1.7 Evolution Flashcards
Define ‘Evolution’
Evolution is the gradual change in the characteristics of an organism over many generations
What is the difference between vertical and horizontal inheritance?
Vertical- passing of genetic material from parent to offspring
Horizontal- passing of genetic material across the same generation by transfer of plasmid between adjacent cells
Give an example of an organism that can transfer genetic material through vertical or horizontal inheritance
Prokaryotes
What are the three types of horizontal gene transfer?
<ul> <li>Conjunction</li> <li>Transformation</li> <li>Transduction</li> </ul>
What is an advantage of horizontal gene transfer?
Allows for rapid evolutionary change
Describe the process of transformation horizontal gene transfer
Bacteria takes up naked bacteria from foreign cell
Describe the process of conjunction horizontal gene transfer
- A conjunction bridge is formed between two adjacent cells allowing a plasmid to be copied and travel through the bridge to the adjacent cell
Describe the process of transduction horizontal gene transfer
Phage inserts the viral DNA into the cell
Define ‘Natural Selection’
Non random increase in the frequency of DNA sequences that increase survival chance of organism
What is a deleterious sequence?
A deleterious sequence is a gene sequence that decreases the organism’s fitness
How are deleterious sequences removed by natural selection?
Decrease the organism’s survival rate and so are selected against, meaning their frequency will decrease
Define ‘Sexual Selection’
Non random increase in the frequency of DNA sequences that increase reproductive success of organism
What are the three types of selection pressures?
Stabilising
Disruptive
Directional
What selection pressure is baby weight an example of?
Stabilising
What type of selection pressure favours the two extremes and is the driving force between sympatric selection?
Disruptive
Describe Directional selection pressure
- favours one extreme
- shifts graph to left or right
- example: peppered moths
What is the main difference between natural selection and genetic drift?
Natural Selection is non random, Genetic Drift is random
Define ‘Genetic Drift’
RANDOM increase/decrease in the frequency of a DNA sequence in the gene pool of a population
What are the mechanisms for Genetic drift
- Chance Events
- Neutral Mutations
- Founder Effect
What is the founder effect?
The founder effect is where a small population becomes isolated and that small population has a gene pool that does not reflect the original population
Mechanism of Genetic Drift
What is the Bottleneck effect?
This is where the majority of the population die out in a chance event(such as natural disaster) and the gene pool of the survivors does not reflect the original gene pool
Mechanism of Genetic Drift
What is ‘Speciation’
The formation of a new species
Why must populations be separated for speciation to occur?
So interbreeding is prevented
Explain why genetic drift is more evident in smaller populations
Smaller populations so will have a bigger effect due to smaller gene pool
What are the three main steps in speciation?
Isolation
Mutation
Natural Selection
Describe what happens in the natural selection stage of speciation
Mutations may confer an advantage in habitat of population and so the the mutation will be selected for and will increase in frequency
What are the two types of isolation barriers?
Geographical
Behavioural/Ecological
What type of isolation barrier does sympatric selection need?
Behavioural/Ecological
Describe Allopatric Selection
Formation of new species with a geographical barrier separating them
How can scientists prove new species have been formed?
If two members of the populations breed and produce infertile offspring
What is a hybrid zone?
A hybrid zone is an area of interbreeding between two closely related species
What does a narrow hybrid zone represent?
Genetically distinct populations
What would the width of the hybrid zone be if the populations were genetically
M
