Population Changes
What two processes are always happening in a population?
Births and deaths
What is a system that stays the same even with things being added and removed called?
A stable system
What do organisms need to reproduce?
Energy
What happens when a resource population increases?
Consumer population can increase
What is it called when two populations need the same resource?
Competition
What happens to a population if births equal deaths?
The population stays the same (stable)
What must be true for a system to stay stable?
The amounts added and removed must be equal
Where do organisms get energy from?
Energy storage molecules (food)
What happens when a consumer population increases?
Resource population decreases
What happens when one competing population increases?
The other may decrease
What happens if births are greater than deaths?
The population increases
What happens if more is added to a system than removed?
The system changes (grows/increases)
What happens when more energy is available to a population?
More reproduction occurs
Why do more consumers cause more deaths in a resource population?
They eat more of the resource
Can populations affect each other even if they don’t directly interact?
Yes
What happens if deaths are greater than births?
The population decreases
What happens if more is removed than added?
The system decreases/changes
What do consumer populations eat to get energy?
Resource populations (plants/animals)
If rabbits increase, what might happen to grass?
Grass decreases
What system connects multiple populations together?
A food web
A deer population has 20 births and 20 deaths in a year. What happens?
The population stays stable
Give an example of a stable system in nature.
population with equal births/deaths
Why would a population stop growing even if there are births?
Not enough energy/food available
Explain how energy moves from resource to consumer.
Consumers eat resources to get energy
Give an example of an indirect effect in a food web.
Example: Wolves decrease → deer increase → plants decrease