1. 2.1 Energy Flow in Ecosystems
Biomass = 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 b/c they make carbohydrates (sugars/starches) 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.
1. Food chains: show the flow of energy in an ecosystem.

4. 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. This dung beetle is a detrivore.
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 primary producers
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. Most organisms are part of many food chains.
2. Food webs
represent interconnected food chains.
They model the feeding relationships in an ecosystem
Arrows in a food web represent the flow of energy & nutrients.
Arrows go UP to the top carnivore(s).
This food web represents a terrestrial ecosystem that could be found in British Columbia.

8. 3. Food pyramids (a.k.a. ecological pyramids):
show the changes in available energy from one trophic level to another
may show amount of biomass, population size, or amount of energy

9. Energy enters at the first tropic level (producers), where there is a large amount of biomass & so, a lot of energy
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. Lower trophic levels have much larger populations than upper levels.
The amount of life an ecosystem can contain is based on the bottom level of the pyramid.
Each level in the energy pyramid = a loss of 90 percent of total energy available.
Lower trophic levels have much larger populations than upper levels.
This shows the importance of maintaining large, biodiverse populations at the lowest levels
of the food pyramid.
Take the Section 2.1 Quiz