5.11 understand that animals with desired characteristics can be developed by selective breeding

Notes


Breeding shifts the distribution curve towards the desired characteristic.

-> Example: Cows milk yield
Gen 1
Cow A: 50 ml
Cow B: 100ml
Cow C: 150ml
-> Cow C is chosen to be the 'breeding cow' - the cow is selected to be the breeding population to develop the desired characteristic.


Gen 2

Cow A: 100 ml

Cow B: 150ml

Cow C: 200ml

-> -> Cow C is chosen to be the 'breeding cow' - the cow is selected to be the breeding population to develop the desired characteristic.

Etc.

NOTE: For selective breeding to take place, the desired characteristic MUST under the control of the genes

5.10 understand that plants with desired characteristics can be developed by selective breeding

Notes


Farmers can use selective breeding to increase plant yield

-> Example: Rice grains
The number of grains produced per plant (yield) is controlled by the genes of that specific plant.
The number of grains produced per plant in a crop field varies - this can be shown with a distribution curve which resembles the one below:

where the left, middle and right sections show the least, average and most number of grains produced in the crop field respectively. Supposing a farmer had three plants - which yielded 6, 8 and 10 grains respectively - to increase crop yield, the farmer would:
-> Harvest the two plants which produced only 6 and 8 grains
-> Re-plant the grains from the 10 grain plant (as these will share the same genes)
-> This would cause the next generation of plants to have 8, 10 and 12 grains respectively instead

Selective breeding (in plants) can be used to shift the distribution curve so that the median percentile of plants produces the desired characteristics, therefore increasing crop yield.
NOTE: The distribution curve shifts - simply because a 10 grain plant seed is re-planted does not guarantee ALL plants will produce 10 seeds (hence, a curve).

5a Food Production

a) Food production

Students will be assessed on their ability to:

Crop plants

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

- Prevents frost from forming

- Retains heat

- Prevents low humidity levels (prevents water loss)

- Prevents

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

Increasing CO2 -> Increases the amount of substrate, therefore more products from photosynthesis, resulting in higher yield

Increasing temperature -> increases the rate of reaction (provided it is not already past optimum temp. of enzymes) and therefore more yield

-> Glasshouses allow both these factors to be controlled = highest yield

5.3 understand the use of fertiliser to increase crop yield

Fertilisers consists of NITRATES AND/OR PHOSPHATES; these help promote growth and increase crop yield

Nitrates -> For amino acids/protein

Phosphates -> DNA/Membrane structure

There are two commonly found types:

Organic

-       Animal waster (i.e. cow dung)

-       These are left to ferment and decompose

-       This results in manure - fertiliser

Inorganic (artificially synthesised)

- Correct amounts of Potassium Nitrate and Ammonium Nitrate are added into a solution, which releases them

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

Monoculture = a field of crops consisting of only one type of crop – these are VERY SUSCEPTIBLE to pests and pesticides (chemicals) which kill and ward off these pests are used

PESTICIDES

Advantages

-       Easy to obtain

-       Effective

-       Easy to spray onto crops

Disadvantages

-       Toxic to both animals and dangerous to humans in large amounts

-       Bioaccumulation is when this toxicity is transferred throughout the food chain

-       Mutation in pests leads to resistance to pesticides

BIOLOGICAL CONTROL

When an alien species (from another ecological system) is introduced; higher in the food chain -> eats pests

Advantages

-       Non-toxic

-       Less direct impact on plant and animal life

Disadvantages

-       Not 100% effective (could find other prey)

-       Difficult to control alien

-       Once pests are gone, aliens might cause own problems

 Microorganisms

5.5 understand the role of yeast in the production of beer

1.    Starch from grains (i.e. Barley)

2.    Starch (polysaccharide) --- Malting (maltose/amylase) -à Glucose

3.    Anaerobic respiration (fermentation)

Glucose --- enzymes (from yeast) --à Ethanol + Carbon Dioxide

4.    Hops from flowers are added to Ethanol for flavor

5.6 describe a simple experiment to investigate carbon dioxide production by yeast, in different conditions

5.7 understand the role of bacteria (Lactobacillus) in the production of yoghurt

1.    Harmful bacteria removed from cow milk by pasteurization

2.    Milk sugars (lactose) are converted into lactic acid

-       45 - 46°C = Optimum temperature

-       Lactobacillus produces enzymes which converts

3.    Acidic conditions stimulate the solidification of the milk

4.    Solidified milk = yoghurt

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 the growth of microorganisms

Fermentation occurs in the fermenter = its goal is to provide the optimum conditions for fermentation in the following ways:

Aseptic Precautions  = this prevents pathogens and unwanted bacteria from contaminating the substrates and products

Optimum temperature = enzymes produced by the microorganism function best at this temperature, so to produce more yield, this temperature is controlled

pH Levels = enzymes also function best at a certain pH, so this is similarly controlled by the fermenter

Oxygenation = Oxygen is needed in the reaction since it is aerobic

Agitation = this ensures that the microorganisms are distributed evenly throughout the fermenter, and prevents clusters of them from forming; also ensures even temperature and nutrient concentration

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.

