http://www.johnkyrk.com/evolution.html

Palaeontology

• Life has existed for more than 500 million years

• Very different than today

• None of the top predators we have around today were around at the time of the dinosaurs

Fossils as evidence for evolution

• First organisms were simple in structure (matches the expected sequence)

• Life forms have increased in size and complexity

• Life forms are constantly changing• Evolutionary dead ends• Punctuated equilibrium vs gradualism

Palaeontology

many living organisms today have no identical form in the fossil record (Apart from organisms such as certain types of sharks, cockroaches or ferns)

Evidence of Evolution

• Sequence also fits with ecology of the groups – plants before animals, land plants before land animals, plants suitable for insect pollination before insects

• Many known sequences that link together existing organisms with their ancestors (Equus)

Evidence of Evolution: Fossil Record

• Strong evidence that evolution HAS occurred• Does not reveal mechanism for evolution

CLADOGRAM ACTIVITY

Adaptive Radiation

Textbook definition:

• Emergence of numerous species from a common ancestor into an environment that presents a diversity of new opportunities and challenges

Is this divergent or convergent evolution????

Homologous

• Similar due to inheritance• Modified structure seen among different

groups of descendants

Homologous Structures: Tetrapod Limb

• They are all built from many individual bones. • They are all spin-offs of the same basic bone

layout: one long bone attached to two other long bones.

Pentadactyl limbs

The difference?

• Homologous: look superficially different, serve different purposes but structures are anatomically similar b/c of shared ancestry…not necessarily used the same way…variations on a structural theme…divergent evolution!)

Homology: Evidence for Evolution

• http://evolution.berkeley.edu/evolibrary/article/similarity_hs_01

Analogous:

• serve the same function, but not constructed similarly, no common ancestry (an example of convergent evolution)

For these four critters, identify and explain whether the structures are homologous, analogous, or neither.

Importance of homology to evolution

• Similar construction = evidence that organisms in question have a common ancestor…”unity of plan”

• Linked to embryological development as well…• Don’t prove anything – but difficult to explain

without evolution• Presence of vestigial structures also linked –

traces of an organism’s evolutionary history

• Differing sizes and variations in morphology• Basic shape and position of the limb bones =

same• Suggests common ancestry

• **Not just limited to structures – also applies to DNA!!! (molecular homologies)

• http://www.pbs.org/wgbh/evolution/educators/teachstuds/unit3.html

Vestigial Structures

Florida Sand Skink

Vestigial Structures

• A structure of little or no importance to an organism

• Historical remnants of structures that had important functions in ancestors.

• Evolution MODIFIES existing structures. Anatomical remodeling…

Embryological Development

• Compare early stages of development• Reveals other homologies not seen in adult

forms• Example: vertebrate tails• Example: vertebrate pharyngeal pouches

Molecular Homologies

• All forms of life use the same genetic machinery of DNA and RNA

• Genetic code is universal• Organisms share many genes• Many of the gene products (proteins) are the

same too Analysis of DNA and proteins: as number of

similarities increases, do does the degree of relatedness.

ACTIVITY

Human, Chimpanzee, and Gorillas…who is more closely related?