| The chromosomes of humans and the great apes are very similar. here in chromosome 4 the human chromosome differs from that of the chimpanzee by an inversion. | |
Life is constructed on a similar plan. A classic example is the verterbrate forelimb. We need to explain why the body plan has been used in creatures with very different ecologies.
Campbell: see page 424, fig. 22.9
A vestigial organ is a structure that appears to have lost its functionality. If organisms were created "de novo," why do they retain these vestiges?
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| The eye bulbs of blind, cave-dwelling creatures, such as the grotto salamander (Typhlotriton spelaeus). |
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| The anthers and pollen of asexual dandelions | |
A good example of a vestigial organ is the presence of hind limbs in whales (Campbell: see page 423, fig. 22.8)
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| Vestigial hind limbs in adult whale | Hind limb bud in whale embryo (source) |
Embryology provides evidence for similarities betwen organisms that might not be so apparent in the adults. Human embryos show close similarity to embryos of other vertebrates (Campbell: see page 424, fig. 22.10)
Molecular biology and genetics is providing evidence of close similarities between the development of organisms at the genetic and molecular level
