1. The Fossil Record 2. Biogeography 3. Comparative Anatomy 4. Comparative Embryology 5. Molecular Biology

Transcription

1 What Darwin Observed. copy 1. The Fossil Record 2. Biogeography 3. Comparative Anatomy 4. Comparative Embryology 5. Molecular Biology

2 Activity in groups

3 copy Provides a chronological record of organisms present throughout evolutionary history Radiometric Dating is the essential technique; determines age of both rock and fossil remains Fossils were identified as mineralized remains or traces of organisms that are now extinct

4 copy Radioisotopes are atoms with an unstable nuclear arrangement that decays and changes the atom into a different atom Carbon-14 has a half life of 5730 years. This is the time it takes for 50% of C14 to become the daughter isotope N14. The half life for isotopes are constant over time and therefore can be used as naturally occuring clocks. The ability to measure relative amounts of radioactive parent and daughter isotopes in rock provide an accurate and reliable method of determining the age of both rock and fossil remains.

5 Parent Isotope Daughter Isotope Half-life (years) Effective Range (yrs) Carbon 14 Nitrogen yrs 100 to 100, 000 Uranium 235 Lead million 10 million to 4.6 billion Potassium 40 Argon 40 Calcium billion billion

6 A sample of igneous rock contains small amounts of radioactive potassium and argon. Using the ratio of Ar-40 to K-40, it is determined that only 25% of the original parent potassium isotope remains. How old is the rock sample? In 1.3 billion years 50% would be left. 25% is half of that so another 1.3 billion years would have gone by, so the igneous rock formed 2.6 billion years ago.

7 Read pages in grade 12 text Answer #1,2 on pg. 515 Answer #1 7 on pg. 516

8 copy Biogeography studies the distribution of plants and animals worldwide. Darwin discovered fossilized remains of tropical forests in the mountains Fossilized sea specimens also found in the mountains Darwin believed this was evidence that Earth s environment had undergone continuous and dramatic change

9 copy

10 copy Organisms have anatomical similarities when they are closely related because of common descent. Homologous structures are body parts in different organisms with entirely different functions but are similar in structure Vertebrate forelimbs contain the same sets of bones organized in similar ways, despite their dissimilar functions. Organisms with homologous structures likely shared a more recent common ancestor

11 on the other hand copy Are similar in function but not in origin or anatomical structure are inherited from unique ancestors and have come to resemble each other because they serve a similar function. Example: wings of birds and butterflies

12 Homolgous features can also appear in during embryonic development. Ex. During development, all vertebrates have a post-anal tail

13 Vestigial structures serve no useful function in a living organism However, are homologous to fully functioning structures in closely related species Pelvic bones and rudimentary leg bones in some pythons and boas Appendix in humans Rudimentary wings in many flightless insects 2 of the 4 digits in pigs

14 Almost all living organisms use the same basic biochemical molecules, e.g., DNA, ATP, enzymes. Organisms utilize the same DNA triplet code and the same 20 amino acids in their proteins. Similarities could be explained by common ancestor Life s vast diversity has come about by only a slight difference in the same genes

15 After excavating a T.rex fossil in 2003, scientists found it was too big to transport by helicopter They carefully broke the thigh bone in half to ship The results of later tests of the broken bone were surprising. The bone held preserved soft tissues! These tissues included connective tissues, blood vessels and possibly even blood cells

16 In 2007, the fossil of the 68-million-yearold T.rex was tested to see if dinosaurs could share genetic markers with modern animals Two independent tests on the soft tissue indicate the T.rex is likely related to the present-day chicken (similar amino acid sequences) This supports the theory that a common ancestor links bird to dinosaurs

17 Chapter 8 review questions (photocopy)