Matter and Energy in Ecosystems Almost all energy in the ecosystem comes originally from the sun. Food chains show the direction of energy transfer. Example: Algae  Fish  Heron

Drawing a Food Chain Food chains represent the flow of energy as one organism is consumed by another. The arrow should be drawn from the organism being consumed to the consumer.

Trophic level: a step in the food chain Trophic level: a step in the food chain. What type of organism is always at the 1st trophic level? autotroph/producer What type(s) of organism can be at the 2nd trophic level? herbivore or omnivore

Ecological Pyramid When you compare the biomass (mass of living things) at each level of a food chain, it forms a pyramid. The greatest mass is always the autotrophs (producers) with decreasing amounts at higher trophic levels.

The Law of Conservation of Energy states that matter can not be created or destroyed. Yet the energy pyramid shows that less energy is available as you move up a food chain. What happens to the rest of the energy? Much of the energy that an organism consumes is given off in the form of heat.

Implications of the Energy Pyramid It takes approximately 16 x more energy to produce a pound of beef as it does to produce a pound of soybeans, since much of the energy consumed by the cow is transformed to heat.

Bioaccumulation and Biomagnification Bioaccumulation: a toxin that remains in body tissue. Toxins that bioaccumulate include PCB’s, DDT and mercury. Biomagnification: an increase in the concentration of a substance in organisms higher up the food chain. This occurs because each step in the food chain must consume a greater amount of the previous level.

Concentration of a toxin increases up a food chain.

King mackerel is a fish that tends to be high in mercury, tilapia is a fish that is usually low in mercury contamination. Predict what that indicates about their roles in the food chain. Fish that are high in mercury contamination tend to be fish at the top of the food chain (king mackerel, shark).

Food Webs Many heterotrophs feed on more than one type of organism. So most communities have energy flow in a food web, made of interacting food chains.

Population Growth Patterns Under ideal conditions, the reproductive rates of species allows for exponential growth. Exponential growth is growth in which the rate of change is proportional to the amount (and therefore increases by an increasing amount, forming a J-shaped curve).

Population Growth Patterns Most populations must compete for limited resources and their growth levels off after a period of exponential growth. This pattern forms an S-shaped graph and is called logistic growth.

Carrying Capacity Carrying capacity is the maximum number of a species that a particular environment can normally support.