BLOG

Mitosis makes two cells with identical sets of chromosomes. Follow the six stages in order in an interactive playground, and see why the lining-up step is what makes it accurate.

If a sperm and an egg each carried a full set of chromosomes, every generation would have twice as many as the last. Reason to meiosis step by step in an interactive playground.

Asexual reproduction is not one process. Sort binary fission, budding, spores and vegetative propagation by how the new organism actually gets started, in an interactive playground.

Sexual reproduction is slow, expensive and needs a partner. Trace what happens when one disease meets a clone population and a varied one, in an interactive playground, and see what the cost buys.

You carry two copies of every gene, one from each parent, at the same place on a matching pair of chromosomes. Label the pair in an interactive playground and the word allele stops being abstract.

Dominant and recessive are usually just defined. Reason instead from what a gene does — build a protein — to why one version hides the other, in an interactive playground.

Given what two parents carry, a Punnett square predicts what their offspring can be and in what proportions. Follow the six steps in order in an interactive playground, and see why the answer is a probability.

Dominant describes what shows in one individual. Common describes how many individuals carry it. Follow both questions from the same allele in an interactive playground and see why neither answer predicts the other.

Some differences are written in the genes, some come entirely from how someone lived, and most are both. Sort four of them in an interactive playground and see why running in a family proves nothing.

A shape has rotational symmetry when turning it about its centre lands it back on itself before a full turn is done. The order counts how many times that happens. Find the order of six shapes in an interactive playground.

Reflecting a shape means sending every corner the same distance to the other side of a mirror line, along a path at right angles to it. Place all four corners of a quadrilateral in an interactive playground.

A translation slides every point of a shape by the same amount across and the same amount up. Nothing turns and nothing flips. Work out where a marked corner lands under four different slides in an interactive playground.

A rotation turns a shape about a fixed centre. Change the centre and the same angle sends the shape somewhere completely different. Match four turns to the pictures they produced in an interactive playground.

A net is a solid opened out flat, so every face lies in one plane. Counting the faces and checking their shapes identifies the solid. Match four nets to the solids they fold into in an interactive playground.

A cuboid has six faces in three matching pairs, so its surface area is the three different face areas added and doubled. Work out four surface areas in an interactive playground.

Volume counts how many unit cubes fit inside a solid. For a cuboid it is one layer of cubes multiplied by the number of layers, which is length times width times height. Practise on four boxes in an interactive playground.

A prism has the same cross-section along its whole length, so its volume is the area of that cross-section times the length — whatever shape the cross-section is. Practise on four prisms in an interactive playground.

An enlargement multiplies every distance from a fixed centre by the same scale factor, so the shape changes size but not proportions. Place four enlarged points in an interactive playground.

A cylinder unrolls into a rectangle and two circles, so its surface area is 2πrh for the curved part plus 2πr² for the ends. Work out four of them in an interactive playground.

A protractor has two scales running opposite ways, and picking the wrong one is the mistake everybody makes. Match four angles to the rays that make them in an interactive playground.