The Food Chain

?

9

月

23

日中美连线——自然界中的食物链

相关主题：

1.

The Food Chain

The

whole

ecology

of

a

given

location

on

the

earth

can

become

unbalanced

with

the

disappearance of

just a single creature.

This

is because of a system called the

food chain.

The

food

chain

is

a

concept

that

was

developed

by

a

scientist

named

Charles

Elton.

In

1927,

he

laid

out

the

process

by

which

plants

get

their

energy

from

the

sunlight,

plant-eating

animals

get

energy

from

eating plants, and

meat- eating animals

get their energy

from other animals. Seen

in black and white,

this looks very much like a chain, with its links all together.

Let’s look at the food chain more closely. The food chain has four basic parts.

The first part is the sun. The sun provides the energy for everything on the earth, food, and every

organism is in part dependent on plants for the oxygen and /or food they need.

Consumers are the third part of the food chain. Consumers are, very simply

, every organism that eats

something

else,

whether

it

is

a

carnivore

(eats

meat),

a

herbivore

(eats

plants),

an

omnivore

(eats

plants

and

animals),

a

parasite

(relies

on

another

living

thing

to

provide

food),

or

a

scavenger

(usually feeds on dead organisms).

The

fourth part of the

food chain

is decomposers.

These organisms, such as

fungi and bacteria,

break down dead matter into important gases that are released back into the ground, air, or water.

Look at the simplified

food chain on

the

fight.

The sunlight

helps the

grass

to

grow,

the rabb

it

eats the grass, and the fox eats the rabbit. Because the fox does not

have a predator, it is the “top”

of

this food chain.

If something happens to the grass- perhaps a drought occurs-and the rabbits have less food, many

may die. Without many rabbits to eat, some of the foxes in the area may also die or leave the location.

While

this

is

a

very

simple

look

at

the

food

chain

(because

rabbits

do

eat

things

other

than

grass).

Y

ou can see that the disappearance of one element in the chain can have a lasting effect.

2.

Loss of Predators Impacts Food Chain

A loss of species at the top of the food chain could have far-reaching effects on the environment,

according

to

a

study

in

the

Journal

of

the

world’s

top

predators

-

including

lions,

wolves

and

sharks

-

are

in

sharp

decline.

Human

activities

like

pollution,

habitat

destruction,

overfishing and hunting are largely to blame.

Jim Estes studies sea otters.

The

University of California, Santa Cruz professor of ecology and

evolutionary

biology

says

these

furry

marine

mammals

-

once

hunted

to

near

extinction

-

are

important

to the

health of coastal North Pacific ecosystems. J.

Estes

：

“We

have discovered

that sea

otters

have an

important

limiting effect on sea

urchins and

that allows

the kelp

forest to persist,

he

says.

forests,

in

turn,

have all sorts of

important

functions.”

In the absence of sea otters,

the

ocean's

kelp

forest

-

which

provides

a

habitat

for

fish

and

absorbs

climate

changing

carbon

emissions

from the atmosphere -

is

left barren by sea

urchins.

The kelp

forests also provide

habitat

for

fish

and

absorb

climate

changing

carbon

emissions

from

the

atmosphere.

Estes

says

this

close

connection between species health and the health of global ecosystems is a “ubiquitous phenomenon

and that it o

ccurs worldwide in all ecosystem types.”

Estes

compiled

the

work

of

24

scientists

in

six

countries.

He

says

the

research

shows

the

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