Evolution and Biodiversity

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  • Created on: 27-03-18 16:26
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  • Evolution and Biodiversity
    • Introducing Evolution
      • Definition: The changes that occur in living organisms over many generations.  A change in heritable characteristics
      • Only in populations of organisms
        • Only in heritable characteristics
      • Continuous variation has made it difficult to determine if some populations are the same species despite living in different geographical areas
      • Heritable Characteristics: Characteristics an organism possesses due to its genetic make-up
    • Evidence for Evolution
      • Homologous structures
        • Homologous: Having the same relation, structure or relative position
        • Homologous structures share the same origin or structure but NOT the same function necessarily
          • E.g. digging, swimming, walking, jumping etc
        • Pentadactyl limbs shared between humans, dolphins, bats, anteaters, moles and other mammals (all vertebrate limbs)
          • Divergent evolution that all these organisms evolved from one common ancestor
            • DIVERGENT = DIFFERENT FUNCTIONS
          • 3 long bones, a wrist and phalanges (finger projections)
        • Analogous structures
          • Functions seem similar but structurally or ancestrally not
          • For example, the tail of an orca and a shark
          • Convergent evolution
            • Organisms not closely related evolve similar structures for similar purposes
        • Adaptive Radiation
          • When species diverge rapidly from the ancestor into several  forms and evolve characteristics specialised to make use of their different environmental niches
      • Fossil Record
        • Cannot find fossils of organisms alive today, suggesting organisms change over time
        • Rocks can be dated and the age of fossils calculated and when they lived on Earth
          • Radioisotopes allows more accurate dating methods
        • Sequence of organisms in the fossil record matches their complexity
          • E.g. Begins with bacteria, simple algae then fungi and worms then vertebrates
        • Link existing organisms to their likely ancestors
          • E.g. Acanthostega 365 million year old fossil has 4 limbs (8 toes on front limbs, 7 toes on back) like amphibians, reptiles and mammals but has gills, a fish tail and lives in water
            • Land vertebrates could have evolved from fish via an aquatic animal with legs
          • See changes within a certain species over time
            • E.g. Evolution of the horse
      • Selective Breeding/ Artificial selection
        • Definition:  Selecting specific individuals with desirable characteristics and breeding from them to create a breed or plant line with these desirable characteristics
          • ARTIFICIAL and only through HUMAN INTERVENTION
        • Example: Domesticated dogs have many breeds all with the wild (grey) wolf ancestor.  They have been selectively bred for certain uses e.g. working, sporting, hunting etc which are heritable characteristics that have now developed into their own breeds (evolution)
        • Quicker than natural selection form of evolution
      • DNA base sequences/ amino acid sequences change over time
    • Example of Evolution
      • Peppered moth is active at night and roosts on trees with lichen in the day for camoflage so prey will not get it
      • Industrial revolution meant large amounts of sulfur dioxide released into the atmosphere which killed lichen and soot made tree bark darker
      • Darker moths more favourable in industrial areas while lighter moths variable in less industrial areas where there is lichen
        • Lighter peppered moths more visible on darker bark so were eaten while darker ones survived to reproduce because were camoflaged
      • Melanistic:  Darker varieties of typically light coloured insects
    • Natural Selection
      • Causes of variation
        • Meiosis
          • Crossing over and independent assortment of bivalents means new combinations of alleles are formed by breaking up existing combinations in a diploid cell
        • Mutations
          • Changes in the DNA sequence either by removal and replacement of one base or removal of a section of the sequence.  This enlarges the gene pool
        • Sexual Reproduction
          • A fusion of maternal and paternal gametes gives offspring a combination of alleles
      • Species tend to produce more offspring than the environment can support
        • Not all will survive and ensures there is a power struggle where indirectly, those better adapted for the environment survive thanks to variation
      • Those that have more favourable characteristics for the environment survive and produce more offspring.  Those with less favourable characteristics for the environment will die or produce less offspring
      • Adaptation: A characteristic that makes an individual  suited to its environment and way of life
      • Those individuals that survive to reproduce are well adapted and pass on their advantageous characteristics onto their larger number of offspring
        • Those individuals that do not survive to reach reproductive age have their genes or specific alleles eliminated from the gene pool
      • Arctic fox started out as having a variety of coat colours from brown to white but now it is white for camoflage
