Evolution: natural selection & speciation

• Biologie
• Middelbare school
• vwo
• Leerjaar 4

Evolution

 Natural selection & speciation

What is 'Evolution'? Give a definition.

Darwin - Origin of species

“ As many more individuals of each species are born than can possibly survive, and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form.”

EVOLUTION

Changes in gene frequencies / gene pool / heritable traits in a population over time / across generations due to genetic variation and natural selection

Learning objectives

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

Look at the picture

Evolution according to Lamarck (1744-1829)

and

Evolution according to Darwin 

('On the origin of species...', 1859)

- Summarize how evolution took place according to them

- Explain what is wrong and what is correct

Write down for yourself!

What are the five fingers that lead to evolution

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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 

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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

Use the 4 steps to describe the process of natural selection for the example of yellow and grey mice.

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:

1. part of a population becomes separated from the rest of the species.

2. adaptation to different environmental conditions.

3. 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, for example temporal, behavioral or habitat isolation

learn.genetics.utah.edu

Questions

1.Brown mice survive better and plant more frequently in a desert environment because lighter mice are more likely to be seen and eaten by owls.

Who or what is responsible for selection pressure here?

2. Yellow toucan females prefer males that are the same color as themselves. The gene pool will change due to ??

Questions

3. Right or wrong? Individuals undergo evolution!

4. A small number of deer leave their own habitat

  and end up in a new plot where no deer have lived yet. Their gene pool turns out to be different from the original population because of??

Learning objectives

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

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Work to be done

Study: https://learn.genetics.utah.edu/content/evolution/barriers/

Assessment Questions Glencoe pg 445: Q 1-7.  

Biozones 206-208.