food web represents a terrestrial ecosystem that could be found in British Columbia.

8. Food Pyramids • Energy enters at the first tropic level (producers), where there is a large amount of biomass & therefore a lot of energy

9. It takes large quantities of organisms in one tropic level to meet the energy needs of the next trophic level. • 80% - 90% of energy taken in by consumers is used in chemical reactions in the body, or is lost as heat energy.

10. The amount of life an ecosystem can sustain is based on the bottom level of the ecological pyramid, where producers capture energy from the sun. This shows the importance of maintaining large, biodiverse populations at the lowest levels of the food pyramid.