Tracing Evolutionary History Chapter 15

Earth History & Macroevolution

1. Macroevolution

 The fossil record which is stored in layers of rock chronicles evolutionary history  Macroevolution- the major changes in the history of life on Earth.  Studying fossils in rock strata allows biologist to trace macroevolution

2. Geologic Time Scale

 Geologic Time Scale- A table that gives an overview of macroevolution measured in millions of years (mya)  Divided into four major groups called Eras: 1.Precambrian 2.Paleozoic 3.Mesozoic 4.Cenozoic

 Each era ends w/ a mass extinction  Mass extinction- many forms of life disappeared from the fossil record & were replaced w/ species that diversified from the survivors

 Radiometric Dating- technique used to measure the actual age of rocks by measuring the radioactive isotopes  The isotopes of elements build up in the organism when they are alive  Ex:

 Ex: living organisms have a lot of Carbon - 12 & small amounts of Carbon- 14 ; that it absorbs from the atmosphere. When an organism dies the Carbon stops building up & the C 14 slowly decays to a different element.

Radiometric Dating

 Half-life- the time it takes an element that is decaying to decrease by half  Carbon-14 has a half-life of 5,730 years.  It takes 5,730 years for half of a sample of C-14 to decay & turn into another element

The table below shows the reduction of a quantity in terms of the number of half-lives elapsed. Number of half-lives elapsed Fraction remaining Percentage remaining 0 1/11/ /21/ /41/ /81/ / / / / n1/(2 n )100/(2 n )

3. Continental Drift

 Earth was on large land mass called Pangaea  Tectonic plates are drifting apart 2cm/yr.  North America & Europe are moving farther apart. Lungfish distribution, a result of continental drift

4. Mass Extinctions An artist's rendering of the asteroid impact that took place 65 million years ago and likely killed off nearly every large vertebrate species on the planet, including, many think, the dinosaurs. (Credit: Don Davis/NASA)

99% of all of the species on earth are now extinct

 There have been six periods of mass extinction  Key adaptations allowed some species to survive and proliferate & evolve while others died out  Exaptation- a structure that evolved in one situation & later adapted to a different function. A pineapple plant, a bromeliad adapted to arid (dry) soils. The bottom of the leaves form a catch-basin to collect rainwater & the plants roots absorb water from the catch basin

6. Phylogeny A phylogenic tree for Galapagos finches

 Phylogeny- the evolutionary history of an organism  Phylogenic trees- a diagram that traces evolutionary relationships. A phylogenic tree for dogs

7. Classification

Classifucat

Classification of the Brown Bear