Interactions Within EcosystemsChapter 2

Grade 7 ScienceUnit 1

SymbiosisInteractions between the biotic parts of the environment.

There are 3 types:1.Parasitism2.Mutualism3.Commensalism

1. ParasitismOne organism will benefit (the parasite) and the other is harmed (the host).

2. Mutualism Both organism benefit.

Lichen = algae + fungus

3. CommensalismOne organism benefits while the other neither gains or loses.

Salty Seeds

Core Lab Activity 1-2B p. 22

Roles of Organisms in the Ecosystem

1. Producers2. Consumers3. Decomposers4. Scavengers

1. ProducersPlants can produce their own food from the abiotic environment. (photosynthesis)Water + carbon dioxide +

Sunlight

Food (sugar) + oxygen

2. ConsumersAnimals must consume, eat other organisms. (the biotic environment)

Can be classified as... herbivores, carnivores, or omnivores.

Herbivore:Animals that eat ONLY plants (producers).

Omnivore:Animals that eat both plants AND animals.

Carnivore:Animals that eat ONLY other animals.

3. DecomposersOrganisms that break down dead and waste materials into their basic parts.

They release chemicals that break apart dead tissues and cells and absorb the nutrients for their own use.

Examples include bacteria and other microorganisms, fungi and worms.

4. ScavengersAnimals that eat decaying animals and waste materials.

Examples include vultures, dung beetle larvae, houseflies, crows and some gulls.

Microorganisms...are found in a variety of habitats (air, soil, water)

play important roles in relation to human food supplies

have been studied to enhance food preservation techniques

Conditions that affect Microorganism Growth

1. Temperature2. Moisture3. Light4. Acidity5. Salinity

Food PreservationCreates an environment which destroys existing decomposers and then prevents or slows down their growth rate.

Methods of Food Preservation

1. Pickling2. Salting3. Drying4. Smoking(the above started out of

necessity )

1. Refrigerating2. Freeze-drying3. Radiation4. Canning

(These are more modern and

technology based.)

Food ChainsThe transfer of energy from organism to organism. Arrows show the direction of energy flow.

Green plants are the food (energy) source for all consumers and decomposers.

Producers

Primary Consumers

SecondaryConsumers

A Sample

Food Chai

n

Food WebsInterconnecting food chains.

A Marine Food Web

Energy PyramidsDescribes the gradual loss of energy in food chains

About 10% is lost as you move from one level to the next and 10% of the new energy is lost as you move up and so on.

Energy in grass: 10 000 J

Energy in mice: 1000 J

Energy in weasel: 100 JEnergy in hawk: 10 J

Note: Energy pyramids are not exact. Energy is transferred to other types (eg. heat) as it moves from one level to the next. ie. Not all of the 10% is transferred.

Nutrient CyclesNutrients, such as nitrogen and carbon, are recycled in the environment.

All organisms are eventually recycled and their nutrients are returned to the soil by the action of decomposers.