4.3 Classification + Evolution

• Classification


  the act of arranging organisms into groups based on their differences and similarites
• Taxonomy 


  the study of classification
• Phylogeny


  the study of the evolutionary history of groups of organisms
• Why classify organisms

  • Taxonomy provides a vivid picture of the existing organic diversity of the earth. The more diverse the more an organism can adapt and survive
  • Taxonomy allows a reconstruction of the phylogeny of life
  • Taxonomy reveals numerous interesting evolutionary events
  • Taxonomy establishes consistency and avoids problems associated with common names
• Taxonomic groups

  1. Domain - what cells are present
  2. Kingdom - five traditional kingdoms
  3. Phylum - same body plan
  4. Class - same general traits
  5. Order - more information than class
  6. Family - closely related genera
  7. Genus - group of closely related species
  8. Species - basic unit of classification
• Taxonomic classification system 


  More recent in time is at the top

  Common ancestors are where the different circles join

  
• Bacteria

  • Kingdom - Prokaryote
  • Cell type - Prokaryotic cells
  • Cell wall feature - made of peptidoglycan + is always present
  • Number of cells - unicellular
  • Nutrition - Autotrophs + saprotrophic
• Archea

  • Kingdom - Prokaryotes
  • Cell Type - Prokaryotic cells
  • Cell wall feature - no peptidoglycan
  • Number of cells - unicellular
  • Nutrition - Autotrophs + saprotrophic
• Eukarya 


  Protoctista (kingdom)

  • Cell type - eukaryotic cells
  • Cell wall - cellulose
  • Number of cells - most unicellular, some multicellular
  • Nutrition - autotrophs + saprotrophic
• Eukarya 


  Fungi (kingdom)

  • Cell type - Eukaryotic cells
  • Cell wall - chitin
  • Number of cells - most multicellular + some unicellular
  • Nutrition - Saprotrophic
• Eukarya

  Plantae (Kingdom)

  • Cell type - Eukaryotic cells
  • Cell wall - cellulose
  • Number of cells - all multicellular
  • Nutrition - Autotrophs
• Eukarya

  Animalia (Kingdom)

  • Cell type - eukaryotic cells
  • Cell wall - No cell wall
  • Number of cells - multicellular
  • Nutrition - Ingestive heterotrophs
• Archaea

  • first discovered living in extreme environments
  • No nucleus and are prokaryotic
  • Separate from bacteria as they have a unique liquid in membranes of cells, no peptidoglycan in cell walls, ribosomal structure is more similar to the eukaryotic ribosome than bacteria
  • Similar size range to bacteria
  • DNA transcription is more similar to eukaryotes
• Bacteria

  • Prokaryotic cells + no nucleus
  • Vary in size over a wide range
  • Divide by binary fission
• Eukarya

  • Eukaryotic cells with nuclei and membrane bound organelles
  • Vary massively in size
  • Divide via mitosis
  • Reproduce sexually or asexually
• Scientists have encountered many difficulties when trying to determine evolutionary relationships of species based on the method or classifying organisms based on the features that they share. This is due to having many limitation which can often lead to wrong classification
• DNA Analysis

  • DNA is extracted from the nuclei of cells either from blood or skin samples
  • Extracted DNA is processed, analysed and the base sequence is obtained
  • The base sequence is compared to that of other organisms to determine evolutionary relationships
  • This can be used from either living organisms or fossils
• Evolution

  • can be referred to as the way species have changed over time and continue to change
  • another way is through natural selection which includes random mutations
• Darwin's Observations

  • theory of evolution by natural selection
  • organisms produce more offspring than could ever actually survive
  • populations fluctuate but not significantly
  • populations of the same species of organisms show how variations via random mutations in characteristics between individuals
  • those with desirable alleles survive to pass on and inherit to their fertile offspring
  • key sources of evidence is fossil and molecular evidence
• Fossil Evidence for Darwins Theory

  • fossils show that environments have changed significantly over millions of years
  • fossils can be dated, putting fossils in sequance from oldest to youngest and see how organisms have changed
  • allow us to see similarites between extinct species
• Molecular Evidence for Darwins Theory

  • DNA found in the nucleus of cells can be sequenced and used to provide evidence of evolutionary relationships between species
  • can also show how the genetic code of species have changed
  • difference between nucleotide sequences can tell you how related a species is (more similar the sequence)
  • DNA sequences can be analysed and compared can be used to create a phylogenetic tree
• Variation 


  the difference that exist between two or more things
• Genetic Variation 


  the variation in genotypes (genes) between species or within species
• Phenotypic Variation 


  variation in phenotypes (other features, NOT genes) between species or within a species

  could be variation in height or mass
• Interspecific Variation 


  variation between species
• Intraspecific Variation 


  variation within a species
• Interspecific Variation

  • useful in identifying + classifying different species
  • even between species which look very similar, there are forms of phenotypic variation that can help differentiate them
  • species that look similar will live in slightly different habitats or fulfil different roles within the same habitat which can help distinguish between them
  • some species have such similar phenotypes however there will always be some level of genetic variation between species so genotypes are used to identify them
• Intraspecific Variation

  • in relation to natural selection
  • variation observed in the phenotypes of individuals from the same species can be due to qualitative or quantitative differences
• Discontinuous Variation

  • qualitative differences in the phenotypes of individuals within a population give rise to it
  • fall into discrete categories with no intermediates
  • example: there are only 4 possible blood groups in human and one person can only have one of them
  • easy to identify which present in table or graph

  
• Continuous Variation

  • occurs when there are quantitative differences in the phenotypes of individuals within a population for certain characteristics
  • do not fall into discrete categories
  • instead they have a range of values between two extremes
  • example: mass or height of human
  • lack of categories and presence of a range of values can be used to identify continuous variation

  
• Causes of Variation 


  genetic factors, environmental factors or both
• Causes of discontinuous variation

  • solely due to genetic factors
  • phenotype = genotype
  • different genes have different effects on the phenotype
  • can be caused by random mutations of genes that get passed down to offspring, meiosis which has crossing over and random independent assortment which increases genetic diversity and fusion of gametes which is random
• Causes of continuous variation

  • causes by interaction between both genetics and environment
• Why is a greater diversity a good trait to have within a species

  greater genetic diversity means that the species is more likely to be able to adapt to a changing environment
• different environmental factors

  • length of sunlight hours
  • supply of nutrients
  • availability of water
  • temperature
  • oxygen levels
• Adaptations

  • interspecific + intraspecific variation means that some organisms are better adapted to survive in their environment than others
  • increases chances of survival + reproduction so therefore more likely to survive and pass of the beneficial alleles to their offspring
  • these adaptations develop because of evolution through natural selection
• Behavioural Adaptation


  the way an organism behaves
• Physiological Adaptation 


  biological processes within the organism
• Anatomical Adaptation


  structural physical features
• Convergent Evolution


  The process by which species which don't share common ancestors and live in different parts of the world, show very high levels of similarity in terms of the adaptations they possess