Transcript Chapter 4: The Human Body: From Food to Fuel

Community
Interactions
• Competition
• Predation
• Symbiosis
Figure Source: http://www.animalintelligence.org/images/deerbunny1.jpg
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.
What is Competition?

Competition
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.
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

Figure Source: http://www.lynescreations.com/
images/LynxAttackRabbit2.jpg
In today’s lab, we’ll examine a predator-prey
relationship.
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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
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.

What is Symbiosis?

Symbiosis
 Refers
to the close interactions between members
of two species.
3

major types
► Parasitism
► Commensalism
► Mutualism
Let’s look at each type…
Figure Source: http://www.camacdonald.com/
birding/CattleEgret(JM).jpg
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?

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?
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).

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Can you think of any others?
Symbiosis

You can think of the various types of symbiosis as
almost a continuum…
Parasitism
(+/-)
Commensalism
(+/0)
Mutualism
(+/+)
 An extreme
 In the middle
 An extreme
 Helps one
member
Helps one
member
 Helps both
members
 Hurts other
member
 No affect on
other member
Checking your understanding–
Quick Questions
1.
2.
3.
4.
5.
6.
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?
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.
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.
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Unit 2 Test will be on Friday! 10/5
In class review on Thurs. 10/4
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