Biodiversity, Evolution & Classification

• human alteration to habitat is the single greatest threat to biodiversity
  • destroying tropical rainforests
  • overfishing
  • clearing lands for crop production/human populations
• extinction is a natural process occuring since the first life evolved
  • current rate underlies biodiversity problems
  • human activity increasing rate of extinction at alarming rate
  • mass destruction for farming agriculture urbanisation forestry mining drilling pollution
• earlier extinctions e.g dinosaurs where a result of climatic geological biotic changes
• main causes of loss of large mammals are loss of habitat over hunting and competition from introduced species, and deforestation pollution and wetland drainage
• each species can represent an important human asset
  • food, chemicals, disease resistant genes
  • extinction of plant species with potential medicinal properties before being fully investigated could be an incalcuable loss
  • need for species consrvation and preservation of wildlife

• processes that have transformed life on Earth from its early beginings tovast diversity of fossilised and living forms known
• theory proposed by Charles Darwin
  • travelled to south america and galapogas islands formed in recent geological time by volcanic activity
  • studied flora and fauna on both lands- any plants on the islands must have reached via the mainland
  • observe describe and classify his findings, colecting fossils showing the different life forms of the past
  • natural selection was the force to cause changes in the populations
  • studied finches onislands, which are unable to fly long distances as such to reach the mainland
    • acestors of the finches reached the island by prevailing winds species flourished due to no other bird species and a variety of food individual finches differed in size and shape of beaks related to type of food eaten seeds fruit insects
    • characteristics best suited to the finch where passed to offspring, all finches had common ancestor type of beak developed through adaptie radiation via food

• sorting living groups of organisms into groups of a managable size
• look for differences and similarities between organisms placing similar organisms close and different ones apart
• hierarchical system devised to distinguish large groups of organisms with a series of rank names
• kingdom, phylum, class, order, family, genus, species

phylogeny

• taxonomic ranks based on evolutionary line of descent
• phylogenic relationships represented by a tree 
• oldest speces at the base while recent at the ends

• naming according to the binomial system based on latin 
• each organism has two names, genus and species
• precise identification worldwide
• each organism has unique scientific name and allows for easy identification of relation to other species
  • genus name is the fiirst word and has a capital
  • species name comes second with no capital
  • first time used in a scientific text should be names in full afterwards it can be abbreviated
  • printed in italics or underlined

prokaryote

• unicellular organisms incl. bacteria and blue green algae
• no organelles
• cell wall not of cellulose

proctoctista

• small eukaryotic organisms
• membrane bound organelles and nucleus
• not plant animals or fungi incl. algae mouldss slime protozoa

fungi

• eukaryotic with a body of a sytem of threads called hyphae forming a mycelium
• rigid cell wall of chitin
• no photosynthetic pigments; feed heterotrophically- saprophytic/parasitic
• reproductionby spores w/o flagellum yeast mushroom

Plants

• multicellular
• carry out photosynthesis
• eukaryotes with cellulose walls, vacuoles with cell sap & chloroplasts with photosynthetic pigments
• mosses liverworts frns conifers flowering plants

animals 

• multicellular
• heterotrophic eukaryotes
• cells do not have cell walls
• nervous coordination

• non-chordates/invertebrates 
• chordates- vertebrates with a vertebral column

annelida

• earthworms leeches
• long thin segmented ringed body separated internally by septa
• fluid filled body cavity
• hydrostatic skeleton
• head with primative brain/nervous system
• thin permeable skin for gaseous exchange
• closed circulatory system with repiratory pigment

• body divided into segments
• well developed brain
• open circlatory system/cavity surrounding body organs
• hard outer exoskeleton
• paired jointed legs
• key features 
  • joined legs modified for a variety of functions swimming jumping walking
  • exoskeleton for protection of internal organs, attachment of muscle, suppor, reducing water loss
  • exoskeleton does not grow- must be shed leaving animal vunerable
• classes
  • crustacea 10-20 pairs of legs
  • spiders 4 pairs
  • insects 3 pairs

• most successful group- inhabt most habitats and air
• adult insects have different features to other arthropods
  • 3 pairs of legs, one to each segment of thorax
  • head has antennae and compound eyes
  • gas exchange by gills in aquatic forms and tracheae in terrestrial
  • evolved wings, only invertebrate to fly

• frogs snakes eagles humans
• vertebral column or backbone
• well developed brain enclosed in a cranum
  • fish- scales gills fins aquatic
  • amphibians- first land vertebrates, semi terrestrial, soft moist skin, eggs fertilised externally in water. young are aquatic with gills adults normally terrestial with simple lungs
  • reptiles- mainly terrestial with dry scaly skin, lungs and internal fertilisation of eggs with a shell and laid on land
  • birds- fly and have feathers, forelegs adapted as wings, lungs, and eggs with hard shell
  • mammals- skin with hair, born alive and fed on milk, lungs
    • marsupials- kangaroo- young born immaturely and develop in pouch
    • placentals- young born developed from womb, recieve nourishment via placenta before birth

• structures that may have different functions but are similar suggest common origin= homologous. pentadactyl limb of chordata adapted to the need of the vertebrate= human arm, bat wing, whale flipper, horse leg
• possible to construct evolutionary trees
• similar structures developed as a result of environmental conditions performing the same function= analogous bird and insect wings

• new speices develops differences in the sequencing of nucleotide bases in DNA 
• over time these differences accumilate as a result of evolution
• DNA anaylsis confirms evolutionary relationships reducing the number of mistakes in classification due to convergent evolution
• DNA hybridisation involves extraction and comparison of DNA of two species, sequence of bases compared and the more alike the more closely related
• sequence of amino acids determined by DNA degree of similarity n amino acid sequence of the same protein in 2 species reflects the relationship
• enables scientists to draw evolutionary tree for mammals

• antibodies of one species respod to antigens on proteins in the blood of another
• when they respond a precipitate is formed
• more precipitate= more closely related
• human serum injected into bunny>rabbit serum containing anti-human antibodies> added to other species serum