February 19, 2012

5.9 Fish Farming

5.9 explain the methods which are used to farm large numbers of fish to provide a source of protein, including maintenance of water quality, control of intraspecific and interspecific predation, control of disease, removal of waste products, quality and frequency of feeding and the use of selective breeding.

Fish Farming is attractive to farmers because fish are low in fat; high in protein and highly efficient at transferring nutrient into fish matter.
Benefits to fish farming
  • Water quality can be controlled
  • Predators can be removed
  • Pests can be removed
  • Disease can be controlled

Controlling these factors increases the yield of fish.

However the high density of fish in fish farms makes the transmission of disease and number of pesticides greater so farmers use antibiotics and pesticides to control this but as we know, this can cause harm to humans and the environment.

5.8 Fermenter

5.8 interpret and label a diagram of an industrial fermenter and explain the need to provide suitable conditions in the fermenter, including aseptic precautions, nutrients, optimum temperature and pH, oxygenation and agitation, for growth of microorganisms

Fermenter – the reaction vessel where fermentation occurs. The aim is to have optimum growth conditions for fermentation to occur.
  • Inlets
    • Steam – cleaning
    • Microorganisms
    • Nutrients
  • Probes
    • pH
    • Temperature
  • Water Jacket and Heater for temp control
  • Stirrer – to agitate the mixer

5.7 Yoghurt

5.7 understand the role of bacteria (Lactobacillus) in the production of yoghurt
  1. Cow milk is pasteurised to remove harmful bacteria.
  2. The milk sugars are converted into lactic acid
    • Incubated at 45-46°C
    • Add lactobacillus (enzyme)
  3. The acid creates acidic condition
  4. Milk proteins solidify to yoghurt

5.5 Beer

5.5 understand the role of yeast in the production of beer

Glucose is converted from Starch by Amylase and Maltase. The Starch is usually from Barley seeds.
Anaerobic Respiration (Fermentation
Glucose ----yeast/enzymes---> Ethanol + Carbon dioxide
Hops are then added to the ethanol for flavouring.

5.4 Pest control

5.4 understand the reasons for pest control and the advantages and disadvantages of using pesticides and biological control with crop plants

A large field of crops of the same type is called a monoculture. These are very susceptible to pests which use the crop as their food source which reduces crop yield for the farmers.

To overcome this pesticides are used – Chemicals designed to kill the pests
  • Chemicals – easy to obtain
  • Easy to apply – spray
  • Very effective
  • Toxic – harmful to other species other than the pests (inc. humans)
  • Bioaccumulation – the pesticide causes problems in the higher levels of the food chain
  • Mutation in the pests leads to resistance.

Biological Control
Biological control is reducing the population of a pest without using pesticides.
For example if pest enters a country and flourishes it is often important to attempt to remove this species so that the native species can flourish again. In order to do this another alien species must be brought in that is higher in the food chain to reduce the numbers of the problematic plant/animal
  • No toxic chemicals
  • Less impact on man/wildlife
  • Not 100% effective
  • Difficult to control
  • The alien species may not die out once the pest has been removed and could become another problem

5.3 Fertilisers

5.3 understand the use of fertiliser to increase crop yield

To increase crop yield in agricultural farming fertilisers are added to the soil. Fertilisers are usually nitrates, phosphates, or a combination of the two. The compounds enter the plants through the roots in the soil and move through the transpiration stream to the leaf
Nitrates -> Proteins
Phosphates -> DNA/ Membrane structure
Fertilisers can be divided into two groups
  1. Organic fertilisers
    • Animal waste – cow faeces
    • Decomposed/fermented
    • Manure (slurry)
  2. Artificial fertilisers
    • Chemicals - Potassium Nitrate and Ammonium Nitrate
    • Applied in solution to release nitrates and phosphates

5.2 Crop Yield

5.2 understand the effects on crop yield of increase carbon dioxide and increase temperature in glasshouses

Rate of photosynthesis:
CO2 + H2O ----light/enzyme---> C6H12O6 + 6O2

Increasing the concentration of Carbon dioxide (substrate) will increase the rate of photosynthesis producing a higher yield up until a given point.

