13. Unit 4 cramming! Flashcards
A species is defined as …
A group of organisms that interbreed to produce viable and fertile offspring
Explain a silent mutation
Because the code is degenerate and multiple codons code for the same amino acid then even if a DNA base has changed this could still code for the same sequence of amino acids.
Explain a missense mutation
Because a DNA base has changed then this changes the sequence of amino acid/s coded for and therefore changes the tertiary structure of the protein and it will no longer function correctly.
Explain a nonsense mutation
Because a DNA base has changed then this changes the sequence of amino acid to code for an early stop codon therefore changes the tertiary structure of the protein and it will no longer function correctly.
Define evolution
change in allele frequency over time
Define gene flow
The movement of individuals into or out of of a population changing allele frequency
Outline allopatric speciation
Two populations of are geographically isolated (first) by a permanent geographical barrier of _.
There is no gene flow.
There are different selection pressures e.g. _acting on each population of and those with a selective advantage for survive and reproduce.
Mutations accumulate over many generations in each population.
Eventually they can no longer interbreed to produce fertile and viable offspring and would be considered 2 separate species.
Define genetic drift and outline the two types.
Genetic drift is the change in allele frequencies in a population by chance.
The two types are the founder effect where group of individuals, whose allele frequency unrepresentative of the normal population, breakawayand found a new population and bottleneck effect where there has been a severe reduction in genetic diversity due to a catastrophe that may change allele frequency.
Outline selective breeding
Select organisms based on desired traits/based on phenotype of _____.
Breed selected male and female individuals together
Repeat over many generations
Outline how evolution occurs by natural selection
VA – There is variation in the phenotypes in the xxxxxxx population due to random mutations as they have xxxxxxx
ST – All organisms face a daily struggle to survive and reproduce. Thexxxxxx withxxxxxx struggle because xxxxx this is the selection pressure.
SE – The xxxxx with xxxhave a selective advantage as they xxxxx
IN – The organisms that have a selective advantage (xxxx), survive, reproduce and their offspring inherit the alleles for the trait of XXXXXX
E – Evolution occurs by natural selection and there is a change in allele frequency over time and theXXX population becomes better suited to its environment.
Compare antigenic shift with antigenic drift.
Antigenic drift is the small and gradual mutations in the genes encoding for viral surface antigens where as antigenic shift is Sudden and significant mutations in the genes encoding for viral surface antigens.
Antigenic shift produces a new viral strain suddenly (by two viruses merging in a host cell) whereas antigenic drift can produce a new viral strain more gradually (it would be more closely related to the original strain)
Antigenic shift may result in the infection of a new species whereas antigenic drift will more likely result in infection in the same species.
Compare the two types of speciation.
Allopatric speciation involves being geographically isolated first(which leads to reproductive isolation) whereas sympatric speciation involves being reproductively isolated first.
Sympatric speciation occurs in the same geographical area (e.g. Lord Howe Island) whereas allopatric speciation is in different geographical areas (e.g different Galapagos islands).
Allopatric speciation involves a permanent georaphical barrier causing isolation whereas sympatric speciation involves a reproductive barrier causing isolation.
Describe the two types of dating fossils.
Relative dating is where stratigraphy is used to compare the position of rock strata with the knowledge that the lower the rock strata the older the layer.
Whereas absolute dating is where a radioactive isotope is used which decays at a known half life to determine the actual age of the fossil by comparing the ratio of isotopes present ( e.g. carbon to nitrogen or potassium to argon).
Name two molecules that could be compared to show phylogenic relationships.
State a conclusion you would form from this info.
DNA sequence and amino acid sequence.
If the sequence of amino acids are the most similar between two species they are the most closely related and share a most recent common ancestor.
Why are we able to use the number of mutations in DNA to indicate evolutionary relationships
Because mutations accumulate over time, then the less mutations that have occurred indicates that less time has passed and therefore the two species would share a most recent common ancestor
