1. Big Idea: The types and characteristics of organisms change over time.
Unit 1 Lesson 2 Theory of Evolution by Natural Selection
Essential Question: What is the theory of evolution by natural selection?
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2. Darwin’s Voyage What did Darwin observe? p16
Unit 1 Lesson 2 Theory of Evolution by Natural Selection
Darwin’s Voyage
What did Darwin observe?
Charles Darwin became a naturalist, a scientist who studies nature, during a voyage on the British ship HMS Beagle.
On his journey, Darwin observed and collected many living and fossil specimens.
Darwin made his most important observations on the Galápagos Islands of South America.
Darwin formed the theory of biological evolution using the observations that he had made during an almost five-year journey.
Evolution is the process by which populations change over time.

3. Evolution and natural selection
p16
Unit 1 Lesson 2 Theory of Evolution by Natural Selection
Evolution and natural selection
Evolution is the process by which populations change over time.
A population is all of the individuals of a species that live together in an area at the same time.
A species is a group of closely related organisms that can produce fertile offspring.

4. 5 parts of Natural Selection
Unit 1 Lesson 2 Theory of Evolution by Natural Selection
What are the five parts of natural selection?
5 parts of Natural Selection
Over-production
Selection
Adaptation
Genetic Variation
Competition

5. p18
Unit 1 Lesson 2 Theory of Evolution by Natural Selection
Natural Selection
Natural selection is the process by which organisms that inherit advantageous traits tend to reproduce more successfully.

6. p18
Unit 1 Lesson 2 Theory of Evolution by Natural Selection
Natural Selection
1-Overproduction is the process by with a species plant or animal makes more offspring than the environment can support.
Only some will survive into adulthood.
Smaller number of them will then successfully reproduce
Over-production

7. What are the four parts of natural selection?
Unit 1 Lesson 2 Theory of Evolution by Natural Selection
What are the four parts of natural selection?
Genetic Variation
Within a species there are natural differences, or variations, in traits.
Variations come from differences in genetic material. Genetic variations can be passed on from parent to offspring.
An important source of variation is a mutation, or change in genetic material.

9. 2. Variation
Each individual has a unique combination of inherited traits.
Adaptation: an inherited trait that increases an organism’s chances of survival

10. Genetic variation can increase in a population
Unit 1 Lesson 2 Theory of Evolution by Natural Selection
What are the four parts of natural selection?
Genetic variation can increase in a population
The more genetic variation, the more likely that some individuals might have traits that will be advantageous if the environment changes.
As each new generation is produced, new genetic differences may be introduced into a population.
Genetic Variation

11. 3. Competition Individuals COMPETE for limited resources:
Food, water, space, mates
Natural selection occurs through “Survival of the fittest”
Fitness: the ability to survive and reproduce
Not all individuals survive to adulthood

12. p21
Unit 1 Lesson 2 Theory of Evolution by Natural Selection
4-Selection………..
Individuals try to get the resources that they need to survive, including food, water, space, and, in most cases, mates for reproduction.
Darwin reasoned that individuals with a particular trait are more likely to survive long enough to reproduce.
As a result, the trait is “selected,” becoming more common in the next generation of offspring.
Selection

13. 4. Selection
The individuals with the best traits / adaptations will survive and have the opportunity to pass on it’s traits to offspring.
Natural selection acts on the phenotype (physical appearance), not the genotype (genetic makeup)
Ex: When a predator finds its prey, it is due to the prey’s physical characteristics, like color or slow speed, not the alleles (BB, Bb)

14. Selection
Individuals with traits that are not well suited to their environment either die or leave few offspring.
Evolution occurs when good traits build up in a population over many generations and bad traits are eliminated by the death of the individuals.

15. p21
Unit 1 Lesson 2 Theory of Evolution by Natural Selection
5- adaptation
An adaptation is an inherited trait that helps an organism survive and reproduce in its environment.
As natural selection repeats from generation to generation, these adaptations become more common, and new adaptations may arise.
Over time, the population becomes better adapted to the environment.
Adaptation

16. Well-adapted Well-adapted p22
Unit 1 Lesson 2 Theory of Evolution by Natural Selection
Well-adapted
Well-adapted
Adaptations are variations that help a species survive and reproduce.
At first, adaptations are rare. As more of the species survive and reproduce, the number of individuals with the adaptation will increase.
Other adaptations are inherited behaviors that help an organism find food, protect itself, or reproduce.

17. p22
Unit 1 Lesson 2 Theory of Evolution by Natural Selection
Well-adapted
Parents and offspring often have small differences in genetic material, but over many generations, these differences add up.
These differences accumulate so that organisms alive now are often very different from their ancestors.

18. p23
Unit 1 Lesson 2 Theory of Evolution by Natural Selection
All organisms have traits that allow them to survive in specific environments.
If the environment changes, a species is more likely to survive if it has genetic variation, which results in a variation of traits.
If no individuals have traits that help them to survive and reproduce in the changed environment, a species will become extinct.

19. p23 Extinction occurs when all members of a species have died.
Unit 1 Lesson 2 Theory of Evolution by Natural Selection
Extinction occurs when all members of a species have died.
Greater competition, new predators, and the loss of habitat are examples of environmental changes that can lead to extinction.
Because a natural disaster can destroy resources quickly, organisms may die no matter what adaptations they have.
The fossil record shows that many species have become extinct in the history of life on Earth.