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:

1. Obtaining food from the ecosystem

2. Contributing energy to the ecosystem

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 are living organisms that- break-down wastes & dead organisms, - through the process of biodegradation.- Decomposition is the breaking down of - organic wastes and dead organisms.

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

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

Provincial Exam Question

• Consumers in a food chain can be classified as:1.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

2.Herbivores - primary consumers eat plants (producers) only Ex. Horse eating hay

This dung beetle is a detrivore.

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

Provincial Exam Question

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).

Food Pyramids• Energy enters at the first tropic level

(producers), where there is a large amount of biomass & therefore a lot of energy.

• It takes large quantities of organisms in one trophic 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.

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.

2.1 QUIZ