A3.1 Diversity of organisms

• evolution

  heritable characteristics of a species change
• Heritable characteristics are encoded for by genes and may be transferred between generations as alleles
• biological evolution


  A change in the allele frequency of a population’s gene pool over successive generations
• The fossil record provides evidence for evolution
• Something provides evidence for evolution when it demonstrates a change in characteristics from an ancestral form
• The fossil record provides evidence by revealing the features of an ancestor for comparison against living descendants
• fossil

  the preserved remains or traces of any organism from the remote past
• Preserved remains (body fossils) provide direct evidence of ancestral forms and include bones, teeth, shells, leaves
• Traces provide indirect evidence of ancestral forms and include footprints, tooth marks,
• fossil record

  The totality of fossils, both discovered and undiscovered,
• The fossil record shows that over time changes have occurred in the features of living organisms
• Fossils can be dated by determining the age of the rock layer (strata) in which the fossil is found
• Selective breeding is a form of artificial selection
• selective breeding 


  man intervenes in the breeding of species to produce desired traits in offspring
• By breeding members of a species with a desired trait, the trait’s frequency becomes more common in successive generations
• how does Selective breeding provide evidence of evolution


  targeted breeds can show significant variation in a short period
• an organism 


  an organism is any biological system that functions as an individual life form. All organisms are composed of cells
• populations 


  a group of organisms of the same species in the same area - although they're the same species the individual organisms of the population vary from each other population
• community

  populations of 2 or more different species occupying the same geographical area at the same time. There is a great variations between different species
• variations 


  refers to differences between members of a group. Variation can be discrete or continous
• variations is a defining feature of life
• discrete variation

  • traits that can be put into distinct qualitative categories
  • usually influenced by only one or a few genes
  • they can also be influenced by environment
  • (blood type)
• continuous variation

  • traits that vary along a quantitative continuum
  • most toes of biological variation are continuous
  • result from complex interaction between many different genes, often with the environment playing a significant part in the expression of the phenotype
  • height
•  No two individuals are identical in all their traits
• The patterns of variation are complex and are the basis for naming and classifying organisms
• variation exist at every level of biological variation
• intraspecies variation

  • variations within a species
  • genetic variation within a species is inheritable (transmitted from parents to offspring)
• Generic variation within a species can result from

  • mutation
  • gene flow
  • meiosis
  • sexual reproduction
• mutation


  the changes in the sequences of genes in dna
• gene flow 


  the movement of genes between different groups of organisms
• meiosis


  formation of egg and sperm which leads to the creation of new combinations of genes
• sexual reproduction 


  random fertilization between egg and sperm
• • genetic variation in a population of organisms enables some organism to survive better than others in the environment in which they live
  • these individuals are more likely to reproduce and pass on their beneficial variation
  • differential survival and reproduction is part of natural selection
• natural selections is the main force that drives evolution
• • the amount of variation between individual organism depends on how closely related they are to each other
  • individuals with the same species will have less variation than those classified as different species
  • the largest amount of variation would be between organs classified into different domains
• species 


  groups of living thongs recognizable distinct from all others by their shared characteristics
• Linnaeus's system of classification

  • organisms are grouped and subdivided into smaller categories of organisms
  • the first formal system of grouping organism
• morphology 


  based on distinguishable shapes and forms of organims
• Limitations of morphology

  • genetically diverging populations may be hard to distinguish as unique species
  • morphologically similar groups may be the result of covert evolutions and not actually members of the same species
• Linnaeus group organisms into species based on morphology