18-3 Energy TransferProducers and Consumers

Objectives

• Summarize the role of producers • Identify kinds of consumers • Explain the role of decomposers • Compare food chains and food

webs• Explain why there are only a few

trophic levels in an ecosystem

Producers

• Autotrophs: make their own energy/food

–As producers they make energy that other organisms can use

• Photosynthesis: Energy from light

• Chemosynthesis: Energy from chemicals

Deep sea ecosystems survive on chemosynthesis

Riftia tubeworms, mussels, and scavenging crabs found at the hydrothermal vent site

Measuring productivity• Gross primary productivity: Rate that

producers catch sun’s energy– Producers store energy in sugars

• Biomass: All the organic material• Net primary productivity: how much

biomass piles up– GPP minus rate of respiration– Kcal/m2/year– g/m2/year– Where do you think there is high Net PP– What about aquatic environments?

Only 5 % of the Earth’s surface is jungles that account for 30% of its NPPWeather accounts for a lot of NPP. Estuaries also have high levels of NPP because there is so much light and nutrients

Consumers

• Heterotrophs: get energy from outside of themselves– Eat or consume something else

Vore = Eat• Herbivore: eat producers (plants or herbs)• Carnivore: eat other consumers

– Carn = flesh

• Omnivore: eat everything– Omin = all– Most things are really at least a little bit of an

omnivore, even lions

• Detrivore: eat waste– Detri = garbage– Decomposers important

Others

• Insectivore• Bovivore• Planktavore• Cannibal: happens in nature

– Black widows, Mantis : eats the father– Mice will kill the babies if the nest is repeatedly

threatened– Many father’s kill the young– Why do this?

Energy flow

• When you eat something energy moves into you

• Trophic level: where do you fit in the food chain? Who eats you and who do you eat?

Food Webs

• There are many trophic relationships

• Food webs show the many connections between eater and eaten

Energy transfer

• How much does each trophic level store?– Only 10% of the energy makes it up to the

next level

• Why is so much energy lost?– Some prey escape– You can’t eat everything when you do catch

prey– Entropy: energy is always lost

• There are only a few trophic levels because energy runs out

Biological

magnification • toxins become

more concentrated with each link in a food chain.

• top-level carnivores are usually most severely affected by toxic compounds

How do producers and

consumers obtain energy?

• Producers: from light or chemicals

• Consumers: from eating something else

Name four types of consumers

• Herbivore• Carnivore• Detrivore• Insectivore

What important role do decomposers play in an ecosystem?

• Decomposers remove wastes preventing them from building up.

How does a food chain differ from a food web?

• Food chains are linear (straight)

• Food webs are spatial, and show more connections

Give two reasons for the low rate of energy transfer within ecosystems

• Some prey escape

• You can’t eat everything when you do catch prey

• Entropy: energy is always lost

Explain why food chains usually do not exceed three to four levels

• There is a low rate of energy transfer

• Very little energy gets transferred up

• Soon there isn’t enough energy to sustain life

pietà (pl. same; Italian for compassion) is an artwork depicting the Virgin Mary cradling the dead body of Christ. As such, it is a particular form of the devotional theme of Our Lady of Sorrows.

• American Pieta

What happens to an ecosystem if all the plants die? What happens if all the

decomposers die?

• If the plants die then the herbivores die, and then the carnivores die.

• If decomposers die then waste will pile up eventually poisoning the ecosystem

What is unreasonable about an ecosystem with 7 levels?

• There are to many levels because There is a low rate of energy transfer

• Very little energy gets transferred up

• Soon there isn’t enough energy to sustain life

Explain why there are more herbivores than carnivores

• Herbivores get energy from the largest source of biomass: plants

• Carnivores can’t get as much energy by eating other consumers

• This Biology Lecture brought to you by Muppet Star Wars