Transcript Intro to energy in food webs

 Where
does energy in living systems
come from?
 How is it transferred from one
organism to another?


o
o
ENERGY
Where does all of the energy on planet earth
come from?
Sunlight (ultimate energy source)
Chemical (stored in inorganic chemical
compounds)
 Plants
 “Produce”
their own
food using energy from
sun light
 Autotrophs
o Auto = Self
o Troph = Food
Examples:
o plants, bacteria, algae
Photosynthesis
captures light energy
and uses it to power
chemical reactions
that convert carbon
dioxide and water into
oxygen and energy-rich
carbohydrates (sugar).
 Adds oxygen to the
atmosphere and
removes carbon
dioxide.

 Heterotrophs
 Get
their energy by eating other organisms
Herbivore
(primary
consumer):
Carnivore
(secondary
consumer):
Eats plants
Eats meat
Omnivore:
Eats both
 Scavengers

feed on dead organisms
Ex: earthworms, ants, and vultures.
 Detrivores


break down organic matter
Recyclers: turn waste into materials for
producers
Ex: bacteria and fungi
 Energy
always flows from producers to
consumers
 Linear-start
with producer and end with top
predator

a relationship of organisms that depend on each
other for energy or food/energy
 EX:
Algae is food for fish which are food for
squid which are food for sharks.
 Note: The arrows point the way energy
flows, NOT what it eats!
 Food
chains connected
together
 Arrows pointing in the
direction of energy
flow.
 If one organism is
removed, other
organisms may be
endangered or possibly
die out.
 Life
creates a pyramid when converting energy
 Each level is called a trophic level
 Green
plants (some bacteria & algae) that
are able to make their own food

Lowest trophic level
 1°

consumers are herbivores (plant eaters)
Ex: some insects, deer, or mice.
 2°


consumers are carnivores (flesh eaters)
They feed on herbivores
Ex: Amphibians
 3°

consumers are carnivores
Ex: snakes and hawks
Concentrations
of harmful
substances increase as you
move to higher trophic
levels.
With
every step in a Trophic Level:
 Organisms
loose 90% of their energy to
heat
 Only 10% of energy is passed on
Ex:
an organism on one trophic level
needs to eat 10x more than an
organism one trophic level below
Useable energy decreases from 1 trophic
level to the next!

A pyramid of biomass shows the amount of living
organic matter at each trophic level.

The greatest biomass is at the bottom of the
pyramid.

A pyramid of numbers shows the number of
individual organisms at each trophic level.

In most ecosystems, the pyramid of numbers and
the pyramid of biomass are similar, with the
numbers of individuals on each level decreasing
from the level below it.

In some cases, however,
consumers are much smaller
than organisms they feed
upon.

Thousands of insects may
graze on a single tree, for
example. The tree has a lot of
biomass, but represents only
one organism.

In such cases, the pyramid of
numbers may be turned upside
down, but the pyramid of
biomass usually still has the
normal orientation.