Adaptations and Natural Selection in Evolution

Adaptations

Inherited traits that increase an organism's probability of survival and reproduction​.

natural selection

-favors individuals with advantageous traits, leading to an increase in those traits over generations

-organisms with better adaptations leave more offspring, causing favorable traits to accumulate​

MRSA bacteria resistance

bacteria's resistance to methicillin occurred because resistant strains survived antibiotic treatment and reproduced​ (when attacked)

do individuals evolve?

NO, populations evolve, not individuals

-organisms cannot decide to mutate; beneficial mutations occur randomly and are selected over time

directional selection

favors one extreme phenotype (e.g., dark-colored mice surviving better than light-colored ones)​

-ONE DIRECTION

disruptive selection

favors both extreme phenotypes over intermediate ones (e.g., both very dark and very light mice survive better than medium-colored mice)​

-disrupt EVERYTHING expect “middle” one

stabilizing selection

favors the intermediate phenotype, reducing variation (e.g., medium-colored mice surviving better than extremes)​

-MIDDLE is to “equalize” not distinction in change (reducing variation)

genetic drift is a

random change in allele frequencies due to chance, affecting small populations more​

founder effect

small group leaves a population and starts a new one, leading to different allele frequencies

bottleneck effect

population's size is dramatically reduced (TYPICALLY by disaster), changing allele frequencies by chance

gene flow is

movement of alleles between populations via immigration or emigration​

-movement of genes from one population to another!

genetic drift vs gene flow

genetic drift = random and affects small populations

gene flow = actual movement of genes between populations typically on larger populations

conditions for natural selection

variation in traits = differential reproduction (some traits lead to more offspring)

heritability of traits = more offspring produced than the environment can support​

Cladograms & Phylogenetic Trees

Organisms that share a more recent common node are more closely related​.

derived character

trait appears in recent lineages but not older ones

Extinct vs. extant organisms

Extinct lineages end before reaching the present, while extant organisms reach the top of the tree​.

hardy-weinberg equilibrium

population is in Hardy-Weinberg equilibrium if allele frequencies remain constant because:

- No mutations

- Random mating

- No natural selection

- Extremely large population size

- No gene flow​.

Hardy-Weinberg equations

p² + 2pq + q² = 1 (genotype frequencies), p + q = 1 (allele frequencies)​.

homologous structures are

similar anatomical structures inherited from a common ancestor (e.g., human arm, bat wing)​.

Vestigial structures are

reduced structures that serve little or no function but existed in ancestors (e.g., human appendix)​.

molecular homologies contain similar

DNA and protein sequences showing shared ancestry​

convergent evolution

unrelated species evolve similar traits due to similar environments (e.g., dolphins and sharks)​

-UN is CON is SIM

analogous structures

similar structures in unrelated organisms (e.g., wings of birds and insects)​

-ANA-not

artificial selection

human-driven selection for desirable traits (e.g., breeding dogs, modifying crops)​.

how antibiotic resistance evolves…

genes survive antibiotics and reproduce, leading to a resistant population​

allopatric speciation

population is geographically separated, leading to divergence into new species

sympatric speciation

new species arises within the same geographic area (e.g., due to polyploidy in plants)​

-NE SYM SAME

geographic isolation:

physical barriers prevent breeding

prezygotic isolation:

prevents fertilization:

-behavioral isolation

-habitat isolation

-gametic isolation

-temporal isolation

behavioral isolation:

differences in mating behaviors

habitat isolation:

live in different areas

gametic isolation:

-sperm cannot fertilize egg

temporal isolation:

different breeding times​

Postzygotic isolation

Hybrid offspring cannot survive or reproduce:

-Reduced hybrid viability

-Reduced hybrid fertility

-Hybrid breakdown

reduced hybrid viability:

hybrid dies early

reduced hybrid fertility:

hybrid is sterile (e.g., mule)

-ILI ILE

hybrid breakdown:

offspring of hybrids are weak or sterile​

-WEAK breaksDOWN

taxonomic levels

Hierarchy:

Domain → DO

Kingdom → KIDS

Phylum → PREFER

Class → CANDY

Order → OR

Family → FRIED

Genus → GREEN

Species → SNAKES

-how they show relatedness: Organisms in the same genus are more closely related than those only sharing a kingdom​.

what is mechanical isolation?

prezygotic barrier: morphological differences prevent successful mating

hybrid breakdown vs. reduced hybrid viability vs. reduced hybrid fertility

- hybrid breakdown:

first-generation hybrids are viable and fertile, but their offspring are weak or sterile

- reduced hybrid viability:

hybrid offspring fail to develop properly or survive to reproductive age

- reduced hybrid fertility:

hybrids are sterile and cannot produce offspring (ILI ILE)

what are the two primary modes of speciation?

