Biology: Life Processes
Life processes are the seven characteristics shared by all living organisms, remembered using the mnemonic MRS GREN (movement, respiration, sensitivity, growth, reproduction, excretion, nutrition). At 13+ Common Entrance this topic covers what each process means and how organ systems such as the digestive, circulatory and nervous systems carry them out in the human body.
Method
- Learn the mnemonic MRS GREN and be able to state, in your own words, what each of the seven life processes means.
- Link each life process to the organ system responsible for it in humans, for example sensitivity to the nervous system and excretion to the kidneys and liver.
- Practise naming the substances entering and leaving the body during nutrition, respiration and excretion, and where each substance goes.
- Learn the structure and order of the digestive system, and the difference between mechanical and chemical digestion.
- Compare aerobic and anaerobic respiration, including the word equation for aerobic respiration and when anaerobic respiration happens instead.
- Use command words correctly: 'state' needs a short fact, 'describe' needs detail on what happens, and 'explain' needs a reason or mechanism.
Worked example
A student says that a mushroom (a fungus) is not a living thing because it does not move around like an animal. Explain why this statement is incorrect, referring to the life processes.
- Recall that a living organism must carry out all seven life processes, not just movement.
- Movement does not have to mean moving the whole organism from place to place; it can mean movement of parts, or growth in a particular direction.
- A mushroom carries out nutrition (absorbing nutrients), respiration (releasing energy), growth, reproduction (spores), excretion and sensitivity (responding to light or moisture), so it meets the definition of a living organism.
- Final answer: the student is incorrect, because a mushroom carries out all seven life processes, even though it does not move its whole body from place to place like most animals do.
Practice questions
Try each question, then tap to reveal the answer.
Exam-style questions
Written in the style of a 13+ Common Entrance exam paper, with a full mark scheme.
(a) Name the type of reproduction that involves two parents and produces genetic variation in the offspring. (b) Name the type of reproduction that involves only one parent. (c) State one advantage of sexual reproduction over asexual reproduction.
The circulatory system transports blood around the body. (a) Name the four chambers of the heart. (b) State one difference between the structure of an artery and a vein. (c) Name the type of blood vessel where exchange of substances between blood and body cells takes place.
A student measured her pulse rate at rest and then at one-minute intervals after one minute of star jumps. Time after exercise (min): 0 (rest), 1, 2, 3. Pulse rate (beats per minute): 72, 132, 108, 84. (a) State the independent variable in this investigation. (b) State one variable that should be controlled to make this a fair test. (c) Calculate the percentage increase in pulse rate from the resting rate to the rate immediately after exercise (at 1 minute). Give your answer to 1 decimal place.
Free printable worksheet
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