Increasing temperature shall also increase the rate of reaction we reach the optimum temperature for the enzymes in photosynthesis. After the peak there is a sudden asymmetrical drop as the enzymes denature.
Increasing temperature also contributes to avoiding frost damage and an increased yield

5.1 Glasshouses

5.1 describe how glasshouses and polythene tunnels can be used to increase the yield of certain crops

Both Glasshouses (a.k.a. greenhouses) and Polythene tunnels aim to have the same effect on plants: provide warmth for plants to grow in a humid environment.
How they work

  1. Heat enters the greenhouse from the sun (in short IR waves)
  2. The surfaces in the greenhouse absorb the short waves and reemit this energy as heat
  3. The heat warms the air inside the greenhouse
  4. Most of the heat is reflected back into the greenhouse and doesn't escape

This increases crop yield because…

  • … Warmer temperatures allow enzyme reactions to occur more efficiently
  • … Less water is lost to the environment
  • … Constant temperature around the year
Polythene tunnels are also used to the same effect but are cheaper, easier to move and easier to use for farmers because they can be placed over rows of plants to protect from the frost as in a greenhouse plants must be potted.

2.89 Hormones

2.89 understand the sources, roles and effects of the following hormones: ADH, adrenaline, insulin, testosterone, progesterone and oestrogen.

Endocrine glands, produce chemical signals known as hormones, these travel through the blood stream from an endocrine gland to a target tissue where is has an effect.

  • ADH/antidiuretic hormone – from the Pituitary gland – Target: collecting duct – increases absorption of water into the blood
  • Adrenaline – Adrenal glands (on top of kidney) – Heart (many others) – increase Heart Rate
  • Insulin – Pancreas – Liver – Storage of glucose (reduce blood sugar levels)
  • Glucagon (opposite of Insulin) – Pancreas – Liver – Puts sugar into blood stream
  • Testosterone – Testes (low levels in women, produced in ovaries) – Testes (sperm cells) – Sperm cells mature
  • Progesterone – Ovary – Uterus lining – maintain uterus lining
  • Oestrogen – Ovary – Lining of the Uterus – Build up the lining of the uterus

2.88 Temperature regulation

2.88 describe the role of the skin in temperature regulation, with reference to sweating, vasoconstriction and vasodilation

Stimulus: Temperature of internal body temperature (blood temp)
Receptor: Hypothalamus (as blood flows through this part of the brain)
Coordinator: Hypothalamus (the part of the brain associated with thermoregulation)
Effector: Skin

Cooling down

  • Sweat glands produce sweat which evaporates from the body creating a cooling effect.
  • Vasodilation - Blood flows to the surface of the skin through dilated vessels so that heat can potentially radiate off of the body.
  • Furthermore the radiating heat from the blood increases the evaporation of sweat, this is known as latent heat of evaporation.
Heating up

  • Vasoconstriction - Capillaries near the surface of the skin narrow to keep heat inside of the body
  • Shivering – a reflex to increase body temperature, muscles groups near vital organs shake in an attempt to create warmth.
  • Hair erection – hair stands up to trap a layer of air close to the skin. (air is a poor conductor of heat)

2.87 Eyes’ response to Stimuli

2.87 understand the function of the eye in focusing near and distant objects, and in responding to changes in light intensity

Most of the bending of light is done by the Cornea
The Lens bends rays slightly to make an image clear and sharp
To focus on far objects the rays entering the eyes are almost parallel so less bending is required. The ciliary muscles relax tightening the suspensory ligaments so the lens is thin to focus the object on the retina
To focus on near objects, the rays are highly diverged so the cilary muscles contract, slackening the suspensory ligaments causing the lens to fatten focusing the light onto the retina
Light Intensity
The amount of light that enters the eye is controlled by the Iris this is done by changing the pupil size. The iris contains circular and radial muscles
In bright light
Circular muscles contract, radial muscles relax. Making the pupil smaller so less light can enter the eye. (Too much light can damage)
In Dim light
Circular muscles relax, Radial muscles contract. Making the pupil bigger to let more light into the eye.

February 6, 2012

2.86 The Eye

2.86 describe the structure and function of the eye as a receptor

The eye is a photoreceptor that detects changes in visible light. When light stimulates the rods in the back of your eye a nerve impulse is sent to the brain along the optic nerve, your brain then interprets these impulses to make a picture.

  • Ciliary muscles – Contract or relax to alter the shape of the lens (to focus)
  • Cornea – Transparent cover allows light in and does most of the bending of light.
  • Iris – Alters pupil size (to vary light intake)
  • Vitreous Humour – Clear jelly that gives the eye ball shape
  • Lens – changes shape to focus light on the retina
  • Retina – Contains the light-sensitive receptor cells which change light into electrical impulses
    • Rods – sensitive in dim light but only sense black and white
    • Cones – sensitive in bright light and can detect colours
  • Sclera – Protective tough outer layer of the eye
  • Suspensory ligaments – Hold the lens in place
  • Optic nerve – Carries the electrical impulses to the brain
The Gif below shows the human eye dilating due to a change in light intake this is controlled by the Iris