1. What is Ecology?

2. ___ __ _______ What is ecology?
The scientific study of the interactions that determine the distribution and abundance of organisms
Distribution = where an organism is found
Abundance = how common an organism is

3. Questions for Ecologists:
Why are organisms found where they are?
Why do some places have more organisms than others?
Why do the numbers of individuals change over time?

4. Before we go any further, lets have a look at the way things are structured here on Earth…

5. Levels of Biological Organisation:
Biosphere
Ecosystems
Communities
Populations
Organisms
Levels of Biological Organisation:
biosphere
ecosystems
communities
populations
organisms
organ systems
organs
tissues
cells
organelles
molecules

6. What is the role of Ecology in society?
To provide impartial information gathered from scientific study that can be used to guide public policy (laws etc)
It is NOT to make moral judgments on issues and policies

7. An Example: Otters, oil, and killer whales
In 1989: the Exxon Valdez ran aground in Prince William Sound, Alaska
The largest oil
spill ever in the US
Plants and animals
devastated

10. One role of ecologists was to document the short term impact on the organisms
NOT decide whether or how much Exxon should pay

12. What about the sea otters?
Its been almost 20 years since the spill and they still haven’t recovered
Should Exxon pay more -- are they at fault?

13. Sea otter (Enhydra lutris)
A small (≈ 25kg) marine mammal
Relies on fur, not fat, for insulation
Oil mats fur and reduces insulation

14. Historically hunted for fur (nearly driven to extinction in 1800’s)
They recovered in parts of US, but still protected by law

15. Ecologists job So is Exxon responsible ?
Ecologists have been studying the sea otters and this is what they found:
— Sea otter populations throughout Alaska began crashing in 1980’s
— Most of these populations were not impacted by the oil spill
Indicates that the current problem with otters is not due to the oil spill…

16. But why are they only eating otters now?
But what then?
We need to look at the eating habits of the killer whales…
Scientists observed killer whales eating otters (which they don’t usually do)
A single killer whale could eat 2000 otters a year
But why are they only eating otters now?

17. What’s going on? The killer whales used to eat sea lions & seals
But now these prey items have become rare
Why?

18. Overfishing
Pollock and Salmon – the 2 foods that sea lions & seals love to eat.
If there is not enough food for sea lions & seals they will starve
If there are not enough sea lions & seals, the Killer whales will starve
As a result: Killer whales started eating sea otters

19. Food web: before overfishing
Humans
Killer whale
Sea lion
&
Seal
Sea Otter
Urchins
Pollock
&
Salmon
Kelp

20. Sea otter eating an urchin
Urchins
Sea lion eating
a salmon

21. A killer whale eating a Sea lion

22. Food web: after overfishing
Humans
Killer whale
Sea lion
&
Seal
Sea otter
Pollock
Urchins
&
Salmon
Kelp