1. Charles Darwin An English Naturalist – studied
An English Naturalist – studied
animals and their environment
how different species interact
with their environment
5 year voyage on the HMS Beagle
studied and collected biological
specimens at every port
Natural selection is the basis
for the modern evolutionary
theory

2. Voyage of the HMS Beagle
Many species of plants and animals that were similar to
those found on the main land
Species can change over time

3. Economist – essay on the principals of population
Thomas Malthus
Alfred Wallace
Economist – essay on the
principals of population
Biologist – Came to similar
conclusions as Darwin and
presented their findings
to the scientific community
Human population grow
Faster than earth’s food
supply

4. What kinds of struggle are there?
Competing for food
Competing for living space
Escape from predators
Finding a mate
Finding shelter
What individuals do you think would
survive to produce offspring?
Strongest
Smartest
Healthiest
Those most likely to survive the struggle for survival

5. Evolution
By Natural Selection

6. Natural Selection A mechanism for change in a population
Organisms with variations that aid in survival, reproduce, and pass their variations to the next generation
Organisms without these favorable variations are less likely to survive and reproduce
Subsequent generation consists largely of offspring from parents with the favorable variations

7. What are some variations?
Traits that vary
Skin or coat color
Eye color
Size of body or parts of body like tail, beak, claw or antlers

8. What is the source of variation in traits or characteristics?
Arise by Genetic Mutation
Build up on Existing Traits

9. How are these traits passed on to the generations that follow?
DNA

10. Sometimes we use this natural variation
Largest Hogs
Fastest Horses
Best hunting dogs
Cows that produce the most milk

11. Artificial Selection Selective Breeding Occurs when nature provides
variation among different
organisms and humans select
the variations they find useful
Selective Breeding

12. Natural Selection
Sometimes the environment acts as a selective agent by favoring individuals in the population that have a certain trait (like a specific color).

13. The bird prefer the green beetles over the orange ones.
As the birds select only the green beetles to eat the percentage of available green beetles decreases.
After many generations, the population has changed and green beetles are rare.

14. Darwin describes natural selection as
"Survival of the Fittest"
Fitness - the ability of an organism to survive and reproduce in its specific environment

15. Natural Selection Cannot be seen directly
Takes place over many generations
No human influence
Natural Selection increases the number of individuals with the beneficial trait, so the characteristics of a population change over time

16. Case of the Peppered Moth
England, late 1800s (Industrial Revolution period)
The gene for DARK is dominant over light
At one time light-colored forms of the moth were most common
Over a 50 year period, the dark form became the most common

17. Case of the Peppered Moth
Biologists hypothesized that this was an adaptive shift in response to a changing environment
Increased burning of coal during the Industrial Revolution had led to high levels of air pollution that killed the pale-colored lichens (tree moss) growing on tree trunks

18. Case of the Peppered Moth
The tree trunks, which previously appeared
to be a light, scaly color from the lichens,
became very dark
Tree trunk color is important to the survival
of moths. Moths rest on tree trunks during
the day
Birds, their primary enemies, mostly eat
varieties that are easy to find. Thus the
light form of this moth became rare

19. Light Peppered Moth
Light-colored peppered moth on a tree with a lichen

20. Light Peppered Moth
Light-colored peppered moth on a tree covered with soot

21. Dark-colored peppered moth on a tree covered with lichen
Dark Peppered Moth
Dark-colored peppered moth on a tree covered with lichen