1.1Chapter 1: Classification and Life

What is life? — Alhussan Biology - Stage 7 Revision Notes & Topical Questions

5 min read 7 parts Lesson 1 of 11 2 quizzes

📚 Alhussan Biology - Stage 7 Hub / Topical Revision

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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

Part 1 of 5Biology and living organisms

Biology

Biology the study of living organisms, and the scientists who study it are biologists.

Organism

Organism a living thing;
- organisms differ in size and shape, from a bacterium to a blue whale, but all show the same seven characteristics.

Memory word

MRS GRENMovement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.

Part 2 of 5Movement, reproduction and sensitivity

Movement

Movement living things move their whole bodies or parts of their bodies, and even plants move parts of themselves to face the Sun.

Reproduction

Reproduction all living organisms make more of themselves, which is important so that organisms do not die out.

Sensitivity

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.

Part 3 of 5Growth, respiration, excretion and nutrition

Growth

Growth living organisms get bigger, which often happens as a young organism gets older.

Respiration

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

Excretion living organisms get rid of the waste they produce, such as carbon dioxide or urea.

Nutrition

Nutrition all living things need food, as plants make their own food and animals eat plants or other animals.

Part 4 of 5Respiration, breathing and excretion

Respiration, breathing and excretion

Respiration

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

Breathing moving air in and out of the lungs, which is different from respiration.

Excretion versus egestion

Excretion versus egestion excretion removes waste made by chemical reactions inside cells, while faeces are undigested food removed by egestion.

Part 5 of 5Deciding whether something is alive

Rule

Rule an object is alive only if it shows all seven characteristics, and one feature alone is not enough.

Car

Car it moves and uses fuel, but it cannot grow, reproduce or sense its surroundings by itself, so it is not alive.

Seed

Seed it respires slowly and grows when conditions allow, so it is alive.

Fire

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

Evidence give evidence for each characteristic claimed for a living thing.

Key terms

Term	Meaning
Organism	A living thing.
Stimulus	A change in surroundings that an organism can detect.
Respiration	Chemical reactions in cells that release energy from food.
Excretion	Removal of waste made by chemical reactions in cells.
Nutrition	Taking in materials needed for energy and growth.
Reproduction	Producing more organisms of the same kind.