Darwin s Conclusions. The Theory of Evolution

Transcription

1 The Theory of Evolution More Evidence for Evolution Notes Pt. 3 Darwin s Conclusions 1. Many traits are heritable 2. Mutations result in variation populations have individuals with many different traits 3. Populations are limited in size. Only organisms that can obtain resources can survive and reproduce 4. Some traits help individuals survive over others. Those traits are passed on. 1

2 Evidence for Evolution 1. An organism can show mimicry (looking like another organism for protection). 2. Some organisms have structural specializations that help the organism evolve (adapt) to its environment. (Anatomical Characteristics) 3. Other camouflage (blend) themselves into their environment. This is also known as cryptic coloration. 4. Embryology is the study of growth & development in embryos 5. Change in DNA or Genes 6. Fossils Some of these adaptations can happen quickly. 1. Mimics Species organisms that are similar and can breed to produce fertile offspring. EX: Homo sapiens, Canis familiaris Model/mimic relationship One species changes over time to look more like the other. Looking like the other species provides the organism with an advantage 2

3 Mimics 2. Anatomical Characteristics Some other biological adaptations / biological evolution are changing species over long periods of time. Examples: a. Homologous Structures b. Analogous Structures c. Vestigial Structures 3

4 A. Homologous Structures These are structures that suggest a common ancestor because they have a similar function AND a similar DNA link. Example: Bird wing & alligator forelimb B. Analogous Structures These are structures that have NO common DNA link, but have similar functions. Example: Butterfly & bird wings. CONVERGENT EVOLUTION: Birds, insects & bats all developed similar structures, but are not closely related. 4

5 C. Vestigial Structures These are structures that show an important link in an organism s past that is not as important now as it once was. They have no current function. Example: Ostrich wings or gill slits, tails & appendix in humans. 3. Cryptic Coloration: The Peppered Moth Cryptic coloration = camouflage What happened to this moth species in England over the last part of the 1800 s (Industrial Revolution)? 5

6 4. Embryology An embryo is the earliest stage of growth & development. Looking at developing embryos can help determine evolutionary links in species. Example: most vertebrates have similar looking embryos 5. Change in DNA or Genes Natural Selection will eventually change the genes of an organism and lead to evolution. These changes in DNA will change what the species looks like or how the species acts for future generations. Evolution = change over time in a SPECIES / POPULATION, not an individual. 6

7 Bacterial Resistance Bacteria are also evolving. This can be very bad for humans. Examples: H1N! (Swine Flu), Super Flu, SARS Bacteria are growing stronger because our current antibiotics aren t working as well. WHY? People are not taking their medicine for the entire time & the bacteria are becoming resistant to it. 7

8 What do you think should be done about antibiotic resistance? 8

9 6. Fossils History In Rocks Scientists think that life has existed for millions of years on earth. One reason they think this is because of the existence of fossils. Fossils are remains or traces of earlier life forms. Paleontologists have found 6 types of fossils in layers of sedimentary rock on the earth. Fossils must be formed quickly and remain undisturbed. Types of Fossils 1. Trace: A footprint, burrow, trail or some other proof that an organism was present, without the actual organism being found 2. Petrified: Water in the cells of an organism has been replaced with minerals and turns to stone 3. Imprint: Stamp or picture of an organism left on a rock or other hard surface 4. Whole Organism: Entire organism is preserved in ice or amber, most commonly 5. Mold: Empty space left behind by a decaying organism 6. Cast: Minerals fill in the mold to leave an exact copy of the organism as it once was 9

10 Trace Fossils Petrified Fossils Preserved Remains Imprint Molds and Casts Age of a Fossil/Rock There have not been fossils found for every existing (or previously existing) organism, so the fossil record is incomplete. In rock, the deeper the rock layer, the older the fossil. (And so fossils found on the surface are more recent). To figure out how old a fossil is, scientists use the amount of carbon in the fossil and radioactive dating or relative dating. 10

11 Fossils tell us that evolution took place very slowly! It took 60 million years for a 3 toed horse to evolve into a modern horse! 11