Movie Notes: Some animals are more equal than others – keystone species

What are the possible habitats for animals.

Jungle, desert, forest, mountain, sea

Does everyone has a community with different species?

Yes and they are present in different numbers.

In 1963, what did Robert Paine do?

He pried a purple starfish and threw it off the rocks

What happened in the classroom in U of Michigan?

Tree began to bud out

What did prof. Fred Smith asked his students? What was he talking about?

He asked why is that green? and he was talking about food chains

What are producers in a food chain?

they are energy providers

Where are herbivores like consumers?

on top of the food chain

Does the amount of producers limit the amount of herbivores?

Yes, which also limit the amount of predators that feed on them

Every level of the food chain was regulated by the bottom, what does it not explain?

It doesn’t explain why herbivores don’t eat every leaf on the tree

Who proposed a new idea?

Nelson and Lawrence

How are herbivores controlled?

From the bottom up but also from the top down

Can all plants be defoliated?

yes but there were not enough insects to do that

Why is the world green?

Because predators keep herbivores in check

What is the green world hypothesis?

predators have a role in regulating ecosystems

Where was Robert Paine a student at? What did he do?

U of Washington, he identified all of the organisms and who ate whom (Acom Barnacle-->Sea Snail )

What was at the top of the food chain ? Can they be deadly hunters ?

large purple and orange starfish called Pisaster ochraceus

Yes, eating mussels

What did Paine ask? What did he do?

What happened when you moved the single predator ?

He threw the starfish into deeper H2O, 60-70 feet at low tide

Did the ecosystem started to change?

Yes

The number of the rock decreased from what to what?

It decreased from 15 to 8 then to 7 then to a monoculture

What happened to the line of mussels?

It advanced down the rocks and pushed all other species out

What was regulating it?

Starfish- keystone species

NOTE: if its pulled out the structure collapses, had huge impact besides their primary prey

Does all species have the same impact on the ecosystems?

No, Paine removed various species but they had little to no impact

Lots of tide pools, some had urchins which meant?

less kelp

No urchins meant?

more kelp, when he removed all of the urchin, kelp started growing almost immediately

Alaskan Islands (1971) ?

James Estes graduate student (production and energy through the food web)

What happened to otters in North Pacific?

Fur trade otters were hunted to extinction until 1911

Starting with Anchita what did they compare? What did they see?

Otters and without otters.

They saw sea urchins were common but not abundant

What about other islands? Chemy Islan?

It was full of Sea urchins, no kelp, no otters

What was the green world hypothesis?

otters were controlling the sea urchins but once they were removed all of the sea urchins ate the kelp

Cascading effects-trophic cascades-predators ?

This controls the distributions of species and indirect effects

Is kelp fed on by a lot of aquatic animals

Yes

What are the keystone for coastal marine species?

Otters

Did otters pop seemed to be declining?

Yes

When did otters have a steady pop?

When no orcas

Why were orcas eating otters when they usually eat whales?

Because 1960s whales were depleted by 90%-broadened their diet

What did orcas do? What happened to the urchin and kelp?

they added a 4th trophic level and ate all of the otters

urchin pop increased and kelp decreased

Examples of how the concept of equivalent cascade happens in nature

Wolves, sharks, lions, owls , bears

What is the main point?

Transitioned thinking to top-down effect

Does apex predators play a role in the food chain ?

Yes