5.11 Selective breeding 2

5.10 Selective breeding

5.9 Impact of fish farming

5.8 Fermenter

5.7 Yoghurt production

5.5 Yeast in beer production

5.3 Fertiliser

understand the use of fertiliser to increase crop yield

Fertilisers - replace the missing nutrients in the soil

Usually in the form of nitrates and phosphates

Taken up into the plant via the roots, transpiration stream, leaf

Nitrates: Proteins

Phosphates: DNA and membrane structure

1. Organic fertilisers

• Produced from animal waste
• Goes through process of decomposition and fermentation to form slurry
• Gives supply of nitrates and phosphates to the soil

2. Artificial fertilisers

• Chemicals
• Potassium nitrate, ammonium nitrate
• Turns into solution in the soil water

NPK fertilisers

• Nitrogen: growth of leaves and stems
• Phosphorus: healthy roots
• Potassium: healthy leaves and flowers

5.2 Crop yield

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

Photosynthesis equation

CO2 + H2O => C6H12O6 (glucose) + 6O2


Things that will increase the rate of reaction, the rate of photosynthesis and consequently the crop yield

1. Carbon dioxide concentration

• Increasing the concentration of a substrate will result in the rate of reaction 
• increasing and then remaining constant after a certain point
• In this case, carbon dioxide
• The rate / crop yield will increase until a certain point (the optimum)

Source: michellebiology.blogspot.com

2. Temperature

• Higher temperature - higher rate of reaction until the optimum temperature is surpassed and the enzymes denature
• (Particles can collide into each other more frequently due to increased kinetic energy, but a temperature surpassing the optimum would cause the substrate to no longer be able to bind to the active site)
• Avoiding frost damage, maintaining constant temperature

Source: michellebiology.blogspot.com

5.1 Glasshouses and Polythene tunnels

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

Glasshouse - allows plants to grow earlier in the year, and/or in places where they would not normally grow well

Provides warmth, light, carbon dioxide and water

Increases crop yield - best possible conditions for photosynthesis to take place

• Optimum temperature for photosynthesis (enzymes work efficiently // fastest rate of reaction)
• Allows constant temperature throughout the year // constant production
• Prevents loss of water vapour // constant supply of water
• Frost damage to seedlings avoided
• Warmed by burning of fossil fuels // increasing CO2 levels

Temperature

• Sunlight heats up the inside of the glasshouse
• Glass stops (most of) heat from escaping
• Electric/paraffin heaters can be used in cold weather
• Ventilator flaps can be opened to cool greenhouse

Light

• Glass lets in sunlight
• Artificial lighting can be used to grow plants if sunlight gets too low
• Blinds can shade out overly strong light

Temp+Light

1. Solar radiation (initial source of energy) in the form of light, is let in through the glass into the glasshouse
2. Light absorbed by surfaces inside the glasshouse (soil, wooden surfaces, plants)
3. Surfaces reemit energy as heat
4. Heat warms the air
5. Temperature increases - creates a convection current inside the glasshouse

Carbon dioxide

• Growers can pump CO2 into glasshouses
• Paraffin heaters are used sometimes
• Increase both temperature and CO2 (paraffin burning => releases CO2)

Water

• Many glasshouses have automatic watering systems
• Sprinklers, humidifiers

Source: www.indiana.edu

Polythene tunnels 

• Allows light to pass through into the interior
• Used in less developed countries (cheaper)
• Adjustable and movable but less efficient and has less shelter for the plant

Source: www.thegardensuperstore.co.uk

2.89 Hormones

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

http://www.medicalook.com/systems_images/Endocrine_System_large.jpg

1. Hormones
- Made in endocrine glands
- Travel through blood

2. ADH - Anti-diuretic hormone
- Increases amount of water reabsorbed into the bloodstream in the collecting tubule [kidney]
- Produced in pituitary gland [brain]

3. Adrenaline
- Activates fight-or-flight response
- Increases heart rate, depth of breathing/breathing rate, sweating
- Hair stands on end (goosebumps), dilated pupils, pallidness (blood redirected to muscles)
- Produced in adrenal glands

