Evolution: natural selection & speciation

• Biologie
• Middelbare school
• vwo
• Leerjaar 4

Evolution

Chapter 12&13

Lesson 2: natural selection & speciation

Which term refers to the process by which individuals that are better suited to the environment survive and reproduce therefore passing down their genes to their offspring?

1. Evolution
2. Variation
3. Adaptation
4. Natural Selection

Brown mice survive and reproduce in their desert environment better than white mice because owls can see and eat the white mice more easily. In this situation, what part of the environment is doing the selecting?

1. predator
2. soil composition
3. mouse fur color
4. sexual preferences

Individuals undergo evolution.

1. True
2. False

A phenotype that improves an organism’s chance of survival in their environment is considered a(n):

1. natural selection
2. adaptation
3. speciation
4. extinction

Natural selection is best described as:

1. a change in an organism in response to a need of that organism
2. a process of nearly constant improvement that leads to an organism that is nearly perfect
3. differences in survival rates as a result of different inherited characteristics
4. inheritance of characteristics acquired during the life of an organism

Learning objectives

• Describe and identify the five processes that can lead to evolution
• Describe the steps of natural selection
•  Identify different effects of natural selection on phenotype distribution
• Describe why reproductive isolation is required for speciation
• Identify the difference between allopatric and sympatric speciation
• Describe different reasons for reproductive isolation
• Describe the steps of speciation

0

Evolution

Change in gene frequency/gene pool/heritable traits over time/generations

Five processes that lead to evolution

1. Small population/genetic drift: chance will start to play a role
2. Non-random mating/sexual selection
3. Mutation
4. Gene flow: immigration and emigration 
5. Natural selection 

1

4

A few deer wander out of their native woods into a completely new park where no deer had ever been before. They go on to create an entirely new population.

1. Genetic drift
2. Non-random mating
3. Natural selection
4. Gene flow

Five hundred years after the deer had established a flourishing population in the park, a few of them venture back to their original woods and have babies with the deer there.

1. Genetic drift
2. Non-random mating
3. Natural selection
4. Gene flow

Yellow toucan birds seek out one another to make babies together and tend to avoid the green toucan birds.

1. Genetic drift
2. Non-random mating
3. Natural selection
4. Gene flow

Properly describing natural selection

1. There is genetic variation in the population caused by mutations
2. Some individuals have a higher chance of survival due to an advantage/adaptation(describe the advantage)
3. The better adapted individuals will reproduce more (higher fitness) 
4. The genes of the better adapted individuals will therefore become more common in the population

Practice

Step by step

There is genetic variation in the population caused by mutations:

There is genetic variation for fur colour in the population of mice

Step by step

Some individuals have a higher chance of survival due to an advantage/adaptation (describe the advantage):

The individuals with a darker fur have better camouflage which makes them less likely to be spotted and killed by the predatory birds

Step by step

The better adapted individuals will reproduce more (higher fitness):

Because the darker coloured mice have a higher survival chance they will have more reproductive opportunities and will produce more offspring

Step by step

The genes of the better adapted individuals will therefore become more common in the population:

The allele for dark fur colour will therefore be passed on more and become more common in the population causing the percentage of dark mice to increase

Effect natural selection on phenotype distribution

Speciation

Formation of a new species

An important requirement is reproductive isolation. As long as the two groups interbreed they share the same gene pool and remain the same species

Forms of speciation

Allopatric speciation: reproductive isolation is caused by a geographical barrier

Sympatric speciation: there is no geographical barrier, but something else stopping them from reproducing

Adaptive radiation

The evolutionary diversification of a species or single ancestral lineage into various forms that are each adaptively specialized to a specific environmental niche.

Homework

Complete the worksheet natural selection & speciation