Genetics, energy and forces
Clear notes with worked examples, then 4 practice questions with answers. Written by Beyond Tutors tutors for the KS3 National Curriculum.
Dna and genes
DNA is in the chromosomes inside the nucleus. A gene is a section of DNA that codes for a characteristic.
Body cells: 46 chromosomes (23 pairs). Sex cells: 23.
Variation and evolution
Inherited (eye colour) vs environmental (scars, language).
Natural selection: the best-adapted individuals survive, reproduce and pass on their genes.
Energy
Energy (kWh) = power (kW) × time (h)
Efficiency = useful energy out ÷ total energy in (500 J in, 400 J useful → 80%)
Electricity
(power = current × potential difference)
Forces and motion
(force = mass × acceleration)
Density = mass ÷ volume
Waves
Sound: longitudinal. Light and all EM waves: transverse.
EM spectrum: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma
Practice questions
Try each one, then tap to see the answer and why.
- Question 1 · Electricity
What is the power of a device with current 5 A and potential difference 230 V?
- A46 W
- B235 W
- C11.5 W
- D1150 W
Show the answer
D: 1150 W
W.
- Question 2 · Genetics
How many chromosomes are in a normal human body cell?
- A23
- B44
- C46
- D92
Show the answer
C: 46
Body cells have 46 chromosomes (23 pairs); sex cells have 23.
- Question 3 · Variation
Which of these is caused only by genes (inherited)?
- ANatural eye colour
- BA scar
- CLanguage spoken
- DHair length
Show the answer
A: Natural eye colour
Natural eye colour is inherited; the others depend on the environment.
- Question 4 · Evolution
What does 'natural selection' mean?
- AIndividuals best suited to their environment survive and pass on their genes
- BAnimals choose their food
- CHumans breed animals
- DAll organisms survive equally
Show the answer
A: Individuals best suited to their environment survive and pass on their genes
Better-adapted individuals are more likely to survive and reproduce.