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These notes have been written by Ian Daniels.

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3.5.1 Human impacts on evolution

Evolution:

  • Changes allele frequency in population.
  • Individuals show variation.
  • Phenotypic variation due to:
    • Genetic Factors,
    • Environmental Factors,
    • Combination of both.
  • Competition results in differential survival and reproduction.
  • Selection acts on populations.
  • Organisms with a selective advantage:
    • more likely to survive
    • reproduce
    • pass on genes to next generation.
  • Selection may change allele and phenotype frequencies.
  • Populations reproducing in isolation can result in the formation of new species.
    • Allopatric Speciation:
      • Geographically separated sister species are now so different - no interbreeding is possible.
    • Sympatric Speciation:
      • Genetic variation occurring in same geographical location.
  • Human activities have, and continue, to alter environment of many organisms.
    • Changes selection pressures
    • May effect evolution of species.

3.5.2 People change communities

Ecosystems and the stability of populations

  • Introduction of plant/animal species to different countries
  • Changes stability of native species:
    • populations
    • communities
    • ecosystems.
  • ECOSYSTEMS include:
    • living organisms
    • physical factors
    • chemical factors
  • POPULATION = All organisms of one species in particular habitat
    • Populations of different species form COMMUNITIES.
  • COMMUNITY:  found in one particular habitat
    • based on Dynamic Feeding Relationships
  • Species occupy particular NICHE within habitat.
  • Governed by:
    • adaptation to food availability
    • and/or prevailing abiotic conditions.
  • Ecosystem supports certain size population of any single species.
  • Influencing factors:
    • Abiotic Factors
    • inter-organism interactions
    • inter-organism competition
    • predation
  • NOTE:  Be able to evaluate evidence and make balanced judgements between meeting human demands and the need to conserve the environment.

Winners and Losers

  • Domesticated/introduced plants/animals affect ecosystems by competing with native species.
    • Examples:
    • domestic cats
    • grey squirrels
    • Japanese knotweed
  • Growth of the urban environment has increased habitat and niches for:
    • foxes
    • rats
    • pigeons
    • and others

GM Organisms

  • Environmental Impact Assessment.
    • Impact of large-scale introduction of GM organisms
    • Eg. Soya and Maize.

3.5.3 Humans’ health can be affected when they change their environment

Diet, Crops, Food Allergies

  • Our diet has changed.
  • Vegetable oil seen large increase in demand.
  • Linked to increase in range of allergies.
    • Nut allergy.
    • Hay fever
  • Allergic responses produce illness.
  • Allergens = antigens that produce abnormal immune response.
  • Hypersensitivity:
    • Allergic Reactions involving Histamine production:
      • Hay fever
      • Food allergies
      • Allergic asthma
      • Hives
    • B cells produce antibody (IgE) in presence of allergen.
    • IgE binds to Mast Cells.
    • Mast Cells produce histamine when exposed to the allergen.
    • Histamine leads to symptoms of allergy.
  • Anaphylaxis = Sudden, Acute reaction to allergen.
  • Can result in:
    • oedema (inflammation) in airways
    • large, sudden fall in blood pressure.
  • Treated with adrenaline.
  • Use:
    • skin test for possible allergies
    • antihistamines

Air pollution and Respiratory illnesses

  • Claims of links between air pollution and respiratory illnesses, Eg:
    • Asthma
    • bronchitis

Water Pollution and illness

  • Polluted water can lead to illness.
  • Beaches and coliform standards:
    • Coliform bacteria and faecal streptococci = pollution indicators
    • Blue Flag Beaches meet water quality standards.
  • Cryptosporidium:
    • single celled parasite.
    • Causes cryptosporidiosis.
    • Oocyst = resistant form
    • Present in infected faeces (human and animal)
    • Oocyst infects new host.
    • Pollution of waterways from:
      • Infected farm animal slurry → rivers
      • Sewage discharge → rivers

3.5.4   Human activities can damage ecosystems and create new ones

Succession

  • Ecosystems are dynamic systems.
  • Communities move from: Colonisation → Climax
  • Known as Succession.
  • Communities change with time, due to interaction between:
    • Species
    • Environment.
  • Certain species may change their environment -
    • result may be more beneficial for other species!

