Evolution

Bottom line : Evolution is descent with modification. The environment selects who is fittest, which allows them to have more offspring. Over time these inherited traits become more common in a population (remember populations?). Charles Darwin was one of the first to describe it. It is a theory because it has massive scientific support with None disproving it. It has nothing to do with religion.

I.Charles Darwin – 1809 – 1882 A. See WOTD for early life ***Had a wicked beard.

B. Many observations leading to Evolution theory from 1831 Journey on the Beagle (naturalist voyage)

1. Many observations from Galapagos Islands.

2. Difference in finch beak shape suggested evolution to suite different islands. a. Similarities between finches suggested common ancestor.

C. Didn’t publish his book “On the Origin of Species” until Proposed the theory of Natural Selection (a driving force of evolution) = Those best adapted to an environment, live and pass on inherited traits.

a. These “traits” can be physical or behavioral. b. This Natural selection causes species to change over time.

c. Natural selection causes an “arms race” between competitors or predator/prey relationships….Antelopes and Lions are an example. d. Natural selection requires Natural Genetic Variation to work.

2. Fitness is the ability to survive and pass on ones genes. Yellow toothpicks more fit than blue toothpicks in our particular environment. a. Fitness determined by the Environment.

3. This all means that Darwin’s theory depends on more offspring being born in a population than can survive (Some must die).

D. Evidence for Evolution. 1. Fossil record – Using geologic dating one can observe changes to a population over time.

2. Geographic Distribution of living Species 1. Organisms in similar climates (on different continents) have similar adaptations)

3. Homologous Body Structures – Structures from same origin with different function = wings and arms.

4. Similarities in early development. See Pic.

II.Evolution in Populations A.Genes and Variation. 1. Gene Pool a. Remember members of a population are all of members of the same species.

2.Sources of genetic variations. a.Mutations – change in DNA due to a “mistake” in DNA.

b. Gene Shuffling – Each human can produce 8.4 million combinations of genes in sex cells. i. That means the chances of having an Identical non-twin is Ridiculously Low (almost infinitely low.

c. Single-gene and polygenic traits. 1. Single-gene traits are simple. Ex. Widow’s peak. 2. One gene determines trait

3.Polygenic traits – many genes for 1 trait. a. Phenotypes (the way the traits look) in a population best shown as a bell- shaped curve.

B. Evolution as Genetic Change –Evolution acts on Physical traits, but those traits have genetic origins = NATURAL SELECTION

1. Natural selection of Polygenic traits= three general effects. Or…………………… Or………………….

a. Directional selection- individuals at only one end of a bell curve of phenotype (traits) frequencies have high fitness. i. Result = population becomes more like that extreme.

b. Stabilizing selection – When individuals with and average form of a trait have the highest fitness. i. Result = population becomes more “average” less diverse.

c. Disruptive Selection – When individuals at upper end and lower end of curve have highest fitness (ie. Average is least fit). i. Result= Speciation …population evolves in two different directions = finches with short parrot-like beak and others with long, narrow beak.

2.Genetic drift – another evolutionary force apart from Natural selection. a. When an individual leaves more offspring in a population due to simple Chance. b. Happens only in populations with small numbers.

c. Founder effect- genetic drift in which a new habitat is colonized by a few individuals. Their genes will be dominant regardless of fitness.

C (capitol C). The process of Speciation 1. Isolating mechanisms- how populations become reproductively isolated (essential factor for forming new species) from each other. 3 types

a. Behavioral Isolation (courtship)– 2 populations capable of mating but do not due to behavioral (eg. Courtship) differences.Behavioral Isolation (courtship)–

b. Geographic Isolation (space)– populations become separated by mountains, rivers bodies of water etc.

c. Temporal Isolation (time)– populations that begin to reproduce at different times. i. if some flowers begin to open at midday and other flowers at night, they will not breed.

