Bio p2

• Levels of organisation in an ecosystem

  • Individual organism
  • Population
  • Community
  • Ecosystem
• Competition


  If a group of organisms all need the same resource in order to survive and reproduce but there is a limited amount of the resource available, they are said to compete for the resource
• Intraspecific competition


  Competition between members of the same species
• Interspecific competition

  Competition between members of different species
• Adaptation

  If an organism has certain features, behaviours, or other characteristics that help it to survive and reproduce in its habitat, it is said to be adapted to its habitat
• Ecosystem

  The interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment
• Ecosystems can vary greatly in size and scale
• Examples of ecosystems


  • A garden pond
  • A woodland
  • A coral reef
  • A desert
• Interactions within an ecosystem


  Members of a species will often interact with members of its own species or other species in order to survive and reproduce
• Examples of interactions within an ecosystem

  • Predators (carnivores) eating prey
  • Herbivores eating plants
  • Plant species being pollinated by bees
• Competition in plants

  Plants in a community or habitat may compete with each other for certain limited resources
• Resources competed for by plants

  • Light
  • Water
  • Nutrients
  • Space
• Competition in animals

  Animals in a community or habitat may compete with each other for certain limited resources
• Resources competed for by animals

  • Food
  • Mates
  • Nesting sites
  • Territory
• Interdependence


  Within a community, each species depends on other species for food, shelter, pollination, seed dispersal etc. If one species is removed it can affect the whole.
• A stable community is one where all the species and environmental factors are in balance so that population sizes remain fairly constant
• Food web


  Shows the interdependence of organisms
• If the population of earthworms decreased

  The population of grass plants would increase, the populations of frogs and mice would decrease significantly, and the population of sparrows would decrease slightly
• Abiotic factors that affect a community

  • Temperature
  • Light
  • Water availability
  • Oxygen levels
  • Soil pH
  • Carbon dioxide levels
• You should be able to extract and interpret information from charts, graphs and tables relating to the effect of abiotic factors on organisms within a community
• Effect of CO2 concentration on plant height

  • At 5% CO2, average plant height was 10cm
  • At 30% CO2, average plant height was 60cm
• As CO2 concentration increases

  Average plant height also increases
• This shows that the higher the CO2 concentration, the greater the plant growth rate
• CO2 is used by plants for photosynthesis, which allows the plant to produce glucose for energy to grow
• When answering questions that refer to a chart, graph or table, remember to reference specific figures from the data to support your answer
• Homeostasis


  Maintaining a stable internal environment
• Homeostasis


  • Keeps the conditions your body needs to be kept stable when the environment changes
  • This is really important because your cells need the right conditions to properly function, including the right conditions for enzymation
• Homeostasis


  1. Involves the regulation of the conditions in your body (and cells) to maintain stability

  2. In response to changes in both internal and external conditions
• Automatic control systems in the body

  • They regulate your internal environment
  • Include both nervous and chemical (hormonal) systems
• Negative feedback

  1. Receptor detects a stimulus (level too high)

  2. The coordination receives and processes the information

  3. Effector produces a response which counteracts the change and restores the optimum level

  4. The effector will just carry on producing the response for as long as they are stimulated by the coordination opening
• Negative feedback is a mechanism that stops things going out of balance
• The nervous system is made up of different parts - the central nervous system (CNS) and the peripheral nervous system (PNS)
• Receptors


  • Cells that detect stimuli
  • There are many different types of receptors, such as receptors on the tongue and sound receptors in the ear
  • Receptors can form part of larger, complex organs e.g. the retina of the eye
• Effectors

  • Respond to nervous impulses and bring about change
  • Muscles and glands are known as effectors - they respond in different ways. Muscles contract in response to a nervous impulse, whereas glands secrete hormones
• The central nervous system (CNS) coordinates the response


  1. It receives information from the receptors and then decides what to do about it

  2. The response is carried out by effectors
• Reflexes are automatic responses to certain stimuli that don't involve the brain
• The reflex arc

  1. Receptor detects stimulus

  2. Sensory neurone carries impulse to the CNS

  3. CNS processes the information

  4. Motor neurone carries impulse to effector

  5. Effector (usually a muscle) responds
• Reaction time

  • How quickly you respond to a stimulus
  • Can be affected by factors such as gender or caffeine intake
• Measuring reaction time using a ruler

  1. Person catches the ruler as it is dropped

  2. The further down the ruler it is caught, the higher the number, the slower their reaction time
• Measuring reaction time using a computer

  1. Person clicks the mouse or presses a key as soon as they see a stimulus on the screen

  2. Computer can give a more precise reaction time in milliseconds