      • Acquired characteristics are characteristics acquired during a living organisms' lifetime and do not alter the genetic make-up so are not passed onto offspring
      • Natural Selection in Action
        • Beaks of finches on Daphne Major (A Galapagos Island)
          • Medium ground finches feed on variety of seed sizes
            • From 1973, beak sizes were measured every year (length and width)
          • Variable weather conditions consisting of warm ocean temperature and heavy rain (El Nina) and cold temperatures bringing drought (La Nina)
            • Few small soft seeds available in droughts
          • Birds with smaller beak size killed in drought between 1974 and 1977 and those adapted to eat larger seeds survived to reproduce and produce more offspring with larger mean beak size
            • In 1983, there was a heavy rain season with lots of small soft seeds so mean beak size dropped because smaller beaks are better adapted to feeding on small seeds
        • Antibiotic Resistance in Bacteria
          • Rise in the production of beta lactamase enzymes which break down the beta lactam ring in penicillin and other antibiotics, making them useless
          • Causes
            • Antibiotics for general use or animal feed.  Often people do not finish courses of antibiotics, leaving residual bacteria that have been exposed and develop partial or full resistance
              • Kills those not resistant and resistant bacteria survive to reproduce and pass on their resistant genes to their offspring
            • Antibiotic resistance is coded by a gene or multiple genes in plasmids which can be exchanged even between bacteria of different species or strains by conjugation
              • These plasmids can be in naturally occurring microorganisms that compose the antibiotics but come into direct contact with the pathogenic bacteria
            • In hospitals there is enormous selective pressure because patients with severe infections are treated with high dose antibiotics
          • The more antibiotics used, the fewer bacteria present that are not resistant and the more present that are resistant
    • Naming and Identification
      • Binomial System
        • 'Genus species'
          • Written in italics or underlines
          • Or 'G. species'
        • Genus: A group of species that share characteristics
        • Universal to avoid confusion between different names different cultures use
      • Dichotomous keys
        • A series of paired statements that guides the user to the identity (or allows classification) of the item or organism
        • Relies on visible and reliable features
        • Eventually gives the genus and species of an organism
        • Numbered stages  giving guidance on where in the key to go next
    • Classification
      • Putting species of living organisms into groups
      • Store and access information about different living organisms
      • Artificial classification: Grouping together organisms not similar enough to be grouped together
        • E.g. all animals with wings (different structures)
      • Natural classification: Grouping together species thought to have evolved from one common ancestral species
        • Species share many inherited characteristics
        • Allow prediction and identification of species
        • Sometimes, taxonomists end up re-classifying a species when they realise they are from a different ancestral group as seen by DNA base sequences
      • Five kingdoms
        • System of classification of living organisms developed in the 20th century
        • All prokaryotes in one kingdom and eukaryotes in the other four kingdoms
        • However, soon it was discovered after looking at the nucleic acids of prokaryotes that there were two very different groups of eukaryotes so a higher grade taxonomic group was developed
          • Introduction of DOMAINS
          • Prokaryotes diverged into eubacteria and archaea early in the evolution of life so they cannot be classified in the same kingdom
          • Carl Woese
      • Three domains
        • Archaea
          • Thermophiles and halophiles
        • Eubacteria
          • E.coli and photosynthetic cyanobacteria
        • Eukaryota
          • Animals, plants and fungi
        • Found using base sequences of ribosomal RNA
          • Found in all organisms and evolves slowly so suitable for studying early evolutionary events
        • Viruses not classified because not regarded as living organisms
      • Taxon: A grouping of organisms
        • Domain
        • Kingdom
        • Phylum
        • Class
        • Order
        • Family
        • Genus
        • Species
        • Did King Phillip Come Over For Good Sausages?
        • Each higher level includes a larger number of organisms
          • Hierarchy of taxa
      • Examples of taxa hierarchies
        • Human
          • Eukaryota, Animalia, Chordata, Mammalia, Primates, Hominidae, Homo, Sapiens
        • Meadow Buttercup
          • Eukaryota, Plantae, Angiospermophyta, Dicotyledonaea, Ranales, Ranunculacae, Ranunculus, Acris
      • Classification of Eukaryotes
        • Plants (phyla)
          • Bryophytes
            • Mosses, liverworts, hornworts etc
            • Root structures called rhizoids similar to root hairs but not for water or nutrient absorption.  No roots or vascular tissue.  Simple leaves and stems
            • Spores produced in a capsule that develops at the end of a stalk
          • Filicinophytes
            • Ferns
            • Roots, leaves, short non-woody stems, vascular tissue.
