Evolution & Biodiversity

• Evolution = cumulative Δ in the heritable characteristics of a popu over time
• Evi of evo:

  • Fossil records
  • Layers of sedimentary rock are put down & the inorganic components of living things are preserved. These fossils show a transition over time that shows the development of species through the theory of evolution.
  • Gaps in fossil record due to:
  • Special circumstances req for fossilisation to occur
  • Only hard parts of an organism are preserved
  • Dmg fossils = only fragments remain to be discovered
  • Transitional fossils show link btw groups/ species by exhibiting common traits of both ancestor & descendant. Eg: Archaeopteryx (dino → bird)
• Evi of evo:

  • Homologous struc (similar shape struc in diff organisms)
  • Comparative anatomy of groups of animals or plants shows certain structural features are basically similar. Structures or anatomical features having similar basic structure as in other species said to be homologous. The structural similarities imply a common ancestry. Eg: pentadactyl limb.
  • Selective breeding
  • Process by which humans breed animals and plants for particular traits. Eg: Munchkin 
  • Vestigial (useless) structures 
• Natural selection:


  = the implication of variation that some individuals are more suited to particular conditions & hence more likely to survive.
• Variation is the result of random mutation/ sexual repro. Antibiotic resistance good eg. Adaptive radiation (AR) = birds who came over island from storm and each bird on diff island has diff characteristics. For AR the > the geographical separation and the > the populations have been separated the > the divergence. 
• Adaptive radiation:


  the evolutionary process by which many species originate from 1 species in an area and radiate to different species.
• Allele freq is the proportion of all copies of a gene consisting of a particular gene variant (allele). Gene pool = ttl collection of different alleles in an interbreeding population. New combos of alleles → new phenotypes that can then be selected for/ against the envi → evolutionary Δ in the species. If the selective pressures applied to a popu do not Δ then popu won’t evolve and if they do, then they will, but how it evolves depends on which phenotypes experience the > pressure.
• Selective pressure:

  • Directional
  • Medium ground finch (Selective pressure: during dry years small seeds are not abundant. Result: Birds with larger tougher beaks become more frequent)
• Selective pressure:

  • Stabilising
  • Human baby (Selective pressures: Babies of < weight lose heat more quickly & get ill from infectious diseases more easily. Babies of > weight are difficult to deliver. Result: Medium weight babies have a < mortality & hence freq of medium weight babies ↑)
• Selective pressure:

  • Disruptive
  • Grass (Selective pressure: soil close to mine workings contaminated with metals, e.g. copper. Result: 2 distinct grass populations arise; slower growing metal-tolerant & faster growing non-tolerant popu)
• The circumstances preventing diff species from interbreeding aka reproductive isolating mechanisms. Popu can be isolated to prevent repro via temporal (timing), behavioural (this affects only animals) & geographic. Reproductive isolation only promotes selection in sexually reproducing organisms, it doesn’t apply to unicellular organisms.
• Temporal:


  Pinus radiata and Pinus attenuata are prevented from hybridising cus they have separate pollination times. They can be made to hybridise by pollinating them manually. It’s the “fickle hand of fate” lol.
• Behavioural:


  Animals exhibit courting behaviour (song, dance etc.)/ release pheromones to attract mates. Indi only attracted to, and will only mate with, members of the opposite sex who perform the appropriate ritual/ release the correct chemical.
• Variation in species:

  Phyletic Gradualism:

  Evo occurs at a constant pace over a long period of time (due to the accumulation of mutations). Eg. the change in size & hoof of the modern horse. 

