Chameleon and Grasshopper from Animal Planet, http://animal.discovery.com/tv/a-list/creature-countdowns/cheats/cheats-08.html

    Lizard Evolution Lab 

Evolution

• evolution is the change in the traits of a species over time.
• evolution is not changes in an individual organism during its life.
• evolution is changes that happen to a group of organisms over generations 

Evolution of Peppered Moths

Peppered moths show two traits for color: white and black.

How did a group of peppered moths change over time?

Which color is better?

What decides which color is better?

Peppered Moths Activity - click the link

• then click the circle with the bird

• then read the text
• click the arrow to continue

• answer the questions below as you do the simulation

Peppered Moth Phenotypes

Peppered moths in two environments

http://anthro.palomar.edu/evolve/evolve_2.htm

Questions

• Which forest did you choose?
• Which moth was the easiest to see and eat?
• Why? 
• What happened to size of the white population?
• What happened to size of the dark population?
• What happened to the whole population of moths? 

Natural Selection

Natural selection - the theory that explains how species change over time.

It has four parts:

1) Overproduction and competition: A lot of species produce more offspring than can survive. This leads to competition for resources like food and water.

2) Variation - species have variations of their traits because of mutations and sexual reproduction.

3) Selection of adaptations - traits that are beneficial for survival are called adaptations. The environment selects which traits are adaptations.

4) Descent with modification - over generations the number of individuals with adaptations increases because individuals with adaptations survive and reproduce more than individuals without adaptations.

Changes in traits of a species over time is evolution.

Define and give examples of each component of natural selection:

• overproduction:

• competition:

• variation:

• selection:

• adaptation:

• descent with modification:

Sickle Cell Anemia

What is it?

What causes it?

Genetics

What are the alleles?

What are the genotypes?

What are the phenotpyes?

What will happen to the sickle cell allele over time?

Environment

What is malaria?

How does the sickle cell trait affect malaria?

What will happen to the frequency of the sickle cell allele in an environment where malaria is common?

Compare the frequency of the allele and the incidence of malaria in a geographic location.

Charles Darwin

Who was Charles Darwin? When did he live? Where did he live?

What was The Beagle?

Where are the Galapagos Islands?

What are Darwin's finches?

What are their adaptations?

What was Darwin's big idea?

Evidence of Evolution

What does the term common ancestor mean?

Fossils

What are fossils?

How does fossil evidence show evolution?

Find an example of fossil evidence.

Anatomy

What is anatomy?

What are homologous structures?

Find examples of homologous structures.

Biochemisty

How can DNA and proteins show evolution?

What happens if we compare the DNA or proteins for two different species?

Genetic variation within a population

• Genetic variation causes phenotypic variation (differences in traits)

• Natural selection acts on phenotypic variation.

• A gene pool is the genetic variation of a population. It is all the alleles of a population.

• Allele frequencies measure genetic variation. The allele frequency is the percentage of an allele in the population compared to the total number of alleles in the gene pool.

Mutations cause changes in DNA and create new alleles. The new alleles can be passed on if the mutation happens in a sex cell.

Sexual reproduction creates new combinations of existing alleles.

Evolution is defined as a change in allele frequencies over time.

Questions

1. What is a gene pool?
2. What is allele frequency?
3. How are allele frequency and gene pool related?
4. What two things increase genetic variation?
5. Why is genetic variation good? How does it help a population survive?

Other mechanisms of evolution

Evolution by gene flow, genetic drift, and sexual selection

• Natural selection is not the only cause of evolution.

• Gene flow, genetic drift, and sexual selection also cause evolution.

1. Gene flow is the movement of alleles between different populations. It is caused by emigration and immigration when individuals leave one population and move to a new population.

• Gene flow makes two populations similar because they share alleles.

• No gene flow allows two populations to evolve differently.

There are two kinds of genetic drift: bottleneck effect and founder effect.

• The bottleneck effect is when a random event reduces the size of population. The surviving population is very small and has less genetic variation.

