B3 Life on Earh

B3 Life on Earh

1. Adaptation and variation

   • Species adaptation
     • A species is a group of organisms that can breed together to produce fertile off spring
     • Make a species more likely to survive in the environment they have adapted to
   • Cactus
     • Rounded so less surfaces meaning less water loss
     • Thick waxy layer and leaves that reduce to spikes to reduce water loss
     • Thick stem to hold more water
     • Shallow but extensive roots to absorb water quickly
   • Fish
     • Have gills to extract oxygen from the water
     • Tail fins with a large surface area to propel them through the water
     • Bodies streamline to move through water with little resistance
     • Swim bladder that holds air and then adjusts the amount of gas to change depth
   • Same species differences
     • Called variation
     • Some variation is genetic
     • Cause of genetic variation is when genes change
     • These changes are called mutations
       • Can be causes by radiation or chemicals or by a mistake when a cell copies
     • If mutations occur in body cells it has no effect but may lead to cancer
     • If there is a mutation is sex cells then the effect can be passed on to offspring
       • Can lead to a change in characteristics which can be bad but can also help them to survive

2. Natural selection

   • Process that causes evolution
   • Resources are limited so same species have to fight for resources
   • Some varieties have a better chance of surviving
     • Increased chance of reproducing
   • This means the next generation will have some characteristics that helped the parents to survive
   • Naturally selected features help the species to adapt to there environment

3. Selective breeding

   • Done by humans
   • Deliberately select features they want
   • Don't help survival

4. Evolution

   • Life started 3500 million years ago
     • There are a huge number of species
       • Vast amount are extinct
         • First living thing was very simple
           • Everything that ever lived has evolved from the first creatures on earth
   • Process of evolution
     • Same species may be isolated on different island for example
       • Cannot interbreed
       • Factors combine so the same organisms become so different they become different species
         • Different mutations
         • Natural selection work on the new features so there is a benefit
         • Environmental changes
           • Different adaptations are needed to survive in different places
   • Evidence
     • Fossil records show organisms becoming more and more complex
     • DNA controls characteristics which mutates overtime meaning characteristics change overtime
   • Revolutionary idea
     • Charles Darwin theory of evolution by natural selection
       • Through observations
       • Creative ideas
     • Larmack
       • Believed if a characteristic was used a lot it would be passed on to off-spring
       • Example
         • If a rabbit ran a lot and got big leg muscles they would be passed on to off-spring so the off-spring would have big leg muscles
     • Larmack's theory was rejected as there was no genetic base for the characteristics to be passed on so Darwins theory was chosen

5. Bio-diversity and classification

   • Biodiversity
     • Includes...
       • The number of species on earth
       • The range of different types of organisms
       • The genetic variation of organisms in the same species
     • Maintaining biodiversity
       • More plants means more resources for new food crops
       • Many new medicines have been discovered using chemicals produced by living things
   • Rate of extinction
     • Rate of extinction is increasing
     • Correlation between the rate of extinction and population growth
     • Hunting to extinction
     • By destroying habitat
   • Classification
     • Group organisms together according to similarities in their characteristics
     • All the millions of species can be grouped into 5 kingdoms
       • Bacteria
       • Fungi
       • Algea
       • Plants
       • Animals
     • Each kingdom is divided into more groups which are further grouped into more
     • Shows evolutionary relationships between different organisms
     • Evolutionary relationships can be shown for all living an fossilised organisms that have beeen classified

6. Interaction between organisms

   • Resources from environment
     • Factors for life
       • Light
       • Food
       • Oxygen/carbon dioxide
       • Water
     • Any of the factors in short supply then the species have to compete
       • Some organisms won't survive if there is not enough
     • This limits the size of the population
     • Rely on other organisms (interdependence)
   • Changes in the environment
     • Can have a knock on effect
     • Changes that cause extinction
       • Environmental conditions change so organisms can't adapt
       • A new species introduced (competitor, diseases organisms or predator)
       • Organism in the food web come extinct

7. Energy in an ecosystem

   • Efficiency of energy transfer
     • Energy available to next stage divided by Energy that was available to the previous stage x100
   • Energy comes from the sun
     • Plants convert the light energy to chemicals to make cells
       • Energy is transferred between organisms when animals eat plants and other animals
         • Energy is lost at each stage
           • Most energy is lost eventually as heat
             • Energy is also lost at each stage a waste
           • Respiration

8. Carbon cycle

   • Powered by photosynthesis
     • Plants convert CO2 into sugars and carbon is now incorporated into carbs,fats + proteins
       • Eating passes the carbon compounds onto animals
         • Animals then release CO2 into the atmosphere when they respire
           • Plants and animals die and decompose
             • When plants and animals decompose they're broken down by mircoorganisms that release CO2 into the atmosphere
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               • When fossil fuels are burnt they release CO2

9. Nitrogen cycle

   • 78% nitrogen in the air. It is very unreactive so animals and plants cannot use it directly
     • Nitrogen is needed for making proteins for growth
       • Plants get their nitrogen from the soil
         • Animals can only get protein by eating plants or other animlas
           • Nitrogen fixation is the process turning nitrogen in the air to nitrogen compunds
             • Can happen in two ways...
               • Lighting - there is so much energy in a blot of lighting that it is enough to make nitrogen react with oxygen
               • Nitrogen-fixing bacteria - in roots and soil
             • Decomposers break down protein in dead plants and animals and urea into ammonia
               • There are 4 types of microorganisms:
                 • Decomposers - decompose proteins and urea and turn it into ammonia
                 • Nitrifying bacteria - turns ammonia into nitrates
                 • Nitrogen fixing bacteria - atmospheric nitrogen into nitrogen compounds
                 • Denitrifying bacteria - turns nitrates back into nitrogen gas (No benefits to living organisms)

10. Measuring environmental changes

    • Non living indicators
      • Temperature
        • Temperature of a period of time could indicate climate change
      • Nitrate level
        • More nitrate in water could show sewage or fertiliser leaking meaning more polution
      • Carbon dioxide
        • Measured in the air an increase could be caused by burning fossil fuels which could increase the rate of global warming
    • Living indicators
      • Lichen
        • Particular lichen are sensitive to sulfur dioxide. The number and type of linchen will indicate how clean the air is
      • Mayfly nymphs
        • If you find mayfly nymphs near water it means the water is clean as they are sensitive to oxygen levels in water
      • Photoplankton
        • Population increase if there is fertiliser or sewage in the water and it creates an algal bloom

11. Sustainability

    • - Means meeting the needs of this generation without harming the environment so that future generations can still meet their needs
    • sustainable planning
      • humans damage the environment
      • We place greater pressure on finite resoures
      • Maintaining biodiversity to produce new food and new medicines
      • Monoculture - growing one crop which means fewer species will be supported by the crop reduces biodiversity
    • Sustainability of packaging
      • Now
        • Not sustainable
        • Takes a lot of energy to produce
        • Most is throw in landfill
        • Resources are non renewable
      • Future
        • Using renewable materials
        • Using less energy
        • Creating less polution