Class Midterm 1 Flashcards
What are Phenotypes
Structure and behaviour of individual organisms
What determines phenotypes
Genetics and environment (environment = what organism is exposed to)
What does protein do
Preform functions in cells, function depends on protein structure
What is the Central Dogma of Biology
DNA to RNA to Proteins
What determines protein structure
Sequence of AA
How is DNA made
A string of nucleotides packed into chromosomes
What are genes
Sequences of DNA that code to produce RNA and/or protien
What are alleles
Different versions of info encoded at a given gene
What causes mutations
Cell replication
What is evolution
Process that results in changes in the proportion of heritable traits within a population from 1 gen to the next
What drives evolution (4)
1) Natural selection
2) Mutation
3) Genetic drift
4) Gene flow
What did Peter and Rosemary Grant do
Research medium ground finches on Galapagos islands
Evolution
The process that results in changes in the proportion of heritable traits
within populations from one generation to the next.
Genetic Drift
Changes in allele frequencies that happen as a result of sampling error (random chance)
What are the impacts of genetic drift
Decreases the total amount of allelic variation in a population over
time
Can cause deleterious alleles to increase in frequency
Founder effect
When a subset from a larger population
leave and ‘found’ a new population
How does founder effect impact population
Can be dramatic if the founding population is particularly small - only bring small amount of alleles
Bottleneck
When a population shrinks dramatically,
and differential survival/reproduction
does not depend on phenotypic traits
What can cause bottlenecks
Think of events that ‘equalize’ chance of
survival
- Floods, fires, etc
Gene flow
The flow of alleles between two or more
populations (of the same species)
How does gene flow effect populations
Gene flow keeps populations genetically
similar to one another
- This can have negative or positive impacts on the fitness of the populations involved
What happens if there is no gene flow
When there is no gene flow –
evolutionary changes in each population
is independent of one another
– which allows them to diverge from one another (genetically/ phenotypically)
Are mutations random
Random with regards to evolution and natural selection
How do mutations impact population
A single mutation does not immediately have a major impact on allele
frequencies – but serves as the source of new variation
How do mutations affect reproductive fitness
Random with regards to reproductive fitness
- Beneficial mutations are not ‘more likely’ to occur
What is a null hypothesis
Defining the outcome(s) we would expect to see if the effect we are
interested in does not exist/isn’t happening
Whats the ultimate source of genetic variation
Mutations
What is the HWE
A null model used to test if evolution is occurring
Whats a model
A simplified representation of something
What are the 5 assumptions of the HWE
- Population size is infinite – otherwise there will be sampling
error (and genetic drift will occur!) - No mutations
- No migration
- No natural selection
- Mating is completely random
Why can we not make fixed models for evolution
Not as simple as a static image or
object – because evolution is not a
static process
How do we simplify the HWE
- Only tracking one gene and assume it only has two alleles
- Assume there is a clear F0 generation who all reproduce at the same time
- Not including different sexes (males or females) – all gametes are capable
of ‘fertilizing’ one another
Formula for HWE
p2 + 2pq + q2
P = dominant allele
Q = recessive allele
- Formula used to determine allele frequency
Why is it helpful to understand evolutionary processes
Conservation efforts
- Addressing issues related to health and disease
What is the extinction vortex
Graph that shows how fragmentation affects population which leads to possible extinction.
Whats the impact of inbreeding
Inbreeding can cause increases in homozygous
phenotypes (and increased rates of deleterious
phenotypes!)
Population
A population is a group of
individuals from the same
geographic region that
regularly mate together.
What’s required for populations to become separate species
Genetic isolation (barriers to gene flow)
Genetic divergence (mutation, genetic drift, natural selection)
What is speciation
Speciation is the process of genetic isolation and genetic
divergence that is responsible for the creation of new species
What is allopathic speciation
A physical barrier to gene flow
Species is split due to a
geographic barrier or because
some individuals move to a
separate place.
What is sympatric speciation
Other barriers to gene flow
- Species is split by
reproductive separation even
though they are in the same
place)
What are species
- An evolutionary independent unit in nature—meaning,
- a population or group of populations that is genetically isolated
from others and is thus changing under the effects of natural
selection, genetic drift, and mutation independently of others
What is the biological species concept
“groups of actually or potentially interbreeding natural
populations that are reproductively isolated from other such
groups.”
What three things does the biological species complex not work for
- Asexual reproduction
- Sometimes hybrids are viable
- Cannot use for fossils
What do phylogenetic tree do
Depict evolutionary relationships
between different taxa
What are phylogenetic trees based on
- Based on common ancestry
- Species are more closely related if they have
a more recent common ancestor
Why are phylogenetic trees helpful
1) Determine common ancestry among taxa
2) Understand trait evolution
3) Track emergent diseases
What data is used to construct phylogenetic trees
- Molecular traits have become the
gold standard - Genetics, protein sequences, etc.
What is a clade
Monophyletic: A common ancestor
and all its descendants
* A natural unit in evolution – often
defined
Paraphyletic
- Paraphyletic: Common ancestor
and a subset of its descendants
Polyphyletic
Polyphyletic: Usually two species
that share a trait because of
convergent evolution
Homoplasy
Homoplasy occurs when two (or
more) taxa independently evolve
the same trait
Are evolutionary trees proven
No! They are hypothesis’
Homology
Homology occurs when two (or
more) taxa share the same trait
because they both inherited it from
a shared ancestor