• The founder effect is when a small group leaves a population and starts a new population. Because of the small size, the new population has less genetic variation.

Genetic drift is bad. The decrease in genetic variation decreases the possibility of adaptations.

3. Sexual selection happens when specific traits increase the chance for reproduction.

There are two kinds: intrasexual and intersexual selection.

Intrasexual selection is competition between males.

• Example: male lions fight to decide which one reproduces with the females.

Intersexual selection is males using traits to attract females.

• Example: male birds show their feathers to attract females for reproduction.

Questions 

1. Describe gene flow.

2. Describe genetic drift.

3. What are two kinds of genetic drift? 

4. Label the diagrams with these titles: gene flow, bottleneck effect, and founder effect.      

A. 

B.

C.

5. Does gene flow increase or decrease genetic variation? 

6. Does genetic drift increase or decrease genetic variation? 

7. Are traits that are good in sexual selection also good in natural selection

Give an example of how the trait could be good or bad or both.

Speciation

How do new species evolve?

Speciation is the process of two species evolving from one original species.

1. A population is separated into two populations of the same species.

2. No gene flow happens between the populations

3. The environments are different for the two populations.

4. Natural selection chooses different adaptations for each population.

5. The two populations slowly become different by natural selection.

6. Over many generations, the two populations become very different and are no longer the same species.

7. Speciation had happened when the two population are so different that they cannot reproduce togther.

In steps 6 and 7, reproductive isolation is the last part of speciation. Reproductive isolation is when the two populations are too different to successfully reproduce together.

A species is usually defined as a group of similar organisms that can reproduce together.

The reproductive isolation can happen in three ways:

1. geographic isolation: the populations are isolated by a physical characteristic of the Earth, like mountains, rivers, oceans, etc.

2. behavioral isolation: the populations are isolated because their reproductive behavior is different, like courtship displays and songs, and chemical signals (pheromones) to attract mates.

3. temporal isolation: the populations are isolated because of the time when they reproduce, like plants making gametes during specific seasons.

Questions

1. Define speciation.

2. What does isolation mean?

3. What does reproductive isolation mean?

4.  What are three kinds of reproductive isolation?

5. If two populations are isolated, is gene flow happening?

6. Why does gene flow stop speciation?

7. Besides no gene flow, what else happens to cause speciation?

8. Give an example of one kind of reproductive isolation

Patterns in Evolution

Three kinds of patterns in evolution are:

1. convergent evolution: evolution of similar traits indifferent species. For example, fins in fish and dolphins.

2. divergent evolution: evolution of different traits in closely related species. For example, fur color in the kit fox and the red fox.

3. coevolution: two species evolve together – changes in one species cause changes in the other species. For examples, changes in flowers cause changes in insects.

Extinction is the elimination of a species from Earth.

There are two kinds of extinctions:

1. background extinction: a small amount of species are normally becoming extinct regularly over time.

2. mass extinction: hundreds or thousands of species become extinct over a short period of time.

Darwin believed that new species evolved slowly over time – called gradualism. New evidence has changed his theory.

Punctuated equilibrium is the theory that states that speciation occurs quickly followed by long periods without change. Speciation happens during large changes in the environment. Then the environment becomes stable, and species stay the same.

 Gradualism                     

Punctuated Equilibrium

Punctuated Equilibrium

During large changes in the environment, speciation can create many new species.

Adaptive radiation is when one species evolves into many new species.

• During adaptive radiation, the new species often have different adaptations for different environments.

• The finches of the Galapagos Islands evolved through adaptive radiation.                                                

Questions

1. Why do fish and whales have similar body structures?

2. What causes closely related species to evolve differently?

3. Describe an example of coevolution?

4. If the blue-dashed line shows the average rate of background extinction, what to the tall peaks of the red line show?

5. Extra question: about 65 million years ago, what animals went extinct?

6. Describe the graph of punctuated equilibrium: