Q. Why do muscles feel tired after a marathon?
A. There is a build-up of lactic acid in our muscles due to anaerobic respiration (respiration when our muscles have run out of oxygen).
Q. Which animal would win in a fight between a shark and a crocodile?
A. Probably the shark. A crocodile can't metabolise build-up of lactic acid that occurs when exercising or fighting. Exertion of more than 30 seconds could prove fatal to the crocodile.
Q. What is hibernation? Do humans hibernate?
A. Hibernation is the reduction of body temperature and the slowing down of all the body processes (metabolism) during winter. Bears can do this. In fact, human body temperatures do drop slightly before and while sleeping, so this may be regarded as a form of hibernation.
Q. What happens to all the food we eat?
A. 'Warm-blooded' animals eat a lot of food, much of which is broken down and used to keep us warm. Other food is digested for all the many chemical reactions that occur in our bodies for growth and repair. What is not used by the body is eliminated as waste.
Q. How does yeast make bread rise?
A. Yeast is a living organism - a fungus. When yeast respire as humans do, they give out carbon dioxide. This is the gas that makes the bread rise.
Q. Why are fish so colourful in water, and yet they are lacking in colour after being caught?
A. Fish have pigment cells all over their skin. They lose their pigment within minutes of dying.
Q. Why are many cells spherical?
A. The spherical cell shape is the most efficient shape to have the least amount of surface area (or cell membrane) to enclose the greatest amount of cytoplasm. However, not all cells are spherical, due to their various functions.