1. Energy in Ecosystems Review

2. Organic = is currently living or lived in the past
What is a Food Web?
a group of food chains showing all of the feeding relationships in an ecosystem.
Trophic level — a layer in the feeding relationship of an ecosystem, one link in the food chain/web.
Biomass — total amount of organic material present in a trophic level.
All Food Webs:
Original Energy (SUN)
Producers
Consumers
Decomposers
Soil
Arrows showing energy flow!
So, all producers are at the same trophic level and all primary consumers are at the next trophic level.
Food Web = multiple food chains so you can see multiple relationships
Relationships – how organisms are connected
Trophic Level – one layer of a food chain/food web
For example:
- All producers are in the same trophic level
- All primary consumers are in the same trophic level
Biomass:
Bio = living
Mass = matter or weight of material
ORGANIC = is currently living or lived in the past
Organic = is currently living or lived in the past

3. Energy/Ecological Pyramids
Another way to look at trophic levels.
a diagram showing the relative amounts of energy/biomass in the different trophic levels.
Lowest trophic levels are at the bottom: Producers have the greatest biomass.
Energy/Ecological Pyramids – another way to look at trophic levels
Lowest trophic levels are at the bottom = producers = the most biomass
The primary consumers that eat those producers are the next step up on the pyramid (lower biomass – in the whole world and in each smaller ecosystem, there are fewer primary consumers than producers)

4. Example of an Energy Pyramid
1 MAN
10 FOXES
100 RABBITS
1000
Bunches of
GRASS
MAN
0.1%
Energy Lost during conversion to heat, waste….
10%
100 %
of the
sun’s energy
FOX
90% 1%
10%
Rabbit
RABBIT
10%
90%
10%
Grass
90%
Example of an energy pyramid using a single food chain:
The decreasing size of the pyramid shows that each level of the pyramid has a smaller and smaller number of those organisms.
The arrows showing 10% mean that only 10% of the energy that an organism gets actually goes into making part of the organism’s body.
The blue arrows showing 90% leaving the pyramid represent energy that is used up by the organism just to live (and is NOT available for whatever eats that organism later).
- The decreasing size of the pyramid shows that each level of the pyramid has a smaller and smaller number of those organisms.

5. Carrying Capacity:
Population: How many of a specific species can live in an area?
The maximum population a community can tolerate for extended periods of time.
Community = the plants and animals found in an area
An extended period of time … the environment remains healthy and future generations of organisms are able to continue to live within the community
Carrying capacity can also be defined as the number of living things (plants and animals) any area of land or water can support at any one time. Different organisms will have different carrying capacities in the same area. Thus, the carrying capacity of an ecosystem affects everything that lives in it.
Populations of most living things tend to fluctuate naturally around a certain level. That level is the carrying capacity.
The graph is of a population that is fluctuating (rise and fall) depending upon the year with the blue line showing the carrying capacity within that ecosystem.

6. Look at this picture called “The Full Bucket”
How does this illustration explain this concept?

7. What causes populations to spill over (die or leave)?
Carrying Capacity is usually due to Abiotic Factors
Abiotic Factors = non-living characteristics of the environment.
For example:
Sunlight
Moisture
Space
Pollution
Landscape/Terrain

8. What is this illustration trying to tell you about carrying capacity?
This ecosystem is overflowing
What are some of the reasons this ecosystem is “spilling over.”
This is what limits a population from becoming too large?

9. Limiting Factors:
Anything that keeps a population from over-growing the resources available.
Consider how changing the factors that affect carrying capacity can alter the population size of a species.
Predation
Disease
Floods
Accidents
Drought
Shade
Fire
Parasites
Storms
Hunting
Starvation
Habitat Loss
Pollution

10. New Predator/Prey Website