1. You say you want an Evolution
    
You say you want an Evolution

2. 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…

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

4. 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

5. May have occurred something like this…

6. Evolution
Evidence and Theory
Chapter 15

7. 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.

8. 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

9. 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…

10. 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

11. 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

12. 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

13. 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

15. 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

16. 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

17. 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