- allopatric:

a population is geographically divided, leading to reproductive isolation and divergence(LL)

- sympatric:

occurs within the same geographic area due to factors like polyploidy, sexual selection, or habitat differentiation (S=SAME)

what are the conditions necessary for reproductive isolation to lead to speciation?

- lack of gene flow

- genetic divergence

- accumulation of reproductive barriers (prezygotic and postzygotic)

how does gene flow impact speciation?

it counters speciation by mixing genetic material between populations, preventing divergence (accumulation of genetic/structural differences)

can two species interbreed and produce viable offspring?

In most cases, NO

-however, some closely related species can hybridize, though hybrids often have reduced viability or fertility

why is reproductive isolation important in speciation?

prevents gene flow between populations, allowing them to evolve independently into distinct species

what are analogous structures evidence of

NATRUAL SELECTION - not common ancestry

* arise due to convergent evolution

what is selective breeding

(artificial selection) - humans intentionally breed organisms with desirable traits to enhance or modify specific characteristics in future generations

homolgous structures contain

- same structure

- different function

- recent common ancestor

- CLOSLEY related

vestigial structues contain

- reduced function

- past use

- distant common ancestor

- DISTANTLY related

molecular structures contain

- similar DNA, proteins

- most precise relation

- VERY RECENT common ancestor

what increases genetic variation when animals move from one population to another?

gene flow

artificial selection can be represented as:

recognized breeds of dogs

five factors that can lead to evolution are

-gene flow (GF)

-genetic drift (GD)

-mutation (M)

-natural selection (NS)

-sexual selection (SS)

why is genetic variation important in helping a species survive?

environment changing = some species will have adaptations that enable them to survive and reproduce

in stabilizing selection, what occurs in a population?

intermediate phenotype’s become more common

a bird that can easily outcompete other birds for food and that can produce many eggs has a high:

fitness

the observable change in the allele frequencies of a population over time is called:

microevolution

a feature that allows an organism to survive better in its environment

adaptation

hardy-weinberg equation is used to

predict the frequencies of genotypes and alleles in a population

seals and the penguins both have streamlined, fishlike bodies with a layer of insulating fat, but aren’t closely related…. this similarity results from:

convergent evolution

adaptive radiation is

the evolution from one common ancestor of many different species of organisms living in different environments and being exposed to different selection pressures

-MASTER moved to new reproductive site

what is co-evolution

evolution that results from two species interacting with one another and influencing each other’s adaptations over time (ex. pollinators and flowers)
-one spec + one spec CO-workers

what is parallel evolution

two organisms have ancestors that were closely related and over time the two origins were subjected to the same selection pressures

- now resemble one another

what is the smallest unit that can evolve

populations

what does inducing mutations in a population do

increases the genetic variation in the population

-induce = increase!

what does it mean for an organism to have high fitness

organisms in an environment can survive and reproduce

what is suggested by the similarity of early embryos of different species of vertebrates

evolution from a distant common ancestor

individuals is likely to be most successful in an evolutionary sense where

the organism that dies after five days of life but leaves 10 offspring, all of whom survive to reproduce

a mutation introduces a new skin color in a lizard population, which factor might determine whether the frequency of the new allele will increase

whether the mutation makes some lizards more fit for their environment than other lizards

natural selection that changes the distribution of a trait to favor one extreme phenotype is called

directional selection

-DIRECT contact with an EXTREME

which is not a cause for the actual proportions of homozygotes and heterozygotes to differ from Hardy-Weinberg predictions

natural selection acting on genotypes

which of the following describes natural selection

acts on existing physical traits

small number of birds, blown off course during migration, find an island and colonize it

-these are the first of this bird species on this island

-this population will most likely experience genetic drift as a result of the….

founder effect

actual allele frequencies in a population do not match genotype frequencies predicted by the Hardy-Weinberg equation, the population is

evolving

similarity of these structures suggests that the organisms

have a common ancestor

what makes up scientific name

genus + species

natural selection decreases what

genetic variability

allopatric =

geographical isolation

genetic drift does not involve what

mutations or selection (only randomness)

allopatric vs sympatric

ALLO = barrier

SYM = NO barrier (prezygotic)

H-W

q² = bb - homozygous reccesive

p² = BB - homozygous dominant

2pq = Bb heterozygous

the evolution of similar features in distantly related groups that live similar lifestyles is..

convergent evolution

_{Evolution ....}

_{happens when the conditions for H-W equilibrium are not met}