Ecosystems “You only need sit still long enough in some attractive spot in the woods that all its inhabitants may exhibit themselves to you by turns.” Henry David Thoreau

Abiotic Relationships Living Organisms Biotic Relationships Ecosystems Living Organisms Physical Environment Ecology is the study of the inter-relationships among living things and their environment. Abiotic Relationships

Biosphere - Ecosystem The biosphere consists of the zones of the earth where living things exist. These include the atmosphere, the bodies of water and the surfaces of the earth. An ecosystem is a smaller unit of the biosphere. It

an Ecosystem : abiotic and biotic factors An ecosystem includes the living (biotic) and nonliving (abiotic) features in a defined space. It is easier to study than the entire biosphere.

an Ecosystem – abiotic factors sunlight weather elements water rocks soil Abiotic factors are those nonliving factors that exist in an ecosystem that influence, and are influenced by, the biotic factors coexisting there.

an Ecosystem – Biotic Factors animals plants fungi bacteria Biotic factors are those living organisms that exist in an ecosystem. They influence, and are influenced by, the abiotic factors coexisting there.

an Ecosystem – species Biologists sort organisms into groups and subgroups based on their genetics, appearance and evolutionary history. A group of similar organisms (plant, animal, bacteria, fungi, etc) that can interbreed and product fertile offspring is defined as a species. Species A

Populations of Species Ecologists and population biologists define a population of organisms as a collection of individuals belonging to the same species, living in the same area. If individuals belonging to the same species are separated in time and/or space, they are treated as separate groups or populations. Species

Community A Community is a collection of different populations that interact within a defined space. Species C Species B Species A

Habitat - home location abiotic factors food and energy shelter other biotic factors A habitat is an orgamism’s home. It describes the area where the organism lives and the abiotic and biotic factors that affect it. Species C

Niche: habitat and role A niche is a term used to describe the interrelationship of a species with the abiotic and biotic factors in its ecosystem. It can be thought of as the organism’s habitat and its role in it. Species C

Food Webs Food webs show the interrelatedness of species within an ecosystem. It’s really a graphic organizer showing who eats whom. There is one convention. The arrow points from the food to the eater.

Food Webs – Trophic Levels The organisms in a food web can be organized into trophic levels. Trophic levels are used to show how far away an organisms are from the main source of energy that powers their ecosystem. This organization structure provides biologists with a quick visual way to determine how matter (carbon, hydrogen, oxygen and other elements) and energy cycle through an ecosystem. Matter is recycled in the ecosystem but energy is not. It is lost as it is passed up the trophic levels. The organisms that capture energy directly from the sun or chemicals and use inorganic compounds to make their own food are called producers or autotrophs. Organisms that rely on other organisms for their food and energy are called consumers or heterotrophs.

Food Webs – Energy Flow and Loss Energy is lost as one moves up the food chain. Organisms use energy to carry out life processes and therefore when they are eaten or recycled, that energy is not available to be passed on. A rule of thumb is that only 10% of the energy is one trophic level is passed on to the next trophic level. To estimate the amount of energy that is transferred through a food chain we apply the 10% rule. Example: If we use the 10% rule to the grain-beef-food chain, we can predict that 100 kilograms (220 lbs) of grain will produce 10 kilograms (22 lbs) of beef, which in turn will produce on 1 kilogram (2.2 lbs) of persons. Hence, only a relatively small amount of feed energy is transferred from one trophic level to the next.

The Wolves of Yellowstone Wolves were reintroduced to Yellowstone in the 1990’s. Ecologists have been studying their impact for over 15 years. Early on they believed that the wolves had a tremendous impact, not only on their target prey population (elk) but on a large variety of indirectly dependent organisms and even on the river itself. They coined a term trophic cascade to describe this effect – what happens when a top predator is reintroduced into an ecosystem. Today the results are not so clear cut. We will research and discuss these findings in class. Wolves in Yellowstone