biology

• Community


  Populations of different species in a habitat
• Habitat


  The place where an organism lives
• Habitat examples


  • water
  • woodland
• Ecosystem

  The role of a species within its habitat (includes the biotic and abiotic environmental factors in which it can survive and reproduce)
• Population

  All the organisms of one species in a habitat
• Interdependence


  The dependence of different organisms on each other for survival
• Stable community


  The size of populations of all species remain relatively constant over time
• Abiotic conditions


  The non-living features of an ecosystem
• Abiotic conditions


  • Temperature
  • Availability of water
• Biotic conditions


  The living features of an ecosystem
• All living things are made of cells, they're the basic unit of all life
• Eukaryotic cells


  Have a nucleus
• Eukaryotic cells


  • Plant cells
  • Animal cells
• Prokaryotic cells


  Don't have a nucleus, they have rings of DNA called plasmids and strands of DNA
• Prokaryotic cells


  • Bacteria
• Prokaryotic cells are also much smaller than eukaryotic cells
• Labelling a prokaryote cell

  1. Cell membrane

  2. Cell wall

  3. Cytoplasm

  4. Ribosomes

  5. Plasmids

  6. Circular strand of DNA

  7. Flagella
• Prokaryotic cells do not have mitochondria or chloroplasts
• Cell specialisation and differentiation

  • As an organism develops, cells differentiate to form different types of cells
  • Most types of animal cells differentiate at an early stage whereas many types of plant cells retain the ability to differentiate throughout life
  • In mature animals, cell division is mainly restricted to growth and repair
  • As a cell differentiates it acquires different sub-cellular structures to enable it to carry out a certain function. It has become a specialised cell
• Embryo stem cells - examples of pros & cons


  • long term effects not known or may be more risky
  • harm / death to embryo
  • can treat a wide variety / lots of diseases/problems
  • embryo can't be 'asked' / 'embryo rights' idea
  • many available / plentiful
  • using them better than wasting them
  • painless
  • (relatively) untested/unreliable / may not work
• The body cells divide in a number of stages

  1. Replication of DNA

  2. Cell divides in two

  3. Nucleus divides
• Cell cycle


  Known as the process of cell division called MITOSIS. It produces two identical cells from a parent cell. That means they contain the same genetic material.
• The small intestines are in the digestive system
• Function of the small intestines

  Break down food, absorb nutrients needed for the body
• Why the small intestines are long

  • It needs the maximum amount of surface area to increase digestion
• How the small intestines are adapted to do their job

  • It's long to give a lot of time to digest nutrients, villi to increase surface area for absorption and the villi walls are so thin one cell thick so the nutrients need to travel far to be absorbed
• Why the muscle of the wall of the left ventricle is thicker than the right ventricle

  To generate more pressure to force blood over the body
• Function of the heart valves

  Prevent backflow of blood
• Properties of solids


  • Regular pattern
  • Particles very close together
  • Fixed shape and volume
  • Lowest amount of energy
  • Highest density
  • Strong forces of attraction between particles
• Properties of liquids


  • Irregular arrangement
  • Particles close together
  • Take the shape of a container
  • Fixed volume
  • More energy than solids
• Properties of gases


  • Random arrangement
  • Lots of space between particles
  • Fill a container
  • No fixed volume or shape
  • Highest amount of energy
  • Lowest density
  • Weakest force of attraction between particles
• Density and forces of attraction for particles in a liquid (compared to a solid and gas)
• Density

  The mass for a given volume
• Density examples

  • Brick has high density (lots of mass packed into its volume)
  • Polystyrene has low density (many air spaces in its volume)
• Equation for Density

  Density (kg/m³) = Mass (kg) / Volume (m³)
• Measuring density of regular objects

  1. Determine mass using balance

  2. Measure dimensions with ruler to calculate volume
• Measuring density of irregular objects

  1. Determine mass using balance

  2. Displace water in Eureka can to measure volume
• Internal energy


  The energy stored in a system by the particles (atoms and molecules)
• Changes of state


  1. Heating solid increases internal energy until melting point

  2. Heating liquid increases internal energy until boiling point

  3. Cooling gas reduces internal energy until condensation point

  4. Cooling liquid reduces internal energy until freezing point
• Sublimation is when a solid turns directly to a gas