Patterns of Evolution

• Fossil: the remains or impression of a prehistoric plant or animal embedded in rock left behind in sediments by there activities
• Biogeography: The study of the distribution of organisms and their evolutionary relationships.

  Movement of landmasses= Geographical isolation- differing selection pressures

  Original species evolved into different but related species
• What are the two main evidence of Evolution?

  1. Comparative anatomy- Talks about different structure in animals= Homologous, Analogous and, vestigial
  2. Molecular Biology - Talks about the Amino acid differences, mtDNA, and Y chromosomes
• What are types of comparative anatomy?

  • Homologous - Similar structure but used in different functions (Shares common Ancestry)
  • Analogous - Different Structures but used in the same functions (Unrelated species)- Brought together by convergent evolution
  • Vestigial- Part of an species original structure which eventually lost its function due to evolution like pelvis of whales
• Molecular Biology Determines nucleotide sequence
• Analysing nucleotide sequence of two specie

  Contains large number of genetic differences to their amino acid=Unlikely that they shared common ancestor

  If they contains small number of genetic differences= Likely that they share common ancestor
• Degeneracy over redundancy in Amino acid sequence is the number of different amino acids that can be encoded by a single gene
• mtDNA is only found and can be passed down maternally, it is found ouside the nucleus hence it is not a subject of Meiosis
• Meiosis: a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores
• The only way for genetic variation to enter mtDNA is via mutation
• Characteristics of mtDNA?

  Never undergoes genetic combinations e.g crossing over

  Pass down to female lineage

  Acquired mutations at constant rate, presence of mutation in mtDNA can be compared to determine when species diverged
• Y chromosome is One of the two sex determining chromosomes found in nucleus of males (subject of meiosis)
• Why does Y chromosome pass down unchanged information?

  Have a smaller size than the X chromosome

  Can only exchange allele from its tips - (pseudoautomal region)

  Majority is conserved from father to son

  Any changes that occurred here are due to mutation
• Different Evolutions:

  Divergent Evolution

  Convergent Evolution
• Divergent evolution originated from the same ancestor but evolved in different directions- Two or more distinct species
• When do divergent evolution occur?

  occurs when gene flow is blocked between two distinct population

  Occupies different niches- different conditions
• Gene flow blocked in divergent evolution means accumulation of different characteristics due to Genetic drift - Change in allele frequency due to random chance

  Natural selection-
• Homologous structure relates to Divergent Evolution
• special type of Divergent Evolution is called Adaptive Radiation where Large number of species evolved over short period of time to fill in different niches - came from one common ancestor like finches
• What causes adaptive radiation?

  • Natural selection
  • Extinction events
  • Colonisation of new Habitat (founder effect)
  • Overall form new species
• Convergent Evolution

  • Similar traits arise in two or more unrelated species
  • Unrelated species responding to similar selection pressures-(Same niche- same problem-same solution)
  • Can't hybridise due to RIM's
• Analogous structure relates to convergent evolution
• Comparative Anatomy is the comparison of bone structures between different species
• Mitochondrial DNA acquires mutation at constant rate
• mutation in mtDNA can be compared to determine when species diverged
• pseudoautosomal region tip of Y chromosome
• Nondisjunction is the failure of homologous chromosomes to separate properly during meiosis