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Chapters 22 and 23 - Coggle Diagram
Chapters 22 and 23
23: The Evolution of Populations
23.2: The Hardy-Weinberg Equation
Hardy-Weinberg Equation = used to test whether a population is evolving
Definitions
Population
A localized group of organisms that belong to the same species
Gene Pool
The entirety of all the alleles in a population
Hardy-Weinberg equillibrium
Evolution not present; allele + genotype frequencies constant
Allele frequency = percentage of population with certain alelle
Hardy-Weinberg equation
If frequencies the same, suggests population not evolving
If frequencies change, suggests evolution
23.3:Natural Selection, Genetic Drift, and Gene Flow
Natural selection = organisms w/ certain traits survive and reproduce better than others
Definitions
Gene Drift
Fluctuations in gene frequencies result in lower variation
Gene Flow
Transfer of alleles between populations, reduces genetic difference overtime
23.1: Genetic Variation makes Evolution Possible
Genetic Variation
Genetic variation = differences between individuals in gene composition or other DNA sequences
"either-or" basis
E.g. Gregor Mendel's pea plants
Typically altered by single gene locus
Along continuum
Usually single phenotypic character influenced by multiple genes
Sources of Genetic Variation
23.4: Natural Selection
Relative fitness = an organism's contribution to the gene pool of the next generation
relative to other individual's contributions
Disruptive selection
Favors both ends of the phenotypic range
Stabilizing selection
Removes extreme phenotypic variants and preserves intermediates
Directional selection
Shift's population's overall makeup by favoring one extreme
Sexual selection = When individuals with certain traits are more likely to attract mates than others
Can lead to sexual dimorphism
Intrasexual selection
Same-sex males competing directly for mates
Intersexual selection
Individuals of one sex selectively choose their partners
22: Descent with Modification
22.2: Descent with Modification
Darwin's voyage on the Beagle
Led him to theories new species occurred via adaptation
Published book Origin of the Species, proposed natural selection
Observations
Individuals in a population vary in inherited characteristics
Example: Darwin's finches
Organisms produce more offspring than can be supported
22.3: The Support for Evolution
Evidence
Fossil evidence of extinction and differences between organisms now and in the past
Evolution's ability to explain some biogeographic patterns
Variations in how animals are similar
Homology
When organisms share characteristics due to having a common ancestor
Convergent evolution
When different species in similar environments share characteristics w/out a common ancestor
Direct observation of natural selection by researchers
22.1: The Darwinian Revolution
Scala Nature and Classification of Species
Aristotle believed species fixed and unchanging
Arranged on ladder of increasing complexity (scala naturae)
Carolus Linnaeus developed binomial naming system + nested classification system
Darwin suggested classification based on evolutionary relationships
Ideas About Change Over Time
Darwin studied fossils
Many found in strata (strata = layers of compressed sediment)
Paleontology = study of fossils
George Cuvier theorized extinction as common occurrence, did not believe in evolution
Hutton proposed Earth's geology could be explained by gradual mechanisms
Lyell theorized change in geologic processes operating today at same rate
Lyell + Hutton influenced Darwin's reasoning behind evolution
Endless Forms Most Beautiful
All organisms share characteristics
Species also differ
3 Key observations
They share many characteristics
Life is diverse and rich
Organisms are well-adapted to their environments
Darwin concluded that life evolves
Evolution = Descent with modification (change in genetic composition of a population from generation to generation)
Can be viewed 2 ways
As a pattern
As a process
Lamarck's Hypothesis of Evolution
Proposed incorrect theory of use and disuse
use and disuse = characteristics not used often fade away
Also proposed inheritance of acquired characteristics (organisms could pass acquired characteristics down to offspring)