1. Evolution
Chapters 15

2. 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

3. 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?

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. Natural Selection

12. 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

13. 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

14. 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