YEAR 12

UNIT 1 REVISION

DIGESTION SPOT THE MISTAKE –

AND CORRECT IT!

•Variables: These are the factors involved in an experiment. Controlled variables must remain the same, the independent variable is changed throughout and the dependent variable is measured •Reliability: An experiment is reliable if it has been repeated and results are similar to the mean result. The only way to improve reliability is to repeat and take an average result •Accuracy: This relates to the method and how the variables are measured. To improve accuracy the correct and most accurate measuring equipment should be used •Validity: An experiment is valid if the factors not under investigation are controlled, or taken into account if they can’t be controlled. Thus leaving one independent variable to be investigated

The iris

Controlling the pupil size…

http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/electrical/thenervoussystemrev4.shtml

How the iris works to change the size of the ...

Pupil, so to control the...

Amount of light entering the eye, using...

Circular and radial muscles (this is the pupillary reflex)

In the iris: Circular muscles lie in circles around the pupil – when they contract the pupil constricts/gets smaller Radial muscles run outwards from the edge of the pupil – when they contract the pupil dilates/gets larger

The Lens

How the ciliary muscles and ligaments work to control the...

Shape of the lens, to...

Refract then focus light on the retina, this is called...

Accomodation

The eye 5 task question...

Eye and Phototropism 5 tasks – ANSWERS

1. A = Iris

B = Lens

2. Eye lashes stop dirt and dust entering; conjunctiva is a physical barrier; tears

contain enzymes to destroy microorganisms

3. DESCRIBE: In bright light the pupil gets smaller. EXPLAIN: Circular muscle

contracts and radial muscle relaxes.

4. FAR AWAY IMAGE: Ciliary muscles relax and pull the suspensory ligaments

tight. They stretch the lens thin so it doesn’t refract the light as much.

CLOSE OBJECT: Ciliary muscle contracts and moves towards centre.

Suspensory ligaments slacken and lens become thick to refract the light more.

5. - Light detected in the tip

- Auxin hormone created in the tip

- Diffuses down the non-lit / shaded side of the shoot

- Elongates the cells on that side more

- They become larger

- Plant bends towards the light source

- Will photosynthesise more and grow more

1.6 Sensitivity and 1.7 Ecology

6 mark questions

Whilst observing mouse behaviour, a student drops a pen near the

mouse’s cage. The mouse jumps at the noise. Describe, as fully as you

can, the processes by which the mouse responds to the stimulus of

the dropped pen.

Receptors in the ear detect sound waves / vibrations

Impulses travel to the brain

along the sensory neurone

And travel across the synapse

To association neurones

the impulses travel along motor neurones

To muscles / effectors (in the mouse’s neck)

which contract

To bring about a response

It is important for the body to control blood sugar levels. Explain what would happen if somebody

ate some glucose tablets.

Glucose is absorbed into the blood

Blood glucose levels rise

The pancreas detects this rise in blood glucose level

And releases the hormone insulin

Insulin travels in the blood

To the liver

Insulin causes the liver to absorb glucose form the blood and the blood glucose level falls

The liver uses the glucose in respiration

Or converts it to glycogen for storage

ECOLOGY

Describe how carbon compounds in the leaves can be recycled so

that they can be used again by the trees.

Micro-organisms / bacteria / fungi / decomposers

Digest / break down / decompose organic matter / leaves

Using enzymes / correct named example (e.g. carbohydrase / protease …)

The products are absorbed by plants by diffusion / active transport

As decomposers / plants respire

they release carbon dioxide into the air

This may be used by plants (trees) in photosynthesis

Plant uses glucose in respiration and releases CO2

Fossilisation of plant and eventual combustion will release carbon dioxide

Explain how the overuse of nitrate fertilisers can cause problems in

the environment.

eutrophication

Nitrates in water cause algal blooms / small plants to grow rapidly

Blocks out the sunlight

Plants find it difficult to carry out photosynthesis

Plants die

Dead organisms are decomposed / broken down by micro-organisms / decomposers / bacteria

Micro-organisms use up oxygen in respiration

There is less available for other living organisms

Fish and invertebrates die

TRY THE 5 TASK CARBON CYCLE QUESTION

Carbon cycle 5 task – ANSWERS 1. The carbon cycle. 2. As a gas it diffuses through the open stomata and into the air spaces of the

spongy mesophyll and into the mesophyll cells. 3. In the process, photosynthesis. Along with water and using sunlight energy

they turn carbon dioxide into glucose and oxygen. 4. In process 3, decomposition, bacteria and fungi breakdown the carbon

compounds in the plant during respiration and release carbon dioxide into the air

In process 4, the carbon compounds are fossilised and fixed into fuel and

will only be released as carbon dioxide during combustion 5. - Combustion - When fossil fuels are burned using oxygen - e.g. coal, oil and gas - Releases carbon dioxide into the air - There is a need for more renewable energy sources to be used

Remember to make sure you know the key words! They are in your specification e.g….

...you could be asked to define one of them!

Benedict’s reagent

Vacuole

Carbon dioxide

Enzyme specificity

DCPIP

Synapse

Limiting factor

Protein

Active transport

Negative feedback

Apices

Pleural fluid

BMI

Compensation point

Diabetes

Destarch

Total magnification

Bile

Ciliary muscle

Organ

Chlorophyll

Carbohydrates

Plasmids

Digestion