AP Bio: Unit 7- Evolution

not done

Species

Population whose members can interbreed & produce viable, fertile offspring. They are reproductively compatible

how/why do new species originate

a series of evolutionary process, populations become isolated (geographically & reproductively).

Isolated populations evolve…

independently

Allopatric speciation

Speciation by isolation, geographic seperation

sympatric speciation

Speciation that happens at the same area. Can happen because of habitat isolation, behavioral isolation, sexual selection, polyloidy

Ecological isolation

Species occur in the same area, but occupy different habitats so rarely encounter each other.

Geographic isolation

Species occur because of a geographic barrier

Temporal isolation

species that breed during different times of day, different seasons, or different years. So cannot mix gametes.

What speciation is temporal isolation?

sympatric speciation

behavioral isolation

unique behavioral patterns & rituals isolate species (like bird dances)

What speciation is behavioral isolation?

sympatric (? from powerpoint uhh)

Mechanical isolation

Morphological differences can prevent successful breeding/mating.
ex. different shaped reproductive organs for insects

What speciation is mechanical isolation?

sympatric

Gametic isolation

sperm of one species may not be able to fertilize eggs of another species. Can be biochemical barrier or chemical incompatibility

ex. sea urchin release sperm & eggs, but different species gametes do not fuse.

what speciation is Gametic isolation

sympatric

prezygotic barriers

reproductive isolation mechanisms that prevent species from mating or fertilizing

postzygotic barriers

Prevent hybrid offspring from developing into a viable fertile adult.

• reduced hybrid viability (hybrid unhealthy)

• reduced hybrid fertiliity

• hybrid breakdown

Reduced hybrid viability

genes of different parent species may interact & impair the hybrid’s development

What speciation is reduced hybrid viability

sympatric

reduced hybrid fertility

even if hybrids are vigorous, but may be sterile. Chromosomes of parents differ in number/structure. Meiosis in hybrids may fail to produce normal gametes.

Hybrid breakdown

Hybrids may be fertile & viable in first generation, but when they mate offspring are feeble or sterile

Gradualism

Belief that speciation happens in small changes over time. Rate of speciation is constant

Punctuated equilibrium

belief, that with a massive environmental change there will be big change fast. Rapid bursts of change and long periods of little/no change.

Directional selection

a type of natural selection where individuals with traits that are either higher or lower than the average value for the population have a better chance of survival and reproduction. This leads to a shift in the average value of the trait over time.
Graphically, entire bell curve shifts

• selection for one extreme phenotype

• selection against the other phenotypes

Disruptive selection

a type of natural selection that simultaneously favors individuals at both extremes of the distribution.
Graphically, shift from the mean- 2 bell curves emerge

• selection for 2 extreme phenotypes

• selection against the intermediate phenotype

Stabilizing selection

a type of natural selection that favors intermediate phenotypes over extreme variations, promoting the stability of a population by reducing variation. This process helps maintain the status quo in traits that are advantageous for survival and reproduction, leading to a decrease in the extremes of a trait spectrum. In this way, stabilizing selection can enhance the overall fitness of a population, ensuring that successful traits are preserved through generations.
Graphically, shift towards the mean

• selection for intermediate phenotype

• selection against the 2 extreme phenotypes

Natural selection

a process where individuals with certain inherited traits (phenotypes) are more likely to survive and reproduce at higher rates than other individuals because of those traits, leading to an increase in the frequency of those favorable traits in the population over generation

Evolutionary fitness is measured by ….

reproductive success

reproductive success

an individual's ability to produce viable, fertile offspring that survive to reproduce themselves, thereby passing their genes to the next generation

