What is an Ecosystem? (An introduction)

Ecosystem An ecosystem is a community of organisms and its environment, functioning together as a unit.

Ecosystems Ecosystems.mpg

Abiotic Factors Abiotic factors are the nonliving components of the environment air and water rocks and minerals temperature and weather

Biotic Factors Biotic factors are living things  

Food Chains

Definitions Producer (autotrophs) – stores the sun’s energy as sugars; i.e. makes its own food from the sunlight e.g. plants Consumer (heterotrophs) – eats other organisms to gain its food and passes on the energy to other animals e.g. animals Decomposer – decomposes dead organisms to get food and recycles nutrients e.g. bacteria, fungi

Definitions Herbivore – an animal that eats plants Carnivore – an animal that eats meat Omnivore – an animal that eats meat and plants Food Chain – Diagram showing the flow of energy through an ecosystem Food Web – Diagram of interconnected food chains

Discussion What kinds of organisms are at the start of every food chain? Why? Do any of your food chains have more than three links? For what species might you become a source of food? Where does the energy in a food chain come from?

Food Chain Food Chains.mpg

What Eat’s What? Get into groups of 3-4 Each group will be given a pack of cards. Steps: Sort your cards into three groups. (What is the best way to sort them?) Arrange the organisms into food chains. Each food chain should only be 3 chains long. Make as many 3-link chains as possible. Have one person record them on a piece of paper.

Energy Flow and Feeding Levels

Energy Living things require both a source of energy and a source of matter to survive. Ultimately, the source of energy in all ecosystems is the sun.

Why do living organisms need energy? Organisms need energy to carry out life functions (in order to survive) reproduction growth Life functions are: repair storing information acquiring nutrients (food) response to surroundings acquiring water and necessary gases using energy eliminating waste Organisms need energy to stay alive

Trophic Levels Feeding level of one or more organism in a food chain producers, secondary consumers, etc… A way of categorizing living things according to how they gain their energy. The number of steps an organism takes to receive energy from the sun

Trophic Levels

1st Trophic Level Autotrophs Producers – plants Use the sun’s energy to directly fuel their activities and produce new plant matter

1st Trophic Level The energy captured by plants through photosynthesis determines the amount of energy that is available for all other organisms in the ecosystem

2nd Trophic Level Heterotrophs Herbivores (plant eaters) Primary consumers They cannot make their own food They feed on producers in order to survive. They digest the plants they eat and release the energy stored in the plant cells for their own use

3rd Trophic Level Heterotrophs Carnivores/Omnivores Secondary consumers They cannot make their own food; instead they need to eat other organisms in order to survive. They digest the plants they eat and release the energy stored in the plant cells for their own use

4th Trophic Level Heterotrophs Top carnivores Tertiary consumers They cannot make their own food; instead they need to eat other organisms in order to survive. They digest the animals they eat and release the energy stored in the animal cells for their own use

5th Trophic Level Decomposers Detritivores – worms, maggots Break down dead material and animal wastes to allow for nutrient recycling in an ecosystem (mostly bacteria and fungi). Detritivores – worms, maggots

Assignment Handout: “Getting to the Top” Handout: “Matching Feeder Term” You have 20 min to work on this assignment now. It is due tomorrow!

Energy Flow With each transfer from one organism to another (one trophic level to another) a large part of the chemical energy is lost as heat The flow of energy is greatly reduced with each successive trophic level. Only a small percentage (10%) of the energy remains stored in each organism

Energy Flow Example For every 100 kJ of plant energy consumed by a mouse, 10 kJ is left The rest is converted to thermal energy (heat) and waste

Energy Flow Diagram

Energy Flow At subsequent trophic levels energy transfer is approximately 10% efficient Example: If 150 calories of light energy shines on green plants, then approximately 15 calories end up as plant production, 1.5 calories as herbivores and 0.15 calories as carnivores.

Why is energy lost moving up the food chain? Producers capture only about 10% of the sun’s energy They use 90% of this energy for their own life processes Only 10% is stored in its tissues and available to primary consumers Primary consumers use 90% of the energy obtained from the producer for life processes Stores only 10% in its tissues The energy pattern repeats itself at each trophic level in the food chain

Pyramids

Ecological Pyramids Fourth trophic level Third trophic level Each level in the pyramid represents a different trophic level Second trophic level First trophic level

Types of food pyramid 3 types of food pyramid are normally used: pyramid of numbers shows the number of organisms at each trophic level in the food chain pyramid of biomass shows biomass (dry weight) of organisms at each trophic level in the food chain pyramid of energy shows energy available at each trophic level in the food chain

Pyramid of Numbers Each level in a pyramid of numbers shows the number of organisms in that trophic level. This pyramid can be inverted if an organism at a lower level is large enough to support many organisms in a higher level, e.g. trees

Pyramid of numbers… continued

Pyramid of Biomass A pyramid of biomass shows how much mass all the organisms have in each trophic level. It is usually calculated using the dry mass of organisms. This pyramid can also be inverted.

Inverted Pyramid of Biomass The bottom trophic level is smallest because the organisms are being eaten as quickly as they are reproducing. This means there is very little mass at any given time in this level. This occurs in ocean food chains where the phytoplankton (like algae) is quickly eaten by the zooplankton (tiny little animals).

Pyramid of Energy A pyramid of energy flow displays how energy is distributed within a food chain Producers have the most energy available to them The base of the pyramid will always be the largest As you move up each trophic level less energy becomes available This is because 90% of the energy received by the organisms in a trophic level is used up for movement and heat This means only 10% of the energy is passed on to each successive trophic level.

Pyramid of Energy Diagram

Pyramid of Energy Diagram

Comparison…

Assignment Handout: “Ecology Terms” Handout: “Interaction Pyramids”

Cycles

Cycles Energy does not cycle. Why?

Cycles Energy flows in a one way direction from the sun, through plants, then through animals, and decomposers in what is known as a food chain or food web.

Cycles The energy that is consumed by living organisms is either used up by the activities that living things do or it is lost as heat. The energy lost as heat does not return to refuel the sun. Matter; however, cycles.

Cycles The 3 most important types of matter which living things require are carbon, oxygen, and nitrogen. These elements are also known as nutrients.

Cycles These and other nutrients are freed from wastes and dead organisms by decomposers which recycle them through the “carbon cycle”, and the “nitrogen cycle.”

Homework Textbook: Science Power 10 Read pgs. 38, 40, 42 Q. # 1-4, & 5 or 6 (on pg.42) Due Tomorrow!