EcologyMarch 2013

Pre AP biology

What is an ecosystem?Ecology is the study of

organisms and their interactions with their living and nonliving environment .

Where we start this study is with an ecosystem which is an area of study that includes living and non living parts.

What makes up an ecosystem?

• An Ecosystem has two parts:

1. Biotic factors – all the living organisms

2. Abiotic factors – physical, nonliving aspects

Use the picture below to list all the biotic factors you see or can assume are there

•

Use the picture below to list all the abiotic factors you see or can assume are there

•

Habitat, Population, Community

• A habitat is the place where a particular population lives.

• A population is all the individuals in a particular species living in one place

• A community is all the populations living in one habitat

Biomes

A large region

composed of similar ecosytems; biomes have a specific climate and animal and plant communties.

Where does an ecosystem fit in?

Individual organisms make up populations which make up communities which make up

ecosystems which make up biomes

Energy Flow in Ecosystems

• Everything that organisms do in an ecosystem requires energy.

• How much energy is available directly influences biodiversity

• Our ultimate source of energy is the SUN.

Producers and ConsumersProducers are organisms that first capture energy They include: some bacteria, all plants, and algae. Producers make energy-storing molecules

Consumers are organisms that consume producers or other organisms in order to obtain the energy they need.

Trophic Levels

Sun Producer Consumer Consumer

Organisms are assigned to a trophic level (feeding level) based on the organism’s source of energy. Energy moves from one trophic level to the next.

Trophic Levels

Sun Producer1st Trophic Level

Consumer Consumer

Producers are always on the 1st trophic level. They receive the sun’s energy and, through photosynthesis, convert it to organic molecules.

Trophic Levels

Sun Producer1st Trophic Level

Consumer2nd trophic level

Consumer

Consumers are on all levels except the first. Anything that eats a producer is on the 2nd trophic level. All herbivores are on the 2nd trophic level. Herbivores are also called primary consumers

Trophic Levels

Sun Producer1st Trophic Level

Consumer2nd trophic level

Consumer3rd trophic level

Any consumer that eats herbivores is on the 3rd trophic level and is called a secondary consumer.

Trophic Levels

Sun Producer1st Trophic Level

Consumer2nd trophic level

Consumer3rd trophic level

Consumers either eat both producers and consumers (called an omnivore), or they eat only organisms in the 2nd trophic level and above (called carnivore).

Above the 3rd trophic level

• Some organisms like humans, sharks and hawks are carnivores that eat other carnivores and can be placed on the 4th trophic level.

• They are called tertiary consumers.

It is very rare for an ecosystem to have more than four trophic levels

Food chain

• The path of energy through the trophic levels of an ecosystem is called a food chain

• In a food chain the arrows always point to the organism doing the eating. (Imagine an arrow pointing into the eater’s mouth)

Detritivores• Detritivores are organisms that

obtain their energy from the organic wastes and dead bodies that are produced at all trophic levels.

• They include worms, fungus and bacteria

• Bacteria and fungus are known as decomposers because they cause decay.

• They are important because they recycle nutrients back into the environment

Food Web

• Most ecosystems do not follow simple straight paths because individual animals often feed at several trophic levels.

• This creates a series of interconnected chains called a food web.

Loss of energy• A plant stores only a small amount of the energy it

absorbs. The rest is given off as heat or used by the plant to support its daily processes.

• The same is true for a primary consumer. It will take in energy stored in the plant, but will either use the energy immediately or it will be given off as heat. It will only store 10% of the energy it took in.

• During every transfer of energy in an ecosystem, energy is lost as heat or used by the organism and only about 10% is stored at each step.

The 10% Rule• You can calculate the amount of energy available

to each trophic level by remembering the 10% rule.

• Sun – 100,000 kcal (kilocalories)• Grass 10,000 kcal is available to the next trophic

level• Zebra 1,000 kcal is available to the next trophic

level• Lion 100 kcal is available to the next trophic level• Humans 10 kcal is available to the next trophic

level

Energy Pyramid

• The flow of energy in an ecosystem can be illustrated using an energy pyramid

• It is a diagram in which each trophic level is represented by a block that represents the amount of available energy.

Energy Pyramid

• If you ate a snake, how much energy would be available in you?

• If a falcon ate the snake and then a wolf ate the falcon, how much energy would be available in the wolf?

Limitations of Trophic Levels

• Read page 349 and explain why we can’t depend on the beef industry as the solution to feeding the world. Why do they always ship grain to countries experiencing famine? Should we give them calves so they can have ranches? Why not?

Cycling of Materials in Ecosystems

• Certain nutrients cycle through the environment and get reused over and over.

• The most important nutrients to cycle are water, carbon, nitrogen and phosphorus.

• Biogeochemical cycle – the cycling of these materials from the living to nonliving aspects of an environment

• This DOES NOT apply to energy