Evolution

SQA Higher Biology 2022

Evolution Evolution

________ is defined as the changes in organisms over generations as a result of genomic variations.

Sympatric Speciation Sympatric speciation

________ is when new species arise despite occupying the same geographical area, due to: ❥ Ecological barriers- although groups are not geographically isolated from each other they may be isolated by a difference in flowering time (in plants), breeding areas, pH and salinity.

Allopatric Speciation Allopatric speciation

________ is when new species arise due to isolation of a population by geographical barriers.

Speciation Speciation

________ is the generation of new biological species by evolution as a result of: ❥ isolation ❥ mutation ❥ selection Isolation barriers are important in preventing gene flow between sub- populations during speciation.

Natural selection

________ is more rapid in prokaryotes as prokaryotes can exchange material horizontally, resulting in a faster evolutionary change than in organisms that only use vertical transfer.

natural process

There is no ________ that creates entirely new genes, all new genes must be the result of changes to the existing pool of genes.

❥ Behavioural barriers

________- a population may have different mating calls (such as pitch or tone) or mating rituals which would prevent breeding.

Types of Selection There are 3 types of selection caused by a change in phenotype frequency

Directional In directional selection, one extreme of the phenotype range is selected for

Speciation Speciation is the generation of new biological species by evolution as a result of

❥ isolation ❥ mutation ❥ selection Isolation barriers are important in preventing gene flow between sub-populations during speciation

❥ Behavioural barriers

a population may have different mating calls (such as pitch or tone) or mating rituals which would prevent breeding

What is evolution?

Evolution is defined as the changes in organisms over generations as a result of genomic variations.

What are new genes the result of?

There is no natural process that creates entirely new genes, all new genes must be the result of changes to the existing pool of genes.

How can changes to the pool of genes arise?

Changes to the pool of genes can arise by one of the following:

❥ gene transfer \n ❥ natural selection

❥ speciation

What are the two types of gene transfer?

Vertical gene transfer and horizontal gene transfer.

What is vertical gene transfer?

Where genes are transferred from parent to offspring as a result of sexual or asexual reproduction.

What is horizontal gene transfer?

Where genes are transferred between individuals of the same generation. This does not occur due to reproduction.

What is natural selection more rapid in? Why?

Natural selection is more rapid in prokaryotes as prokaryotes can exchange material horizontally, resulting in a faster evolutionary change than in organisms that only use vertical transfer.

What is natural selection?

Natural selection is the non-random increase in frequency of DNA sequences that increase survival and the non-random reduction in the frequency of deleterious sequences.

What are the three types of selection and what are they caused by?

There are 3 types of selection caused by a change in phenotype frequency- directional selection, disruptive selection and stabilising selection.

What is directional selection? Give an example.

In directional selection, one extreme of the phenotype range is selected for. For example, giraffes with longer necks are favoured as they can reach more vegetation on the trees.

What is disruptive selection? Give an example.

In disruptive selection, two or more phenotypes are selected for. For example, small male salmons are able to sneak and breed. Large male salmons can fight off competition. Medium males are disruptive.

What is stabilising selection? Give an example.

In stabilising selection, an average phenotype is selected for and extremes of the phenotype are selected against. For example, birds that lay too many eggs are more likely to lose offspring due to starvation, but too little eggs have a decreased chance of the birds surviving, so an intermediate number is favoured.

What is a species? What must they have to remain one species?

A species is a group of organisms capable of interbreeding and producing fertile offspring, and which does not normally breed with other groups. As long as a population has the opportunity to interbreed and exchange genes, they remain one species.

What is speciation?

Speciation is the generation of new biological species by evolution as a result of isolation, mutation and selection.

Why are isolation barriers important?

Isolation barriers are important in preventing gene flow between sub-populations during speciation.

Describe the process of speciation.

Once two groups are isolated, different mutations occur in each group. If the environments differ, different adaptations are favoured by natural selection. This leads to different characteristics evolving in each group as time passes. Eventually the groups become so different that if they come together again they are unable to interbreed and are now separate species.

What is allopatric speciation?

Allopatric speciation is when new species arise due to isolation of a population by geographical barriers.

What are geographical barriers?

Features such as rivers or mountain ranges that isolate populations of animals and plants.

What is sympatric speciation?

Sympatric speciation is when new species arise despite occupying the same geographical area, due to ecological and behavioural barriers.

What are ecological barriers?

Groups that may be isolated from each other because of a difference in flowering time (in plants), breeding areas, pH and salinity.

What are behavioural barriers?

When members of a populations are not able to mate due to different mating calls or rituals, as well as different timings, locations or mating dances.