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Darwin's Theory of Evolution (Theory of Evolution (Darwin didn't…
Darwin's Theory of Evolution
Theory of Evolution
animal breeding
observed that even within species, individuals showed variation in traits and that the variations could be passed to offspring
knew that populations could produce far more offspring than the environment could support
predicted that individuals with traits which suited the environment would survive + reproduce to pass their favorable traits to offspring
those with traits less suited to the environment would die
natural selection = how species naturally change over time
became known as principle by which each slight variation, if useful, is preserved
adaptations are examples of how the environment imposes limits on organisms
selects against those who are not fit
rise through gradual accumulation of chance variations
cannot be predicted
Darwin didn't know that genes made of DNA determine traits
reasoned that populations of all species have the capacity to grow
species produce more offspring than can survive
most populations still able to remain stable because of environmental limits
in order for a population to remain stable, many offspring must die
offspring without such beneficial adaptations were more likely to die and either not reproduce
well-adapted individuals produce more offspring
individuals do not evolve, groups evolve
adaptations over many generations within one lineage of organisms, results in a new species
occur through genetic change.
explains how today's organisms could be related
proportion of individuals with a favorable trait will increase
through chance variation, overproduction of offspring, and differential survival and reproduction
result is a population of individuals adapted to their environment
compared to Lamarck
natural selection is not directed or intentional
depends on chance variations, due to genetic variations, and can work only with the “raw material” of existing species
natural selection explains story told through fossil record
history of life on Earth
Darwin's theory
all living species share common ancestors
natural selection explains how species change
common ancestry explains the similarities between present-day species and natural selection in the face of environmental change explains the differences among present-day species
Darwin
Theory of Evolution
explains and unifies all of biology
directs our responses to diseases and our practice of agriculture
lived from 1809 - 1882
love of nature immersed out of his lack of interest in other subjects
active hiker, spent days collecting sea shells
stopped pursuit for medical degree out of disgust for blood and bordeom
later dropped out of medical school
inspired by The Natural History of Selborne book
became studying at Cambridge University
began collecting beetles
befriended the Reverend John Stevens Henslow
member of clergy and naturalist
met geology Professor Adam Sedgwick
became interested in geology
read Preliminary Discourse on the Study of Natural Philosophy
read Personal Narrative of the Travels to the Equinoctial Regions of America During the Years 1799-1804
Beagle Voyage
ideal opportunity for collecting specimens of natural history
Darwin suggested as naturalist for voyage
theory of evolution
postulated that present life has arisen gradually from past life forms
determined that millions of species of plants, animals, and microorganisms that live on Earth today are related to each other because of common ancestors
natural selection explains how the diversity of life has arisen through time
natural selection is cause of evolution
Influences of Darwin
Jean Baptiste Lamarck
one of the firsts scientists to explore change of species
believed that organisms improve traits through increased use and then pass the improved feature on to their offspring
inheritance of acquired characteristics
giraffes have long necks because early giraffes stretched their necks to reach tall trees and then passed the longer necks on to their calves
you can weight-train for years
in order for your children to have same muscles, they must weight train also
Charles Lyell
challenged the belief that the Earth was young
published Principles of Geology
ecorded detailed observations of both rocks and fossils and used present patterns and processes as keys to past events
concluded that many small changes over long periods of time built today’s landscapes and that the Earth must b older than people believed
Thomas Malthus
published An Essay on the Principle of Population
observed that sooner or later populations get checked by famine and disease
human “struggle for existence” is due to exponential population growth and limited food
Alfred Russel Wallace
helped arrange a joint presentation to the Linnean society two weeks later
Darwin's competition
pushed Darwin to complete book
began studying barancales
artificial selection
breeders could achieve remarkable changes and diversity in a relatively short time
chose which animals to breed
variations in traits are heritable
artificial selection: selective breeding
observations of how artificial selection worked helped him develop his concept of natural selection