4. Insulin
- Facilitates entry of glucose into muscle and other tissues
- Stimulates liver to store glucose in the form of glycogen
- Decreases concentration of glucose in the blood
(if one does not have insulin the source of energy will be fatty acids instead of glucose)
- Produced in the pancreas
- Released after a meal to convert glucose to glycogen // insoluble and for storage

5. Testosterone
- Stimulates secondary growth and sexual characteristics (male)
- Produced in the testes

6. Oestrogen
- Stimulates secondary growth and sexual characteristics (female)
- Works with progesterone for the menstrual cycle (produces LH hormone which causes the ovary to release an egg // ovulation)
- Produced in the ovaries

7. Progesterone
- Prevents uterus lining from breaking down so that an egg can plant into it
- Presence of sperm; if there is no sperm present then the ovaries stop producing progesterone and the lining of the uterus breaks down, causing a menstrual cycle

2.88 Thermoregulation

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

Skin - protects body from damage, germs, excessive water loss; allows one to feel touch, pain, temperature and pressure; keeps body temperature constant

1. Vasodilation when hot
- Blood vessels near the surface of skin widen
        - Allows more blood to flow to the surface
        - Heat lost from radiation
- Sweat glands make sweat
        - Sweat evaporates and cools body down
- Hairs lay flat; no air trapped, heat can transfer out of body

2. Vasoconstriction when cold
- Blood vessels close up
        - Allows less blood to flow to the surface
        - Less heat loss from radiation
- Hair erection (goosebumps); muscles contract and makes hair stand up, traps a layer of air to avoid heat from escaping
- Sweat glands stop making sweat
- Shivering; muscles contract quickly and generate extra heat to warm body

2.87 Response: Eyes

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

Light --[Cornea --> Lens --> Focused on retina]--> Eye

1. Retina
- Rods and cones; cells sensitive to light
        - Rods: Dim light
        - Cones: Colour and details
- Responds to stimuli (light) by sending impulses to the brain along optic nerve
- Image on retina is inverted
- Brain flips image right way up

2. Focusing
- Cornea bends most of the light rays
- Lens can also bend rays slightly
- Shape of lens controlled by ciliary muscles

Source: http://www.sapdesignguild.org/editions/edition9/images/accomodation.png

3. Focusing on a distant object
- Ciliary muscles relax
- Suspensory ligaments tighten
- Lens pulled into thin shape
- Distant object focused onto retina

4. Focusing on a near object
- Ciliary muscles contract
- Suspensory ligaments relax
- Lens thickens
- Near object focused onto retina

5. Response to changes in light intensity
- Iris: controls amount of light allowed to enter the eye
- Contains circular and radial muscles

a) Bright light
- Circular muscles contract, radial muscles relax
- Pupil is made smaller/constricts
- Too much light entering the eyes can cause damage

b) Dim light
- Circular muscles relax, radial muscles contract
- Pupil is made bigger/dilates
- Aids seeing in darker places

Source: http://michellebiology.blogspot.com

2.86 Eye

describe the structure and function of the eye as a receptor

Source: http://learning.royallatin.bucks.sch.uk/file.php/163/assets/images/ks4/Eye.gif

Choroid - Black layer containing a high concentration of blood vessels
Vitreous humour - Transparent jelly-like substance which supports the back of the eye
Retina - Inner light-sensitive layer which contains rod cells that work in dim light and cone cells that detect colour and details
Yellow spot or fovea - Most sensitive part of the retina
Blind spot - Point where the optic nerve attaches to the eyes; no light-sensitive cells
Optic nerve - Carries nerve impulses away to the brain
Sclerotic - Tough, white, protective layer
Suspensory ligaments - Holds the lens in place
Iris - Controls the amount of light entering the eye
Lens - Can change its shape to focus light onto the retina
Aqueous humour - Watery liquid filling the front of the eye
Cornea - Shields the eye from germs, dust, etc.
Conjunctiva - Helps lubricate the eye by producing mucus and tears
Ciliary muscle - Changes the thickness of the lens when focusing

- lie in sockets in the skull
- controlled by three pairs of eye muscles
- receptor of light