What is Ecology?

___ __ _______ 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

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?

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

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

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

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

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

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?

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

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

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…

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?

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

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

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

Sea otter eating an urchin Urchins Sea lion eating a salmon

A killer whale eating a Sea lion

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