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Intro to Evolution

Intro to Evolution. College Bio Ch. 16. What we will study. Intro to Evolution The what’s, who’s, when’s, where’s, and why’s Selection Types Natural Artificial Sexual Effects on Populations Formations of Species History of Life. Darwin. Charles Darwin The Father of Evolution

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Intro to Evolution

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  1. Intro to Evolution College Bio Ch. 16

  2. What we will study • Intro to Evolution • The what’s, who’s, when’s, where’s, and why’s • Selection Types • Natural • Artificial • Sexual • Effects on Populations • Formations of Species • History of Life

  3. Darwin • Charles Darwin • The Father of Evolution • Ship’s Naturalist aboard the HMS Beagle • Circumnavigated the globe collecting many specimens • It wasn’t for some time after he returned that he began to take notice of similarities in different species. • He also cited things like seashells on top of the Andes Mountains and the skull of the Giant Ground Sloth

  4. Darwin • He thought about his dogs, and the other dogs around, and why they looked why they did • The real ah-ha moment came when he realized the “blackbirds” he collected on the Galapagos Islands were finches • Each finch looked different, yet they were all still finches

  5. Darwin and His Book His voyage on the Beagle ended in 1836. Some 20 years later (in 1856) he began to put together a little book, that was published in 1859. The Book is On the Origin of the Species by Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life

  6. Darwin and His Book • This book was viewed as a direct attack on the Church • Why? Let’s Discuss. • How did Darwin take the counter attack that ensued? • Darwin’s home life, beliefs, etc.

  7. Darwin’s Bulldog Thomas Huxley Huxley was a wholehearted supporter of Darwin and his ideas He joined Darwin on a debate circuit, as well as went on his own debates Huxley, despite having little formal education, and being unsure about parts of Darwin’s viewpoints, helped sway the thoughts of many

  8. Darwin as a victim? • Darwin was ill intermittently for most of his adult life • A possible explanation is he fell victim to some of the most capable evolvers • Parasites • Darwin may have fallen victim to Chaga’s Disease • Trapanisomacruzi • A parasite that calls South America home

  9. Evolution Defined as decent with modification Or Change over time Or Change of allele frequency in a population

  10. Types of Evolution Microevolution- evolution on the small scale, can be seen within species over varying amounts of time Macroevolution- evolution on the larger scale, history of the species

  11. Evidence of Evolution • There are many different sources of evidence of evolution • Vestigial Structures- remnants of advantageous structures/organs/behaviors that were shared with common ancestors • Derived Loss • Homologous Structures- structures of organisms that are related to each other via common descent • Forelimbs of mammals

  12. Evidence of Evolution Fossil Record- fossils, being the preserved remains of organisms, allow a look back through time. This allows us to look for morphological similarities to present day/ or past organisms DNA- through techniques such as PCR we can look at differences between two strands of DNA. From there we can count the differences at the nucleotide level

  13. Evidence for Evolution • Direct Observation- Given the time, resources, and patience, one can directly observe evolution of a population, both in nature and in labs • Peter and Rosemary Grant and the Finches of The Galapagos • Beak of the Finch • Model Organisms • Fruit Flies, Guppies, Yeast, Roundworms, Stickleback Fish

  14. Mechanisms for Evolution Individuals within a species have different morphologies, biochemistry, and behavior That inherently means some will be better suited for their environment than others This is called biological fitness

  15. Biological Fitness Biological Fitness is an organisms ability to survive and reproduce The more fit an individual is, the more offspring they produce, the more their genes (and alleles) show up in a population

  16. Mechanisms of Evolution • Alleles- Different forms of the same trait • Eye color, hair color, fur color, etc. • Allele Frequency- the percentage of a population exhibiting a particular allele. • Genotypic Frequency- percentage of a population with a particular genotype • AA vsAavsaa • Phenotypic Frequency- percentage of a population with a particular expressed trait • May be a physical, neural, physiological

  17. Mechanisms of Evolution • Four main ones • All focus on genetic variation • Differences in DNA (or RNA for some organisms) • Mutation • Gene Flow • Genetic Drift • Natural Selection

  18. Mutation • Changes in the DNA (or RNA) sequence may lead to new traits • Sometimes these traits may be advantageous • Meaning they will be selected for • Sometimes these traits may be detrimental • Meaning they will be selected against • Being selected against is just as important as selected for.

  19. Gene Flow • Gene flow occurs when individuals move between populations, bringing with them their genes • 2 populations of birds • One bird from population 1 flies to population 2 • The two populations look different • Meaning there are different alleles in the two populations, and they are now mixed.

  20. Genetic Drift • Genetic Drift occurs when alleles are selected at random over time • Has the greatest effects on small populations • 2 possibilities • Bottleneck- an event occurs that wipes out a large % of a pop. Leaving a small amount of genetic variation • Founders effect- a small group establishes a new population. Not a lot of variation.

  21. How Biological Fitness is Observed • When we consider fitness we often see it through the eyes of Natural Selection • Natural Selection- individuals survive at a higher rate, therefore reproduce more, because of inherited characteristics that make them better suited for their environment. • This could also mean that there are traits that are selected against. (this is really a major driving force.)

  22. Natural Selection • It is a dog eat dog world out there. • Its not the size of the dog in the fight, but the size of the fight in the dog. • Therefore, by transitive property, the dogs that are the best fighters (for life in this case) are the survivors • Natural Selection does not mean the biggest, strongest, or fastest. It means best suited • And best suited relies on environment

  23. Natural Selection Natural Selection has 3 effects on a population These can be viewed as Selection Curves Each curve shows the outcome of a populations evolution by frequency of alleles.

  24. Directional Selection • Direction Selection occurs when individuals with one extreme form of a trait are more fit than those with any other form • The peppered moths

  25. Stabilizing Selection Stabilizing Selection occurs when the individuals with the mean version of the trait are the most fit

  26. Disruptive Selection Disruptive Selection occurs when individuals with either extreme form of a trait are better suited for the environment, rather than the median form.

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