Grade 7 Science
Unit 1
Interactions Within
Ecosystems
Chapter 2
Symbiosis
Interactions between the biotic
parts of the environment.
There are 3 types:
1. Parasitism
2. Mutualism
3. Commensalism
1. Parasitism
One organism will benefit (the
parasite) and the other is harmed
(the host).
2. Mutualism
 Both organism benefit.
Lichen = algae + fungus
3. Commensalism
One organism benefits while the
other neither gains or loses.
Core Lab Activity 1-2B p. 22
Salty Seeds
1. Producers
Plants can produce their own
food from the abiotic
environment. (photosynthesis)
Water + carbon dioxide + Sunlight
Food (sugar) + oxygen
Roles of Organisms in the
Ecosystem
Producers
2. Consumers
3. Decomposers
4. Scavengers
1.
2. Consumers
Animals 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. Decomposers
Organisms 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. Scavengers
Animals 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
1.
2.
3.
4.
5.
Conditions that affect
Microorganism Growth
Temperature
Moisture
Light
Acidity
Salinity
Food Preservation
Creates an environment which
destroys existing decomposers
and then prevents or slows down
their growth rate.
Methods of Food Preservation
1. Pickling
2. Salting
3. Drying
4. Smoking
(the above started out of necessity )
Refrigerating
2. Freeze-drying
3. Radiation
4. Canning
(These are more modern and
technology based.)
1.
Food Chains
The 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
Secondary
Consumers Consumers
A
Sample
Food
Chain
Food Webs
Interconnecting food chains.
A
Marine
Food
Web
Energy Pyramids
Describes 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.
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.
Energy in hawk: 10 J
Energy in weasel: 100 J
Energy in mice: 1000 J
Energy in grass: 10 000 J
Nutrient Cycles
Nutrients, 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.