Biology

The big ideas of biology

Biology is the study of living things, and a few big ideas run through all of it. Every living thing is made of cells, the basic building blocks of life; plant cells and animal cells share some parts but differ in others. Cells are organised into tissues, organs and organ systems that keep an organism alive, from the heart pumping blood to the lungs taking in oxygen. Living things need nutrition, a balanced supply of the right nutrients, and they live together in ecosystems where energy passes along food chains that begin with the Sun. Finally, the instructions for each living thing are carried in its genes, which is why offspring resemble their parents yet also show variation. This module tours cells, body systems, nutrition, ecosystems, and genetics and variation.

Biology words

Learn what each of these means before you use it.

Plant cell against animal cell

Both are cells, but a plant cell has three parts that an animal cell does not.

How life is organised

Biology makes sense when you see that living things are built up in levels. The smallest working unit is the cell. Similar cells group into a tissue, different tissues build an organ, and organs that work together form an organ system, such as the digestive system. All the systems together make the whole organism. When you meet any body part, place it on this ladder and ask what larger structure it belongs to. Thinking in these levels links a tiny detail to the whole living thing and keeps an answer organised.

Match the organ to its job

Which kind of cell?

A cell has a cell wall, chloroplasts and a large permanent vacuole. What kind of cell must it be?

• a plant cell, because only plant cells have all three of these
• an animal cell, because animal cells have chloroplasts
• neither, because no cell has a cell wall
• a bacterium, because bacteria have chloroplasts

Processes of life

Select the TWO processes that all living organisms carry out.

• Respiration, releasing energy from food
• Reproduction, producing new organisms
• Photosynthesis, which every organism does
• Refrigeration, to store food

Counting chromosomes

A human body cell contains 23 pairs of chromosomes. Multiply to find the total number of chromosomes in the cell.

Order the levels of organisation

Put these levels of organisation in order, from the smallest to the largest.

• a cell
• a tissue
• an organ
• an organ system

Complete the biology facts

The basic building block that all living things are made of is the _____. A body part such as the heart, made of different tissues, is an _____. The section of DNA that carries the instructions for a feature is a _____. All the living things in an area together with their environment make up an _____.

Match the process to its meaning

Spot the true biology facts

Tap the TWO statements that are true.

• Plant cells have a cell wall but animal cells do not
• Respiration releases energy from food in every living cell
• The heart takes in oxygen and removes carbon dioxide
• Humans have only one chromosome in each body cell

Think like a biologist

Read each case and choose the best response, with a reason.

• You look at a cell under a microscope and see a cell wall and chloroplasts. What type of cell is it?
• You want to place the stomach on the levels of organisation. Which level is it?
• In a food chain, grass is eaten by a rabbit which is eaten by a fox. Where does the energy in the chain come from originally?

Explain the big ideas of biology

A friend is starting GCSE Science and asks what biology is really about. Explain the main ideas of biology.

• Explain what a cell is and one difference between plant and animal cells
• Explain the levels of organisation from a cell to an organism
• Name two organs and what each one does
• Explain the difference between photosynthesis and respiration
• Finish by explaining what a food chain shows in an ecosystem