Evidence that Evolution has occurred
FOSSILS -- Palaeontology
Leonardo daVinci at end of the 15th C found sea shells in Tucson Mountains Nicholas Steno 1669 – discovered and collected mineralized organisms
Types of fossils
--Permineralized fossil – cells are replaced by minerals when trapped in sediment layers -> organism becomes “made of stone” dinosaurs, petrified trees, fish, flesh parts may or may not be visible; need ideal wet conditions
--Intact organisms -> tar pits, ash, peat, permafrost, amber
--Microscope fossils of insect parts, algae (diatoms), pollen
--Fossilized Tracks, holes, footprints
The age of the fossil is determined by which layer of rock it is found in (based on sedimentation rate).
Age of the Earth – determined by radioactive decay is 4.54 billion years Age of the moon is 4.53 b, age of Canadian Shield is 3.9 b
Radiometric dating – based on the decay and half-life of elements over time
14C (carbon 14) is good for 100 to 10000 years ago
235U (uranium 235) is good for 10 million to 4.6 billion years ago
40K (potassium 40) is good for 100,000 to 4.6 billion years
--The distribution and age of the fossils helped Darwin and many other naturalists to examine the evolution of organism.
--transitional forms (like the archaeopteryx...part dinosaur, part bird)
COMPARATIVE EMBRYOLOGY
The relationship of organisms is clear to see by looking at the development of vertebrate embryos and foetuses. They pass through similar stages as if remembering past characteristics. Most embryos are hard to tell apart at some point in their development.
Humans, pigs, chickens, frog, fish all have gill circulation at some point before birth. Humans have a long tail
Comparative Morphology
Homologous Structures à have a common ancestor but a different function
è Example: Flipper, arm bones, bird’s wing have similar patterns of bones because they are from a common ancestor
è AKA morphological divergence
Analogous Structures à have a similar structure because of a similar function but does not have a recent common ancestor
è Example: sharks and dolphins have similar bodies
è Wings of insects, birds, bats, pterodactyls
è AKA morphological convergence
Vestigial Structures à a body part or organ that has no function or is rudimentary but resembles functional structures in other organisms
è Must have inherited part from past ancestor
Examples:-- humans have an appendix in digestive tract
Hips and legs in boa (snakes)
Legs in whales
Parallel Adaptation
Animals and plants in similar climates but far apart have evolved to be similar in forms. Marsupials (pouched mammals) in Australia separated from the main continent many million years ago but developed very similar forms as placental animals.
Distribution
àPlants, animals, and fossils show patterns of distribution. It may depend on how far apart they are, when the land mass separated from the original single continent of Pangaea, or any land connections animals could migrate over.
àIsolated islands have more unique species (Australia had no placental mammals except bats, Hawaii had no land mammals at all).
àDarwin and other biogeographers noticed that islands had species that were similar to those found on the mainland and on other nearby islands but not always identical.
Examples: -- each island in the Galapagos group had a slightly different species of giant tortoise, different iguana lizards, and birds (finches).
-- Marsupial mammals are all originally found in Australia and South America both in the southern hemisphere
-- Large flightless birds are only found in the southern hemisphere
(ostrich in Africa, moa and emu in New Zealand, rhea in South America)
-- polar bears are found in the Arctic; penguins are found in the Antarctic
Comparative Biochemistry / Molecular Biology
The modern biochemical and genetic information fully supports the evolutionary evidence that Darwin used .
àAll living organisms use the same biochemical molecules - ATP, enzymes, metabolic pathways. In addition, the genetic "triplet" code is universal
àEvolutionary trees (or "phylogenetic trees") based on biochemical data are very similar to these based on anatomical data.
àbiological clock compares the genetic code between close species. Genes will mutate at a set rate so the more related two things are, the few mutations (difference) are found in the genetic code and the more identical the DNA will be.
DNA Helix
Phylogenetic tree for bears
Darwin’s First idea about Phylogenetic Tree for major life forms
“Tree of Life”
Artificial Selection
Humans have been artificially selecting for certain traits in our agricultural crops even since we decided to sow and take care of plants. We would chose the healthiest looking, most easily grown plants and continue to do this each time a new crop was harvested for seeds and then re-planted.
Dogs, horses, cow, and other animals have been highly selected for in order that they become good work, food, and transportation animals.
Types of dogs
Types of Horses
Domestication of Corn (in South America)