quick

• classification + taxonomy


  classification - grouping organisms based on similarities/differences

  taxonomy - system of classifying organisms based off of observable features/genetic characteristics
• why do we classify living organisms


  for convenience

  make the study of living things more manageable

  help us predict characteristics of species in a group

  to help organisms be identified

  see evolutionary relationships (phylogeny) between species
• early v new classification


  EARLY

  • morphology
  • anatomy
  • observable features

  NEW

  • DNA base sequence of genes
  • amino acid sequence of proteins (cytochrome C)
  • behaviour/physiology
  • shared evolutionary past
  • embryonic development
• cytochrome C


  short protein found in many different species

  more similar the amino acid sequence the more closely related the species are
• how can evidence from DNA analysis be useful for taxonomists


  • compare the sequence of DNA bases for a gene
  • compare the proportion of different bases in a gene
  • decide which group the organism belongs to
  • the more similar the DNA base sequences the more closely related the two species are
• hierarchy


  organisms are classified into groups which are subdivided into smaller groups due to increasing similarities

  as you rise through the hierarchy, the number of similarities reduces and differences increase
• kingdoms


  PHYLA - each kingdom is divided into phyla - CHORDATA - all share a common body plan

  CLASS - chordata split into 5 - fish, birds, reptiles

  ORDER - 19 for mammals - primates

  FAMILY

  GENERA

  SPECIES
• classifying humans


  KINGDOM - animalia multicellular with no cell wallas

  PHYLUM - chordata - backbone

  CLASS - mammal - hairy skin, produce milk to feed young

  ORDER - primates - forward facing eyes, flat faces, opposing digits

  FAMILY - hominidae - human-like features

  GENUS - homo

  SPECIES - sapien
• classifying cats

  KINGDOM - animalia

  PHYLUM - chordata

  CLASS - mammal

  ORDER - carnivora - almost exclusively eat meat

  FAMILY - felidae - cat-like features

  GENUS - felis

  CATUS - domestic cat
• different species


  • genetically incompatible - DNA is sufficiently different
  • different number of chromosomes
  • may be a physical/behavioural reason for genetic incompatibility - different incubation patterns/eggs remain unfertilised
• why binomial system of naming


  worldwide and universally recognised

  tells us both genus and species of an organism

  some organisms have a different common name which can be confusing

  also tells us what an organism is closely related to
• trophic


  autotroph - use chemical and light energy as well as inorganic molecules (co2) to make complex organic molecules (glucose)

  heterotroph - organisms that ingest and digest complex organic molecules and RELEASE THE CHEMICAL POTENTIAL ENERGY STORED IN THEM

  saprotroph - organisms that gain nutrition by absorption of decaying matter
• molecular evidence


  certain large biochemical molecules are present in all living organisms but are not identical between them, which reflects evolutionary relationships (PHYLOGENY)

  • HAEMOGLOBIN
  • DNA and RNA
  • CYTOCHROME C
• revolution of the 3 domain system


  Woese divided prokaryotae into EUBACTERIA and ARCHAEABACTERIA based on ribosomal RNA, cell membrane lipid structure and sensitivity to antibiotics
• 3 domain


  different cell membrane and flagella structure, different RNA polymerase, cell wall made out of peptidoglycan

  similarities between a and e

  • similar cell membrane structure
  • similar RNA polymerase
  • similar mechanisms for building DNA and RNA
  • histones

  archaea are more closely related to eukaryotes than eubacteria
• domain system


  divides prokaryotes and groups eukaryotes together

  accurately reflects ORIGINS of eukaryotes and prokaryotes

  reflects similarities between eukaryotic kingdoms

  reflects differences between archaea and eubacteria
• why is 3 domain system used nowadays 


  • fits phylogeny better
  • reflects differences between archaea and eubacteria
  • cell membrane structure, flagella structure, RNA polymerase, cell wall made of peptidoglycan
  • differences between eukaryotes and prokaryotes (eukaryotes have a nucleus)
• phylogeny


  basis of modern classification

  the study of EVOLUTIONARY relationships between organisms and the closeness of the relationships

  looks at genome, cytochrome C and amino acid base sequence

  • more closely related two species are, the more characteristics they have in common, the more groupings they share
• more about phylogeny


  • tells us who's related to whom and how closely related they are
  • all organisms have evolved from a SHARED COMMON ANCESTOR who is no longer alive
  • the evolutionary relationships and the closeness of them between organisms can be displayed on a phylogenetic tree
• phylogenetic tree


  • shows evolutionary relationships between organisms
  • show how different species have evolved from a shared common ancestor
  • if two species are more closely related, they share a more recent common ancestor
• phylogeny v Linnaean system


  • takes into account evolutionary relationships that aren't so obvious by just looking at observable features
  • not hierarchal so different groups of organisms are judged on their evolutionary position so can be compared easily
  • not hierarchal so organisms aren't forced into discrete taxonomical groups
• evolution


  change over time
• natural selection


  cd put forward mechanism for evolution - natural selection

  read PRINCIPLES OF GEOLOGY by charles lyell who suggested fossils were evidence of animals living millions of year ago, and popularised the idea of

  UNIFORITARIANISM - idea that the past earth was shaped by forces we still see to this day (erosion, deposition)