The advantages of eating and breeding fish are as follows:

-       High source of protein

-       Low fat content

-       Fish are efficient at converting nutrients into biomass

By fish farming, we increase the yield of fish and fish mass produced:

-       Water quality can be controlled

-       Predators can be removed

-       Disease can be controlled (through anti-biotics)

-       Other pests can be controlled

Note that the higher the density of fish, the higher the chance that disease will spread. Farmers control this by use of antibiotics and pesticides (to keep away pathogen carrying pests) – the disadvantages of this are discussed above.

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

Notes


Hormones are produced in the endocrine glands (i.e. pituitary gland) and released directly into the circulatory system. They travel to the target tissue, this causes effects.

ADH - Pituitary Gland -> Collecting Duct
Controls how much water is re-absorped in the collecting duct; therefore controls water content of blood


Adrenaline - Adrenal glands ->  Heart
Prepares body for stressful situations - 'fight' or 'flight'


Insulin - Pancreas -> Liver
Lowers glucose levels in the blood
-> Glucagon - Pancreas -> Liver
-> Raises blood sugar levels


Testosterone - Testes -> Testes (sperm)
Controls secondary male characteristics
Sperm production


Progesterone/Oestrogen - Ovaries -> Uterus
Controls secondary female characteristics
Menstrual cycle regulation
Build up lining of the uterus

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

Notes


To maintain homeostasis of temperature, the body employs the thermoregulation system. The skin has many aspects which are adapted to assist in thermoregulation to maintain a 37C core body temperature (optimum temperature for enzymes).
STIMULUS is actually the temperature of the blood, this is detected by the
RECEPTOR which is the hypothalamus

Too Cold
- Vasoconstriction is when capillaries narrow - this decreases amount of heat lost as less blood circulates near the skin surface
- Less sweat means less heat is transferred to surroundings
- Shivering means that muscles are activated, which produce heat as a byproduct and ATP
- Hair erector muscles contract, pulling the hair erect - this traps a layer of still air around the body, decreasing heat loss through convection


Too Hot
- Vasodilation is when capillaries widen - this means more heat can be transferred through blood to surroundings
- Sweating transfers heat to surroundings (also, as they evaporate, they lower the average kinetic energy of the surface and therefore the skin temperature decreases known as 'latent heat of evaporation')
- The hairs are not erected, heat can be lost by convection

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

Notes


When the lens shape is changed to adjust to varying distances of objects, this is known as accommodation and is how we focus light.
- The ciliary muscles are attached to the suspensory ligaments which in turn are connected to the lens (ciliary body -> suspensory ligaments -> lens)
- The lens, when no force is exerted on it, is naturally a rounded, disc-like shape
- The fovea is where the light is focused, it is a small point on the retina

Near objects
- When objects are near, the light from objects are more spread out (not very parallel)
- To focus this light onto the fovea, the lens must be more rounded to bend the light more
- The ciliary muscles contract and the suspensory ligaments go slack, since the lens is naturally spherical, light is bent through it's spherical shape

Far objects
- When objects are far, the rays of light are more parallel to each other
- To focus this light onto the fovea, the lens must be as little distorted as possible, so that the light is not bent much
- The ciliary muscles relax and the suspensory ligaments are pulled which in turn pulls the lens into a flatter disc shape

Process of pupil reflex
- When light enters your eye, it hits photoreceptors on your retina.
- These convert light energy to electrical impulses which are sent along sensory neurones in the optic nerve
- This information is unconsciously interpreted by the brain and as such it is known as a reflex; the motor neurones send information to the effector (iris)
- The effector muscles react
- Response is a change in pupil size, allowing more or less light in

Stimulus (light intensity) -> Receptor (retina) -> Sensory neurones -> Unconscious part of brain -> Motor neurones -> Effector (iris) -> Response (pupil)

-> The iris consists of radial muscles arranged like the ciliary muscles, when they contract the radius decreases, the surface area of the iris increases (the contracted muscles take up more space when arranged in a circle) and less light is let into the eye
-> Bright light: Radial muscles contract (these run through the diameter of the iris)
-> Dim light: Circular muscles contract (these run along the circumference of the iris)

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

Notes


-> Function
- The eye is a photoreceptor (it detects changes in light) type of sense organ
- It converts light energy to electrical impulses which can be interpreted as images in the brain
- It can respond to changes in light intensity and is able to focus and bend light reflected off of objects in the environment and into the eye so that it is produces a discernible image for the brain to interpret

-> Structure

Note that the ciliary muscles and suspensory ligaments encircles the lens. The ciliary muscles are arranged such that they form a ring of muscle which when contracted, tightens (the radius decreases).