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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
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