2 of 32

Scales of Ecological Organization

Organism

Population

Community

Ecosystem

Biosphere

3 of 32

Consumption � and Secondary Production

A. Food chains and food webs

Grazing

Detrital (decomposer)

B. Energy budget - flow of energy through an ecosystem

C. Trophic levels and ecological pyramids

D. Efficiency of energy transfer

Consumption

Assimilation

Growth

Secondary production

E. Biomagnification

4 of 32

Why are big, fierce animals so scarce?

Where does the energy come from that fuels ecosystems?

What is the fate of that energy?

How does it affect the distribution and abundance

of organisms of different types?

5 of 32

1. The Energy in an ecosystem flows - it comes and goes

2. But nutrients and mass are constantly recycled!

Today’s main idea is that:

6 of 32

How is Energy Moved and Utilized in Ecosystems?

Trophic levels are the “steps” in a food chain moving from producers to different levels of consumers.

The efficiency of energy transfer between different levels puts a limit on the number of trophic levels.

7 of 32

Food chains and food webs

Simplified food web

8 of 32

Detrital food webs

9 of 32

Celebrating Rot and Decay - Detritivores

Energy isn’t only transferred upwards between trophic levels.

Detritivores use the energy available in dead organisms and allow recycling of essential nutrients in ecosystems.

10 of 32

Net Primary Production

11 of 32

Primary Production …

aka Plants at work!

without the sun and plants and photosynthesis, there would be no food webs or chains.

13 of 32

PASTE IN THE OTHER TWO WORKSHEETS AND COMPLETE THEM!

15 of 32

B. Energy Budget: Source and fate of energy

17 of 32

Only a Fraction of the Energy Present in Organisms of One Trophic Level Is Captured by Organisms of the Next

This limits the number of trophic levels.

18 of 32

C. Trophic pyramids

Classic food chain

2. Rule of thumb: 10% energy transfer

between trophic levels

1. Trophic levels: Primary producers, herbivores,

carnivores (predators), omnivores, detritivores

21 of 32

Availability of energy for growth

Consumed

Unconsumed

1^o Prod

Production

Respiration

Assim.

Assimilated

Urine

Consumed

Feces

So, P = C - R - F - U

22 of 32

Can this ever happen with pyramids based on energy flow

(productivity)?

1^o producers

herbivores

carnivores

Biomass at each trophic level

Inverted trophic pyramids

23 of 32

D. Efficiencies of energy transfer

Why is biomass of top carnivores so small?

Where does all the energy go?

Why is transfer efficiency of energy so low?

24 of 32

Trophic energy losses: a Michigan old-field

25 of 32

Biomagnification

Refers to the progressive build up of persistent toxic substances by successive trophic levels.
This means that it increases the concentration ratio in a tissue of a predator organism as compared to that in its prey.

In order for a pollutant to biomagnify, the following conditions must be true:

The pollutant must be long-lived.

The pollutant must be concentrated by the producers.

The pollutant must be fat-soluble.

26 of 32

Watch and take notes on the following bioaccumulation video

27 of 32

the set of changes in community composition that occur over time in a new or disturbed community.

Succession at Mt. St. Helens.

Ecological Succession

Succession after the Yellowstone fires.

28 of 32

Retreating Glaciers at Glacier Bay Alaska Make It a Natural Laboratory for Studying Primary Succession

Primary succession occurs when organisms colonize a barren environment.

30 of 32

Primary Succession at Glacier Bay, Alaska

A climax community is the stable community at the final stage of succession.

31 of 32

Succession

Succession shows some general trends that include:

1) Biomass increase over time.

2) An increase in the number and proportion of longer-lived species.

3) Increased species diversity.

Succession on Mt. St. Helens – another site of intense study.

32 of 32

Molles fig.18.16

Molles fig.17.4

Molles fig.18.17

Molles fig.17.2

1 of 32