              • Leaves curled up in a bud and divided into pairs of leaflets (pinnate)
            • Spores develop in sporangia, usually on the underside of leaves
              • Sporangia: The case or sac in which spores are produced
          • Coniferophytes
            • Conifers
              • Shrubs or trees
              • Cedars, spruces, yews, redwoods
            • Vascular tissue, roots, leaves and woody stems
            • Leaves are narrow with a thick waxy cuticle
            • Male cones produce pollen; Seeds develop from ovules on surface of scales on female cones
          • Angiospermophytes
            • Vascular tissue.  Very variable but normally have roots, leaves and stems.
            • Shrubs and trees have woody stems
            • Seeds develop in ovule in the ovaries in flowers
            • Fruits develop from ovaries and disperse the seeds
            • Flowering plants
      • Animal Phyla
        • Chordata
          • Notochord
          • Dorsal nerve cord
          • Post-anal tail
          • Pharyngeal gill slits
          • Humans, whales, dogs etc
        • Porifera
          • Pores through body
          • No mouth or anus
          • No clear symmetry
          • Attached to a surface
          • Sponges
        • Cnidaria
          • Radially symmetrical
            • Divided into equal portions from the centre
          • Tentacles
          • Stinging cells
          • Mouth but no anus
          • Jellyfish, corals, sea anemones
        • Platyhelminths
          • Bilaterally symmetrical
          • Flat bodies
          • Unsegmented
          • Mouth but no anus
          • Liverflukes, tapeworms, planaria
        • Annelida
          • Bilaterally symmetrical
          • Bristles often present
          • Segmented
          • Mouth and anus
          • Earthworms, leeches, ragworms
        • Anthropoda
          • Jointed apendages
          • Bilaterally symmetrical
          • Segmented
          • Exoskeleton
          • Scorpions, insects, spiders, crabs
        • Mollusca
          • Muscular foot or mantle
          • Shell usually present
          • Mouth and anus
          • Segmentation not visible
        • PAMPACC
      • Types of vertebrates (chordates)
        • Birds
          • Feathers grow from skin
          • Lungs with parabronchial tubes
          • Wings instead of front legs
          • Eggs with hard shells
          • Beak with no teeth
        • Reptiles
          • Dry scaly impermeable skin
          • Soft shells around eggs
          • Internal fertilisation
          • One type of teeth
          • Lungs with extensive folding
        • Amphibians
          • Protective gel around eggs and larval stages in the water
          • Soft, moist permeable skin
          • Lungs with small internal folds
          • External fertilisation in the water
        • Bony ray-finned fish
          • Scales grow from skin and gills with single gill slit
          • External fertilisation
          • Swim bladder for buoyancy
          • Fins supported by rays
    • Cladistics
      • Clade: A group of organisms that evolved from a common ancestor
      • Use DNA base sequences  or amino acid sequence of a protein (e.g. hemoglobin).  Not physical features because hard to distinguish between homologous and analogous structures
      • Cladogram/ phylogenetic tree:  A tree diagram showing the most probable sequence of divergence in clades
      • Nodes = branching points showing groups of organisms that are related
      • Definition: Method of classification
      • Use numbers of differences in base sequences as evolutionary clock
      • Reclassification of figwort  family of plants into different species and genera and the merging of other families thought to share common ancestry with figwort family
      • The more nodes between species, the more distant their relationship
      • Changes to DNA or protein level though to occur at a constant rate
        • E.g. 1 base every 109 years
      • If extinct species are included, must make clear if the cladogram is based on morphology (DNA might not be available for analysis)
  • Types of vertebrates (chordates)
    • Birds
      • Feathers grow from skin
      • Lungs with parabronchial tubes
      • Wings instead of front legs
      • Eggs with hard shells
      • Beak with no teeth
    • Reptiles
      • Dry scaly impermeable skin
      • Soft shells around eggs
      • Internal fertilisation
      • One type of teeth
      • Lungs with extensive folding
    • Amphibians
      • Protective gel around eggs and larval stages in the water
      • Soft, moist permeable skin
      • Lungs with small internal folds
      • External fertilisation in the water
    • Bony ray-finned fish
      • Scales grow from skin and gills with single gill slit
      • External fertilisation
      • Swim bladder for buoyancy
      • Fins supported by rays

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