1. Topic 4 – Ecosystems & Ecology Statements: G – I
Ecological Pyramids
Topic 4 – Ecosystems & Ecology
Statements: G – I

2. What are Ecological Pyramids
A pyramid is a kind of graph/model that can be used to quantitatively represent differences in the trophic levels in a single ecosystem.
Three types:
Pyramids of numbers
Pyramids of biomass
Pyramids of productivity

3. Ecological Pyramids
Label the trophic levels in the pyramid to the right
Why does a pyramid shape make a good model for food chains/webs?
It Mimics the typical number, biomass, and energy of ecosystems

4. Pyramid of Numbers
Ecological pyramid based on the number of organisms at each trophic level.
Generally:
Producers > primary consumers > secondary consumers, etc.

5. Pyramid of Numbers Pyramids of numbers can be inverted
Pyramids of numbers depend on the size of organisms
Explain an example of when a pyramid of numbers can be inverted:
Since trees are so much bigger, a forest ecosystem will have more primary consumers

6. Pyramids of numbers
These pyramids shows that forests have a smaller number of producers than grasslands

7. Pyramids of Biomass What is biomass?
The pyramid of biomass is an ecological pyramid based on the mass of dry tissue of organisms at each trophic level in an area.
Also called the “standing stock” of each trophic level measured in grams (or kg) of biomass/square meter (g m-2 or kg m-2) … can also be measured in units of energy (J m-2 or kJ m-2)
Example of when this pyramid could be inverted?
Ocean Biome

8. Inverted Biomass Pyramid

9. Inverted Pyramids Which ecosystems have inverted biomass pyramids?
Inverted numbers pyramids?
OCEAN/MARINE
Terrestrial/ Forest

10. Pyramid of Productivity
Shows the flow in the total available energy at each higher trophic level. These show the amount of energy that is passed from one trophic level to the next.
Measured in (g m-2 yr-1 or kg m-2 yr-1) or (J m-2 yr-1 or kJ m-2 yr-1), which are units of flow over time instead of the momentary standing stock.
Can these pyramids be inverted? Why?
NOPE! ~ b/c 2nd law of thermodynamics

11. Implications of Pyramids
Why are food chain lengths limited?
Also b/c of 2nd law of Thermodynamics.
10% law.
Top carnivores are very vulnerable if there is a disturbance anywhere in the food chain.
Why?
b/c top carnivores rely on lower trophic levels to survive!

12. Bioaccumulation
Organisms absorb, breathe and ingest non-biodegradable (persistent) toxins from the environment
If the organisms do not digest and excrete the toxins out of their bodies they will be stored in body tissues
Over time, organisms will build up a large concentration of the toxins in their bodies – this is called bioaccumulation
The gradual buildup of toxins in a living organism
What happens to bioaccumulated toxins in the food chain?
They get passed on to next level and build up faster.

13. Biomagnification
Accumulated non-biodegradable (persistent) toxins are passed up from one trophic level to the next
Concentration of toxins in living organisms increases (or magnifies) at each trophic level – this is called biomagnification
Which trophic levels are most vulnerable to biomagnification?
Top Carnivires/Omnivores

14. Bioaccumulation and Biomagnification

15. Biomagnification: DDT
DDT is a highly successful pesticide once used in great abundance throughout the U.S. and World
DDT (a non-biodegradable toxin) breaks down very slowly in the body
Therefore, DDT bioaccumulated and biomagnified through the food chain

16. Biomagnification: DDT
The hazard of DDT was to “non-target animals”
Who were the “target animal”?
Who were the “non-target animals”?
Why were they so affected?
How were they affected?

17. Biomagnification: Mercury
How could biomagnification affect humans?