Evidence Supporting Theory of Evolution (pages 126 –

133)Comparative Embryology and Anatomy

Fossil RecordDNA and Chromosomes

Evolution, simply put, is change in form over time.

~ Darwin

Fossil Record

Darwin got the ball rolling with the theory of evolution and how it worked by using his knowledge of the immensity of time, actual fossils in the rocks and how variation existed within populations.

www.pbs.org/wgbh/aso/tryit/evolution/#

Hominid evolution

Comparative Anatomy – Homologous Structures

Structures that, although they may have quite different functions and external form in different animals, are constructed of the same anatomical elements. The forelimbs of vertebrates are a classic example of this phenomenon. The human arm and hand, the fore-limb of a cat, the flipper of a whale, and the wing of a bat are highly divergent in terms of function, yet are built from modified versions of the same basic bones (origin) which suggests these organisms came from a common ancestor.

Comparative Anatomy – Analogous Structures

• Analogous structures are those that have a similar function but a different origin

• They evolved from different ancestors but in similar physical environments

One of the strongest pieces of evidence for evolutionary change provided by the fossil record are vestigial structures; structures found in an organism with little or no known function. Such structures are thought to be remnants of a structure that at one time had a function in an ancestral species. For example, both whales and snakes have vestigial pelvic and leg bones, left over from ancestral species that walked.

Comparative Embryology

• Again, support suggesting common ancestry if embryos all develop the same

Comparative Biochemistry• All cells rely on DNA to

make protein, suggesting that this has been passed down from an ancient common ancestor.

• Using new technologies, biologists are able to determine the amino acid sequences in proteins to determine evolutionary relationships among various species of organisms.

• Biologists have found that the more closely related two species are, the greater the similarity in amino acid sequences of their proteins.

DNADNA molecules are highly

conserved and passed from one generation to the next. Base sequence pattern should indicate evolutionary relationships.

Matches in base sequence between species indicate a high degree of relatedness. For example, in the figure on the left you can see that more matches are made between a human and a chimp than between a human and a chicken.

This indicates that the human and the chimp shared a more recent common ancestor than the human and the chicken and are closely related.