1 Evolution Change Through Time

2 Evolution explains the diversity of species and predicts changes….. We’ll talk about- ADAPTATIONS Definition of Evolution EVIDENCE for evolution How Life on Earth Began- one theory  TIME FRAME for Evolution

3 ADAPTATIONS Structures, behaviors, or internal processes that enable an organism to better survive in an environment. All organisms are perfectly adapted for their environment.

4 Examples of Adaptations- Dolphins have streamlined bodies built for swimming Powerful tails are for speed Sharp teeth are for capturing fish

5 Examples of Adaptations The Morning Glory flower opens in the morning to keep from being exposed to harsh afternoon sun Tendrils climb upon other plants’ stems so the flower doesn’t have to produce strong stems

6 Examples of Adaptations Insects are small, -can often fly, -have exoskeletons, and developed nervous systems -lay a lot of eggs

7 Examples of adaptations Humans have a large brain to change their environments when needed

8 If the environment changes…… The original adaptation may not be the best for that new environment- Take the Peppered Moth, for example-

9 The Peppered Moth- Lives in England, near the industrial center of Birmingham. There are two forms: the common light- colored moth and the uncommon darker version-

10 The light colored moth- -matched the lichens on the trees around Birmingham for an almost perfect camouflage-

11 BUT, the Industrial Revolution -added pollution to the atmosphere that turned the lichens on the trees dark colored from the soot (carbon) - now the light moths were “easy pickings “ for the birds

12 And the dark colored moths- -suddenly had the better adaptation. They survived and passed their “new best” adaptation to their offspring, changing the look of the population to mostly DARK – colored moths

13 What would happen…. -if the environment changed again? Suppose they cleaned up their smokestacks…. Then what would happen?

14 Remember- The variation was already there in the population-genes do not just “appear” when needed. How did those variations happen? Due to Meiosis, crossing over, sexual reproduction and MUTATIONS-the mechanism of evolution AND the population wouldn’t have changed except that THE ENVIRONMENT CHANGED.

15 If a better-adapted organism appears in the environment- -the competition will probably drive the original organism out. For example, FAST FOXES will catch the rabbits and LIVE LONGER to reproduce more. They’ll pass that “fast” gene on to their offspring. The population of foxes will change this way.

16 This ALSO changes… The RABBIT population. The FASTEST and/or BEST CAMOUFLAGED rabbits will be the ones to live and pass on those genes to their offspring.

17 Definition- Evolution means change. Darwin’s theory of evolution (called Natural Selection) is not a theory that says you came from apes. You came from your Mom and Dad! (Only people who misunderstand Darwin’s theory of natural selection think it says man came from apes.)

18 EVIDENCE Fossils show that life on earth has changed. Dinosaurs once roamed the earth! Biochemical similarities, allowing humans to use pig insulin, show “common ancestry”. Homologous structures, such as a bat’s wing and a human hand, also show common ancestry. Remember the human embryo? It was difficult to tell if it was human or cat at the beginning because mammal embryos develop in similar stages, showing “common ancestry”.

19 And, we all share the DNA code- A-T C-G

20 Current Evidence: Let’s think about ALFALFA, a legume (The plant, not the Little Rascal…) When alfalfa is first planted, plants are of varying heights. After three years of grazing by cows, seeds are gathered from the remaining plants. Those plants are all short! WHY?

21 Why?-COWS, that’s why…… Grazing cows will grab the tallest plants first. They are eaten before they get a chance to reproduce more tall plants

22 SO…… Being the tall plant that gets the sun is good… Unless you are in a different environment where being tall is not so good. This is how populations change.

23 Another thing to remember- Populations change in response to a change in the environment. Change does not occur on an individual organism level.

24 TIME FRAME Remember…the incredible variety and complexity of life on earth has developed over billions of years. It is believed the earth is 4.7 billion years old!

25 TIME FRAME- Two thoughts One-Punctuated Equilibrium-long periods of stability of the earth’s environment and the species that inhabited it, followed by short periods of instability and many new species that eventually decrease in variety followed by long periods of stability again-

26 Two- Gradualism- Slow, very small changes in a species over a long period of time. There are examples that show both of these time frames. The general agreement is that evolution seems to have followed the punctuated equilibrium time frame.

27 NOW YOU KNOW… ………a lot about evolution. We’ll be learning about the parts of Darwin’s theory of natural selection next!