The Theory Evolution via natural selection How did different organisms arise? How are they related?

Voyage of the Beagle 1831, ship sets sail for a voyage around the world 1831, ship sets sail for a voyage around the world Aboard is Charles Darwin, a 21 yr old college graduate, serving as ships’ naturalist (unpaid) Aboard is Charles Darwin, a 21 yr old college graduate, serving as ships’ naturalist (unpaid) Observations and evidence collected on this voyage changed biology forever. Observations and evidence collected on this voyage changed biology forever.

The voyage of the HMS Beagle

Darwin’s observations Fossils: he finds evidence of extinct animals Fossils: he finds evidence of extinct animals Diversity: animals and plants vary widely in similar habitats Diversity: animals and plants vary widely in similar habitats Why are some species widely found, others live only in one place? Why are some species widely found, others live only in one place? Giant sloth claw Land and marine iguanas

Ideas that shaped Darwin’s thinking Lyell: Geology shows evidence of an ancient earth with geologic processes happening over extended periods of time Lyell: Geology shows evidence of an ancient earth with geologic processes happening over extended periods of time Lamarck: traits of a parent can be passed on to the offspring Lamarck: traits of a parent can be passed on to the offspring Malthus: population size is determined by limiting factors: food, living space Malthus: population size is determined by limiting factors: food, living space

Publication of “On the Origin of the Species” In 1859 Darwin proposes a mechanism to explain the complexity of life In 1859 Darwin proposes a mechanism to explain the complexity of life Theory: evolution has been going on for billions of years, and continues today. Theory: evolution has been going on for billions of years, and continues today.

Evolutionary theory Inherited variation: all species have individuals that are slightly different from each other Inherited variation: all species have individuals that are slightly different from each other Over reproduction: species produce excess offspring Over reproduction: species produce excess offspring Struggle for existence: there is competition to survive Struggle for existence: there is competition to survive Natural selection: the weak will die off Natural selection: the weak will die off Survival of the fittest: the members best adapted to their environment will live to reproduce, and their traits will be passed on to their offspring Survival of the fittest: the members best adapted to their environment will live to reproduce, and their traits will be passed on to their offspring

How Does Natural Selection Work? Survival of the fittest? Survival of the fittest? What is fitness? What is fitness? Being: big? fast? Strong? beautiful? Being: big? fast? Strong? beautiful? Blue Whale Cheetah Rhinoceros beetle

Then why do small, slow, weak, and ugly animals exist? Because fitness is simply the ability to live long enough to pass on as many genes as possible. A variety of qualities can be adaptive (fit) depending upon an organism’s environment. That environment includes other living things, including members of the same species.

Are these insects easy to see? If you were a bird would you try to eat one of these insects? Why? What’s for Dinner?

How do obvious, yet harmless insects survive? Robber fly Bumblebee Flower fly Conopid fly Honey fly Wasp Harmless mimics need unpleasant models. I’ll have a taste

The models must out number the mimics so the negative reinforcement is more common than the reward. Better not take the chance Do the math

The signal must be consistent Looks like trouble

Crazy, beautiful birds Have you ever wondered why there are so many colorful birds and why they sing? Did you know that some birds dance?

Does this mean you have to be bold to mate? Rock – Orange throat, aggressive w/ large territory & many females in harem Paper – Blue throat, defends small territory, 1-2 females Scissors - Yellow throat, no territory, sneaks around and mates with females from the harems of other males Meet the side-blotched lizard – AKA the “rock, paper, scissors” lizards

Competition & deception is not the whole story cooperation can be a very successful strategy as well. Do you remember how mitochondria & chloroplast became part of the eukaryotic cell? Competition & deception is not the whole story cooperation can be a very successful strategy as well. Do you remember how mitochondria & chloroplast became part of the eukaryotic cell?

To Summarize natural selection Natural selection is more complex than a simple competition for food resources. There are different aspects to selections: Sexual selection - because mates are resources necessary to pass on genes Kin selection – helping a closely related individual survive & breed is equivalent to breeding yourself. Co-evolution –Some survival strategies are dependent on others – the mimic needs the model Ecosystems - are complex, there are many successful survival strategies in nature.

Evolution is Descent with modification Each species alive today descended, with changes, from other species Each species alive today descended, with changes, from other species All species, living and extinct, were derived from common ancestors All species, living and extinct, were derived from common ancestors A single “tree of life” A single “tree of life” links us all together