Biodiversity

• Tropical rainforests depleting - make room for and support increasing population.
• Ocean's, stocks of fish depleting - over harvesting, stress on coral reefs and estuaries.
• Human alteration - greatest threat to biodiversity.

• A natural process - rate of extinction biodiversity crisis.
• Human activity in tropical areas has increased extinction rates between 1000 and 10000 times.
• Massive destruction of habitats - brought by agriculture, urban development, forestry, mining ane pollution.
• Marine life also affected - one-third of fish rely on coral reefs, half of reefs could be lost in the next 20 years.
• Earths earlier occupants became extinct due to - climatic, geological and biotic changes.
• Main cause for loss of animals - loss of habitat, over hunting by humans, competition from introduced species, deforestation, pollution and drainage of wetlands.
• Reason's for extinction - potential source of food, useful chemicals or disease resistant genes.

• The process by which new species are formed from pre-existing ones over very long periods of time.
• Processes which have transformed the life on earth from early beginnings to vast diveristy of fossilised and living forms today.
• First proposed by Charles Darwin - studied the flora and fauna of the Galapagos islands and South America.
• Individual finches differed from one island to the next depending on what food was available.
• Characteristics best suited a particular finch to its environment - all developed from a common ancestor the beak had developed over time - adaptive radiation.

• Kingdom - Animals/Plants
• Phylum - Insects/Spiders/Centipedes/Millipedes/Crustaceans.
• Class - Insecta
• Order - Orthoptera
• Family - Roasaceae
• Genus - Locusta
• Species - Locusta migratoria

King Patrick Comes Over For Great Sandwiches

• The hierchical order of taxonomic ranks based on evolutionary line of descent.
• Oldest species at the base.
• More recent ones at the ends of the branches.
• Most related organisms come off same branch.

• Prokaryotae
  • Bacteria and blue green algae.
  • No internal cell membranes.
  • No nuclear membrane.
  • No Endoplasmic Reticulum.
  • No Mitochondria.
  • No Golgi body.
  • Possess a cell wall - not made from cellulose.
• Protoctista
  • Small eukaryotic organisms.
  • Membrane-bound organelles.
  • Nucleus with a nuclear membrane.
  • Organisms not plants/animals/fungi.
  • Includes algae/water moulds/slime moulds/protozoa/
• Animals
  • Multicellular
  • Heterotrophic
  • Eukaryotes - cells lack cell walls and show nervous co-ordination

• Fungi
  • Eukaryotic.
  • Network of threads called hyphae - form a mycelium.
  • In subgroups hyphae have no cross-walls - in others cross-walls/septa are present.
  • Rigid cell wall made of chitin.
  • No photosynthetic pigments.
  • Feeding heterotrophic.
  • Members either saprophytic or parasitic.
  • Reproduction through spores which lack flagella.
  • Penicillium/Yeast/Mushroom
• Plants
  • Multicellular.
  • Carry out photosynthesis.
  • Cells eukaryotic - cellulose walls, vacuoles containing cell sap, chloroplasts containing photosynthetic pigments.
  • Mosses/liverworts/ferns/conifers and flowering plants

• Include earthworms/leeches and lugworms.
• Have a long, thin body, segmented body - segments visible as rings body divided internally by partitions (septa).
• Fluid filled body cavity (haemocoel)
• Hydrostatic skeleton.
• Head with primitive brain and nervous system running whole length of body.
• Thin permeable skin - gaseous exchange occurs here.
• Closed circulatory system containing an oxygen-carrying pigment.

• Body divided into segments.
• A well-developed brain.
• Open circulatory system and cavity surrounding body organs.
• Paired jointed legs - for walking, swimming, jumping, feeding, reproduction.
• Hard outer exoskeleton - outermost layer of cells of body, secretes thick cuticle consists mainly of chitin.
  • Protection of internal organs.
  • Point of attachment for muscles
  • Support.
  • Exoskeleton covered in layer of wax reducing water loss.
  • Fixed in size, does not grow.
  • Arthropod must shed its exoskeleton leaving it vulnerable.
• Myriopoda - many pairs of legs - millipedes and centipedes.
• Crustacea - 10 and 20 pairs of legs - crab
• Spiders - four pairs of legs.
• Insects - three pairs of legs.
  • Three pairs of legs - one pair to each segment of the thorax.
  • Head has antennae and compound eyes.
  • Gas exchange by gills in aquatic insects and tracheae in terrestrial forms.

Frogs, snakes, eagles and humans.

• Vertebrates - posses vertebral column or backbone.
• Well-developed brain, enclosed in cranium.
• Subdivided into:
  • Fish - aquatic forms with scales, fins and gills.
  • Amphibians - first land vertebrates, partly terrestrial and partly aquatic, soft moist skin/eggs fertilized in water/larvae aquatic and have gills/adults terrestrial have simple lungs.
  • Reptiles - mainly terrestrial, have dry skin with scales, lungs, eggs fertilisd internally, covered with shell, laid on land.
  • Birds - able to fly, development of feathers, fore legs developed as wings, lungs, hard shell.
  • Mammals -skin with hair, born alive, fed on milk, lungs either;
    • Marsupials - young born at immature state develop in females pouch.
    • Placentals - young undergo development in mothers womb, recieve nourishment via placenta.

• Evolution suggests widely separated groups of organisms share a common ancestor - therefire share basic structual features.
• How similar they are indicates how closely related they are in terms of evolution.
• Groups with little in common are assumed to have diverged from a common ancestor much earlier in geological history than groups with a lot in common.

• Homologous - having a common origin but serve a different function
• Pentadactyl (having five digits) limb of chordata found in; vertebrates, amphibians, reptiles, birds and mammals.  Structure of the limb is basically the same in all classes, however the limbs of different vertebrates have become adapted for different functions; grasping, walking, swimming and flying.
• Examples of pentadactyl limb - human arm, wing of a bat, flipper of a whale, wing of a bird, leg of a horse.
• Using info. like this can help construct evolutionary trees where the end products of evolution have certain structual features in common with each other and with ancestral stock.
• The more similar - the more recent to have diverged.
• Analagous - having the same function but different origin.
• Shark and Dolphin have similar fore-limbs because they live in similar envirnments and have become adapted to that environment - not because of a similar ancestor.

• Convergent evolution - the tendecy of unrelated organisms to acquire similar structures.
• DNA hybridisation:
  • Extraction and comparison of DNA of two species.
  • Sequence of bases compared, more alike sequences, closer organisms are related in terms of evolution.
  • Sequence of amino acids in proteins determined by DNA.
  • Degree of similarity in amino acid sequence of same protein in two species will reflect how closely related the two species are.
  • Fibrinogen molecule of mammals compared and sequence differes in varying degrees from one species to another - scientists drawn up evolutionary tree for mammals.
• Immunological techniques:
  • Proteins of different species compared.
  • Antibodies of one species will respond to specific antigens in proteins i.e. albumin in blood serum.
  • Antibodies will respond to corresponding antigens - precipitate forms - greater degree of precipitate closer the evolutionary relationship.