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

January 28, 2012

2.85 Reflexes

2.85 describe the structure and functioning of a simple reflex arc illustrated by the withdrawal of a finger from a hot object

In some cases the response to a stimulus is always the same and needs to be applied quickly in order to not damage the body. In order to reduce reaction time the brain is removed from the process such that the impulse travels up the sensory nerve through a small relay nerve in the spinal cord that connects directly to the motor nerves so the reflex response can take place.
Nevertheless it is important to note that the receptor does still relay the impulses to the brain so that we are aware that we have touched a hot/sharp object (for example) and this creates the response of us saying “ouch” but this is significantly later than the reflex response... The reason reflex responses work is because the decision and response is always the same.

2.84 Responses

2.84 understand that stimulation of receptors in the sense organs sends electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses.

Impulses from our sensory organs are passed from the receptor to the coordinator (CNS) by sensory nerves. The impulse is then passed up the spinal cord to the brain where the brain generates a response and sends impulses back down the spinal cord through motor nerves which create the response.
For example if the eyes saw a red pen the co-ordinator (the brain) could decide “I like red; pick up the pen” this signal will be sent back down the spine through a motor nerve in the arm where the effectors (arm muscles) pick up the pen. It is important to note that all of this takes place reasonably fast but can be sped up by removing the interaction of the brain…[see 2.85]

2.83 Central Nervous System

2.83 Recall that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves

The Diagram shows the Central Nervous System (CNS) consisting of the Spinal Cord and Brain. Linked to the spinal cord are nerves which carry impulses sent by the brain to the effector. These nerves are known as the Peripheral Nervous System.

2.82 Communication

2.82 Describe how responses can be controlled by nervous or by hormonal communications and understand the difference between the two systems.

There are two ways in which responses are controlled in the body: the first is by using nerves. The diagram below shows a motor nerve cell. The cell body would be embed into the spine and the Synaptic knob at the opposing end would be embedded into the effecter (usually a muscle). Electrical/nerve impulses travel down the axon from the cell body; in mammals the axon is surrounded by a second kind of cell called the Schwann cell and these form what is called a Myelin sheath to increase the speed of nerve conduction.

The second way of linking a receptor to an effector is known as the Endocrine system. This involves an endocrine gland which produces Hormones (Proteins or Steroids). The Hormone then enters the blood stream and travels through the blood to the target tissue/organ where it will have an effect. Because of this it is possible for hormones to have multiple targets and effects.

Bill's Coffee

Bill wakes up to the smell of fresh coffee (Chemical Stimuli). He leaps out of bed and makes his way downstairs intent on gulping down a fresh brew.
Identify the:
  • Stimuli: Smell of coffee (chemical)
  • Receptor: Nose
  • Coordinator: Central Nervous System (CNS)
  • Effector: Muscles
  • Response: running downstairs, or gulping the coffee
Other examples of Stimuli: Chemical, Light, Pressure, Temperature

January 22, 2012

2.77 Homeostasis

2.77 understand that homeostasis is the maintenance of constant internal environment and that body water content and body temperature are both examples of homeostasis

Homeo~ = ‘same’/’constant’
~stasis = ‘conditions’
Homoeothermic = constant temperature

Mammals maintain a constant body temperature no matter what the environmental temperature; these are homoeothermic organisms and carry out Thermoregulation.
Mammals must contain this constant body temperature in order to maintain optimum temperatures for enzyme catalysed reactions.

A negative feedback loop is used to regulate body temperature in the human body about a constant condition. For human body temp, this constant condition (the co-ordinator) is roughly 37°C.

In thermoregulation the receptor is the Hypothalamus, a region of the brain that responds to a stimulus: the temperature of Blood. The hypothalamus compares the body temperature of blood to the theoretical level (37°C). If the body temperature needs to be increased or decreased effectors such as the skin are used to create a responsive increase or decrease in body temperature. This temperature feeds back to the hypothalamus to produce a new output.

Using Skin to Regulate body temperature:
There are several important features of the skin used to regulate body temperature: these include sweat glands, hair, and blood vessels.

On a hot day when body temperature needs to be lowered blood flow to the surface of the skin increases through dilated blood vessels and the body is cooled through the evaporation of sweat and radiation of heat from the blood.

On a colder day less blood is pumped towards the surface of the skin as the blood vessels constrict allowing less heat to radiate from the body. The hairs also stand upright in order to trap air as an insulation layer.

2.76 Sensitivity

New Topic: Coordination and Response

2.76 understand that organisms are able to respond to changes in their environment

MRS GREN: S = Sensitivity
Changes in environment (stimuli):
  • Light levels
  • Temperature
  • Pressure levels
  • Chemical

In order to detect these changes, organisms must have receptors, and in order to respond to these changes in the environment organisms have effectors such as muscles and glands.