1. Community Interactions
Competition
Predation
Symbiosis
Figure Source:

2. 3 Major Types of Community Interactions
Recall: What is a community?
Community = assemblage of populations interacting with one another within the same environment
Organisms within a community interact with each other in 3 major ways:
- Competition
- Predation
- Symbiosis
Let’s look at each of these interactions in more detail.

3. What is Competition? Competition Competitive Exclusion Principle
Occurs when members of different species try to utilize a resource (such as light, space, or nutrients) that is in limited supply.
Results in a winner and a loser.
Think of sports teams when they compete.
Scenario #2 in our opening demonstration
Competitive Exclusion Principle
No two species can occupy the same ecological niche in the same habitat at the same time.

4. What is Predation? Predation
Occurs when one living organism feeds on another living organism.
Involves predator and prey
Predator = organism that feeds
on another organism
Prey = organism that is the food
Example: Lynx and bunny
In today’s lab, we’ll examine a predator-prey relationship.
Figure Source:
images/LynxAttackRabbit2.jpg

5. Mimicry- An Antipredator Defense
2 main types– Batesian & Mullerian
Batesian Mimicry
A harmless species resembles a poisonous or distasteful species
The harmless mimic is protected b/c it is often mistaken to be its dangerous look-alike
Example: A king snake (nonpoisonous) resembles a coral snake (poisonous)
King Snake Coral Snake

6. Mimicry- An Antipredator Defense
Mullerian Mimicry
When 2 or more dangerous or distasteful species look similar.
Each species involved benefits b/c a predator that encounters an individual of 1 species will avoid similar individuals.
Example: Bees & wasps have similar patterns of alternating yellow & black stripes.

7. What is Symbiosis? Symbiosis Let’s look at each type…
Refers to the close interactions between members of two species.
3 major types
► Parasitism
► Commensalism
► Mutualism
Let’s look at each type…
Figure Source:
birding/CattleEgret(JM).jpg

8. Parasitism
What is it?
A relationship in which one organism lives on or in another organism and gets its nourishment from it.
One organism is harmed (host) and one organism benefits (parasite)
Example:
Deer ticks on dogs
Can you think of any others?

9. Commensalism What is it?
Relationship in which one organism benefits and other organism is not hurt or helped.
One organism often provides a home and/or transport for the other organism.
Example:
Barnacles that attach themselves to backs of whales
The whale is not affected.
The barnacles benefit from transportation and eat small food particles in the water.
Can you think of any others?

10. Mutualism What is it? A relationship in which both members benefit.
Think of a “mutual agreement”  both parties benefit!
Example:
Bees and flowers.
Bee benefits because eats
nectar (food).
Flower benefits because the bee
spreads its pollen (reproduction).
Can you think of any others?

11. Symbiosis
You can think of the various types of symbiosis as almost a continuum…
Parasitism Commensalism Mutualism
( + / - ) ( + / 0 ) ( + / + )
An extreme
Helps one member
Hurts other member
In the middle
Helps one member
No affect on other member
An extreme
Helps both members

12. Checking your understanding– Quick Questions
What is a community?
What is the Competitive Exclusion Principle?
What is predation?
What is the name of the symbiotic relationship in which both organisms benefit?
What is the name of the symbiotic relationship in which one organism benefits and other is not helped or harmed?
What is the name of the symbiotic relationship in which one organism benefits but other is harmed?

13. Find an example
Using a computer or a smart phone, please find one example of a predator/prey relationship, a symbiotic relationship (be able to determine the type: mutualism, commensalism or parasitism)
Please find examples that we haven’t discussed in class.

14. Homework for tonight: Read pages 128-147 about biomes.
We will be playing biome bingo and doing an activity about biomes over the next two days.
Unit 2 Test will be on Friday! 10/5
In class review on Thurs. 10/4