Phylogeny card 1

Natural Selection

depends on the differential success, in terms of surviving and reproducing, of variants in a pop.

How does natural selection happen?

Genetic Variation (existing at multiple scale)

Species

a group of individuals that can exchange genetic material through interbreeding or share alleles through reproduction

Genes

functional unit of heredity, affects one or more traits

Alleles

different form of gene, correspond to different DNA

Speciation

species are not set but are challenge to define something over a period time —> formation of new species

Gene pool

all the alleles present in all individuals in a species

Population

an interbreeding group of organisms of the same species living in the same geographic area

genetic diversity

the gene pool is all alleles in a species / more different alleles = greater genetic diversity

Evolution

change in allele frequencies across generation

Where does genetic variation comes from?

1. Mutation 2. Recombination

Mutation

• its random 

• changes the DNA sequence of gene

• can be somatic (cant pass) or germ-like (can pass trait)

• can be harmful / neutral / advantageous

Recombination

• occurs in meiosis

• crossing over homologous chromosome result in new combination of alleles

• these alleles can be new and inherited from parent

Hardy-weinberg equilibrium

1. NO difference in survival and reproductive success of individuals in the population

2. The population size is not changed by the movement of individuals

3. No mutation in the gene being studied in the population

4. The population is large enough to prevent sampling errors

5. Individuals in the population mate at random

= allele frequencies are in equilibrium

Diploid (somatic) 

some cell has pairs of each chromosome 

haploid (germ-like cells)

singlets of each chromosome

Students kick-netting in a creek are asked to return the largest crayfish from the samples they collect. If this practice continues for a long period of time and the distribution of crayfish moves away from the smallest size of animals this would be…

Directional selection

The concept of parsimony states:

Constructing phylogenetic trees with the fewest evolutionary steps possible

phylogeny

a hypothesis of ancestor descendent relationship

Nodes 

represent common ancestor

sister taxa

2 species that are the most related to each other compared to any other taxa in phylogenetic

For a gene, 2 individuals in a population can have different genotypes, but the same phenotype. 

True 

Animals with spherical symmetry can be described as:

having any possible plane that passes through the centre of the body, creating mirrored halves

which of the follwoin gis best defined as a uniquely derived trait

autopomorphy

homology

similar traits inherited from common ancestor

Analogy

similar traits that evolved independently, not from common ancestor

Synapomorphies

A shared derived trait is a new trait that 2 or more species have due to getting it from common ancestor

Apomorphy

a character/trait that is new or different from the ancestor - derived trait

Plesiomorphy

a trait that is ancestral - inherited from earlier ancestor

autapomorphy

a uniquely derived character state

monophyletic group

includes a common ancestor and all of its descendants

paraphyletic group

include common ancestor and some but not all of its descendants

polyphyletic group 

group is formed based on similar traits that evolved independently (not from common ancestor)

Parsimony

simplest explanation (requiring fewest evolutionary changes)

In order for natural selection to occur: 

1. must be variation in population

2. Variation in population must be heritable

3. Competition for resources among individuals in the population must occur

4. individuals in the population that are better able to obtain resources must be more likely to survive and reproduce

Fitness

individuals with traits best suited to their environment leave more offspring, so those traits become more common

how much an individual’s genes are passed on to the next generation

type of selection

• can inc. the frequency of a favourable allele (positive selection)

• Decr. the frequency of harmful allele (negative selection)

balancing selection

natural selection that keeps an alleles at an intermediate frequency, maintaining multiple alleles in the population 

Stabilizing selection

favours average (reduce extreme / population middle)

negative selection against extreme values for a specific character, resulting in an increase in an individual with an intermediate character value

Directional selection

positive selection for a character value that is above or below the mean value for that trait 

• favours one extreme

Disruptive selection

selects fro extreme character trait values, or againest intermediates values 

artificial selection (directional selection)

successful genotypes are selected by the breeder, not through competition 

gneotype

genetic info - every human have a gene for eyes

phenotype

physical traits - different eye

sexual selection

highlights how favourable traits can’t help with survival but inc mating success

intasexual selection

member of same sex complete with each other for a change to mate with other sex

intersexual selection

one sex (often males) advertises to attract the other sex (often females), like bright colour or displays 

—> these traits can inc. mating success but may reduce survival

non adaptive mechanism of evolution

1. Genetic drift

2. migration / gene flow

3. mutation

4. nonrandom mating

Genetic drift

random changes in allele frequencies from one generation to the next

• stronger in small population

what are the 2 type of genetic drift?

1. bottleneck

2. founder effect

founder effect

A few individuals start a new population

—> only carry a small sample of the original alleles

bottleneck

big population suddenly gets very small

—> lost of alleles lost

migration / gene flow

When individuals move between populations, they bring their alleles with them

—> makes the population more similar and reduces genetic differences over time

mutation

They are rare and usually do not change allele frequencies much by themselves

ex: in 100 individuals , 1 new mutation = very low frequency

Noonrandom mating

Some individuals choose mates based on traits, so certain phenotypes becomes more common

species and divergence

The population have lots of genetic variation. if pop. get separated or become genetically different enough, they can form new species

• happens when pop. are genetically isolated, so mutations build up separately  

Allopatric 

When groups are geographically separated

types of allopatric

1. dispersal 

2. vicariance

dispersal

individuals moved to a new area (like island to island)

vicariance

A physical barrier splits a pop. (like rising water)

if you made a taxonomic group that included both birds and bats on the basis of wing similarities, this group would be best described as:

polyphyletic

HW equilibrium assumes

mutations are rare and alleles are stable

homology refers to

similar traits due to common ancestry

fitness, in evolutionary context, means an organism

produces more offspring than other members of the pop

If you grouped the following taxa together (D,E,F,G,H) that group would be described as

paraphyletic

Members of the same (blank) can pass traits through interbredding ; these traits can be seen or measured as the individuals’s (blank)

species; phenotype

Students kick-netting in a creek are asked to return the largest and smallest crayfish from samples they collect. IF this practice continues for a long period of time and the distribution of crayfish moves closer to the average size of animals, this would be …

stabilizing selection

All animals

more than one of the above but not all of the above

which of the following is best defined as a shared derived trait

synapomorphy

A new alleles in a species may come from…

recombination

All animals

produce collagen in their extracellular matrix

Vultures are known for their bald (featherless) heads, which is quite unique among birds. Both New World Vultures and Old World Vultures share this features. However, this traits is not inherited from their common acestor, it developed independently through convergent evolution. If you were to group New Wold Vultures and Old World Vultures into taxonomic group called culture, this group would be described as:

polyphyletic

Jellyfish, which may be divided into mirrored portions if diveded like slice of pizza can be described as…

having at least 2 possible planes that pass through the centre of the body, creating mirrored halves