NATURAL SELECTION!!

• Watch DISCOVERY VIDEO on natural selection• How have marine environments played an

important role in study the development of populations?

Darwin’s Finches

What is a variation?Variations – differences among organisms of the same

species

* For example, a species of rabbit has different colors of fur like white, grey, mixed

* Occurs largely as a results of SEXUAL reproduction

* Can also occur because of mutations

Review Key Terms!

What is an adapation?Adaptations - an inherited characteristic that increases an organism's chance of survival

*for example, cats have night vision to better hunt prey

Review Key Terms!

Reviewing and USING Key Terms!There are two tropical birds in the jungle, named

Megan and Sammy. Megan and Sammy are brother and sister, but Megan’s wings are about 4 inches longer than Sammy’s wings.

1. What is the variation between the birds?2. Which bird has the adaptation?3. What is the adaptation?

What is fitness?Fitness- the ability to survive AND reproduce

*fitness is the result of adaptations

*fitness depends on the environment

*those that are more fit will reproduce, those that are less fit will die

Add to “Natural Selection Notes!”

Natural selection is the process of evolution. Individuals that are better suited to their environment are able to survive and reproduce more successfully (they have adaptations to be more fit)

*this is also known as survival of the fittest

*after many generations of time, only certain individuals of a population produce new individuals

What is natural selection?

Which variation of cheetah is best adapted to live in the environment shown here?

“Nerds Natural Selection Lab!”• Groups of 2

– 1 warden (timer), 1 hunters– Warden: spread Nerds onto environment– Environment Cloth– 15 seconds per hunt! (3 trials)

____picked up

_____picked up

____picked up

Trial 1

Trial 2

Trial 3

• EVERYONE: graph results– POINTS will be awarded as follows:

• Name on graph• Data on graph• Labeled X axis• Labeled Y axis• Title for graph

“Nerds Natural Selection Lab!”RESULTS:

1. What were the variations of nerds?

2. What variation of nerd was best adapted to survive in your environment?

3. What is this process called?

“Nerds Natural Selection Lab!”CONCLUSION SHORT ESSAY:

Review Key Terms!What is NATURAL SELECTION?:

1. the process of evolution2. Those individuals who are favored in the

environment are SELECTED FOR, and therefore reproduce and pass traits to their offspring!

SHORT ESSAY – Evolution and Natural SelectionA species of birds lives on an island. The thickness of the birds' beaks varies within the population. The birds feed mainly on seeds from plants. Birds with thinner beaks can eat only small seeds. Only birds with thicker beaks can crush and eat large seeds. There are many small seeds during years with more rain. During dry years, there are very few small seeds and many large seeds. The large seeds are harder to crush than small seeds.

The graph below shows the average beak thickness in the bird population from 1979 to 1985: 1980 and 1982 were dry years; 1984 was a wet year; 1979, 1981, 1983, and 1985 received normal rainfall.•Explain why the average beak thickness changed between wet and dry years.•Explain how beak thickness would have changed during the next ten years, 1986 to 1996, if these years were wet years.•Name and explain the process that led to this change.

Extra Slides Below

Optional BSCS Independent Research Mutations as a Source of Variation

• Read this selection beginning on Page 139 of the BSCS BOOK!

• Summarize the reading in your own words.

• Explain the following:Mutations variations adaptations

• How are mutations a part of natural selection?

1. What variations must have existed to begin this process? What possibly caused these variations?

2. What did the original bear population look like in the Artic? Which bears were more fit for the environment? How did the population change over 100,000 years?

3. Describe several ‘differences’ that have enabled polar bears to survive in their environment. What are these ‘differences’ called?

4. What scientific process does this scenario illustrate? 

Polar Bear and Brown Bears

1. What variations must have existed to begin this process? What possibly caused these variations?

2. What did the original bear population look like in the Artic? Which bears were more fit for the environment? How did the population change over 100,000 years?

Polar Bear and Brown Bears

Variations in fur color; caused by differences in genes through either sexual reproduction or mutations

Original population was probably brown, but lighter bears were more fit. The bears with the lightest (whitest) coats survived the best.

3. Describe several ‘differences’ that have enabled polar bears to survive in their environment. What are these ‘differences’ called?

4. What scientific process does this scenario illustrate? 

Polar Bear and Brown Bears

These ‘differences’ are called ADAPTATIONS!• Better sense of smell, vision and hearing• Sharper teeth• Longer neck• Warm thick fur and large paws

NATURAL SELECTION ! ! !

1. Variations exist in a population.

2. Some organisms are better suited for the environment (more fit).

3. Nature “selects” the best individuals to survive! (Usually based on specific adaptations.)

4. The surviving individuals reproduce more offspring like themselves.

5. Over many generations, the population changes and new species evolve.

Evolution by Natural Selection