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Transcript
Procedures • Get your journals. Find the classmate who has the same number as you. They are your partner for today – sit by them. • Take out your chromebooks and go to Socrative to take the evolution pre-quiz. This is not a grade I want to see what your prior knowledge is. • Go to my Moodle page – Evolution toggle and pull up the “natural selection” PowerPoint. Natural Selection Do bacteria change over time? How do they change? How do they become resistant? Which bacteria will survive and reproduce? So over time, which bacteria will be more abundant? Lammark • Pre-Darwin (early 1800s) • Believed organisms evolved through inheritance of acquired characteristics. • However you modify your body during your life will be passed onto your offspring. Lammark continued • Example1:Giraffes stretched out their necks to reach leaves on tree tops, and the stretched neck was passed on. • Example 2: A father that pumped iron will produce a body builder baby. Darwin and Wallace Darwin wrote a paper on his thoughts of evolution in 1842, but fear of rejection caused him not to publish it. In 1856 Darwin received a draft of a paper written by Wallace with some of his same ideas. OH NO! I BETTER TURN IN MY PAPER NOW! So in 1858 Darwin and Wallace submitted separate papers to the Linnaean Society in London. • In 1859 Darwin published his book “On the Origin of Species” * This is when we really started to study and understand evolution! Darwin’s 4 Postulates 1. Individuals in a population differ from one another. (Diversity) Darwin’s 4 Postulates 2. Some differences are due to characteristics that are passed down from parent to child. (Inherited variation) Darwin’s 4 Postulates 3. More offspring are produced than can survive, so some will survive and reproduce and others will not. Darwin’s 4 Postulates 4. Survival and reproduction depend on advantageous traits. Those with traits that give them an advantage will survive and have more offspring than those that do not have advantageous traits. Natural Selection • Natural Selection explains the changes in populations over time. • Natural Selection is also known as descent with modification because each species has descended with changes from other species over time. Natural Selection • Natural Selection is also known as “survival of the fittest” meaning that the most fit organism in the environment will survive . • Fitness refers to an organisms ability to survive and reproduce. • Remember adaptations are characteristics that give organisms an advantage in their environments. Remember that natural selection selects for the best in context of a particular environment. Giraffe’s long necks are good for eating leaves up high! Giraffe’s long necks are bad for drinking because it causes them to be vulnerable to predators. http://www.sciencenetlinks.com/interactives/evolution.html Remember that Natural Selection changes the population not individuals. • Individuals do not change when selected, they produce more offspring than others. • Thus their alleles become more frequent. GREEN BEETLES- GG ORANGE BEETLES- gg Which alleles are more frequent? GG or gg How many green beetles? 10 How many orange beetles? 6 Which alleles are more frequent? GG or gg Now, which alleles are more frequent? GG or gg Which genotype would have an advantage in any environment? GG Gg or gg Evidence of Natural Selection • Do you believe in artificial selection? • Humans pick 2 dogs with desirable traits and breed them. •Why not believe in natural selection? •Nature picks 2 organisms with desirable traits and allows them to successfully reproduce. More evidence :Experiment • Anolis Sagrei Lizards were removed from their home plentiful with trees. • They were released onto 14 small islands that had few trees. • Researchers returned 14 years later to discover that the lizards had evolved shorter, thinner legs. Selection can lead to 3 patterns of evolution Directional Selection Stabilizing Selection • Selects extreme •Favors average value value •Example: Small •Example: Longer lizards can’t defend nose of anteater is territory and large selected for. lizards are easily eaten, so average size lizards are selected for. Disruptive Selection •Favors both extremes •Example: Light clams and dark clams survive better in light and dark sand. The yellow can’t blend in. Humans can cause evolutionary events. 1. Our liberal use of pesticides has led to resistant pests. So we are having trouble protecting our food supply. 2. Our overmedication has led to resistant “super-germs”. So diseases are becoming more difficult to treat. 3. Our heavy fishing has led to smaller fish that slip through nets. So we not able to extract as much food from the sea.