Unit 1 Key area 1.7 Flashcards
How are genomic sequences inherited? And what does this mean?
Genomic sequences are inherited vertically. This means that the genetic material is passed from parent to offspring either sexually or asexually.
What do changes in genomic sequences mean?
Changes in genomic sequences in organisms result in changes to the organisms over-time - this is called evolution. The changes depend on random alterations in the genome due to mutation.
How can advantageous mutations help organisms?
It helps them to survive to reproduce, and so the mutation is passed onto offspring.
What is natural selection?
Its the process which leads to non-random increase in the frequency of DNA sequences that increase survival and the non-random reduction in unfavorable sequences.
Describe sexual selection.
The sequences that increase in a non random way directly to successful reproduction.
What does stabilising selection result in?
In phenotypes in a range becoming more aligned with a mean value.
What is directional selection?
This tends to move the average phenotype towards an extreme value in a range. In cliff swallows for example, larger body size is a selective advantage.
What is disruptive selection?
It tends to favour two extreme phentotypes, and results in two or more common phenotypes.
What is genetic drift?
a random increase or decrease in the frequency of DNA sequences within the gene pool of a population, as a result of neutral mutations and founder affects, is called a genetic drift.
What is speciation?
The evolution of a new biological species as a result of isolation, mutation and natural selection.
What is an allopatric speciation?
A population is split into two sub-populations, A and B which are separated by a geographical barrier, preventing gene flow. Mutations occur in populations A and B followed by natural selection over many generation, resulting in two new species A and B which can now no longer interbreed.
What is sympatric speciation?
Two sub populations become isolated from the original population due to behavioral or ecological barriers, or by polyploidy occuring within a population. This prevents gene flow between the two sub populations which begin to evolve along different routes, and can eventually become two distinct species.
What is a hybrid zone?
In a small number of cases, zones can form in which ranges of two very similar and closely related species overlap.
