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Cassie Henderson-Moulton

on 4 February 2016

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Transcript of Evolution

Darwin's Ideas
In 1859 Darwin published
The Origin of Specie by Means of Natural Selection
Natural Selection
Natural Selection has many things that work together to make it selective and effective:
Variations: In any population, individuals have many traits that show variation. (It's why I have brown hair and why Hailey has blonde hair.)
Heritablity: Many of these traits are determined at least partly by genes and so they are heritable: they can also be passed on to our offspring.
Natural Selection: the trait either helps or it hinders. If it helps you get to pass it on to offspring. If it hinders, you won't.
Adaptation: organisms with advantageous traits leave more offspring, and become more common because they aren't dying. (Their advantageous trait is helping them survive).
How does one species become a new one?
Adaptation: traits that make organisms good at living (surviving!) and reproducing.
Thank you!
Change Over Time
Read chapter 26.
Complete pages 566-568.
Review 1-18
Think and Do 1
Think and Explain 1-14 even
Multiple Choice 1-10
Chapter 26
Evidence that Supports Evolution
One important thing to keep in mind: fossils have been dated as far back as 3.5 million years ago. Science assumes that life started on Earth around 3-4 million years ago.
Scientist Jean Baptiste Lamarck was the first to argue that animals today were descendents from ancestors that were different than they currently looked/acted/seemed. The common idea during Lamarck's time was that everything stayed the exact same way and would never change. His idea was controversial.
Lamarck's idea was that organisms acquired traits that made them more successful, and those traits get passed down to their offspring. His idea turns out was wrong.
Darwin proposed that evolution (inhereted changes in organisms over time) had produced the diverse speciation of our planet. He argued that this happened because of
natural selection
Natural selection: organisms with advantageous traits are able to survive and leave more offspring than organisms with other traits. Because these offspring inherit the advantagous trait, the trait becomes more common in the population of that species.
Darwin observed that the giraffe with a longer neck (because of natural variations in their genes) would be more likely to gather and eat food. This means that giraffe is most likely going to survive and pass that trait onto its offspring.
KEY POINT: Although natural selection acts on individuals within a population, allowing some individuals to leave more offspring than others, it is the population as a whole that evolves and becomes adapted to its environment.
Survival requires that organisms be able to obtain food and other resources. For many organisms, it also requires that they avoid predators.
Genetics and Evolution
Allele frequencies are used by science to catalog certain traits, and it shows how common traits are or aren't.
Natural selection only acts on an organisms phenotype, not on their genotype.
Genetic Drift: is how evolution acts on a species due to random chance. For example: a storm wipes out a bunch of dark variations of a moth - then the allele frequency changes to encorporate a great percentage of the lighter variation of the same moth.
Speciation: the formation of a new species. It is caused by the evolution of reproductive barriers that stop two different groups of organisms from breeding.
Geographic barriers can cause two populations of the same species to not be able to reproduce together - this causes each group to evolve seperatly and causes speciation.
Species: is a group of organisms whose members can breed with one another but not with members of other species.
1 Observations of natural selection in action.
2. Artificial selection: occurs when humans breed organisms with traits that they like. Think of dogs, cats and various crops.
through artificial selection, humans have cause distinct evolutionary changes in organisms.
3. Vestigal organs: the remains of an organ that was found in an ancestor. Legs on a whale, and the human appendix.
4. Similarities in body structures.
5. DNA of organisms: related species
have similar base pair sequences.
6. Development of organisms: related species develop in similar ways.
7. Fossils of organisms: fossils show how organisms evolved over time.
8. Biogeography: Where an organism is found.
The Arctic and the Antarctic have completly different species.
Final Note: this is wrong!
Full transcript