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Evolution
Darwin - show how evolution occurs
Happens by natural selection
Origin of Species - 1859
384-322 B.C. - Aristotle - father of evolutionary theory
History of the Animals - earliest attempt at classifying animals
Based on physical similarities
Graduated ladder of nature - life proceeds from simple to complex
Late 1600s to early 1700s
Western/European Thought
 World view shaped by Platonic and Aristotelian philosophy
 The earth was a few thousand years old
 All species were created as we see them today
 Considered the earth and all species to be unchanging and organized according to the divine plan
EVOLUTION - change in properties of populations of organisms or groups of organisms over the course of
generations
Population - united by reproducing; group of actually or potentially interbreeding individuals of one
species; not a property of an individual organism
Examples:
Teddy bear -1902; Changed over time
Giraffes
Ancestral - short necks
Today - long necks
- descent of modification
Entities descend from one another through time and modified between generations
History of Evolutionary Theory
John Ray - 17th century naturalist
Robert Hooke - late 1600s; microscopy
Adaptations - allow them to survive
Linnaeus - classification (1707-1788)
Binomial nomenclature = Genus species; Example - Homo sapiens
1st comprehensive system of classification of animals, plants, and minerals
System of Nature (1735)
Buffon (1707-1788)
 Geographical distribution
 Arguably 1st early theory of evolution
Large cats; Living world is divided into different regions; Close link between species and their environment
 Species were created in many different world-wide regions
Cuvier (1769-1832)
Anatomist; Worked with fossils (paleontology)
 Many species were extinct
 Extinct species were replaced by other species
 The older the fossil, the more it differed from modern counterpart
Erasmus Darwin (1731-1802)
Zoonomia AKA The Laws of Organic Life (1794-1796)
 Sketched out theory of evolution; species changed through time
Lamarck (1744-1829)
 Influential
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Coined the term “biology”
Proposed evolution happens by acquired characteristics; characteristics would be passed down to offspring
1st mechanism for evolution
Embryology
Lyell (1797-1875)
 Geologist
 Principles of Geology (1839)
 Extinction was a routine event
 Extinction were explainable in terms of ecological and geological patterns
 Must have new species
 Variability - different individuals
 Geographical distribution
 Struggle for existence - competing for survival
1830-1840
Broad outline of fossil record
Invertebrates  fish  reptiles  mammals
Robert Chambers (1802-1871)
 Vestiges of Natural History of Creation (1844)
 Raised question “Where do species come from?”
Darwin - doctor  naturalist
 Beagle voyage - 1831-1836
 1837 - wrote journals; species change from one to another
 Key factor - explaining how adaptations rise
Essay on Principal of Population - written by Malthus (1838)
 Human populations grow geometrically; Animals grow in a similar fashion
 Food is limited
 Strong struggle for existence
Any variation that gave an individual an advantage in struggle for life would tend to be preserved through time;
Disadvantages would be eliminated
Breeding under selection (artificial & natural) gives rise to adaptations
Darwin wrote preliminary essay (1844)
Wallace (1823-1913)
 Geographical distribution
 Patterns of distribution explainable in evolutionary terms
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 Realized that patterns of distribution are explainable in evolutionary terms
 Greatly influenced by Lyell’s Principles of Geology
 Paleontological evidence could be explained if later species were related to earlier ones by evolutionary descent
Wallace’s Law
Every species has come into existence coincided in both space and time with a preexisting allied species
1855 - Wallace had made public his ideas
1856 - Lyell and Darwin read Wallace’s paper which outlined theory of evolution by natural selection
1858 - Wallace read Malthus’ “Essay on Populations”; Sent Darwin a paper outlining natural selection
Lyell and Hooker urged Darwin to present his ideas professionally
Darwin’s and Wallace’s papers were presented jointly to the Linnean society
Two Main Points in Origin:
 Evolution has occurred; all living things have descended from one or a few common ancestors
 Primary cause of evolution is natural selection operating on random heritable variations
Huxley’s reaction - “How stupid not to have thought of that…” *something like that?*
1876 - Wallace’s “Geographical Distribution of Animals”
Distribution of plants and animals can only be understood in terms of changes in the past
 Laid foundation for future work on geographical distribution
Darwin could not explain heredity
Mendel - Father of Inheritance
His works were discovered in 1920
He showed how inheritance happens; Worked with pea plants
DNA - contains genetic information
Chromosomes - long thread like associations of genes found in the nucleus of all eukaryotic organisms; Consists of
DNA and protein
 Generally comes in pairs; members of a pair = homologous chromosomes; Humans = 23 pairs
Each chromosome has a number of genes
Specific location of genes = locus
A gene is a discreet unit of hereditary information consisting of DNA
Alleles - alternate expressions of a gene
Dominant - masks the recessive allele; noted with upper case
Recessive - noted with lower case
Heterozygotes - two different alleles
Homozygotes - same alleles
Homologous Chromosomes
 Same length
 Same centromere position
 Possess traits genes for same trait at corresponding location
The offspring will get one homologue from mom and the other from dad
Genotype - sum of all genetic material; or specific alleles
Phenotype - physiological, morphological, or behavioral expression of an individual’s genotype; can be influenced
by environmental factors
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Individuals don’t evolve but populations and species do
Populations
 To understand evolve, we need to understand how features of individuals vary w/in a population
 Different alleles
All members of a population share some traits that are similar
 Morphological - physical
 Physiological - cellular/metabolic processes; internal functioning
 Behavioral - responses to various stimuli
Details of these traits vary
Almost every trait is variable
Some traits vary qualitatively
 Either/or - say that trait is in two or more distinct forms (morphs)
Vary quantitatively
 Continuous
Variations that we see in a population is a result of variations in the genes that control the traits that we’re looking at
Gene pool - pool of genetic resources available w/in a population
Peromyscus maniculatus - mice
Species can be divided into subspecies based on phenotypic variation
Francis Sumner - early 1900s; 1874-1945
P.m. gambali - South Cali
P.m. sonoriensis - Mojave
Coat color is genetically controlled
 Differences between subspecies are strongly inherited
 Differences between subspecies were dependent on the action of many independent genes
 Differences between subspecies do not evolve in a single mutational leap
1930s
Which alleles end up in a gamete and thus in a new individual in a population?
Five things
 Gene mutation - heritable changes in DNA structure = new information
 Crossing over during meiosis - novel combinations of alleles on a chromosome
 Independent assortment at meiosis mixes paternal and maternal chromosomes
 Fertilization - combination of alleles of two parents
 Change in chromosome number or structure - loss or duplication of genes; 2-5 - reshuffling information
1 out of 10600 possible combinations
1010 humans alive today