Local Wildlife

  • Human activities may produce 'bare' areas of land and water.
  • Wasteland = unmanaged land, vegetation in early stages of succession.
    • Includes corridor habitat, eg. railway/roadside embankments.
  • Brownfield sites = sites previously developed for human use.
    • Can be reclaimed
    • Provide habitats for flora and fauna threatened by urbanisation/intensive agriculture
  • Ecosystems range greatly in size.
  • Increase area by 10 - doubles number of species.
  • Important to enhance biodiversity in urban environment.
  • Corridor habitats allow movement of plants/animals between habitats.
  • NOTE: Be able to describe techniques to measure biotic/abiotic factors in an ecosystem.

Waste Disposal

  • Should be environmentally sustainable.
  • BPEO = Best Practical Environmental Option.
  • The waste hierarchy:
    • Prevented/Reduced at source
    • Re-used
    • Re-cycled (used as raw material)
    • Or (if not pos) use as substitute for non-renewable energy source
    • Only landfill if none of above possible.
  • Microorganisms decompose organic remains.
  • Anaerobic bacteria produce methane.
  • Collect from landfill sites to use as a fuel.
  • Polluter Pays Principle:
    • Polluter pays for direct/indirect environmental consequences.

3.5.5 Plants can reduce the impact of the use of fossil fuels on climate change

  • Carbon Footprint:
    • Measure of greenhouse gasses produced by human activities.
    • Units of kilograms of CO2 produced per year.
  • NOTE: Be able to describe how:
    • primary /secondary contributions are calculated
    • to reduce household contributions
    • to off-set CO2  emissions.

Climate Change

  • Burning of fossil fuels → production of greenhouse gasses.
  • Changing climate: UK is getting warmer.
  • Affecting distribution of plants and animals
  • NOTE: be able to describe effects of climate change on:
    • Natural range of species
    • breeding seasons
    • availability of food
  • Plants can reduce the impact of fossil fuels on climate change.
  • They remove CO2  from the atmosphere via Photosynthesis
  • Photosynthesis is the major route energy enters ecosystems
  • Energy transferred through trophic levels of food chains/food webs
  • and is dissipated.
  • Energy transfer used to produce ATP and reduced NADP
    • in light-dependant stage of photosynthesis
  • ATP and reduced NADP used in light independent stage
  • incorporation of  CO2  → produces sugars.
  • ATP synthesis associated with electron transfer chains -
  • located in the chloroplasts.
  • Therefore: tree planting used to off-set CO2  emissions.
  • Carbon is sequestered in bio-mass of trees.
  • Biofuels reduce use of fossil fuels.
  • Renewable energy sources.
    • Biomass from fast-growing plants = fuel to burn
    • Vegetable oils = diesel substitute
    • Ethanol from fermented plants = petrol substitute/additive.
  • Large scale production of plants needed.
  • Impacts environmental
  • Reduces food available for human consumption.

Respiration → CO2   → Atmosphere

  • ATP = source of energy for biological processes.
  • All cells/organisms respire
  • In respiration:
    • Glycolysis occurs in cytoplasm,
    • is anaerobic.
    • Remaining steps occur in mitochondria.
    • Associated with electron transfer chain,
    • in membranes of mitochondria.
    • Oxygen = the final electron acceptor.
    • CO2  = waste product.

3.5.6 People and their microorganisms

The Human Ecosystem

  • Human body supports populations of bacteria and fungi.
  • These microorganisms:
    • carry out extracellular digestion of biological molecules
    • absorb products of digestion
    • use these in their own metabolism.

The ecology of the skin

  • The skin supports communities of microorganisms, including:
  • Staphylococci
  • Micrococci
  • Corynebacterium
  • Fungi, eg. yeast.
  • Can cause spots/blemishes, number of skin conditions.
  • Acne vulgaris caused by Propionibacterium acnes 
  • growing in/near sebaceous glands in the skin.
  • Antibiotics/antiseptics can control populations.

The ecology of the gut

  • The human gut supports populations of bacterial species,
  • form a bacterial community.
  • Human actions (eg. antibiotics) can change dynamic of community,
  • may adversely affect functioning of the gut.

Antibacterial Resistance

  • Humans have introduced large amounts of antibacterial agents into environment.
  • This selective pressure → evolution of resistant microbes.
  • Eg. MRSA
  • Originally MRSA meant methylin resistant staphylococcus aureus -
  • now means multiply resistant!