UNIT 4

UNIT 4

1. ALLELES

   • alternative forms of a gene (variation of genes)
   • MUTATIONS is the source of all alleles and variation
     • point mutations (substitutions)
       • substitutes a nucleotide for another
     • frameshift
       • a shift in the reading frame of the genetic mutation message.
         • insertion: an addition of a letter which can effect the a.a chain
         • deletion: removing a letter from the codon which changes the a.a chain
     • silent mutation: if there's a change in the codon but the same a.a
     • nonsense mutation: if a codon changes in which a.a chain is significantly shorter
     • missense mutations: if the codon changes and the a.a chain is completely different, then the structure changes
     • block mutations
       • changes to segments of chromosomes leading to large scale changes to the DNA of an organism
         • duplication: when there is two copies of the same genetic information
         • inversion: a chromosome rearranges segments within itself
         • deletion: genetic information in the chromosome being removed
         • insertion: when genetic information in the chromosome is in the wrong section
         • translocation: swapping positions of the chromosomes
         • karyotype: when you have a complete picture of chromosomes in a somatic cell
           • 22 pairs + 2 sex chromosomes (XY)(XX)

2. NATURAL SELECTION

   • external agents that affect an organism's ability to survive in a given environment. eg- climate, a habitat being destroyed, predators
     • survival of the fittest: living long enough to produce offspring, giving their offspring their alleles
   • DARWINS THEORY OF NATURAL SELECTION
     • GENETIC MUTATION
       • CAUSES SPECIES VARIATION AND ADAPTATIONS
         • RIGHT ADAPTATION HELPS ANIMAL OR PLANT TO SURVIVE THE ENVIRONMENT (SURVIVAL OF THE FITTEST)
           • SURVIVORS REPRODUCE
             • PASS ON THEIR GENES TO THE NEXT GENERATION
               • MORE OFFSPRING WILL HAVE THE RIGHT ADAPTATION
   • gene flow: is the exchange of genes between two populations
   • gene pool: all the possible variation of alleles in a population
   • genetic drift: allele frequencies of a population change over generations due to chance, especially small populations
     • bottleneck effect: a random population crash by some dramatic incident that creates a smaller population with less diversity
     • founder effect: when very few individuals move and create their own population

3. SPECIATION

   • divergent evolution
   • allopatric speciation: when two populations of the same species become isolated from each other due to geographic barriers such as rivers, canyons, oceans, mountain ranges, deserts, rain forests
   • when seperated over time a new species could be made on either side, due to mutation or adaptation creating speciation
     • selection preassures on different sides which theyre isolated on, and species adapt to survive, creating a difference in two groups
   • two groups are considered to be different species if they cannot reproduce to create fertile offspring togeteher

4. EVOLUTION

   • FOSSILS
     • formation of fossils
       • 1. Rapid burial required hides remain from scavengers, decomposers. Sediment, volcanic ash/debris, ice, landslides, tree resin (amber) can bury remains
         • 2.Better preservation in areas with low 02 levels (so bacteria cannot get in), cool temperature, such as swamps, aquatic environments, areas surrounding volcanoes, cold climates
           • 3. preassure exists on top of fossil, minerals move into spaces where remains once existed
             • 4. fossils are uncovered/exposed at later dates through erosion and earth movement
     • dating fossils
       • Relative dating (approximate): determining the relative order of past events, without necessarily determining their absolute age
         • index fossils:fossils used to define and identify geologic periods
           • needs to be abundant (lots of and in many places)
           • easy to recognise
           • existed for a fairly short period of time. example- 50,000-75,000 years ago, existed for 25,00 years
         • using stratigraphy, studying the layers of strata can determine the age of the layers and the fossils within
       • Absolute dating: determining the absolute age of fossils, with the use of laboratory technology
         • involves the breakdown of radioisotopes (unstable), which can then be tracked by its proportion of radioactive form to the fossils breakdown product
     • trace fossil: any indirect evidence left by an organism.Footprints, burrows, and fossilized feces
     • molds & casts: an impression of an organism. A cast is a mold filled with sediment
     • replacement: original material of an organism is replaced with mineral crystals that can leave detailed replicas of hard or soft parts
     • petrified or permineralized: empty pore spaces are filled in by minerals, such as petrified wood.
     • amber: preserved tree sap traps an entire organism. The sap hardens into amber and preserves the trapped organism
     • original material: mummification or freezing preserves original organisms
   • molecular evidence for relatedness
     • Amino Acid/DNA sequences can be compared between species for common protein
     • phylogenetic trees: a diagram that represents evolutionary relationships among organisms, based on similarities and differences in their physical or genetic characteristics
       • bigger the number of similarities the closer they're realted
       • the most closely related species share a more recent common ancestor
   • human evolution
     • primates: group that contains all the species commonly related to the lemurs, monkeys, and apes, with the latter category including humans
       • qualities: opposable thumb, binocular vision, well developed cerebral cortex, bicuspid teeth
     • hominoids: a member of the family Hominidae: all of the great apes, also a subcategory of primates
       • qualities: No tail, arms shorter than legs, upright gait
     • hominins: which comprises those species regarded as human, directly ancestral to humans, or very closely related to humans.
       • qualities: bipedal, flat face, s-shaped spine allowing flexibility and suspension, speech, larger cranium, brow ridge becomes less prominent, foramen magnum changes to the middle of the skull, smaller jaw due to the introduction of utensils and cooking, smaller arm: leg ration,pelvic gurtle is wider
     • Denisovans and Neanderthals evolved outside of Africa, around European areas
     • Africans only evolved from homo sapiens

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