1. Interactions in Communities
SB.4.a Interactions in communities can take many forms from predation to mutual “friendships”. Symbiosis – a relationship in which to different organisms live in close association with each other

2. Predator-Prey Relationships
One of the most common interactions in the communities.
Predation – an interaction between two organisms in which one organism, the predator, kills and feeds on the other organism, the prey.
Example:

3. Herbivory Relationships
Herbivores are animals that eat plants.
Plants have adapted and try to defend themselves.
Chemicals to make them taste bad
Spines that can puncture their mouths
Toxins
In response herbivores came up with ways to defend themselves against the plants
Curious? What are your thoughts on that?

4. Parasitism! http://www.youtube.com/watch?v=o0LuJ6Fe0bw&feature=related
Parasitism – a relationship between two species in which one species, the parasite, benefits from the other species, the host, which is harmed.
The host is almost always bigger than the parasite
Parasites live on or in their host
We always have some form of parasite living within us
What are ways to defend ourselves from parasites?

5. Mutualism
A relationship between two species in which BOTH species benefit.
Ex. The Crocodile and the Egyptian Plover Bird
What are some
other examples?

6. Commensalism
A relationship between two organisms in which one organism benefits and the other is neither harmed nor benefits.
Ex. Nemo and his home.
Where else do you see commensalism?

7. Energy Transfer: Food Chains
SB.4.b
Every living being on this planet requires energy to be able to function and are interdependent of each other.

8. Producers
Autotrophs manufacture their own food by capturing energy and use it to make organic molecules (i.e. glucose).
Autotrophs are also called “Producers”
Producers can either be photosynthetic (use solar energy) or chemosynthetic (use inorganic molecules to make carbohydrates).

9. Consumers
“Heterotrophs” – obtain energy by consuming organic molecules made by other organisms. + =

10. Five Categories of Consumers
What are they?

11. Herbivores
Herbivores – Ex. Cows, Rabbits – eat producers

12. Omnivores
Omnivores – Ex. Humans, Bears – eat producers and other consumers

13. Carnivores
Carnivores – Ex. Lions, Wolves – eat other consumers

14. Detrivores
Detritivores – Ex. Vultures – feed on the “garbage” of an ecosystem (dead plants and animals)

15. Decomposers
Organisms that break down dead or decaying organisms, and in doing so carry out the natural process of decomposition – Ex. Fungi, Bacteria

16. Food Chains
A single pathway of feeding relationships among organisms in an ecosystem that results in energy transfer.

17. Food Web
The interrelated food chains in an ecosystem.

18. Energy Flow
Whenever one organism eats another, the molecules are metabolized and energy is transferred.
Energy goes from producers to consumer
A way to keep track of energy flow is to place the organisms in a trophic level pyramid according to how they obtain energy (Who eats who?).

19. Trophic Levels
Indicates an organism’s position in the sequence of energy transfer.
Producers are always placed in the 1st trophic level.
Most ecosystems only contain 3 to 4 trophic levels –What could possibly explain this?
Secondary Consumers
Primary Consumers
Producers

20. Apple vs. Burger Which do you think is more satisfying?
Which is a better source for a quick source of energy?
Why?
The 10% “Rule”:

21. Why Such A Low Amount?
Some organisms escape and not eaten (lucky them)
Even if they are eaten, certain molecules (i.e. cellulose) can not be broken down by the consumer.
The energy used by prey for cellular respiration cannot be used by predators to synthesize new biomass.
No transformation or transfer of energy is 100% efficient

22. Does This Explain Why There Are Only A Few Trophic Levels In An Ecosystem?
Yes
Because of the 10% Energy Transference from one trophic level to the next.
Also, this explains why plants are more abundant in an environment than herbivores, and there are more herbivores than carnivores.