1. Variations in Populations
SPI
Variations in Populations
Notes
Science
Learning Intention: Examine variations in a population to predict which sub-group will most likely survive.
Purpose: to understand how species populations adjust their bodies and their actions to survive and thrive.
Success Criteria:
I will show that I understand this by passing the quiz with
a 90 or higher.
I Can Statement:
By the end of this unit I will be able to say...
...I can explain how variations in populations makes a species
more adaptable.

2. Variation in Populations
Variation refers to a variety or diversity of traits
(different kinds) within any given population.
Three causes of variation
1) Diversity of genetic traits from sexual reproduction
2) Diversity of genetic traits that result from mutations
3) Changing environmental conditions
Adapt or Die
Environments always change, sooner or later.
Organisms must adapt to these changes or die.
If too many individuals die, then the species goes extinct.
When a significant environmental change occurs, having a variety of traits within a population provides the species a better chance that at least some small portion will have traits that are suited to the new environmental condition.

3. Four Phases of Natural Selection
Bunny Rabbits
Overproduction
Too many offspring are born.
Phase 1
Genetic Variation in a Population
Offspring are born with a variety of traits. Some offspring are better suited to survive than others.
Phase 2
Genetic Variation in a Population
Offspring are born with a variety of traits. Some offspring are better suited to survive than others.
Struggle to Survive
Offspring compete for limited resources. Many die or are eaten by predators.
Phase 3
Successful Reproduction
The stronger, smarter, faster offspring survive to breed with each other.
Phase 4

4. Variation in Populations
The Galapagos Islands are located in the Pacific Ocean about 600 miles west of Ecuador (see picture below).
At some point in the past, a small population of Finches (birds) were blown from South American to these islands.
Each island has a slightly different ecosystem, and these finches adapted accordingly. This lead to significant variation in the shapes and sizes of their beaks.
South American Finch
Galapagos Islands
Consists of 18 larger islands
and 3 smaller islands.

5. Variation in Populations
Over time the finches developed different beak shapes and sizes in order to eat the local food (structural adaptations).
Food Source
Only Bugs
Food Source
Nuts & Bugs
Food Source
Only Nuts
narrow-pointed beak for eating insects
Moderately wide beak with a sharp point for cracking nuts and eating insects
Very wide beak for only eating nuts

6. Finches on the Galapagos Islands
Essential Question
What is the link between genetic variations, the environment, and
the survival rate of sub-groups in the population?
Finches on the Galapagos Islands
The Finches had offspring with a variety of traits.
This included different shaped beaks.
Some offspring had larger/wider beaks.
Some offspring had narrow/pointed beaks.
Food Sources
Some islands had mainly seeds/nuts
Other islands had mainly insects.
Natural Selection:
On each island, Finches with the most effective beaks dominated
while those with less effective beaks died out

7. Review Questions

8. Note: Termination refers to the percentage of bugs that were killed
Review Questions
Note: Termination refers to the percentage of bugs that were killed

9. Review Questions

10. Review Questions

11. Review Questions