Lamarckian statements

UNTRUE: ideas that evolution is driven by the inheritance of acquired characteristics and the principle of use and disuse. These ideas suggest that individuals change within their lifetime to meet environmental needs and pass those changes to their offspring, rather than populations evolving over generations via natural selection

do not use

Artificial selection

organisms with certain traits are bred until the population has that trait

the 5 fingers of evolution

1. (pinky) Small population → genetic drift

2. (ring) Non-random mating → sexual selection

3. (middle) Mutation

4. (index) Movement → gene flow

5. (thumb) Natural selection → better trait = thumbs up

Gene flow

the addition/removal of alleles from population
the transfer of genetic variation from one population to another. If the rate of gene flow is high enough, then two populations are considered to have equivalent allele frequencies and therefore effectively be a single population. Basically migration can change allele frequencies for a population

Mutations do what in evolution

provides new genetic variation

Genetic drift

nonselective process in small populations changes allele frequencies

Bottleneck effect

population size reduced

ex. natural disaster killed most of the population (does not have to because of a trait)

Founder effect

Population separated from other members of a population

ex. In the 18th century, a small group of around 200 German immigrants founded the Amish community in Pennsylvania → The community remained largely isolated, marrying only within their own group

Drivers of evolution

• mutations

• migration (gene flow)

• genetic drift

Advantage of variation in populations (genetic variation)

• genetically diverse populations are more resilient to environmental perturbation because they are more likely to have individuals that can withstand the environmental pressure

• alleles that are adaptive in one environmental conditions may be deleterious in the other because of different selective pressures

If the 5 fingers of evolution are not met, than…

they provide a valaubale null hypothesis and evolution does not happen

Hardy-Weinberg equilibrium

a approximation that

• the frequency of the dominant allele + frequency of recessive allele is equal to one (100% of the population)

• the frequency of the dominant allele² + 2(heterozygous allele) + recessive allele² is equal to one (100% of the population)
  
  
  serves as a null model or baseline in population genetics to determine if a population is evolving. It predicts that allele and genotype frequencies remain constant across generations in the absence of evolutionary influences like mutation, natural selection, migration, and genetic drift
  
  deviations from the equations suggest that evolution is happening

formula to use if hardy-weinberg question only gives number and not frequencies 7 ALL GENOTYPE NUMBERS ARE GIVEN

Always start with… in hardy-weinberg equations

finding q²

Evidences of evolution

• fossils

• biogeography

• biochemical data

• morphological (similar characteristics)

• ancestral/derived traits

• common ancestry

biogeography

distribution of species and ecosystems in geographic space & through geological time

Analagous structures

Due to convergent evolution. Traits that have similar functions but different evolutionary origins. They are not derived from a common ancestor.

Homologous structures

traits of different organisms that have similar structure but not necessarily the same function, indicating a common ancestry.

Phylogeny

the study of evolutionary relationships among species, represented by branching trees showing divergence from common ancestors

Phylogenic tree

visual hypotheses representing evolutionary relationships among species based on shared ancestry, molecular data (DNA/amino acids), or morphological traits

shows the amount of change over time calibrated by fossils or a molecular clock

Cladogram

visual hypotheses representing evolutionary relationships among species based on shared ancestry, molecular data (DNA/amino acids), or morphological traits

Does not show time scale or evolutionary difference between groups

morphological traits

the physical characteristics and structures of organisms, including their shape, size, and overall form.

outgroup

species or group of organisms that is used as a reference point when constructing a phylogenetic tree. It is chosen because it is believed to be less closely related to the other organisms being studied.

Speciation

2 populations become reproductively isolated from each other

reproductive isolation

when different species are unable to interbreed and produce viable offspring due to physical, behavioral, or genetic barriers.

• behavioral

• temporal (mate at different times)

• geographic

• habitat/ecological

• mechanical

• gametic

hybrid breakdown

phenomenon where the hybrid offspring of two different species are viable and fertile in the first generation but produce offspring that are inviable or sterile in subsequent generations. This concept highlights the complexities of reproductive isolation and the mechanisms through which new species can emerge, emphasizing how genetic incompatibility can manifest over generations.

… could be the earliest genetic material

RNA