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 grass Abiotic 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 NameProducerPrimary Consumer Secondary Consumer Tertiary Consumer Oak Trees Moths Voles Weasels Shrews NameProducerPrimary Consumer Secondary Consumer Tertiary Consumer Oak Trees X Moths X Voles XX Weasels XX Shrews XX

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 3 rd consumers Producers 1 st consumers 2 nd consumers

10 PERCENT LAW Energy available at each trophic level is about 1/10 the energy available from the level below producers 1 st consumers 2 nd consumers 3 rd 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 (1 st ) consumers, fewer secondary (2 nd ) consumers and very few tertiary (3 rd ) or quaternary (4 th ) 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 2 nd consumers so they eat even more of the toxin The secondary consumers eat many of the 1 st 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