BIOL301- Group 1 Exam

evolution

examines the origins of biological diversity and the factors that mold their characteristics

1. evolution by common decent

2. evolution by natural selection

• there must be a struggle for existence

• in struggle there is variation, so survival is random

ecology

the study of the distribution and abundance of an organism

evolution with common decent

all species are related to each other through common ancestors

• properties are predictable

natural selection

differential survival and reproduction in organisms based on phenotype

• if some differences among phenotypes are based on genetics, natural selection results in a change in allele frequency

facts:

1. all living things show heritable variation

2. all populations are capable of exponential growth

3. no population can grow exponentially (despite factors 2), as some are more fit for the struggle of existence

mutations

error or modification in DNA copy

point mutation

changes the bases at one point of the sequence

• most redundant

synonymous mutation

change in DNA sequence with no consequences

non-synonymous mutation

change in DNA sequence that has consequences

can either be neutral or non-neutral

1. neutral- no consequences on the fitness of the organism

2. non-neutral- has consequences on the fitness of the organism

frameshift mutation

adding a base, which moves all other bases down (inserting and shifting the entire copy down)

chromosomal mutation

1. deletion/insertion- parts of the chromosome are removed or added

2. gene duplication

3. inversion- a break in DNA where it is flipped and then repaired in a different orientation

4. translocations- breaks off of one chromosome and fuses to another

5. triploidy- chromosomes are not replicated

6. tetraploidy- entire nondisjunction of the genome

mobile genetic elements/ transposons

replicate themselves, remove themselves, then insert themselves elsewhere in the genome

sexual recombination

reassortment of standard genes

• resorting of chromosomes during meiosis

• crossing over

*gene flow

the introduction of new variations of genes from different populations

hardy-weinberg equilibrium

distribution of genetic variation in populations

p= allele A= frequency(A)

q= allele B= frequency(B)

p²+2pq+q²=1

p+q=1

assumptions:

1. random mating

2. no inbreeding

• inbred= less heterozygotes

• outbred= more heterozygotes

1. infinite population (large population)

2. no mutation

3. no migration/ gene flow

4. no selection

positive assortative mating

like likes like

leads to too few heterozygotes

negative assortative mating

opposites attract

leads to too many heterozygotes

genetic drift

randomly changes allelic frequencies over time

• more rapid in smaller populations

founder effect

small number of individuals start a new population

EX: asian clams can self-reproduce, so the introduction of one clam will allow for quick genetic drift and lack of variation

population bottleneck

population collapse determines the future genetic composition

EX: DDT would weaken the shells of bird’s eggs, making nesting birds crush them (like bald eagles)

effective population size

the number of individuals (N) within the population in comparison to the number of effective individuals (Ne, breeding population)

effects on effective population size:

1. variation in reproductive success- people have more offspring than others

2. variation in numbers of each sex

• EX: one male competes for multiple females

3. inbreeding 

• how many ancestors

• how many mate choices

4. variation in population size throughout time

5. age structure (more old people in the population?)

fundamental principle of evolution

natural selection can be classified based on how it distributes phenotypes

directional selection

one extreme has more reproductive success than other extremes

EX: peppered moth in england

stabilizing selection

selection against the intermediate and in favor of both extremes

*probably most common form of selection

EX: human birth weight

disruptive selection

selection against the intermediate and in favor of both extremes

• causes flattened distributions and in extreme cases a bimodal distribution

EX: bill size in black-bellied seed crackers (birds)

frequency-dependent selection

reproductive success of a phenotype depends upon the frequency with which it occurs

• selects against the most common phenotype

EX: the flu

sexual selection

one sex chooses particular individuals of another sex based off of phenotype

1. intersexual selection- female chooses mate pushing more flamboyant phenotypes (between the sexes)

2. intersexual selection- males compete with other males for access to the female (within the same sex)

coevolution

selection driven by the biological environment in which reproductive success depends upon how much an individual looks like another species

1. bayesian mimicry-  model and mimic

2. mullein mimicry- involves 2 or more species that are all toxic

sickle cell anemia

disease under stabilizing selection as the heterozygote is relatively immune to both sickle cell anemia and malaria (therefore has the advantage)

sickle cell allele is under directional selection

adaptation

accumulates phenotypes with highest reproductive success in a particular environment

• only produced by natural selection

novelty

natural selection provides novel traits

1. accumulative power of selection

EX: fruit flies tummy bristle is totally changed

2. building upon pre-existing structure

EX: human immune system

3. building upon “duplication”

EC: the sense of common eyes

allopatric speciation

speciation caused by a geographic barrier that interrupts gene flow

biological species concept

a species is a group of actually or potential interbreeding populations that are reproductively isolated from other such groups

• acquisition of reproductive isolation

problems:

1. too much interbreeding

EX: sycamore trees and european plane trees

2. too little interbreeding

EX: dandelions reproduce asexually, is every individual its own species?

*no interbreeding= separate species

behavioral barriers

individuals from two populations may no longer recognize each other as potential mates

EX: anoles with colorful throat patches

seasonal/temporal barriers

populations may have diverged due to when they reproduce

• not active at the same time

EX: american toad and the fowler toad 

ecological barriers

populations may have diverged with respect tot to their habitat requirements

EX: pocket gophers like damper soil while eastern populations like drier soil

mechanical isolation/ unsuccessful mating

the egg does accept the proteins of the sperm

developmental malfunction

successful fertilization, but mis-regulated gene expression, leading to issues with development

• leads to the termination of the pregnancy

• mom’s mRNA produce the early stages of development

hybrid sterility

the embryo proceeds with development, but there is a mis-regulation of the genes in the germ line, which results in sterility

EX: the mule

speciation

occurs when two populations become biologically incapable of interbreeding

• reproductive isolation will make the two species continue un divergence

evolution by common decent