A2 Biology

A2 Biology

Ecosystems
1. Producers
  1. Synthesises their own glucose
  2. e.g. plants
2. Consumers
  1. Obtain energy by feeding
3. Decomposers
  1. Feed on dead waste
  2. e.g. bacteria, fungi, maggots
4. Trophic Levels
5. Energy Losses
  1. 1-3% lost from sun to producer
    1. May not hit a leaf
    2. 90% of sun reflected or absorbed by atmosphere, clouds & dust
    3. Only 680 & 700 nm wavelengths used in photosynthesis
  2. 5-10% lost from producer to consumer
    1. Energy used in respirtation
    2. Movement
    3. Heat Loss
    4. Some organisms left uneaten
    5. Some material is egested as faecal matter
Pests and Productivity
1. 'Pests are any organisms that have a negative impact on food or space for humans, or cause disease
2. Control pests = increased productivity
3. Effective pesticide
  1. Cost Effective
  2. Specific
  3. Easy to apply
  4. Kills pests quickly
  5. Not accumulate
  6. Biodegrades
4. Chemical
  1. +
    1. Fast Acting
    2. Easy to apply / acquire
  2. -
    1. Non-specific
    2. Can pollute water
    3. Reduce Biodiversity
    4. Resistance
    5. Expensive
5. Biological
  1. Uses natural enemies to control pests
  2. +
    1. Specific
    2. 1-time application
    3. No resistance possible
  3. -
    1. Can affect non-pests
    2. Expensive
    3. Time lag
    4. Control may become a pest
Senses
1. Used to respond to stimuli and enable survival
  1. Better senses = better ability to respond = survival
  2. A stimulus is a detectable change in the internal or external environment
  3. Stimuli are detected by receptors in sense organs
    1. A receptor is a cell which transforms energy from the stimulus to another form
2. Stimulus
  1. Receptor
    1. Sensory Neurone
      1. Intermediate Neurone
        Motor Neurone
        Affector Organ
        Response
3. Messenger Systems
  1. Chemicals / Hormones
  2. Neurones / Nervous System
4. Responses
  1. Taxis
    1. Simple response with a direction
  2. Kinesis
    1. Rapid , random movement in unpleasent stimulus
    2. Until -ve stimuli is gone
  3. Tropisms
    1. Growth movement of a plant
      1. Cels on outside of the turn must grow most
      2. Growth hormone is Auxin aka IAA
        Accumulates on lower side of plant
    2. Light - phototropism
    3. Into ground - geotropism
    4. Water - hydrotropism
  4. Nervous Systems
    1. Central (CNS)
      1. Brain
      2. Spine
    2. Peripheral (PNS)
      1. Nerves (Neurones)
        Sensory
        Motor
        Voluntary
        Muscles
        Autonomic
        Cardiac
        Muscles
        Glands
    3. Autonomic
5. Reflex Arcs
  1. Involuntary, so keeps brain free
  2. Protects the body from harmful stimuli, effective at birth.
  3. Fast, few synapses

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