You say you want an Evolution      You say you want an Evolution

Last Time We looked at DNA A very important biomolecule which, through all of its many processes and functions, makes us… Us! But what happens when our DNA “decides” it is time for a change…

Which Brings us to Today! EVOLUTION Fossil evidence Early evolutionary theorists

BRAIN TAP What do you know already know about Evolution? 3m Write down everything you can regarding Evolution 1m share out answers with your partner

May have occurred something like this… https://www.youtube.com/watch?v=faRlFsYmkeY

Evolution Evidence and Theory Chapter 15

Evolution AKA Descent with modification Is the change in heritable phenotype traits of biological populations over successive generations. In other words… Change in our physical traits, passed on from our ancestors over time.

But where is the Evidence? Nowadays, thanks to molecular sequencing of our genetic code, we are able to see the similarity of our genes to our ancestors Recall: near universal genetic code for all organisms We are able to see similar gene sequences between humans and any other organism on the planet

But where WAS the evidence? OK, so genetic sequencing has not always been around Evidence for evolution was right under our feet, in the FOSSILS, buried deep beneath the ground…

FOSSILS A fossil is a trace of a long-dead organism, often found in layers of sedimentary rock. Sedimentary fossils usually develop around the hard body parts of an organism (bones, teeth, trunks/stems of plants)  Eventually hard minerals replace the tissue of the organism

FOSSILS Different Types Mold- Imprint in the rock, taking the shape of an organism Cast- A mold, that is filled with hard minerals Amber- fossilized sap of trees, sometimes containing preserved life inside Trace Fossil- tracks, scratches, fecal matter

So how does this tie in with evolution? Well first, let’s take a look back at those sedimentary rocks Steno (17th Century) made an important contribution to both the geological and biological history of Earth… The Law of Superposition States that successive layers of rock or soil, were deposited on top of one another by wind or water

Sooooooo… This scientific law then meant that fossils within a single stratum (layer) are the same approximate age Fossils above that strata are younger, fossils below are older This was used to establish a fossils RELATIVE AGE The fossils ABSOLUTE AGE (its age in years) could be estimated by radiological evidence E.g. Carbon Dating

Succession of Forms (See Table 15-1) Fossil-bearing strata have shown that organisms appeared, existed for x number of years then disappear Extinction Several mass extinctions… who can name a famous one? Mass extinctions were the result of mass changes in the environment In turn, new species continue to arise  same areas where similar, older forms exist

Biogeography Study of the geographical distribution of living organisms Comparison of recently formed fossil types of living organisms in the same areas where similar forms already lived See Figure 15.2

So given what we’ve discussed… In your Journal Tell me how the principles of fossils we have discussed today may have lead early scientists to the theory of evolution. Recall: Descent with modification Look at Table 15-1: Note some of the important timelines in both geological and biological history of Earth Note all the mass extinctions, and what arose after them. Section 15-1 Review