Classification, body systems, nutrition, life cycles, adaptation & disease.
All living things can be sorted into groups by shared features, and share many of the same life processes. This workbook takes you from classifying animals to how the human body works.
Scientists use classification to organise the huge variety of life on Earth. The five main vertebrate groups are:
Cold-blooded (ectothermic) animals rely on their environment to control body temperature. Warm-blooded (endothermic) animals generate their own heat internally.
Food is broken down as it travels through the mouth → oesophagus → stomach → small intestine → large intestine, so nutrients can be absorbed into the blood. Enzymes speed up this breakdown at each stage.
The heart pumps blood through blood vessels. Blood carries oxygen and nutrients to cells and takes away waste like carbon dioxide. An adult heart beats roughly 60–100 times a minute at rest.
Breathing draws air into the lungs, where oxygen passes into the blood and carbon dioxide passes out — gas exchange. This happens across millions of tiny air sacs called alveoli.
The skeleton supports the body, protects organs, and works with muscles to move. Muscles work in pairs — as one contracts, the opposite one relaxes — to move a joint.
The brain and spinal cord (the central nervous system) send and receive signals through nerves, controlling everything from thought to reflex actions.
A balanced diet needs the right mix of:
Herbivores eat only plants (longer guts for tough fibre). Carnivores eat only animals (shorter guts, sharp teeth). Omnivores eat both — humans are omnivores.
Living things reproduce to pass on their genes. Mammals (including humans) reproduce sexually, with offspring developing inside the mother. Most fish, amphibians and insects lay eggs outside the body.
A butterfly goes through complete metamorphosis (egg → caterpillar → chrysalis → adult). A frog (egg → tadpole → adult) has incomplete metamorphosis — no fully inactive pupal stage.
Over many generations, animals develop features that help them survive their environment — adaptation, through natural selection.
Pathogens — bacteria, viruses and fungi — cause disease by invading the body and disrupting normal function. The immune system defends against them using white blood cells, which recognise and destroy invaders.
Vaccination trains the immune system to recognise a specific pathogen before a real infection, giving faster, stronger protection if exposure happens later.