Origin of Species. Key Questions:. How do existing species give rise to new species? How do species diversify? What does the “family tree” of species look like? Are there any challenges to the idea of evolution?. 1. How do existing species give rise to new species?.
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ADAPTIVE RADIATION = Spreading out of related species into new niches
1. When an environment supports no similar, competing species
Ex. 3mya: A small group of finches migrated from South or Central America. They radiated into different environmental niches and evolved into 14 different species!
2.When EXTENSIVE EXTINCTION wipes out competing species in a set of environments
Ex. 65 mya: Mammals survive Cretaceous/Tertiary (K/T) extinction of dinosaurs
3. When a new group of a related species is adaptively GENERALIZED, it can disperse successfully into different niches, displacing species already there
Ex. 40 mya: Monkeys more generalized than Prosimians b/c larger brains, diurnal, arboreal, mixed diet, so…radiated to the New World, displacing most prosimians in Old World
1. DARWINIAN GRADUALISM: Evolution occurs in slow changes in species over time, so “family tree” of species has few, gracefully diverging branches.
2. PUNCTUATED EQUILIBRIUM: Species tend to remain stable, experiencing “oscillating selection.” Evolution occurs in spurts of relatively rapid change.
A BUSH WITH MANY TWIGS!
Twigs = evolution’s experiments, potential new species
Natural Selection = “Editor” (not author) of Evolution, maintains adaptation of a species to its environment
Ex. Grants’ finches beaks changed back and forth as environmental conditions changed
1. FOSSIL RECORD: Fossils and the order in which they appear in layers of sedimentary rock (strongest evidence)
2. BIOGEOGRAPHY: Geographical distribution of species
3. Presence of TRANSITIONAL fossils
15 bya Universe forms (“Big Bang”)
12 bya Galaxies form
5 bya Solar System forms
4.5 bya EARTH forms
3.8 bya LIFE on Earth (single-celled organisms)
543 mya CAMBRIAN EXPLOSION!
(all major body plans of complex multicellular organisms evolve!)
Opabinia is thought to have lived in the soft sediment on the seabed, although it presumably could have swum after prey using its side lobes. On the bottom, the proboscis could have plunged into sand burrows after worms. Sizes ranged up to 3 inches, plus that unique, amazing 1 inch proboscis!
425 mya Fish evolve, Plants & Animals colonize land
400 mya Insects evolve
350 mya Reptiles evolve
250 mya MASS EXTINCTION (volcanic eruptions in Siberia?, 95% marine & land species extinct!)
256 mya Mammal-like Reptiles evolve
235 mya Dinosaurs evolve
220 mya True Mammals evolve
150 mya Small Dinosaurs w/feathers evolve, ancestors of Birds
100 mya Flowering Plants evolve
65 mya CRETACEOUS/TERTIARY (K/T) EXTINCTION (6 mile asteriod crashes through Earth in the MX Yucatan, dinosaurs extinct!)
55 mya PRIMATES evolve