Life on earth

• Photosynthesis

  Process of converting light energy into chemical energy
• Two stages of Photosynthesis

  Stage 1 - The Light Reactions, Stage 2 - Carbon Fixation
• Energy transfer in stage 1

  Conversion of light energy into chemical energy
• What traps light energy in the leaf

  Chlorophyll
• Describe the Light reaction stage

  Light energy from the sun is converted into chemical energy to make ATP. Water is split into hydrogen and oxygen.
• Products of light reaction stage

  Oxygen (released), Hydrogen & ATP (passed onto stage 2)
• What controls carbon fixation


  Enzymes
• Use of sugar produced during photosynthesis

  Respiration, starch (storage), cellulose (cell walls)
• Product of carbon fixation stage

  Glucose (sugar)
• Requirements to make sugar during carbon fixation


  Carbon Dioxide, Hydrogen, ATP, Enzymes
• Limiting factors in photosynthesis

  Temperature, Light intensity, Carbon Dioxide concentration
• Pyramid of numbers


  Shows the number of organisms at each stage of the food chain
• 3 ways energy is lost in a food chain

  Movement, Heat, Undigested material
• Use of energy passed on in a food chain


  Growth
• Plants need nitrates for

  amino acids/proteins synthesis
• Methods to increase crop yield


  Adding fertilisers, using pesticides
• Pyramid of energy


  Shows the total energy available at each stage of the food chain
• Species


  Group of interbreeding organisms that produce fertile offspring
• Usefulness of variation within a population


  Allows population to evolve in response to changing environment
• What factors (mutagenic agents) increase the rate of mutations

  Radiation (UV), some chemicals (mustard gas)
• Alternative to using fertilisers

  Genetically Modified Crops, Biological Control
• Effect of algal blooms on fish


  Dead plants provide food for bacteria, and they use up the oxygen so the fish die.
• Process of Algal Bloom

  1. Fertilisers wash into water adding unwanted nitrates to the water.

  2. This causes the algal to grow, causing an algal bloom.

  3. Algal blooms reduce light levels, killing aquatic plants, due to lack of light for photosynthesis.

  4. The dead plants become food for bacteria which increase in number.

  5. The bacteria use up the Oxygen, reducing oxygen available for other organisms.
• Mutations


  Random changes to genetic material
• Consequences of using pesticides on a food chain


  Accumulation in organisms, increasing toxicity
• Alternatives to using pesticides

  Genetically Modified Crops
• Organism's niche


  Role an organism plays within a community
• Ecosystem


  Consists of all the organisms (the community) living in a particular habitat and the non-living components with which the organisms interact.
• Herbivore


  Animal that eats plant material only
• Carnivore

  Animal that eats animal material only
• Omnivore


  Animal that eats both plant and animal material
• Stages of speciation


  I'M a New Species

  Isolation - population is split into subgroups by isolation barrier.

  Mutations - different mutations occur in each sub-group.

  Natural Selection - the advantageous genes are passed onto the next generation.
• Types of isolation barriers

  Geographical (mountain/river forming.

  Ecological (pH, salinity, different habitats)

  Behavioural (males and females not attracted to each other).
• Natural selection


  the best adapted individuals in a population survive to reproduce, passing on the favourable alleles to their offspring. These alleles increase in frequency within the population over time
• Producer


  Organism that can produce its own food
• Consumer


  Organism that must eat other plants or animals for energy
• Biodiversity


  Variety of life in different ecosystems
• Population


  All animals or plants of one species in a particular area
• Using a quadrat


  Place quadrat and count the plants within the square
• Sources of error in using a quadrat

  Non-random sampling