Darwin’s Voyage of Discovery

Darwin’s Epic Journey Charles Darwin- born in England on February 12 th, 1809 (same day as Abraham Lincoln) Born in a time of changing thoughts about the Earth and about life Traveled the world in the HMS Beagle in Developed a scientific theory of biological evolution that explains how modern organisms evolved over long periods of time through descent from common ancestors.

Darwin’s Ideas 1- Species vary globally 2- Species vary locally 3- Species vary over time

Vary Globally Flightless, ground dwelling birds Rheas – grasslands of South America Ostriches- grasslands of Africa Emu- grasslands of Australia

Vary Locally Different, yet related, animal species often occupied different habitats within a local area. – Example- 2 species of rheas living in South America. One in nice climate grasslands of Argentina One in the colder, harsher grass and scrubland to the south. – Example- Tortoises of the Galapagos Islands

Darwin’s Finches Collected finches with varying sizes of beaks

Vary over time Darwin Collected Fossils He noticed that some fossils of extinct animals were similar to living species. – Example – Glyptodont vs. armadillo

Other Ideas that Shaped Darwin’s Thoughts An Ancient, Changing Earth Lamarck’s Evolutionary Hypothesis Population Growth Artificial Selection

An Ancient Changing Earth Hutton and Lyell- Earth is extremely old and processes that changed the Earth in the past are still happening. – Examples Volcanic eruptions- builds up Erosion- tears apart

Lamarck’s Evolutionary Hypothesis Suggested organisms could change during their lifetimes by selectively using or not using various parts of their bodies. Also suggested that individuals could pass these acquired traits on to their offspring, enabling species to change over time.

Population Growth Thomas Malthus- reasoned that if the human population grew unchecked, there wouldn’t be enough living space or food for everyone. – Leads to war, famine, and disease Darwin realized this applied to other organisms in a more obvious way. Maple trees- produce thousands of seeds. Most don’t sprout and of those that sprout, most don’t reach the age of reproduction. WHICH ONES DID SURVIVE AND WHY?

Artificial Selection We pick which traits we want passed on by only allowing those with the desired trait to reproduce.

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Darwin Presents His Case Lamarck was ridiculed for his radical ideas about evolution. Darwin didn’t publish his work for 20 years. Alfred Wallace wrote an essay mirroring Darwin’s thoughts. Darwin Publishes “On the Origin of Species” in 1859.

Evolution by Natural Selection The Struggle for Existence- Members of a population must compete to obtain food, living space, and other limited living necessities. Variation- Nature provides the variation (some of which are better suited to life in their environment than others). Adaptation- Any heritable characteristic that increase an organism’s ability to survive and reproduce in its environment

Interesting Adaptations Female Caibou have antlers in the winter when males do not. Advantage?

Interesting Adaptations New Zealand weta- Is a cricket that can freeze solid, thaw and live. Advantage?

Interesting Adaptations Albatross can sleep while they fly. Advantage?

Interesting Adaptations Platypus spurs have venom. Advantage?

Survival of the Fittest Fitness- how well an organism can survive and reproduce in its environment. Individuals with adaptations that are well suited to their environment can survive and reproduce and are said to have high fitness. Those with low fitness die without reproducing or leave few offspring. The difference in rates of survival and reproduction is call survival of the fittest.

Darwin coins Natural Selection Natural Selection- process by which organisms with variations most suited to their local environment survive and leave more offspring. Natural Selection occurs when… – More individuals are born than can survive – There is natural heritable variation – There is variable fitness among individuals

End Result Adaptations don’t have to be perfect- just good enough to enable an organism to pass its genes to the next generation. If local environmental conditions change, some traits that were once helpful may no longer be useful, and different traits may become adaptive. It environment changes faster than a species can adapt to those changes, then it may become extinct.

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