Lesson 3-How Do Organisms Interact?
Objectives
- Observe how organisms help each other
- Describe how organisms compete within an
ecosystem
- Explain symbiotic relationships
Vocabulary
• Competition
• Symbiosis
• Parasite
• Host
Lesson 3
A. Limiting Factors – Competition for Resources
1. In an ecosystem, organisms compete for space, light,
food, water, air & nutrients.
2. Competition is the struggle among organisms for limited
resources in an area.
3. Every ecosystem and species must compete to stay alive
4. A predator is an animal that feeds on other living animals
5. Prey is an animal that gets eaten by the predator.
Vocabulary
• 166-Competition –
The struggle among
organisms for limited
resources in an area.
Write this Question in your books…
Q: Why does an increase in the number of prey
affect the number of predators?
A: The more prey there are, the more predators
can be supported.
Lesson 3
B. Organisms Interact to Meet Their Needs
1. Some organisms live together in a relationship called
symbiosis.
2. Symbiosis is a close relationship between organisms of
different species in which one or both of them benefit.
There are 3 types of Symbiosis (you will learn the 3 one tomorrow!).
3. Parasitism: one species benefits while the other is
harmed
4. Parasite is an organism that lives in or on another
organism
5. Host is the organism that the parasite lives on
6. Mutualism: both organisms benefit
rd
Vocabulary
168 - Symbiosis –
A close relationship between organisms of
different species in which one or both of the
organisms benefit.
168 – Parasite –
An organism that lives in or on another
organism.
168 – Host –
The organism that a parasite lives on.
Write this Question in your books…
Q: What effect does mutualisms have on
organisms?
A: Both organisms benefit.
Insta-Lab
Model Behavior
• Think of a relationship between organisms that
shows mutualism. Then make a model of this
relationship with clay. How does this
relationship benefit both organisms?
Lesson 3
C. Neither Help nor Harm
1. The third type of Symbiosis Commensalism: one
organism benefits and the other organism is neither
helped nor harmed.
Write this Question in your books…
Q: How are the effects of commensalism and
parasitism different?
A: In commensalism, one organism benefits, and
the other is neither helped nor harmed. In
parasitism, one organism benefits, but the other
is harmed.
Lesson 3 Review
In your groups, you will work on numbers:
1, 3-6
When you are finished, you may read, draw
in one of the illustration books, work on
other unfinished work or get on one of the
computers if available.