2. Interactions among living organisms
REVIEW:
What is a population?
- A population is a group of the same kind of
species that live in the same area
- They compete for resources like:
3. Populations
• Characteristics:
– Size
• how many organisms
(species!) does this
population have?
– Spacing
• need enough space to live
– Density
• The number of individual
organisms in a certain area
• The size of populations is
always changing
– One way populations
change is through
limiting factors
4. Limiting Factors
• Can populations grow forever?
– No! Why not?
• Limiting factor: Any abiotic or biotic factor
that controls the number of individuals in a
population
5. Limiting Factors
• What limits the growth of a population?
• Abiotic limiting factors:
– Temperature
– Drought and other
weather events
– Space to live
– Others?
• Biotic limiting factors:
– Predators
– Others?
6. Limiting Factors
• Competition
– The struggle among organisms to get the resources
they need to:
• Survive
• Reproduce
– Example: many birds may move to a new tree to live.
They are competing for space to create their nest.
– Example: Students at GI compete with each other to
have a good place in line for pizza at the tienda during
recess
Editor's Notes
Pose these questions as using the students in our class – Size: how many organisms does our population have? Spacing – do we have enough spacing to do our work, be comfortable in class? And Density, which is the how many people for the size of this room
