- 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.
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- 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.
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- 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.
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- 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
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- 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.
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Five Kingdom Classification
- 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.
- Small eukaryotic organisms.
- Membrane-bound organelles.
- Nucleus with a nuclear membrane.
- Organisms not plants/animals/fungi.
- Includes algae/water moulds/slime moulds/protozoa/
- Eukaryotes - cells lack cell walls and show nervous co-ordination
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Five Kingdom Classification
- 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.
- Carry out photosynthesis.
- Cells eukaryotic - cellulose walls, vacuoles containing cell sap, chloroplasts containing photosynthetic pigments.
- Mosses/liverworts/ferns/conifers and flowering plants
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- 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.
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- 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
- 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.
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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.
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Evidence of common ancestry
- 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.
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Using physical features
- 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.
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Using genetic evidence
- 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.
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