Download 4-7-16 Ecology outline 3

Unit 12: Ecology
Content Outline: Community Ecology (12.3)
I.
Community – This term refers to a collection of interacting populations within the same given area.
A. Species Richness – Refers to the number of different species within a given area.
B. Relative Abundance – Refers to the population size for each species within that given area.
1. Rare – few exist; common – many exist
II.
Interspecific Interactions - Are interactions between two different species. “Inter” means “between”
A. Competition ( - );( - ) It is considered a negative- negative relationship.
1. Competition exists because a resource is in small supply.
2. Active competition drains energy away from reproduction. (So populations are smaller.)
3. Two species cannot occupy the same niche.
4. Intraspecific competition –Competition within a species
a. Ex. Male deer fighting for mates
5. Interspecific competition – 2 different species competing for food or habitats
a. Ex. Scorpions and spiders
B. Predation ( + ); ( - ) Considered a positive – negative relationship.
1. Normal predation - Carnivore or Omnivore eats an herbivore.
2. Herbivory - Eating plants is also considered predation…since they are a different species.
3. Parasitism – Death does not occur; but harm is done to another species.
a. Two types: 1) Ectoparasites – These attack from the outside. (mosquito)
2) Endoparasite – These attack from the inside. (tapeworm)
4. Adaptations for being a predator – claws, teeth, poisons, fast locomotion, muscular (All help kill.)
a. Self defense adaptations against predators – long legs, faster, flight, horns, coloration,
very good smell
i. Cryptic coloration – camouflage (like encryption)
ii. Aposematic (warning) coloration – bright colors like reds or oranges
iii. Mimicry– Batesian type – A harmless looks like a harmful organism.
This becomes an associative learning exercise for the
attacking species. They become very scared to attack
organisms that look similar to that bad experience. This
increases survival rates for the mimickers.
- Műllerian type – A harmful looks like another harmful.
C.
Mutualism ( + ); ( + ) Considered a positive-positive relationship.
1. This relationship promotes co-evolution, but remember that co-evolution can either be good or bad, such as
the predator/ prey relationship… it is co-evolution too.
D. Commensalism ( + ); ( 0 ) Considered a positive- no effect relationship.
1. Few exist in nature and it is hard to see if there is no reciprocal effect.
III.
Trophic Structure (Feeding Relationships)( “Troph” means “to feed”)
A. Matter Cycles -Materials (matter) get recycled within the environment. This is related to the Law of
Conservation of Matter… Matter is neither created nor destroyed… only transferred and transformed.
A. Energy Flow - Sunlight enters earth, is received by plants and made into Chemical Energy (sugars). Then the sugars
are passed from organism to the next organism by consuming the previous organism. Eventually all energy becomes
heat with each transfer and metabolism, which is when the heat energy leaves the earth. (Demonstrates the Second
Law of Thermodynamics…All Energy proceeds towards a state of Entropy with each transfer.)
B. Food chains –Food Chains demonstrate an orderly flow of who eats whom. (Producers eaten by consumers,
consumers and producers broken down by decomposers.) Arrow points in the direction of the flow of energy (the
organism that is doing the eating).
1. Most food chains only have four to five trophic levels in them, because you run out of energy to transfer and
support life.
2. Energy Pyramid - The 10 % rule of E (90 % of all energy is lost as heat by metabolism of that organism;
10 % of the energy is passed on to next trophic level each time.)
For example:
10 joules of E (Snake) – END HERE
100 joules of E (Mouse)
1000 joules of E (Grasshopper)
10,000 joules of E (Grass/flower… producers) – START HERE
Each time only 10% of the E gets passed on to the next higher level in the chain. 90% is lost on the
metabolism maintaining the life of that organism before it is eaten or as waste.
3.
4.
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Remember energy is not created or destroyed. It is merely converted from one form to another.
When we say we “lose” energy as heat it doesn’t mean it goes away. It means it escapes our body in the
form of heat, and in this form it is unusable by us. The sun is the ultimate source of energy that
continually powers photosynthesis and supplies all food chains with energy as producers convert the
sun’s energy to glucose. Even though energy is not “created or destroyed” it still flows one way through
a food chain (starting with the sun and ending at the top consumer)
•
Energy is used for growth, movement, homeostasis, etc. It is also lost as heat because
these processes are not perfect (notice when you go run outside in the cold you’ll have steam
coming off of you because you are using a lot of ATP. Some of the energy is being used to move
your muscles and some of it is escaping as heat because the conversion process is not perfect).
•
This is why food chains can only be 4 or 5 trophic levels long. If they were any longer,
there wouldn’t be enough of the original made by the producers left to support the higher trophic
levels. It would require an enormous amount of producers to support a longer food chain.
•
The lower energy percentage in an energy pyramid does not mean that it literally gets less calories.
It means that it gets less of the original energy produced by the producer; therefore, there must be a
greater number of producers (producing a greater amount of energy) to support longer food chains. When
we eat something, we only get the energy that organism had STORED as carbohydrates, lipids, or
proteins to be used later. We do not get the energy from the ATP they’ve already made and used.
o
What would be the best way to cure world hunger – feed everyone grain or meat? Why?
Pyramid of Numbers
•
Population size
•
The population size of each trophic level will also decrease by 90% during each trophic level
because of the fact that we lose 90% of the energy. If there is less energy to support the trophic level,
then there has to be less organisms there (or they would all starve to death).
 Sometimes the number of primary consumers can actually be higher than the producers though. For
example, millions of ants could live on the sap made by one tree.
Pyramid of Biomass
•
biomass = dry weight (all organic material minus water)
•
This pyramid illustrates the total amount of living material at each trophic level.
•
The pyramid of biomass for terrestrial animals also loses 90% for each trophic level for the same
reason described above.
C. Food web – A model showing all possible feeding relationships that could exist within an area. (A food web is
essentially interacting food chains.)
 Organisms DO NOT have to be in the same trophic level in all food chains. Ex. You are in different trophic
levels when you eat a steak and baked potato at the same time.
 Keystone species – Species that are integral to the entire ecosystem. Their niche impacts most (if not all) of
the other organisms in the ecosystem.
D. Food Cycle – A food chain AND the decomposers/detritivores that recycle the organic material back into the soil.
 Detritivores – Eat decaying matter (Detritus = Decaying organic matter)
 Decomposers – Microscopic (bacteria) decomposers that completely break down decaying material.
 Remember that matter is not created or destroyed. It is recycled.
IV.
V.
Stability – A community at equilibrium. (Very little disturbance/change occurs over time.)
Ecological Succession – Change in community composition due to time and disturbance.
A. Two types can occur within environments
1. Primary Succession – This is “starting from scratch” using pioneer species – lichens and mosses.
a. Hawaii going from barren volcanic rock to plush, tropical island.
b. Pioneers make the dirt needed for the plants and birds bring seeds in their feces as they feed upon
lichens.
c. Lichens  grasses  bushes  gymnosperms  hardwood trees  Climax
d. Climax Community – Hardwood forest exists all over the specific area.
2. Secondary Succession – This is “starting over at the grasses level” not from scratch.
(Such as the farming of fields to grow crops.)
a. Dirt already exists.
b. Grasses  bushes  Gymnosperms  hardwood trees  Climax