  Punctuated Equilibrium:

  = long periods of stability that are interrupted by ‘rapid’ evo Δ. Periods of stability come from well-suited organisms that have no reason to evo until large envi Δ (e.g. meteor strikes) → shifting selection pressures. Gaps in the fossil record show mass extinction events.
• Polyploidy:

  When non-disjunction occurs during meiosis in humans, an indi can end up w an extra/ missing chromosome (e.g. extra chromosome 21 = Down's syndrome). Ttl non-disjunction, is when 1 of the 2 cells produced during Meiosis I gets all of the chromosomes. The other cell is not viable & is reabsorbed. This → 2 (2n) daughter cells from meiosis instead of the ≈ 4 (n) daughter cells. Polyploidy > common in plant species as they lack separate sexes & are capable of asexual repro. Tetraploid offspring cannot mate w diploid organisms (triploid offspring ≈ infertile), speciation has occurred. 
• Polyploidy in animals & plants:

  Polyploidy in pants ≈ → to ↑ size, resistance to disease & overall vigour. There exist few polyploid animal species (e.g. salamanders, goldfish & salmon).
• Binomial Nomenclature:


  Bi=2 + nominal= named + nomenclature = naming system. Naming system allows scientists to communicate abt species wo confusion from names w influence from local lang & culture.
• Ribosomal RNA is found in all organisms & evolves slowly so it’s a good way to track evo over long time periods. Recent evi from genetic studies of ribosomal RNA showed that "prokaryotes" are a lot more diverse & this → split into 2 domains, Eubacteria and Archaea.
• Dear King Phillip Came Over For Good Spaghetti:

  Taxonomy is the practice & science of classification.
• Plantae:

  Can separate into 2 subgroups, non-vascular (Chlorophyta, Bryophyta) & vascular (Filicophyta, Coniferophyta, Angiospermophyta). Vascular means has phloem & xylem. 
• Bryo (mosses, hornworts and liverworts):

  • No true TTT
  • Has struc ≈ root hairs aka rhizoids
  • Moss has simple leaves & stems
  • Liverworts has flattened thallus
  • No vasular structure
  • Spores prod in capsules, which develop at stalk end.
• Filicino (ferns):

  • Has TTT
  • Short non-woody stems.
  • Leaves ≈ divided into pairs of leaflets
  • Has vascular structure
  • Spores prod in sporangia on underside of leaves
• Conifero (conifer shrubs and trees):

  • Has TTT
  • Woody stems
  • Leaves ≈ narrow w thick waxy cuticle
  • Has vascular structure
  • Seeds develop from ovules in female cones. Male cones produce pollen.
• Angiospermo (flowering plants)

  • Has TTT
  • A lot variation btw diff plants for leaves & roots 
  • Stems may be woody (shrubs and trees)
  • Has vascular structure
  • Seeds develop from ovules in ovaries, inside flowers. Seeds dispersed by fruits which develop from the ovaries.
• Natural classification groups species that share a common ancestor from which they evolved aka Darwinian principle of common descent. Members of a grp share imp attributes/ 'homologous’ traits inherited from common ancestors. Natural classification is not straightforward as convergent evo, can make distantly related organisms appear similar & adaptive radiation, can make similar organisms appear very different from each other.
• Convergent evo:


  Unrelated species independently develop similar traits/ characteristics cus of similar envi pressures.
• Cladistics:

  Species may evo over time to form new species, thus there are grps of species derived from common ancestor. Such groups aka Clades. Analogous structures mean similar structures that provide similar function btw diff species that have evolved independently, lacking a common ancestry (due to convergent evo). A cladogram is a tree diagram showing the similarities & differences btw diff species. Nodes denote a speciation event when a common ancestor splits into 2/ more, species DUHHHHHHHHHHH. Cladograms are ≈ based on DNA base sequences/ amino acid sequences in a protein.
• DNA evi used to build cladograms can also be used to estimate when species diverged & hence when common ancestor existed cus mutations in DNA that persist and are inherited* occur at a predictable rate.
• Mitochondrial DNA from humans & primates has been completely sequenced & used to construct cladogram btw them. The rate at which mutations occur can be used as molecular clock to calculate how long ago species diverged. If the DNA base sequences of 2 species are similar then few mutations have occurred, ∴ species only diverged relatively recently. Length of the lines separating species on cladograms ≈ used to show estimated time divergence.
• Reclassification of figwort fam:

  DNA evi identified diff common ancestors showing that similarities among members of the old Scrophulariaceae (figwort) family were superficial. General flower shape & form of the seed capsule evo many times from diff ancestors cus diff plant species adapted to similar pollinators & adopted similar seed dispersal strategies (convergent evo).