Evolution Chapters 15

Darwin 15-1 Evolution - Change over time Theory – a well-supported testable explanation of phenomena that occurs in the natural world Charles Darwin – Early-mid 1800’s sailed the world on the H.M.S Beagle Made observations and collected evidence for his hypothesis of evolution Observations: Trees and plants seems super well-suited for their environment Some animals that seemed like they would fit in an environment were not present while others were Ex: Why no kangaroos in England? Darwin collected fossils as well, some of which looked strikingly similar to living organisms The preserved remains of ancient organisms Blue Footed Booby

The Galapagos Islands Darwin spent much time on the Galapagos islands 1,000 km off the coast of South America Each island had different climates and therefore different animal and plant species He paid particular attention to the tortoise species The Isabela Island tortoise had a Dome shaped shell The Hood Island tortoise had a saddle-backed shell Hypothesize…why might these shells be different?

Isabela Tortoise vs. Hood Tortoise Isabela Island has lush vegetation and a fair amount of rainfall The tortoises have short legs with a large dome-shaped shell Hood Island is a much flatter, bare island on which much less vegetation grows. The tortoises have flatter shells but much longer legs. In general, these tortoises are smaller than their Isabela Island counterparts

Scientists Who Helped Shaped Evolution 15-2 Darwin was not the only scientists to contribute to the theory of evolution James Hutton and Charles Lyell– Geologists, noticed that rocks and the Earth changed over time Some rocks appear swirly, while others appear after volcanic eruptions or earthquakes. If the Earth is changing within our lifetime, it must also have changed before and after Darwin noticed that if the Earth’s structure changes, why can’t species (plants and animals) change as well? Metamorphic Rock – Butler Sanctuary Basalt Intrusion in Granite - WPRR

More Scientists Jean-Baptiste Lamarck- WAS WRONG but…he proposed and idea which lead to the current theory of evolution He believed that selective use or disuse of organs led to organisms acquiring or losing certain traits during their lifetime. These traits may or may not then be passed on to their offspring This is untrue. If you have 500 mice and you remove their tails (loss of a trait), no matter what, the offspring from these tail-less mice WILL have tails Similarly, if an organism gains a trait (such as surgically having the shape of their ears altered) their offspring WILL NOT also have the altered ears Thomas Malthus – Economist, late 1700’s. He noted human babies were being born faster than people were dying and therefore, our population was (and is) increasing. He hypothesized that sooner or later we would run out of living space and food. Darwin then asked the question: Why is the globe not covered in Maple trees? Most offspring die, few survive to the age of reproduction

Darwin’s Theory of Evolution 15-3 While Darwin had an incredible compilation of evidence supporting his Theory of Evolution, he did not rush out to publish his findings His ideas challenged iron-clad scientific and religious beliefs of his time It was not until another scientist, Alfred Wallace, published an essay hypothesizing similar ideas. Darwin supported the essay at a conference with his evidence In 1859, he published his famous book, On the Origin of Species

Inherited Variation and Natural Selection Darwin noted that there were differences between organisms of a species in the wild as well as organisms in captivity Ex: Some cows on a farm produce more milk than other cows Some farmers would breed their livestock to pass on genetic traits Selective Breeding This selective breeding is also known as Artificial Selection Nature provided the variation in traits and humans selected the ones they wanted to breed for Plant crops and animals were bred using artificial selection EX: Brussels sprouts, cauliflower, broccoli, kale and kohlrabi all originated from the Mustard Plant A variety of commonly used plants were artificially developed from the mustard plant using selective breeding by farmers

Evolution by Natural Selection Struggle for Existence- All organisms are competing for food, shelter and a mate Fitness – how well adapted an organism is to its environment NOT how physically fit an organism is Adaptation – NOUN – a physical characteristic that increases an organism’s chance of survival Ex: Quills on a porcupine, thumbs on a human

Evolution by Natural Selection Cont. Organisms with high fitness are more likely survive and reproduce. Organisms that lack beneficial adaptations and have low fitness are less likely to survive and reproduce Survival of the Fittest - Only organisms that reproduce can pass on their adaptations (traits) Reproduction is the goal! Natural Selection – survival of the fittest leads to “nature” selecting for the best traits of organisms. Over time, natural selection leads to changes in the species DNA, leading to an increased fitness of the species in its environment

Natural Selection

How Current Species Came to Be Descent with Modification – Each species has descended, with changes, from other species over time. As the environment changes, organisms that have the highest fitness for that environment reproduce and pass on genes Implies all organisms are related to one another Common Descent – all species, living and extinct, were derived from common ancestors. Reptiles, mammals, birds and fish all come from a common origin

Evidence of Evolution Fossil record – a catalog of all fossils ever found Fossils are found in different layers of rock Newer layers are on top, older layers are on the bottom Fossils found in top layers are younger than those below Allows us to see who was here 100,000 years ago vs. 5,000,000 million years ago Shows change over time when old and new fossil structures are compared

Evidence of Evolution Cont. Geographic distribution Homologous Structures – body parts with different adult forms but which come from the same embryo tissues Evidence for descent with modification from a common ancestor for all four-limbed animals Vestigial Organs – organs that once served a purpose in ancestors but are currently useless EX: Appendix in humans, leg bones in a whale Embryology – the embryos of many different species all look incredibly similar Ex: Human embryos look like rat and chicken embryos