Bio unit 7

Natural Selection

1. does not give organisms what they need to survive (no info)

2. does not act for the good of a species (no intentions)

3. it is not a process involving organisms trying to adapt (random mutations)

process where individuals with certain traits tend to survive and reproduce at higher rates than others

• acts on phenotypes

  • some increase/decrease fitness

1. traits are heritable

   1. passed from parent to offspring

   2. adaptions - inherited traits are beneficial

2. more offspring produced than can survive

   1. leads to competition —> differential survival

      1. traits leading to survival will accumulate

POPULATION EVOLVES NOT INDIVIDUALS

1. directional

   1. selection towards one extreme

2. stabilizing

   1. selection towards mean and against extreme phenoypes

3. disruptive

   1. selection towards both extremes and against the mean

Evolution

genetic makeup of a population over time; decent with modification

• heritable traits change from each passing generation

  • to prove this theory darwin proposed natural selection

driven by random occurrences

• mutations

  • random process that results in variation

  • forms new alleles

• genetic drift

  • causes change in allele frequency

  • nonselective process

  • small population diverges from main

  • loss of genetic diversity —> more fixed alleles

  • NO ADAPTATIONS

    1. bottleneck effect

       1. large population is reduced by disaster

          1. flood, famine, fires, etc

       2. alleles become too rare/common or extinct

    2. founder effect

       1. few individuals become isolated

       2. new small gene pool that is different from original - lose diversity

• migration/gene flow

  • movement of alleles in/out of a population

  • alleles can be transferred

  • prevents divergence because the constant exchange of genes ensures that the allele frequencies dont change too much and result in a new species

evolutionary fitness

measured by reproductive success

selective pressure

environment changing - fluctuate —> affect rate and direction of evolution

1. abiotic - drought

2. biotic - drought changed the vegetation and seeds available

variations

more genetic diversity = better response to changes

• higher chance of individuals that can resist

• low genetic diversity —> extinction

• high genetic diversity = types and levels of proteins

artificial selection

selective breeding of domesticated plants and animals for wanted traits

population

same species that live in the same area and interbreed to produce fertile offspring

gene pool

populations genetic make up

• all copies of every allele

• if only one allele is in the locus for all individuals it is called fixed

• more fixed = less diversity

allele frequencies will cahnge

microevolution

hange in allele frequencies within a single species / population

• natural & selection selection

• genetic drift

• gene flow

sexual selection

males have exaggerated structures like colorful feathers becasue females choose that trait

possibility of harm / increased risk of death
colorful feathers are easier to spot

hardy weinberg equation

how to predict allele frequencies in a non evolution population

no differences between observed and expected —> pop. is not evolving
yes differences —> MAY BE EVOLVING

only mendelian genetics and alleles + genotypes reamin constant

5 conditions

• extremely large pop. size - no genetic drift

• no migration - adds alleles

• no new mutations —> leads to new alleles

• random mating - if choosing on specific traits it will lead to unbalanced ratio

• no natural selection -frequencies will change as one trait is better

species

group able to interbreed and produce viable, fertile offspring

speciation

formation of new species, happens when two populations (same specie) become reproductively isolated

1. allopatric

   1. physical barrier divides or separates small group

   2. geogrpahic isolation

      1. stops gene flow

      2. natural disasters

2. sympatric

   1. new species evolves while still living in the same area

      1. exploitation of a new niche

reproductive isolation

both lead to isolation and stop gene flow

1. prezygotic - prevent mating or hinder fetilization

   1. habitat - live in diff areas or habitats

   2. temproal - diff mating seasons, times, days

   3. behvaorial - diff unique rituals

   4. mechincal - diff reproductive anatomy

   5. gametic - diff proteins on the surface of gametes

2. postzygotic - prevent a hybrid zygote from developing

   1. reduced hybrid viability

      1. parent’s genes lead to impairment of hybrids development/survival

   2. reduced hybrid fertility

      1. healthy adult but sterile - differences is chromosomes

   3. hybrid breakdown

      1. first generation works, then becomes sterile

macroevolution

large patterns - adaptive radiation or mass extinction

• stasis - no change over a long period of time

pace of speciation

evolution and speciation occurs at different speeds

• punctuated equilibrium - evolution is rapid then long stasis

• gradualism - slowly of a long time

divergent evolution

divergence of 2 or more species from a common ancestor

when population becomes sepereated

• gene flow stops

• changes accumalate

• new species

leads to homologous traits

adaptive radiation

if a new habitat or niche becomes available then species diversify/evolve rapidly to claim that area

convergent evolutions

2 seperate lineages develop similiar structures because of selective pressures in their environment. leads to analagous trais

RNA world hypothesis

RNA was the first genetic material

• helps explain pre-cellular stage of life

• RNA molecules–ribozymes could process info and act as enzymes

three assumptions

1. genetic continuity was caused by the replication of RNA

   1. RNA came first and was able to copy itself

   2. base pairing

   3. genetically encoed preotiens were not catalusts

      1. DNA codes fro proteins by RNA had to act as catalysts

dna may have developed due to the removal of oxygen from ribose. This led to a stable and longer sequences

milller and urey test

oparin and haldance thought that earth mainly had hydrogen methane ammonia and water

• the test discovered that organic compounds and amino acids formed because of the free enrgy and reducing atmosphere

• m and u that the these organic molecules were the building blocks for macromolecules

organic molecules could have been meterorites or othe events