ENERGY FLOW & ECOLOGICAL PYRAMIDS

NOTES

ECOLOGY DEFINITIONS

Ecology – study of organisms and their interactions with the environment

ECOLOGY DEFINITIONS

Biosphere – region of the Earth that supports life (includes all the land, water and air in which organisms live)

ECOLOGY DEFINITIONS

Ecosystem – all the organisms that live in a particular place, together with their physical environment

Both biotic and abiotic factors interacting

Abiotic Factors (nonliving)Ex: air, temp, water, rocks

Biotic factors (Living)Ex: all plants and animals, bacteria, algae, fungi

Ecosystems

Biotic Factors:

Moose, Bird, Rabbit,

Tree

grassAbiotic Factors:

Water, clouds, rocks

POPULATION DEFINITIONS

Species – a group of organisms so similar to one another that they can breed and produce fertile offspring (smallest level)

Population – all the members of a single species that live in one area

Niche – a particular role a population plays in the community (“its job”); ex. Honeybee pollinates flowers; hawks prey on mice

Community – all the populations that live and interact in one environment

Energy

The main source of energy for life on earth is sunlight

Autotrophs (like plants) go through photosynthesis to produce usable energy (ATP).

ENERGY FLOW DEFINITIONS

Producer (Autotroph) – organism that makes its own food (ex. Plants)

Consumer (Heterotroph) – organism that gets its energy directly or indirectly from producers (ex. Animals)

Decomposer – organism that breaks down and obtains energy from dead, organic matter (ex. Fungi and Bacteria)

FOOD CHAINS

Food Chain – a series of organisms through which food energy is passed in an ecosystem

Example of a Food Chain:

Sunflower Caterpillar Robin Fox (producer) (primary (secondary (tertiary

consumer) consumer) consumer)

FOOD WEBS

Food web – interconnecting and overlapping food chains

Name Producer Primary Consumer

Secondary Consumer

Tertiary Consumer

Oak Trees

Moths

Voles

Weasels

Shrews

Name Producer Primary Consumer

Secondary Consumer

Tertiary Consumer

Oak Trees X

Moths X

Voles X X

Weasels X X

Shrews X X

Energy Flow

Energy & nutrients are recycled by decomposers.

Definitions

A trophic level is the position occupied by an organism in a food chain.Trophic levels can be

analyzed on an energy pyramid.

Biomass is the total mass (amount of living tissue) of all the organisms within a given trophic level

Biomass

Total mass (amount of living tissue) of all the organisms within a given trophic level

Only a small fraction of the biomass from one trophic level moves to the next

2 Reasons for this:Many organisms are not consumed by

organisms at the next trophic level – energy is not available for transfer

Some of the biomass at each level consists of materials consumers won’t eat – bones, teeth, beaks, claws, shells, wood

ECOLOGICAL PYRAMID

Shows the relationships between producers and consumers at the trophic levels in an ecosystem

Plants (grass & flowers)

Rabbits, mice

Snakes

Owls 3rd consumers

Producers

1st consumers

2nd consumers

10 PERCENT LAW

Energy available at each trophic level is about 1/10 the energy available from the level below

producers

1st consumers

2nd consumers

3rd

consumers

20,000 kJ

2,000 kJ

200 kJ

20 kJ

WHY A PYRAMID SHAPE?

In most food chains fewer organisms occupy each higher trophic level (lots of producers, many primary (1st) consumers, fewer secondary (2nd) consumers and very few tertiary (3rd) or quaternary (4th) consumers)

WHY A PYRAMID SHAPE?

The greatest amount of energy is found at the base of the pyramid.

The least amount of energy is found at top of the pyramid.

BIOLOGICAL MAGNIFICATION

The buildup of a pollutant in organisms at higher tropic levels in a food chain

The concentration of a pollutant (like DDT) multiplies as it passes up the food chain from producers to consumers, so the amount of DDT in top-level consumers can be magnified nearly 10 million times

Biological Magnification

The tertiary consumers eat many of the 2nd consumers so they eat even more of the toxin

The secondary consumers eat many of the 1st consumers so they eat more of the toxin

The tiny primary consumers eat a little bit of the toxin.

At every level the amount of toxin increases!

Most toxin

Least toxin