Ecosystems
Food Webs
Energy exchange
Questions
• Which of the following would represent a good
investigative experiment testing for affects of a
drug on pregnancy?
• 1) A pregnant mouse given 1 ml of a drug and
a non-pregnant mouse given 1 ml of a
placebo.
• 2) A pregnant mouse given 1 ml of a drug and
a non-pregnant mouse given 1 ml of a drug.
• 3) A pregnant mouse given 1 ml of a placebo
and another pregnant mouse given 1 ml of a
drug.
• 4) A non- pregnant mouse given 1 ml of a
drug and a non-pregnant mouse given 1 ml of
a placebo.
Ecosystems
• On a blue index card: Write down a definition of
an ecosystem. Time limit is 2 minute.
• Pair-Share your definition and then on a green
index card write a shared definition between you
and your partner.
Ecosystems
• A community of organisms (i.e. plants and
animals) living together with their environment
(non-living aspects), functioning as a unit.
Energy Flow,
Nutrient
Cycling, &
Feeding
Relationships
•Nutrients (purple)
neither enter nor leave
cycle
•Energy (yellow) is
not recycled
–Captured by
producers
–Transferred
through consumers
(red)
–Each transfer loses
energy (orange)
Primary Productivity:
Photosynthesis
Energy
O2
from
released
sunlight
to air
• Life uses < 0.03% of
the sun's incident
CO2
energy
Growth
absorbed PhotosynthesisSugar
synthesized
from air
• Most is lost as heat
from respiration
H2O
absorbed
from soil
Minerals
absorbed
from soil
Colored index cards
• Use a purple index card. It has been said that all
flesh is grass. Explain in a couple of sentences
why that statement could be true.
Food Chains
• (a) A simple terrestrial
food chain.
• (b) A simple marine
food chain.
• 10% law determines
the population size
of each trophic level
• More organisms at
lower trophic levels
3
2
4
4
2
2
2
2
3
1
3 A Food Web
2
1
3
3
4
2
2
3
•Simple food web on
a short-grass prairie
•Numbers represent
trophic levels
1=producer
2=primary
consumer
3=secondary
consumer
4=tertiary
consumer
Energy Transfer and Loss
Heat
Secondary
Consumer
Primary
Consumer
Producer
Detritus
Feeders
Heat
Chemicals
Heat
Energy transfer
• Only 10% of the total energy is used at
each level
– In other words if a producer has 100
calories of useable energy then an
herbivore has only 10 calories of useable
energy and a carnivore only has 1 calorie
An Energy Pyramid for a
Prairie Ecosystem: The 10% Law
Food web exercise
• Grab a name tag
• Wait for instructions
• Producers = candy
– Dinoflagellates=tootsie rolls
– Green algae=butter toffee
– Diatoms=hard candy
– Brown algae=butterscotches
• Consumers
– Primary=Turquoise
– Secondary=dark green
– Tertiary=Fluorescent green
• Primary pickup as many candy as possible in 30 seconds
• Secondary tag as many producers as possible
• Tertiary tag as many secondary
Food web exercise
• Goal: ?
• 10 % rule
• Modify for fourth graders?
Questions
Which of the following statements best
describes the movements of energy
through an ecosystem?
–
–
–
–
1.
2.
3.
4.
Energy flow through
Energy cycles
Energy increases
Energy recycles
Questions
• The amount of life that can be supported by an
ecosystem is determined by the
• 1) Efficiency of the consumers
• 2) Number of producers and their
efficiency
• 3) Number of heterotrophs and their
efficiency
• 4) Number of decomposers and their
efficiency
Questions
• If a wolf eats a rodent that ate a smaller insect
that ate a plant, the wolf would be a(n):
• 1) primary consumers
• 2) decomposers
• 3) producers
• 4) secondary consumers
• 5) tertiary consumers