Biology · KS3 Y8 · Reproduction & Genetics

Reproduction

ReproductionFree3:01Heddy Score 3 of 7, below the standard
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What you need to know

  • Every new organism made by sexual reproduction starts as one cell formed when two gametes join.
  • Body cells contain 46 chromosomes in pairs; gametes made by meiosis contain only 23, one from each pair.
  • In humans the gametes are sperm and egg cells; at fertilisation they fuse to make a cell with the full 46 chromosomes.
  • Mitosis makes identical cells, as in asexual reproduction, while sexual reproduction mixes genes from two parents and creates variation.

In this clip

Runs 3:01, from 0:09 to 3:10 of the full video.

Heddy Score3/7, Below the standard
See the seven stars
  • Trusted source · passed. The creator's own upload, live and playable here.
  • On the map · not judged yet. A teacher watched it: it mainly teaches this map topic.
  • Spec-true · not judged yet. Accurate, and right for the current UK specification.
  • Focused · passed. One idea, short enough to watch in one go.
  • Accessible · passed. Good captions, clear sound and pictures.
  • Safe for children · not judged yet. Right for 11 to 16 year olds, with no sales pitch.
  • Proven · not judged yet. Earned from our students: they learn from it, find it helpful and watch it to the end.
★ passed · ☆ pending · ✕ failed
Our students

Not enough students yet

Our own students' answers. These are what move ★7 Proven.
On YouTube

765K views · 13.2K likes · Professor Dave Explains 4.49M subscribers

As reported by YouTube on 2026-11-02. Not part of the Heddy Score.
How the Heddy Score works

Why we picked it

A clear explanation of why gametes have half the chromosomes and how fertilisation restores the full set.

Professor Dave Explains on YouTubechecked 2026-10-22

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