  THIS INSPIRED DARWIN TO THINK OF EVOLUTION AS A SLOW PROCESS WITH GRADUAL CHANGES ACCUMULATING OVER LARGE PERIODS OF TIME
• charles wallace and darwin


  joint presentation of their findings of the theory of evolution

  weight of evidence increases
• darwin's four observations


  • offspring generally appear similar to their parents - CHARACTERISTICS ARE PASSED ONTO THE NEXT GENERATION
  • no two individuals are identical and organisms have the ability to produce large numbers of offspring, more than that of who can survive - THERE IS A STRUGGLE FOR EXISTENCE
  • population sizes in nature tend to remain fairly stable - INDIVIDUALS WITH BENEFICIAL CHARACTERISTICS ARE AMONG THE FEW WHO SURVIVE
• FOSSIL RECORDS


  evidence that ancestral organisms lived millions of years ago

  GENERAL TREND

  • smaller, simpler organisms were of the distant past and larger, more complex organisms are more recent

  KEY FACTS

  • there are methods to date fossils and rocks
  • show intermediate forms
  • show organisms have changed over time
  • many fossil organisms no longer exist
  • show links and relationships between different species
• problems with the fossil record


  often incomplete

  only hard parts of the organism are fossilised

  conditions may not be suitable for organisms to be fossilised

  rock movement may cause damage to fossils
• molecular evidence


  DNA/RNA POLYMERASE

  GENOME

  CYTOCHROME C
• variation and the different types

  VARIATION - presence of differences between individuals

  INTRASPECIFIC VARIATION - variation between members of the same species

  • relies on mutations within the species
  • acted upon by selection pressures
  • only the fittest will survive and breed and pass on their alleles

  INTERSPECIFIC VARIATION - variation between individuals of different species
• what causes variation

  GENETIC VARIATION - the genes we inherit from our parents

  • the combination of alleles will differ across humans
  • there will never be a complete match due to mutations + the environment

  ENVIRONMENTAL VARIATION - the environment we live in (diet, UV)
• what causes genetic variation


  ALLELES - different forms of the same gene inherited

  CHANCE - down to chance which gametes fuse

  SEXUAL REPRODUCTION - offspring inherit alleles from both parents

  MEIOSIS genetic information inherited from parents mixed up via CROSSING OVER and INDEPENDENT ASSORTMENT

  MUTATION - changes in the DNA base sequence leading to potential changes in protein (may not form)
• environmental variation


  skin colour, weight, height are all affected by the environment

  most characteristics are influenced by both genes and the env.

  not all genes are ACTIVE ALL OF THE TIME (when you hit puberty genes become activated that cause your body to change)

  changes in the environment can cause certain genes to become active
• DISCONTINUOUS AND CONTINUOUS VARIATION


  DISCONTINUOUS

  • bar charts
  • discrete categories with no intermediates
  • influenced by one or a few genes
  • small if any environmental effects
  • QUALITATIVE

  blood group

  CONTINUOUS

  • line graph, normal distribution, histogram
  • no defined categories - range of values present
  • influenced by many genes (polygenic) and the environment
  • QUANTITAIVE - has to be measured, not counted

  weight, surface area of leaf
• GENETIC VARIATION

  leads to evolution to natural selection and allows organisms to adapt to changes in the env. or else whole crops/cattle could be killed

  IF ONE ORGANISM IS SUSCEPTIBLE TO CHANGE (DISEASE) IT IS HIGHLY LIKELY THAT ALL INDIVIDUALS WITHIN THE POPULATION ARE ALSO SUSCEPTIBLE TO THE CHANGE
• adaptations

  any variation that leads to increased chance of survival and long-term reproductive success of an individual

  WELL ADAPTED

  • find enough food/photosynthesise well
  • find enough water
  • defend itself against predators
  • fight off disease
  • respond well to changes in the environment - light, temp and water levels
  • STILL HAVE ENOUGH ENERGY TO REPRODUCE SUCCESSFULLY
• types of adaptation


  BEHAVIOURAL - the way an organism acts (learned/inherited from parents) to increase chances of survival

  • blinking
  • courtship
  • playing dead
  • MIGRATION - find better climate/food source
  • HIBERNATION - body processes slow down to conserve energy
• physiological


  processes that take place inside the body to increase chances of survival

  • water holding
  • temperature control
  • poison/antibody production
  • blinking
• anatomical


  physical features that enhance the survival of an organism

  • body covering - hair/fur, spikes on xerophytes
  • camouflage
  • marram grass have sunken stomata and micro-hairs to reduce WVPG
  • LARGE CANINES
• NATURAL SELECTION


  there is a struggle to survive and competition between individuals

  selection by the environment for particular individuals that show certain characteristics

  these are more likely to survive and pass on alleles onto next generation

  UNDERGO SELECTION PRESSURE

  • availability of nutrients
  • predators
  • physical and chemical factors
  • disease
• natural selection


  there is genetic variation in a population due to mutations which are naturally occurring/pre-existing

  large number of offspring produced

  there is a selection pressure

  individuals with selected advantage are more likely to survive and thus pass allele/mutations onto offspring

  occurs over many generations

  allele frequency of advantageous allele increases