BIOLOGY · Stage 7 · Chapter 1: Classification and Life
Biology 1.1 What is life? — The Seven Characteristics of Living Organisms — Alhussan International Academy - Biology (Stages 7-9) Revision Notes & Topical Questions
5 min read 5 parts Lesson 1 of 11
Lesson summary
Biology 1.1 What is life?
- Memory word
- Reproduction
- Sensitivity
- Respiration
- Excretion versus egestion
- Biology = the study of living organisms, and the scientists who study it are biologists
Section 1 of 5Biology and living organisms
- Biology = the study of living organisms, and the scientists who study it are biologists.
- Organism
- a living thing;
- organisms differ in size and shape, from a bacterium to a blue whale, but all show the same seven characteristics.
- a living thing;
- Memory word
- MRS GRENMovement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.
Section 2 of 5Movement, reproduction and sensitivity
- Movement
- living things move their whole bodies or parts of their bodies, and even plants move parts of themselves to face the Sun.
- Reproduction
- all living organisms make more of themselves, which is important so that organisms do not die out.
- Sensitivity
- living organisms respond to their surroundings, such as animals using eyes to see.
- A change in surroundings that an organism detects is a stimulus.
Section 3 of 5Growth, respiration, excretion and nutrition
- Growth
- living organisms get bigger, which often happens as a young organism gets older.
- Respiration
- this process makes the energy in food available for organisms to use.
- They use the energy to carry out all the other characteristics of life.
- Many organisms need oxygen to respire and produce waste carbon dioxide gas.
- Excretion
- living organisms get rid of the waste they produce, such as carbon dioxide or urea.
- Nutrition
- all living things need food, as plants make their own food and animals eat plants or other animals.
Section 4 of 5Respiration, breathing and excretion
- Respiration
- a chemical process in every living cell that releases energy from glucose.
- glucose + oxygen → carbon dioxide + water (+ energy).
- Plants respire all day and all night, even though they also photosynthesise in the light.
- Breathing
- moving air in and out of the lungs, which is different from respiration.
- Excretion versus egestion
- excretion removes waste made by chemical reactions inside cells, while faeces are undigested food removed by egestion.
Section 5 of 5Deciding whether something is alive
- Rule
- an object is alive only if it shows all seven characteristics, and one feature alone is not enough.
- Car
- it moves and uses fuel, but it cannot grow, reproduce or sense its surroundings by itself, so it is not alive.
- Seed
- it respires slowly and grows when conditions allow, so it is alive.
- Fire
- it seems to move, grow and use fuel and oxygen, but it does not reproduce or respond like an organism, so it is not alive.
- Evidence
- give evidence for each characteristic claimed for a living thing.
Last updated: