The Ecosystem An Introduction

Ecosystem A community of interdependent organisms and the interactions with the physical environment in which they live. It can also be defined as the abiotic and biotic factors and the interactions between them. The interaction between organisms and the environment is the key!

Differentiate between the following terms: Organism Species Population Community Niche Habitat

In your notebook, draw a picture of a bunch of little organisms Label: The organisms of the same type (species) Circle: individuals of the same species (Population) Draw interactions between the populations (Community)

Compare the terms habitat and niche Sometimes people confuse these terms. Figure out the differences between the terms.

Niche vs habitat A habitat is wear an organism lives. The habitat must provide a source of food, water and shelter for the organism. Niche: The role of the organism. This is largely to do with the trophic level of the organism. For example: plants produce food for the rest of the food chain. Tigers keep herbivore populations under control.

Abiotic and Biotic factors Biotic Factor: A living, biological factor that may influence an organism or a system. Example: predation, disease, competition Abiotic factor: A non-living, physical factor that may influence an organism or a system Examples: Temperature, salinity, pH, light

Which factors are biotic? Rabbits Cacti Daylight hours Precipitation Moss Soil composition Bacteria

Limiting factors An abiotic factor can limit the population size if there is too much or too little of it. Even if there is the right amount of other factors Examples to consider: Sunlight Precipitation Salinity Nutrients in the soil

Trophic levels Ecostems are often broken up and described according to feeding relationships. Trophic level: The position of an organism in a food chain A group of organisms that occupy the same place in a food chain

Trophic levels in food chains Be able to give an example of each! Primary producers (autotrophs) Primary consumers (herbivores) Secondary consumers(carnivores) Tertiary consumers (top carnivores) Decomposers Detrivores Scavengers

Energy flow and material cycling

Producer lAutotroph - “self” + “feed” lAn organism that obtains organic food molecules without eating other organisms but by using energy from the sun or inorganic molecules to make organic molecules lRemember: This trophic level supports all of the others lThe role of producers is to convert energy into a form useable for other organisms

Producers lMost producers are photosynthetic (e.g. algae, mosses, diatoms, some bacteria, plants etc.) but some are chemosynthetic (e.g. hydrothermal vent bacteria) (H2)

Decomposer lAn organism that obtains energy by breaking down dead organic matter, including dead plants, dead animals and animal waste, into more simple substances lExamples include: bacteria and fungi L Interconnects all trophic levels since the organic material making up all living organisms is eventually broken down lRole of decomposers is to return valuable nutrients to the system so they can be used again

Compare detritus feeders to decomposers:

Consumer lHeterotroph - “other” + “feed” lAn organism that obtains its nutrition by eating other organisms lPrimary consumer (herbivore) - eats producers e.g. sea urchin, copepod lSecondary consumer (carnivore) - eats primary consumers e.g. wolf eel, herring lTertiary consumer - eats secondary consumers e.g. sea otter, seal lQuaternary consumer - eats tertiary consumers e.g. killer whale

Consumers The role of the consumer is to transfer energy from one trophic level to the next. Notice that consumers have different names, depending on what they eat: Herbivores: plant eaters Carnivores: meat eaters Omnivores: eat plants and animals

Food Chains

Show energy flow through an ecosystem Food webs Show energy flow through an ecosystem L An ecosystem’s trophic structure determines energy flow and nutrient cycling

Food webs

Trophic levels

Pyramid of biomass

Second Law of Thermodynamics There is a tendency for numbers and quantities of biomass and energy to decrease along food chains. The pyramids become smaller at the top because around 90% of the energy is “lost” between each level and only 10% is available in the body of the organism for transfer to the next level.

Energy transfer in a food chain: First law of thermodynamics

The end!