Download food web.

Food Chains, Food Webs,
and the Transfer of Energy
Autotrophs
• A groups of organisms that can use sunlight
or chemicals to convert water and carbon
dioxide into glucose.
• In other words, autotrophs are organisms
that can make their own food.
• Autotrophs are also called producers
because they produce all of the food that
other organisms use.
• Without autotrophs, life on Earth would have
become extinct by now.
• Most autotrophs are photosynthetic.
• Ex. Plants and Algae
Photosynthetic Autotrophs
Chemosynthetic Autotrophs
• Some autotrophs use chemicals available in
their environment to make glucose:
• These are called Chemotrophs
– Chemotrophs get their energy from chemical
substances, like hydrogen sulfide.
– They live deep in the ocean where there is no
sunlight
– Ex. Bacteria and some deep-sea worms
Heterotrophs
• Organisms that DO NOT make their own food.
• Another term for Heterotrophs is consumers
because they have to consume other organisms
in order to live.
• There are several kinds of autotrophs, based on
what they eat.
• Ex. Rabbits, Deer, Mushrooms
Heterotrophs
Heterotrophs
• Herbivores
Eat ONLY plants.
• Ex. – Cows, Elephants, Giraffes
Heterotrophs
• Carnivores
Eat ONLY meat
• Ex. – Lions, Tigers, Sharks
Heterotrophs
• Omnivores
Eat BOTH plants and animals
• Ex. – Bears and Humans
Heterotrophs
• Scavengers and Detritivores
feed on the tissue of dead organisms (both plans
and animals)
• Ex. – Vultures, worms, and pill bugs.
Heterotrophs
• Decomposers
Break down organic molecules and turn them
into simple nutrients or fertilizers
• Ex. – Bacteria and Mushrooms
Food Chains
Whenever an organism is consumed by another,
energy is transferred into the consumer.
• A simple sequence of this type of energy transfer
is know as a food chain.
• A food chain is simple and direct.
• It involves one organism at each trophic level
Food Web
• Most organisms eat more than JUST one
other kind of organism.
• When more organisms are involved, we really
have several interconnected food chains.
• These more complex interconnections are
called a food web.
Food Web
Food Web
Notice that the arrows points in the
direction of the flow of energy.
Trophic Levels
• Energy moves from one organisms to another
when it is eaten
• Each step in this transfer of energy is know
as a trophic level
Flow of Energy
• When a zebra eats grass, it does not get all
of the energy that the grass had (much of it
is not digested).
• When a lion eats a zebra, it does not get all
of the energy from the zebra.
• No organism EVER receives all of the energy
from the organism they just ate
• On average, only 10% of the energy from
one trophic level is transferred to the next –
this is called “the 10% law”.
Ecological Pyramid
• An ecological pyramid (also called an energy
pyramid) shows the relationship between
consumers and producers at different trophic
levels in an ecosystem.
• Shows the relative amounts of energy or
matter (biomass) contained at each trophic
level.
• Shows which level has the most energy and
the highest number of organisms.
Ecological Pyramid
Ecological Pyramid