Evolution Mathew Cobb Flashcards
Define evolution
Evolution is defined as a change in the allele frequence in a population over time
Define natural selection
Natural selection is the mechanism by which evolution occurs. Natural selection occurs when a change in the environment causes certain traits/alleles to be advantageous, allowing certain individuals with those traits to survive, reproduce and pass on traits too offspring.
Explain the difference between evolution and natural selection
Evolution is the change in allele frequency, natural selection describe how that change takes place. NS is one out of many possible mechanisms for evolution (adaptive)
State the 3 pre-conditions required for natural selection
- genetic variation in population
- differential survival and reproductive success
- hereditary (traits have a genetic basis and can be passed on )
What is a tik-taalik and why was its discovery significant
1) It is a fish
2) From late denovian period
3) But it had similiar features to the tetrapod.
4) discovery of the tik taalik sheds light on a pivotal point in the history of life on earth.
Explain why the tik taalik discovery was important
It was a fish that had legs. The existance of tetrapod features in tik taalik marks the earliest appearance of fish having legs in the fossil record. This is the moment when the 1st ever fish ventured from sea to land.
Explain what is meant by a vestige
This is an anatomical structure or organ of the body that is degenerate, having become functionless in the course of evolution.
Define gene flow
Gene flow is defined as the transfer of alleles from one population to another population due to migration of individuals.
Explain why there is restricted gene flow between the Galapagos islands and South america
because galapagos islands are separated from the south america coast by 1000km of deep ocean! thus there is georgaphical isolation between the birds on the galapagos islands and the birds on mainland south america
Explain how Natural selection can sometimes not lead to evolution.
If natural selection acts on traits that do not have a genetic basis. Ie If Kylie jenner reproduces because she has dank lips, this trait will not be passed on to stormy so natural selection has acted, but evolution has not taken place because stormy gets her pre-surg lips.
List the 4 mechanisms that can bring about evolution
Natural selection
Mutation
Migration
Genetic drift
Explain genetic drift
This is a mechanism of evolution and is defined as chance fluctuations in allele frequency in a population. Individuals that survive do not represent healthy/fitter organisms, but just the “lucky” ones.
Does genetic drift produce adapatations
No. It is variation in allele frequency due to chance fluctuations.
Define an endemic species and give some examples
Some animal species found on the galapagos islands are not found anywhere else on earth. Finches are examples of endemic birds.
How many endemic species of finch were found on the galapagos
13
Summarise the Grants’ findings on the Galapagos
Evolution occured quickly enough to observe within a few years.
A single weather event can cause evolution, if there are traits that result in differential survival and there is genetic variation in those traits.
Explain why the Grants were so succesful?
Finches were not used to human contact, so were easy to catch and measure.
The grants measurements of beak legnth were very careful. The change in beak legnth could not be physically observed by eye, as it was so small .
Meticulous measurements allowed them to see even a difference of 0.55mm was enough to make a difference between survival and death in a drought year.
State three examples of vestigial structures in humans
Plica semilunaris
Preauricular sinus
Left laryngeal nerve
What is the preauricular sinus in humans
An evolutionary remnant of fish gills, this is a small hole at the top of the ear.
What is the left laryngeal nerve in humans
Often cited as evidence for evolution. left laryngeal nerve loops under the aortic arch and moves in opposite direction from the nerve it stems from. Despite the function of the branchial arch changing, the left RLN maintained its position despite this.
What is the plica semi-lunaris in humans
This is a vestigial structure
What are trilobites
One of the earliest known groups of Arthopods, they are marine animals.
Why are trilobites important
- Disappeared arond 250 million years ago
- Lived around 280 million years.
- Show clear signs of evolutionary change in v short time.
- Evidence for microevolution
Why is there limited gene flow between the birds of south america and birds of the galapagos
Because birds rarely move between the south american mainland and the islands, due to geographical isolation.