(a) Two sets of rats were used so there would be a control set in both parts of the experiment. The experiment was to see the effect of milk on the development of the rats. By giving one set milk for a certain amount of time then stopping the milk after 18 days and giving the same amount to the other set It was possible to control the variables that may effect the results.
(b) 20 rats were used rather than two to ensure reliability of the investigation. If just 2 rats were used the end results may have been caused by another factor other than milk, such as illness of one of the rats. By using so many rats an average of the results can be calculated and therefore the end result more accurate.
(c) Calcium – a mineral found in milk that is responsible for making teeth and bones. Vitamin A - a vitamin found in milk responsible immune health and for normal growth and development of body tissues.
(d) Young rats were used rather than adults because this investigation was measuring an increase or decrease of mass of the rats. Young rats were going through a time of rapid development, in adults most of the growing would have already occurred and thererfore we would not have such an informed result of the effect of milk on development.
(e) In previous investigations, rats that were given no milk became ill and died, the rats needed to stay alive for ethical reason, reliability and accuracy of the investigation. Switching the diets after 18 days was important for reasons such as;
The rats with no milk in the first set were given milk before they died, therefore this made the full investigation possible.
We can see what happens when milk is added to the previously deprived set, the rats begin to grow normally and in correlation with the set who were given milk in the first place. This adds proof that milk has an effect on growth.
We can see what happens when milk is omitted from the diet, the rats stop thriving and growth rate actually drops. This adds further proof that milk has an effect on the growth and development of rats.
(a) X – Bile duct
(b) B - Stomach
(c) C – Pancreas
(d) G – Ileum (small intestine)
(e) A – Liver
(f) D or F Colon (large intestine) Not clear from diagram if F is rectum or colon.
(a) 1. pancreas 2. Small intestine
(b) Salivary glands and pancreas
(a) The function of the stomach is not to digest food, its fucntion is to break down food using enzymes, digestion takes place in the small intestine.
“The function of the stomach is to break down food using enzymes”.
(b) The small intestine doesn't actually absorb food it is here that food is absorbed.