Food Webs and Energy Transfer

Trophic Levels

-contains all organisms in a feeding level that are the same number of steps away from the sun (because of the huge loss of energy from the 10% energy rule, there is usually no more than 4 or 5 trophic levels)

Food Chains

-energy flows through ecosystems in food chains and food webs -a food chain/web is the flow of energy from one organism to another -the arrows in a food chain represent the energy flow

Ecological Pyramids

-graphic way to represent the relationship energy values in each trophic level -the bases of these pyramids represent the producers -higher trophic levels are layered on top of one another. the source of energy for these pyramids is the sun

Pyramid of Energy

-illustrates the energy content of biomass of each trophic level -energy expressed in kilocalories/square meters -larger at the bottom and gets progressively smaller -shows that most of the energy dissipates at the lower levels (lost as heat to the environment) -energy pyramids explain why there are fewer trophic levels -no biological process is 100% efficient. there will be unusable energy

Food Webs

-interconnecting food chains -gives us a better picture of the ecosystem

10% Rule of Energy Transfer

-moving up each trophic level, there is a 90% loss of heat -that means that only 10% of energy is passed along from one level to another

Trophic Cascades

-occurs when predators in a food web suppress the abundance or alter the behavior of their prey, thereby releasing the next lower trophic level from predation (represented as a dotted line) see notes on page 21 for example

Why learn about food webs?

-show importance of animal relationships and food sources -important tools in understanding that plants are the foundation of all ecosystems and food chains -helpful in explaining how disruptions in populations due to overhunting, poaching, global warming, and habitat destruction result in food scarcities leading to extinction

Ecosystem

energy flux and cycling of nutrients

Biosphere

global processes

Community

interactions among populations

Producer

organism that can make its own food

Consumer

organism that relies on other organisms for food

Omnivore

organisms that eat both plants and animals

Carnivore

organisms that eat only meat

Herbivore

organisms that eat only plants

Detritivore

organisms that shred and consume already dead organisms and matter (other than bacteria and fungi) ex: vultures or hyenas

Population

population dynamics (the unit of evolution)

Secondary Consumer

second level consumer that easts a first level consumer (carnivores or omnivores)

Organism

survival and reproduction (the unit of natural selection)

Primary Consumer

the first consumer that eats the producer (herbivores)

Tertiary Consumer

third level consumer that eats secondary consumers

Decomposer

type of bacteria of fungus that breaks down dead organisms and wastes