Evolutionary Theory 2 Flashcards
Charles Darwin
- he returned to england on the HMS beagle in 1836
- he had many species with him
Charles Darwin 1937
writes down ideas on the transmutation of species in a notebook
Charles Darwin 1839
marries his first cousin, 10 children, only 7 survived childhood
Charles Darwin 1841
writes to a friend that they will work on a book titles “varieties and species”
Charles Darwin 1842
makes a pencil outline of his theory of “descent with modification”
Charles Darwin 1844
expands his sketch into an essay on the origin of species and natural selection
- Rejected scala naturae hierachy/ fixity of species
- relationship between the origin of new species and environmental adaptation
Charles Darwin 1859
published ideas about natural selection in a book titled the origin of species
- had been thinking about for a long time
Charles Darwin 1858
alfred russel wallace sends “on the tendancy of varieties to depart indefinitely from the original type” to darwin
- darwin thinks his lifes work is getting stolen
- papers by him and wallace were presented at the linnean society
alfred russel wallace
- little formal education
- was a surveyor, school master, civil engineer, insect collection
natural selection
- an explanation for how evolution occurs
- an evolutionary process that occurs when certain phenotypes confer an advantage or disadvantage in survival and/or reproductive success
- beneficial traits increase in frequency over time due to different survival/reproduction of individuals with those traits
fundamentals of natural selection
- must be variation in inherited traits
- a trait must be heritable for selection to act on it
- differential survival due to competition
- fitness is a relative measure that changes with the envirnment
- can only act on traits that affect reproduction
speciation
evolutionary process that results in the formation of new species
- ex. natural selection where variants accumulate in a population and groups become extinct from ancestors
geographical isolation
as groups become isolated, they adapt to different environmental contexts, responses to diverse selective pressures may result in distince species
favourable traits
traits that help a species be more likely to survive and create offspring for next generation
environmental context
determines if trait is beneficial in that environment
what happens if more offspring are produced than resources
competition
examples of natural selection
- selection pressures acted to drive beak evolution
- birds with deeper beaks are more successful when there are droughts
- birds with shallower beaks are more successful when climate is wet
- fluctuations in beak length correlate to fluctuations in weather
types of selection
directional, stabilizing, disruptive
directional selection
the change in a phenotype or genotype of a population in one direction away from the mean (average) in a particular environment over time
stabilizing selection
a type of natural selection that favors individuals with average or moderate phenotypes, while selecting against extremes