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!