Simulic
English

Evidence for evolution – anatomy, embryos, fossils and molecules

BiologyEvolutionAges 17–18

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An evidence lab with four stations: colour the homologous bones of the pentadactyl limbs of a human, a bat, a whale and a bird and compare them with analogous insect wings; compare fish, chicken, pig and human embryos at different stages (pharyngeal arches, tail, limb buds) and explore vestigial structures; place dated whale and horse fossils in the right rock layers; and compare amino-acid differences in cytochrome c and haemoglobin, calculate % identity and build a simple tree of relatedness.

Lesson: Evidence for evolution: comparative anatomy, embryology, the fossil record and molecular biology

What it shows

Evolution leaves several independent kinds of evidence. Homologous structures, such as the pentadactyl limbs of humans, bats, whales and birds, share one set of bones inherited from a common ancestor, while analogous wings of birds and insects evolved separately. Vertebrate embryos share pharyngeal arches and a tail, and vestigial structures are reduced remains of ancestral parts. Dated fossils show transitional forms in whales and horses. Protein sequences differ least between close relatives. All drawings are schematic, and the amino-acid counts are illustrative values close to textbook tables.

How to use

Choose a tab. In Anatomy, pick a bone under Colour and tap that bone on each limb, or tick Show answer; switch to Analogous wings to compare. In Embryos, move the Stage of development slider and choose a highlight, or open Vestigial structures. In Fossils, pick a fossil, tap its rock layer and press Check. In Molecules, choose a protein and tap the species from closest to most distant to build the tree.

Parameters you can change

  • Station Anatomy, Embryos and vestigial organs, Fossils, Molecules
  • View (Anatomy) Homologous limbs, Analogous wings
  • Show the bone-colouring answer
  • View (Embryos) Embryos, Vestigial structures
  • Embryo stage (1 = early, 3 = later) 1–3
  • Highlight on the embryos Pharyngeal arches, Tail, Limb buds, No highlight
  • Vestigial structure Whale pelvis, Python spurs, Human coccyx, Kiwi wings
  • Fossil series Whales, Horses
  • Protein Cytochrome c, Haemoglobin (β chain)
  • Show % identity

Questions to explore

  1. Why is a bat wing homologous to a human arm but analogous to an insect wing?
  2. What do pharyngeal arches become in fish, and what do they become in humans?
  3. Why do wheat and yeast have many more cytochrome c differences from humans than a chimpanzee does?

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