Good Learning Co.
SavannahYear 8
← Science
ScienceGCSE biology: inheritance, variation and ecology30 min★★★ difficulty

Inheritance, variation and evolution

Genetics explains why offspring resemble their parents without being identical, and evolution explains how that variation reshapes species over time.

Lesson overview

What you'll learn in this lesson

Explain inheritance, variation, evolution and ecological relationships at GCSE standard.

Key learning points

  • • DNA, genes and meiosis
  • • Genetic crosses
  • • Evolution by natural selection

This lesson at a glance

  • 30 minutes
  • 16 parts to scroll through
  • 4 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

inheritancevariationevolutionecologicalrelationships

Scroll down — the lesson carries on below

Part 1 of 16 · Discover6%
1

Watch & discover

Part 1 of 16

Watch first

Inheritance, variation and evolution

An English teaching video on this topic from LearnScienceWithB. Watch it, then scroll down for the lesson.

In a nutshell

Explain inheritance, variation, evolution and ecological relationships at GCSE standard.

2

Learning cycle

Part 2 of 16

Learning cycle 1 of 2

Part 1 · DNA, genes and meiosis

A short piece of teaching, then a check to make sure it has landed.

3

Explore the idea

Part 3 of 16

Learn

DNA, genes and meiosis

DNA is a double helix carrying genes that code for proteins; the full set is the genome. Meiosis produces four genetically different gametes with half the chromosome number, so fertilisation restores the full set while creating variation. Mitosis, by contrast, produces identical cells for growth and repair.

4

Explore the idea

Part 4 of 16

Learn

Genetic crosses

Alleles may be dominant or recessive; genotype is the alleles present and phenotype the characteristic shown. A Punnett square predicts proportions, not guarantees: a 3 : 1 ratio is a probability for each offspring. Inherited disorders such as cystic fibrosis and polydactyly are standard examples.

5

Quick check

Part 5 of 16

Quick check

Meiosis produces

6

Quick check

Part 6 of 16

Quick check

Genotype refers to

7

Reset break

Part 7 of 16

Pause

That's sitting 1 of 2 done

Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.

Stop here for now
8

Learning cycle

Part 8 of 16

Learning cycle 2 of 2

Part 2 · Evolution by natural selection

A short piece of teaching, then a check to make sure it has landed.

9

Explore the idea

Part 9 of 16

Learn

Evolution by natural selection

Variation exists within a population; individuals with advantageous characteristics are more likely to survive, reproduce and pass on those alleles, so over many generations the population changes. Evidence comes from fossils and from observed antibiotic resistance in bacteria. Selective breeding and genetic engineering apply the same principles deliberately.

10

Quick check

Part 10 of 16

Quick check

Antibiotic resistance spreads because resistant bacteria

11

Quick check

Part 11 of 16

Quick check

A cross of Aa × Aa gives affected offspring with probability

12

Explore the idea

Part 12 of 16

Worked example

Worked answer: two carriers of a recessive disorder have a child. Give the probability it is affected (3 marks)

Both parents are heterozygous, Aa (1). A Punnett square of Aa × Aa gives AA, Aa, Aa and aa (1). Only aa shows the disorder, so the probability is 1 in 4, or 25% (1). Note this is a probability for each child independently, not a guarantee that one in every four children will be affected.

13

Challenge round

Part 13 of 16

Game · Sort it

Which of these are true?

Drag each card into the right column. Tap a card first if dragging is fiddly.

True

Not true

14

Challenge round

Part 14 of 16

Game · Fill the gaps

Finish the sentences

Choose the word that belongs in each gap.

Meiosis produces four genetically different gametes with half the chromosome number, so fertilisation restores the full set while creating ____.

15

Mastery quiz

Part 15 of 16

Marked quiz

End of lesson quiz: Inheritance, variation and evolution

4 questions, marked with the reasoning shown. No timer.

  1. 1. Meiosis produces

  2. 2. Genotype refers to

  3. 3. Antibiotic resistance spreads because resistant bacteria

  4. 4. A cross of Aa × Aa gives affected offspring with probability

16

Lesson round-up

Part 16 of 16

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

Not played

Points this lesson

0

Best run

0 in a row

Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?

Ask Luna

Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Case study

Why the school greenhouse failed

A science club grew tomato plants in the school greenhouse. In June the plants grew well: leaves were dark green and the fruit set quickly. In July the club went away for two weeks and left the greenhouse door shut. When they came back, the leaves were curled and pale and most of the fruit had dropped.

The club had a data logger inside. It showed the temperature reached 46 °C on several afternoons and the soil moisture fell close to zero. The club knew photosynthesis needs light, water and carbon dioxide, and that enzymes in a plant work best in a narrow range of temperature. Above that range the enzymes stop working properly.

The club repeated the summer with the door propped open and a water bottle drip on each pot. Temperature peaked at 31 °C and the plants survived.

Written for Good Learning Co.

Reading questions

  1. Name the variable the club changed the second time, and one variable they kept the same.
  2. Explain, using the words photosynthesis and enzymes, why the plants were damaged in July.
  3. Write a conclusion for the club's report, saying how far the evidence supports it.

  • Method and results

    Writing

    Write the aim, what you changed, what you measured and what you kept the same, then record your results in a table.

    1 page + results table

  • Conclusion

    Writing

    Explain what your results show and why, using the scientific words from the lesson. Say how you know you can trust them.

    6–8 sentences

  • Labelled diagram

    Diagram

    Draw the apparatus or the process in pencil, label it fully, and photograph it.

    1 labelled diagram

  • Reading and notes

    Reading

    Read the lesson text again and write the key ideas in your own words.

    Half a page of notes

Saved as you type.

Part 1 of 16 · Watch & discover

Good Learning Co. — personalised UK curriculum learning, built around what each learner loves.