What is an Ecosystem?
(An introduction)
Ecosystem

An ecosystem is a community of organisms and
its environment, functioning together as a unit.
Ecosystems

Ecosystems.mpg
Abiotic Factors

Abiotic factors are the
nonliving components of
the environment

air and water

rocks and minerals

temperature and weather
Biotic Factors

Biotic factors are living things
Food Chains
Definitions

Producer (autotrophs) – stores the sun’s energy as
sugars; i.e. makes its own food from the sunlight
e.g. plants

Consumer (heterotrophs) – eats other organisms to gain
its food and passes on the energy to other animals
e.g. animals

Decomposer – decomposes dead organisms to get food
and recycles nutrients
e.g. bacteria, fungi
Definitions

Herbivore – an animal that eats plants

Carnivore – an animal that eats meat

Omnivore – an animal that eats meat and plants

Food Chain – Diagram showing the flow of energy
through an ecosystem

Food Web – Diagram of interconnected food chains
Discussion
What kinds of organisms are at the start of
every food chain? Why?
 Do any of your food chains have more than
three links?
 For what species might you become a
source of food?


Where does the energy in a food chain come
from?
Food Chain

Food Chains.mpg
What Eat’s What?



Get into groups of 3-4
Each group will be given a pack of cards.
Steps:
 Sort your cards into three groups. (What is the
best way to sort them?)
 Arrange the organisms into food chains. Each
food chain should only be 3 chains long.
 Make as many 3-link chains as possible.
 Have one person record them on a piece of
paper.
Energy Flow and
Feeding Levels
Energy
Living things require both a source of energy
and a source of matter to survive.
 Ultimately, the source of energy in all
ecosystems is the sun.

Why do living organisms need energy?


Organisms need energy
to carry out life functions
(in order to survive)
Life functions are:




acquiring nutrients (food)
acquiring water and
necessary gases
using energy
eliminating waste





reproduction
growth
repair
storing information
response to surroundings
Organisms need energy to stay alive
Trophic Levels
 Feeding
level of one or more organism
in a food chain
 producers,
secondary consumers, etc…
A
way of categorizing living things
according to how they gain their energy.
 The
number of steps an organism takes to
receive energy from the sun
Trophic Levels
1st Trophic Level
 Autotrophs
 Producers
 Use
– plants
the sun’s energy to directly fuel their
activities and produce new plant matter
1st Trophic Level

The energy captured by
plants through
photosynthesis determines
the amount of energy that is
available for all other
organisms in the ecosystem
nd
2
Trophic Level
 Heterotrophs
 Herbivores
(plant eaters)
 Primary consumers
 They
cannot make their own
food
 They feed on producers in
order to survive.
 They digest the plants they eat
and release the energy stored
in the plant cells for their own
use
rd
3
Trophic Level
 Heterotrophs
 Carnivores/Omnivores
 Secondary
 They
consumers
cannot make their own food; instead they
need to eat other organisms in order to survive.
 They digest the plants they eat and release the
energy stored in the plant cells for their own
use
th
4
Trophic Level
 Heterotrophs
 Top
carnivores
 Tertiary consumers
 They
cannot make their own food; instead they
need to eat other organisms in order to survive.
 They digest the animals they eat and release
the energy stored in the animal cells for their
own use
th
5

Trophic Level
Decomposers

Break down dead material and animal wastes to allow for
nutrient recycling in an ecosystem (mostly bacteria and
fungi).

Detritivores – worms, maggots
Assignment
Handout: “Getting to the Top”
 Handout: “Matching Feeder Term”


You have 20 min to work on this assignment
now. It is due tomorrow!
Energy Flow

With each transfer from one organism to
another (one trophic level to another) a large
part of the chemical energy is lost as heat

The flow of energy is greatly reduced with
each successive trophic level.

Only a small percentage (10%) of the energy
remains stored in each organism
Energy Flow Example
For every 100 kJ of plant energy consumed
by a mouse, 10 kJ is left
 The rest is converted to thermal energy (heat)
and waste

Energy Flow Diagram
Energy Flow

At subsequent trophic levels energy transfer
is approximately 10% efficient

Example: If 150 calories of light energy
shines on green plants, then approximately
15 calories end up as plant production, 1.5
calories as herbivores and 0.15 calories as
carnivores.
Why is energy lost moving up the food chain?


Producers capture only about 10% of the sun’s
energy
They use 90% of this energy for their own life
processes


Primary consumers use 90% of the energy
obtained from the producer for life processes


Only 10% is stored in its tissues and available to primary
consumers
Stores only 10% in its tissues
The energy pattern repeats itself at each trophic
level in the food chain
Pyramids
Ecological Pyramids
Fourth trophic level
Third trophic level
Second trophic level
First trophic level
Types of food pyramid
3
types of food pyramid are normally
used:
 pyramid
of numbers
 shows
the number of organisms at each trophic
level in the food chain
 pyramid
of biomass
 shows
biomass (dry weight) of organisms at
each trophic level in the food chain
 pyramid
 shows
of energy
energy available at each trophic level in
the food chain
Pyramid of Numbers

Each level in a pyramid of numbers shows
the number of organisms in that trophic
level.

This pyramid can be inverted if an organism
at a lower level is large enough to support
many organisms in a higher level, e.g. trees
Pyramid of numbers… continued
Pyramid of Biomass

A pyramid of biomass shows how much
mass all the organisms have in each
trophic level.

It is usually calculated using the dry mass of
organisms.

This pyramid can also be inverted.
Inverted Pyramid of Biomass
• The bottom trophic level is
smallest because the
organisms are being
eaten as quickly as they
are reproducing.
• This means there is very little mass at any given
time in this level.
• This occurs in ocean food chains where the
phytoplankton (like algae) is quickly eaten by the
zooplankton (tiny little animals).
Pyramid of Energy

A pyramid of energy flow displays how energy is
distributed within a food chain

Producers have the most energy available to them
 The base of the pyramid will always be the
largest
As you move up each trophic level less energy
becomes available



This is because 90% of the energy received by the
organisms in a trophic level is used up for movement and
heat
This means only 10% of the energy is passed on to each
successive trophic level.
Pyramid of Energy Diagram
Pyramid of Energy Diagram
Comparison…
Assignment
Handout: “Ecology Terms”
 Handout: “Interaction Pyramids”

Cycles
Cycles
Energy does not cycle.
Why?
Cycles

Energy flows in a
one way direction
from the sun,
through plants,
then through
animals, and
decomposers in
what is known as
a food chain or
food web.
Cycles
The energy that is consumed by living
organisms is either used up by the activities
that living things do or it is lost as heat.
The energy lost as heat does not return to
refuel the sun.
Matter; however, cycles.
Cycles
The 3 most important types of matter which
living things require are carbon, oxygen, and
nitrogen.
These elements are also known as nutrients.
Cycles

These and other
nutrients are freed
from wastes and dead
organisms by
decomposers which
recycle them through
the “carbon cycle”, and
the “nitrogen cycle.”
Homework
Textbook: Science Power 10
Read pgs. 38, 40, 42
Q. # 1-4, & 5 or 6 (on pg.42)
Due Tomorrow!