18 3 Energy Transfer Producers and Consumers Objectives

18 -3 Energy Transfer Producers 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

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/m 2/year – g/m 2/year – Where do you think there is high Net PP – What about aquatic environments?

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

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

• 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

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