Unit 3 Nat 5 biology

• New alleles produced by mutations can result in plants and animals becoming better adapted to their environment
• Variation makes it possible for a population to evolve over time in response to changing environmental conditions
• Adaptation


  An inherited characteristic that makes an organism well suited to its environment or niche
• Natural selection


  Variation exists within a population.<br>

  Species produce more offspring than the environment can sustain.<br>

  Selection pressures result in the best adapted individuals surviving and reproducing - "survival of the fittest".<br>

  This passes on favourable alleles that confer a selective advantage.<br>

  This increases the frequency of favourable alleles within the population
• Process of speciation

  Part of the population becomes isolated by an isolation barrier<br>Over time, the isolated population becomes distinct from the original population
• Isolation


  Part of the population becomes isolated by an isolation barrier
• Over time each sub-population becomes so genetically different
• Each sub-population experiences different selection pressures
• Different selection pressures

  Natural selection selects for different mutations in each sub-population
• Isolation barriers

  • Geographical
  • Ecological
  • Behavioural
• Different mutations occur in each sub-population
• Ecological


  • Different habitats
• Geographical


  • Mountain range
• Behavioural

  • Courtship behavior
• Limiting factors in photosynthesis

  • CO₂ concentration
  • Light intensity
  • Temperature
• A pyramid of numbers shows the number of organisms at each level of a food chain
• Products of photosynthesis

  • Sugar (used for respiration or converted into plant products like starch and cellulose)
• Nitrates absorbed by plants are used to make amino acids for protein synthesis
• Biological control uses natural predators to remove pests and may be an alternative to pesticides
• Most of the energy at each level in a food chain is lost through heat, movement, and undigested material
• Food yields are increasing to meet the demands of an increasing human population
• Information from limiting factor graphs can be evaluated
• Photosynthesis

  1. Traps light energy allowing it to be converted to chemical energy

  2. Carbon dioxide + water are used to produce sugar and oxygen
• Mutations can be advantageous, disadvantageous, or neutral to survival
• Mutations are the only source of new alleles
• When the rate of photosynthesis is limited

  Less sugar is produced and plant growth is slowed down
• Pesticides can accumulate in the bodies of organisms over time, a process referred to as bioaccumulation
• Genetically modified crops reduce the need for fertilisers
• Fertilisers and pesticides can improve crop yield
• Animals consume plants to obtain amino acids for protein synthesis
• A small quantity of energy is used for growth and is available at the next level in a food chain
• A limiting factor in photosynthesis is any factor that limits or holds up the rate of photosynthesis
• Fertilisers can leach nitrates into freshwater causing algal blooms
• A pyramid of energy shows the productivity of organisms measured in g/m² year
• Mutations are random changes to genetic material that can result in a change in characteristics
• Fertilisers supply nitrates to the soil to increase plant yield
• Habitat


  The place where an organism lives
• Producer


  An organism which produces its own food, typically a green plant
• Biodiversity


  The number of different species present in an ecosystem
• Species


  A group of organisms that can interbreed to produce fertile offspring