HUMAN BIOLOGY

prinCiples of eCology 463

What is a food Web?

• A food web is a complex system of feeding relationships in an
  ecosystem.


• Producers and various consumers and decomposers make up
  a food web.


• By way of food webs, different species in an ecosystem are
  interconnected.

taKe-Home message

grasses, sedges purple saxifrage arctic willow

arctic hare

gyrfalcon snowy owl ermine

human (Inuk) arctic fox

flea

TROPHICFIRST mosquito

LEVEL

This is just

part of the

buffet of

primary

producers.

SECOND

TROPHIC

LEVEL

Major parts

of the buffet

of primary

consumers

(herbivores)

vole lemming

Major parasitic

consumers that

feed at different

trophic levels

HIGHER

TROPHIC

LEVELS

A sampling

of carnivores

that feed on

herbivores

and one

another

arctic wolf

tick

Figure 24.6 Animated! An arctic food web on land has several feeding levels. (Top row, left to right: Bryan & Cherry Alexander/Science Source; © Dave Mech;
Ken Grahammagestate Media Partners Limited - Impact Photos/Alamy; Second row, left to right: Tom McHugh/Science Source; Paul J. Fusco/Science Source; E. R. Degginger/Science Source; Third row,
left to right: Duncan Shaw/Science Source; © Dave Mech; Tom McHugh/Science Source; Bottom row, left to right: © Jim Steinborn; © Jim Riley; © Matt Skalitzky; Inset box: Photo by James Gathany,
Centers for Disease Control and Prevention)

Food chains and webs show who eats whom

A linear sequence of who eats whom in an eco system is
sometimes called a food chain. However, you won’t often
find such a simple, isolated chain as the one shown in Fig-
ure 24.5. Most species belong to more than one food chain,
especially when they are at a low feeding level. It’s more
accurate to view food chains as cross- connecting with one
another in food webs. Figure 24.6 shows a typical food
web in an arctic ecosystem.

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