evolution: why are there so many living things? why are there so many living things?
Post on 15-Jan-2016
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Evolution:Evolution:Why Are There So Many
Living Things?
Why Are There So Many
Living Things?
Where Did the Idea of Evolution Come From?
• Middle Ages:– “Ladder of Life”
• Complex organisms found at highest rungs
• Less complex at lower rungs
• 1800’s– Georges Cuvier
brought study of fossils to the level of science.
Where Did the Idea of Evolution Come From?
• Charles Lyell– Proposed theory of uniformitarianism.
• Jean-Baptiste Lamarck– Published theory of the inheritance of
acquired characteristics.
Charles Darwin
• Loved nature• Studied medicine
– Struggled with the inhumane operating procedures
• Switched to religion• Offered position as
naturalist on British survey ship, The Beagle.
Voyage around the World
• Studied animals and fauna.
• Noticed South American fossils differed from contemporaries.
• Collected data for 27 years to support his mechanism for evolution.
Fathers of Evolution
• Alfred Wallace studied in Brazil and East Indies.
• Developed mechanism of evolution independently of Darwin.
• Sent a copy of it to Darwin. – Contained same conclusions as Darwin
• Both presented their data at Linnaean Society of London in July 1858.
How Did Darwin Account for Species?
• In Origin of Species, he developed two main concepts– Evidence that
evolutions has occurred.
– Mechanism for evolution :natural selection.
Major points of Darwin’s theories of evolution and natural selection
• First observation:– Populations have
the potential to increase exponentially.
• Based on thoughts by Thomas Malthus
Major points of Darwin’s theories of evolution and natural selection
• Second observation:– Populations are fairly
constant in size.
Major points of Darwin’s theories of evolution and natural selection
• Third observation:– Natural resources are limited.
• Limited amount of space, nutrients, shelter
• Results in competition for resources to survive.
Major points of Darwin’s theories of evolution and natural selection
• Deduction one:– Only some organisms
survive. There is a struggle for existence among individuals in a population.
• Organisms posses characteristics that enhance survival– Called adaptations.
Three Types of Adaptations
• Morphological-anatomical: modifications in form and structure that enhance survival.
• Biochemical-physiological: modifications in the production and use of chemicals by organisms.
• Behavioral Adaptations: Modifications in animal interactions with others and environment.
Major points of Darwin’s theories of evolution and natural selection
• Fourth observation:– There is variation within individuals of a population
and variations are inherited.
Major points of Darwin’s theories of evolution and natural selection
• Deduction two:– Individuals with
favorable variations are more likely to survive and reproduce.
• Natural Selection:– “preservation of
favorable variations and the rejection of injurious variations”
Major points of Darwin’s theories of evolution and natural selection
• Deduction three:– Accumulation of
inheritable variation over many generations is evolution.
• If changes within a species become great enough, a new species can result.
What is a species?
• Species are considered extinct if they do not interbreed in nature.– Implies offspring must also be able to reproduce.
Evidence supporting Theory of Evolution
• Selective breeding practices used by farmers result in:– “improved”
domesticated plants and animals.
• Darwin wondered if nature could do the same.
Evidence supporting theory of evolution
• Fossil record– Comparing fossils from ancestors with today’s
species demonstrates species have evolved.
Evidence supporting theory of evolution
• Homologous structures– Structures dissimilar in
form and function. • but share underlying
structural similarities
– Similarity due to a common ancestor?