2. Speciation of Darwin’s Finches – How it happened in order. a. Founders arrive – Some finches blown in from mainland = Founder Effect

b. Separation of populations by Geographic Isolation (different islands)

c. Changes in gene pool due to natural selection = Directional Selection dependent on environmental pressures unique to each island (beak shape for different foods).

d. Reproductive Isolation – immigrating birds now have different courtship behaviors (Behavioral Isolation) = no interbreeding.

e. Ecological Competition – These new separate populations (even on same island) have different niches = differences broaden

f. Continued Evolution – finally led to 13 different species of Galapagos Finches. i. Darwin’s finches are an excellent example of speciation.

III.Classifying organisms (Taxonomy) A. Linnaeus’s system of classification 1. Carolus Linnaeus ( ) developed the universally accepted method of Binomial Nomenclatue.

a.The seven categories used by Linnaeus from most exclusive to most general are….. 1. Species 2. Genus 3. Family 4. Order 5. Class 6. Phylum 7. Kingdom

b. In his binomial nomenclature one includes both the genus and species in the name. i. The name is in italics ii. Genus is capitalized while species is lower case. Homo sapein

iii. Example, you are a Homo sapien (homo=genus and sapien is species). iv. Any genus has multiple species a. example: Homo sapiens = humans, Homo neanderthalensis = neanderthal man, Homo erectus = First upright ancestor of man etc. Meet the Homos

2. Example of classification = Brown bear STOP – Draw Fig 18-5 here pp.450 (it’s on the test).

B. Examples from the taxonomic categories. 1. Domain (even more general than kingdom) there are three. **Oh, one thing all domains have in common (All living things) is they have DNA and RNA to pass on information.

** Three domain system based on how long each has been evolving independently ** Domain was added after Carolus Linnaeus developed his binomial system.

a. Bacteria – are bacteria ;-) i. The Domain Bacteria contains only one kingdom which is Eubacteria.

ii. All bacteria are unicellular (one cell) iii. Bacteria are single celled prokaryotes (have no nucleus) iv. Peptidoglycan in cell walls (just know it).

b. Archaea – extremeophiles – live in Really extreme (salty, hot, low oxygen etc.) environments.

i. all are unicellular (one celled) ii. Archaea are Prokaryotes (have no nucleus). iii. NO peptidoglycan in cell walls (how they differ from bacteria)

c. Eukaryotes – everything else (Plant kingdom, Fungi kingdom Protista kingdom, and Animal kingdom. (gagillions of different species)

i. All eukaryotes have a nucleus within each cell.

2. Kingdom –The next most general taxonomic category a. Eukaryote Domain includes the Kingdoms:, Fungi (mushrooms molds), Animalia (us), Plantae (green stuff), and Protista (ameoba). (billions of different species)

**Random stuff you must know about Eukaryotic kingdoms i. Organisms in Fungi have cell walls made of chitin and are heterotrophs (must consume food) ((random fact you must know)). ii. Animals are heterotrophs. iii. Plants are autotrophs (photosynthesize). ** Plant cell walls made of cellulose.

3. Phylum – each kingdom contains several phylum. a. Within kingdom Animalia we are in the phylum Chordata (have spinal cord) (millions of different species)

4. Class – Each phylum contains several classes a. We belong to the class Mammalia (Warm blooded, have body hair, produce milk for young). (hundreds of thousands of different species)

5. Order – Each class has many orders a. we are in order primates (with all monkeys and apes) (thousands of species)

6. We are in the family Hominadae (with gorillas, chimps, orangutans and our dead ancestors).

7. We are in genus Homo (we are the only living Homos…..stop laughing) Eg. Homo erectus 8.Our species is Homo sapein (we are the only one)

C (capital C) Dichotomous Key 1. Dichotomous Keys are used to classify organisms beginning at the very general taxonomic catagories (example: Kingdom) to the most specific (species).

2. Each step asks an either or question. Example: a. Does the organism have a nucleus? -If no, continue to question b. If yes, it is a Eukaryote continue to question c. b. Does it have peptidoglycen in it’s cell walls? - If no continue to Archae -If yes continue to Bacteria Eukaryotes c. Is it a single celled organism? -if yes, it is a Prokaryote continue to question ……. -if no, proceed to question…………..

The End- but not really because evolution continues. ;-)