Lecture 2 Quiz: (end of lecture 1, and majority of lecture 2)

balanced polymorphism

maintenance of two or more phenotypes in stable proportions over many generations

frequency-dependent selection

form of natural selection where rare phenotypes have a selective advantage because they are rare

darwinian fitness

term that describes the contribution to successive generations made by individuals possessing the trait

relative fitness

the proportion of offspring an organism carrying a certain gene is able to have compared to the average number of offspring organisms carrying other genes have

• fitness ratio

stabilizing selection

a mode of natural selection where it favors the mean phenotype over extreme phenotypes

directional selection

mode of natural selection that shifts the mean phenotype toward the end of the distribution favored by natural selection

• one extreme of the normal distribution is selected against

diversifying selection

mode of natural selection which decreases the frequency of the mean phenotype, but increases the frequency of extreme phenotypes

sexual selection

the advantage that some individuals have over other individuals of the same sex and species in relation to reproduction

• seen in mammals and birds, especially in female choice of a mate driving certain traits

sexual dimorphism

term that describes phenotypes within a species is distinct and have nothing to do with reproduction

• e.g) size difference between males and females

microevolution (2)

the small changes in genetic structure in a population over short periods of time, change in allele frequency

macroevolution (2)

term that refers to evolution that happens over millions of years

anagenesis

gradual phyletic change where evolutionary changes accumulate slowly in a lineage as the environment shifts overtime

cladogenesis

pattern of evolution where an ancestral species undergoes speciation producing two descendant species both are distinct from their common ancestor

morphological species

individuals of a species share measurable traits that distinguish them from individuals of other species

biological species

idea of species based on the ability of populations to interbreed and produce fertile offspring

1. genetic cohesiveness of species → experiencing gene flow = mixing genetic material

2. genetic distinctness → reproductively isolated = cannot exchange information

3. explains why individuals of the same species look alike

4. doesn’t apply to those who reproduce asexually

Ernst Mayr

• An evolutionary biologist that fused Charles Darwin’s theory of natural selection with genetics

• proposed the biological species concept

geographical isolation

the first stage of allopatric speciation and it occurs when two populations of the same species are divided by some type of geographic event or object

reproductive isolation

the second state of allopatric speciation where it prevents members of two different species that cross or mate from producing offspring

prezygotic barrier

a barrier that impedes mating/fertilization

1. habitat isolation

2. behavioral isolation

3. temporal isolation

4. mechanical isolation

5. gametic isolation

What are the 5 prezygotic barriers?

habitat isolation

species have the same range but are found in different microhabitats

behavioral isolation

isolation where two species do not mate because of differences in courtship behavior

1. e.g) female fireflies ID males by flashing patterns

temporal isolation

the isolation where the seasonal timing of reproduction is different for species living in the same habitat

mechanical isolation

the incompatibility of reproductive structures

• e.g) insect genitalia is different where there are specific lock and key correlation preventing successful mating with females of another species

gametic isolation

incompatible recognition of proteins on sperm and egg; cant recognize each other in different species

postzygotic barrier

a reproductive isolating mechanism that acts after zygote formation

reduced hybrid viability

the postzygotic barrier that produced puny offspring that dont develop into maturity

reduced hybrid fertility

a post zygotic barrier that produces viable offspring but are reduced in fertility

• e.g) horse x donkey = mule where the rearrangement of chromosomes are different and when it comes to splitting nondisjunction occurs

hybrid breakdown

having a reduced survival/fertility where by the 2nd or 3rd generation death becomes apparent

allopatric speciation

the evolution of reproductive isolating mechanisms between two populations that are geographically separated

peripheral isolates

the relatively small isolated or semi isolated populations distributed around the periphery of a large central portion of a species’ range

adaptive radiation

an event from which a lineage rapidly diversies with the newly formed lineages evolving different adaptations

allopolyploidy

having two or more complete sets of chromosomes from different parent species

autopolyploidy

term that appears then an individual has more than two sets of chromosomes both from the same parental species

parapatric speciation

speciation that is similar to allopatric speciation but has a sharp boundary

• species have an adjacent range but when theres a sharp change in environment it creates a boundary

• e.g) agrostis → adapted to lead contaminated soils → different species overtime (one with lead soil and one not on lead soil), lead soil is the sharp divider

phylogeny

tree like model that refers to the evolutionary history of a group of organisms

clade

term for the grouping that includes a common ancestor and all the descendants of that ancestor

monophyletic

group of organisms that includes a single ancestral species and all of its descendants

paraphyletic

a taxon that includes an ancestral species and only some of its descendants

polyphyletic

taxon that is usually not followed and includes species from different evolutionary lineages

homology

species that are morphologically similar comes from their inheritance of the genetic basis from a common ancestor

• similarity that results from shared ancestry

• e.g) four limbs of all tetrapod vertebrates

homoplasy

characteristics shared by a set of species, often because they live in similar environments, but not present in their common ancestor; often the product of convergent evolution

analogy

regards the structures that have similar functions but dissimilar evolutionary origins

convergent evolution

the process by which unrelated or distantly related organisms evolve similar body forms, coloration, organs and adaptations

synapomorphy

a character which is in a new state and shared by all members of a group; recently derived character; in at least 2 or more species

shared ancestral character (symplesiomorphy)

term for a shared homologous character that has a more distant relationship

character

the specific property of an organism

character state

one or more forms of a character

ingroup

clade under study

outgroup

used to ID and ancestral and derived characters by comparing group being studied to more distantly related species

parsimony

the primary principle used to decide which phylogenetic tree is to be preferred among conflicting alternatives by selecting the hypothesis requiring the fewest evolutionary changes

node-based taxon

groups in phylogenetic nomenclature defined by the last common ancestor of specific named taxa; includes the ancestor and all of the descendants

stem-based taxa

groups of extinct organisms more closely related to a specific crown group than any other lineage but that diverged before the last common ancestor