5.4 Pest Control and Biological Control

• Pest control
• Pests
• Organisms that reduces the yield of crops
• Damages farming
• Pesticides
• Can be used to kill pests
• Advantages
• Doesn't harm humans, only pests
• Helps to keep the yield strong
• All crops capable
• Easy to apply
• Disadvantages
• Expensive
• Pest can develop resistance
• Harmful to environment
• Can kill insects
• Pollinating ones are important
• Can wipe out food chain
• Not 100% effective
• Biological control
• Controlling pests through introducing their natural predetors
• Advantages
• No poison involved
• Almost all crops are affected
• Disadvantages
• Expensive
• Difficult to apply
• Not suitable for allcrops

5.3 Fertilizer

• Fertilisers contain minerals 
• nitrogen, phosphorus and potassium
• Helps plants grow Bigger + faster
• Crop yields are increased
• Nitrogen
• Makes protines
• Phosphates
• Make DNA/Membrane structure
• The minerals are dissolved first in water
• Plants can absorb them through the roots
• Active transport
• Types of fertilizer
• Organic Fertilizers
• Made from farmyard feces
• Mixture of animal manure and straw
• Goes through decomposition and fermentation
• Forms "Slurry"
• Applied to the fields afterwards
• Provides the important minerals for growth
• Inorganic/Artificial
• Made from inorganic compounds
• Potassium Nitrate
• Ammonium nitrate
• Formulated to obtain a specific amount carefully
• Applies as a solution with water
• The nitrates are released and absorbed by the roots
• Eutrophication
• Occurs when farmers apply inorganic fertilizers
• other mineral ions lost from removing the crops
• These ions are very soluble
• Easily leached from the soil
• Carried by water
• Can enter water ways
• Levels of the nitrates increases rapidly in lakes and rivers
• Increase in mineral ions
• Eutrophication
• Natural process resulting in bad waterways
• Due to the leaching ions
• Process
• Nitrate levels increase
• algae rreproduce rapidly
• Using the nitrates to make extra proteins
• Produces algai bloom
• Algea prevents light penetrating into water
• Plants unable to photosynthesize
• Dies
• Bacteria decay on dead plants
• Alge also dies
• Lack of nitrates
• The bacteria reproduces
• large amount of dead matter
• The water becomes anoxic
• without oxygen
• All life in the water dies

5.2 Crop Yields and CO2

• Rate of P/S
• CO2 + H2O -> Glucose + Oxygen
• Glucose -> Starch
• Increasing CO2 -> Increases the rate of reaction of P/S
• Higher Yeild
• Optimum Temperature
• Increasing temperature ->  Increases the rate of reaction of P/S
• Higher Yeild
• Optimum Temperature

5.1 Glasshouses

• Glasshouses are used to improve yield of crop

• Giving best possible conditions for photosynthesis
• Allows plants to grow earlier in the year
• Allows plants to grow in places in which they are not native to
• Can be controlled/manage via computer
• Conditions
• Temperature
• The sunlight heats the inside of the glass house
• The glass keeps the heat inside
• Electric/paraffin heaters can be used in cold weather
• Ventilators can cool the inside when too hot
• Light
• The glass lets sunlight in
• Artificial lights can be used when there is little/no sunlight
• Sunlight can be controlled using blinds
• Water
• Automatic watering systems can be installed
• Humidifiers can be installed to control the humidity

2.84 - 2.85 Nerve impulses and responses

• Nerve impulses pass through the CNS and the effectors create a respons
• Electrical impulses
• Signals/impulses created by the receptors which are send to the coordinator
• Method of transporting information of environmental change from the receptors to the coordinators in order to produce a response 
• Decision making
• When receptors are affected by a change, they sends eletrical signals/impulses through the sensory nerves to the CNS
• The brain then coordinates the response 
• Reflex action

• Very rapid, uncoordinated movement
• Ex: Pulling your leg up after stepping on a lego block in the dark
• Pain receptors detects the lego
• Sensory Nerve sends the electrical signal (Impulse) to the CNS, Brain
• The Motor nerve sends signals to the effector (Skin)
• The effector (Skin) produces a response
• Reflex
• Muscle contracts
• Leg is pulled up

2.83 Central Nervous System (CNS)

• Allows the body to respond to any change in the environment
• Consist of:
• Brain
• Spinal cord
• All the nerves branching out from the cord
•  The CNS refers only to only the brain and the spinal cord
• Impulses from the receptors pass through the sensory nerves til they reach the spinal cord and te brain
• There are two ways in which the CSN handles these changes:
• Response coordinated by the brain 
• Slower
• Reflex action
• Extra rapid responses to stimuli that by-pass the brain

2.82 Communication

• Motor Nerve (Neurone)
• Links coordinators with effectors
• Around a meter long
• Has tiny branches at each end
• Has long fibers at each end
• To carry the electrical impulses from the cell body to the Synaptic  knob
• Connected to the muscle
• Mammals- The axon is surrounded by a scwhan cell
• Contains fat to increase the speed of the nerve conduction
• Endocrine System
• Endocrine Gland 
• Produces hormones
• Can be Proteins/Steroids
• Secreted in to the blood
• Arrives at the "Target organ/tissue"
• May have multiple targets
• May have multiple effects
• Endocrine gland (Adrenal gland) > Blood (Adrenaline) > Target Tissue (Heart)
•                                |Nerves                                    |Hormones                      
  Speed of reaction     | fast                                        |slow                              
  Type of transmission|Chemical signal                       |Electrochemical signal
• Specificity                |Can be a few/many body parts|Affects target cells/organs