BIOL1003 Lecture Notes - Lecture 6: Ancient Dna, Archaeopteryx, Selective Breeding
BIOL1003: Module 1 Evolution
Lecture 6 – Fossils, Natural Selection
Fossils
• Any preserved trace of a living organism in rock
• Subfossils - too recent to have fossilised, like ancient DNA, mummified moas
• Phylogenies: branch lengths mean time or amount of change
• Cladogram: branch lengths are irrelevant (show clades)
• Clade = evolutionary group, groups that are each other's closest ancestors
o Note: great apes not a clade
• If we include fossils, we can get far more detailed cladogram - to show how changes occur
between clades
• These are always an approximation
• Gradual origin of mammals from "mammal like reptiles" or synapsid "reptiles"
• Not: reptiles are not a natural phytogenic group - they are not a clade
• Archaeopteryx:
o Like a bird, it has feathers and wings, but unlike a bird it has teeth, no bill, long bony tail,
fingers with claws
o This was found a few years after the Origin of Species
o This is a dino-bird transitional fossils
o There are quite a few more now
o Even bird like behaviour can be seen in the fossil record
• Same process with whales - with a common ancestor to cows and other hooved animals
o Closest relive is the hippo
• In Darwin's da, there were only a few isolated fossils suggested how major transitions
happened were available
• In the last 30-49 years, the number of fossils illustrated major transitions has skyrocketed
• Cladograms are how we interoperate fossils now
Decent with modification - Natural Selection
• Natural selection - mechanism for change
• Unity of type is explained by unity of decent
• There might be macroevolution within a species when you employ artificial selection - ie. Dogs
• Darwin's premises:
a. Variation among individuals in some attribute and trait
b. A consistent difference between that trait and some measure of reproductive success r
survivorship, such as fecundity or juvenile survival (fitness difference)
c. Inheritance or a consent relationship, for that trait, between parents and their offspring
which is at least party independent or common environmental affects
o THEN…
o BBKSC
• Can natural selection explain very complex adaptations?
o The famous example was the eye
o William Paley's "argument from design": Natural Theology
o Octopus eye just as complex as human eyes
o Some are just light sensitive spots
o When you look at a continuum, not so difficult to believe that complex eyes may have
evolved
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