Download Unit 2 Ecological Interactions

Unit 2 Ecology
Ch. 5 How
Ecosystems Work
Section 5-1: Energy Flow in
Ecosystems
Where does an organism’s energy
come from?
• Ultimate source of energy is the sun
• Producers – make their own food,
autotrophs
• Plants – photosynthesis
• Protists, bacteria in aquatic ecosystems –
photosynthesis
• 6CO2 + 6H2O + sunlight
C6H12O6 + 6O2
• carbon dioxide + water + sunlight  glucose + oxygen
• Consumers – cannot make their own food,
heterotrophs
• Describe the 4 types of consumers in your notes
(p. 127)
Types of Consumers in an Ecosystem
• Herbivores – primary, eat only plants
• Carnivores – meat eaters, capture and eat herbivores
(secondary) and other carnivores (tertiary)
• Omnivores – eat plants and meat
• Decomposers – bacteria and fungi that consume dead
organisms and organic waste
• Recycles nutrients back into the environment
• How do you think energy is transferred in
an ecosystem?
How is energy transferred in an
ecosystem?
• When organisms eat other organisms
• Food chain – a sequence in which energy is
transferred from one organism to the next when
organisms eat each other
• Begins with producers, then herbivores, then carnivores
• Why do you think food chains are not the
best way to illustrate the true transfer of
energy in ecosystems?
• What could be used in place of food chains
to better represent the transfer of energy in
ecosystems?
• Most organisms eat a variety
of food so there are many
food chains in an ecosystem
• Food web – network of food
chains representing the
feeding relationships among
organisms in an ecosystem
• Changes in population of one
organism have effects on
many other populations i.e.
Whales and krill
• More diverse food webs
indicate a more stable
ecosystem
What are trophic levels?
• Each step in a food chain =
trophic level
• Layer in the structure of
feeding relationships in an
ecosystem
• 1st level – producers, entry level
of all energy, biggest level
• 2nd level – primary consumers
• 3rd level – secondary consumers
• 4th level – tertiary consumers
Omnivores, scavengers, and
decomposers feed at all levels
Energy Pyramid (p. 131)
• Draw a pyramid in your notes. Indicate the
following on your pyramid.
• Layers for producers, primary consumers,
secondary consumers, and tertiary consumers
• Layers with highest and lowest energy
• Layers with highest and lowest number of
organisms
• Layers with highest and lowest biomass (total
mass of organisms)
Energy pyramids
• Shows the loss of energy from one trophic level to the next
• Amount of energy passes to next level decreases due to life
functions (heat, cellular respiration) =only 10% moves to the next
level
• Producers at the base and have the most energy, then herbivores,
then carnivores
• Pyramid gets smaller at the top showing loss of energy
• Limits the number of trophic levels in an ecosystem
• Can show
• Energy at each level
• number of organisms at each level
• Biomass
Where Does the Energy Go?
• Open to p. 131 to find out!!!
Section 5-2: The Cycling of
Materials
The Cycling of Materials in an
Ecosystem
• Materials constantly being recycled and
reused
Matter is continually moving through an
ecosystem back and forth between organisms
and the environment
Most abundant elements are: Nitrogen, Oxygen,
Carbon, and Hydrogen
The Carbon Cycle
• Continual movement of carbon around and
through the earth and it’s organisms
• Key players in the cycle = living things
For example,
• Carbon is cycle through photosynthesis and
cellular respiration
• Carbonates make up hard parts of bones and
shells
• Carbon – also stored in rocks and fossil fuels
• Human effect on the carbon cycle
• Release carbon dioxide into atmosphere when we
burn fossil fuels
• Contributes to global warming
The Nitrogen Cycle
• Continual cycling of nitrogen through the earth and
it’s organisms
• Organisms require nitrogen to make proteins and new
cells
• Nitrogen = 78% of gases in air
• Nitrogen-fixing bacteria convert N in air into a usable
form called ammonia for living things
• Live in soil and legume roots (beans, clover, peanuts)
• Plants use the ammonia formed by bacteria
• Other bacteria consumes ammonia to produce nitrites
and nitrates (fertilizer)
• Nitrogen is returned to soil by decomposers
• Human effect: create and use fertilizers that can
runoff into ponds and hurt organisms
The Phosphorus Cycle
• Phosphorus – in cells of organisms
• Enters soil when rocks weather and from decaying
matter or waste
• Plants get P from soil and water
• Animals get P from eating plants and animals that
have eaten plants
• Slow cycle that doesn’t involve the air
• Human effect – fertilizers – runoff into ponds and
lakes causing algae blooms
Section 5-3: How
Ecosystems Change
How do ecosystems change over time?
• Always changing in response to natural and human
disturbances
• Older inhabitants die out, new organisms move in
• Ecological succession – gradual process of change
and replacement of some or all of the species in a
community
• Can take hundreds to thousands of years
• Caused by slow changes in physical environment OR
Caused by sudden natural disturbance
Complete the following data
table in your notes (pp. 137-141)
Primary Succession
Description
Examples
Secondary Succession
What is primary succession?
• Succession on land where
no soil previously existed
• Hardened volcanic lava or
ash
• Rocks exposed from glacier
melt
• Pioneer species – 1st to
populate an area
• i.e. Lichens
• Creates soil
What is secondary succession?
• Succession that occurs where an ecosystem has
already existed
• More common than primary
• Follows a community changing disturbance
• Wild fires, humans clearing land, storms, floods,
earthquakes,
• Climax Communities – ending point of succession
– mature stable community
• Still goes through change over time
Old Field Succession
Occurs on a
field once used
as farmland
Secondary Succession after a fire
Secondary
Succession
of a
Lake