The Theory of Evolution
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Transcript of The Theory of Evolution
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The Theory of Evolution
Chapter 13 – Sect. 1: Natural Selection
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Charles Darwin - 1859
Published convincing evidence that species evolve
Proposed a reasonable mechanism to explain how evolution occurs
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Darwin’s Voyage on the HMS Beagle
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Darwin’s Voyage on the HMS Beagle
1831-1836 (5 year voyage) Darwin was 22 years old at the start Naturalist – someone who studies nature Ships purpose was to survey the coast of
South America
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Darwin’s FinchesDarwin observed that many
of the plants and animals of the Galapagos Islands resembled but were not the same as those on the nearby coast of South America
Population – all the individuals of a species that live in a specific geographical area and that can interbreed
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Natural Selection
Individuals that have physical or behavioral traits that better suit their environment are more likely to survive and will reproduce more successfully than those that do not have such traits These advantageous traits are adaptations
As a result, the nature of the population will gradually change – evolution!
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Harsh Criticism
Darwin wrote down his ideas about evolution and natural selection in 1844
He did not try to publish his work until 1858
The theory of evolution goes against religious beliefs and was not accepted by the public in general
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On the Origin of Speciespublished in 1859 (pg. 280 1-4)
Inherited variation exists within the genes of every population or species (the result of random mutation or translation errors)
In a particular environment, some individuals of a population or species are better suited to survive and have more offspring
Over time, the traits that make certain individuals of a population able to survive and reproduce tend to spread in that population
There is overwhelming evidence from fossils and many other sources that living species evolved from organisms that are extinct
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Reproductive Isolation
Two populations of the same species do not breed with one another because of geographic separation, a difference in mating periods, or other barrier to reproduction
These isolated populations will become more different over time until they are no longer able to breed with one another
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The Tempo of Evolution
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The Theory of Evolution
Chapter 13 – Sect. 2: Evidence of Evolution
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Most Scientists Agree on the Following:
Earth is about 4.5 billion years old. Organisms inhabited Earth for most of its
history. All organisms living today share common
ancestry with earlier, simpler life forms.
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The Fossil Record
The preserved or mineralized remains or imprint of an organism that lived long ago.
Provide a record of Earth’s past life forms
Evidence of evolution can be seen in the fossil record.
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Formation of Fossils
The fossil record is not complete. Fossils do not form in all environments
Most fossils form when organisms are rapidly buried in fine sediments Bodies may decay too quickly or be eaten or
scattered Fossils are most likely to form in:
Wet lowlands, slow-moving streams, lakes, shallow seas, and areas near active volcanoes
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Anatomy & Development
Comparisons of the anatomy of different types of organisms reveal basic similarities in body structures The structures may have different functions
in different organisms Ex.) bones may be present in both organisms but
are reduced in size and have no use or less important function
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Vestigial Structures
Reduced in size or function, but may have been complete in an ancestor Ex.) hind limbs of
whales
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Homologous Structures
Structures that share a common ancestry ex.) forelimbs of
vertebrates
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Changes in DNA
Mutation – a change in the nucleotide-base sequence of a gene or DNA molecule If species have changed over time, then the
genes that determine the species’ characteristics should also have changed by mutation
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The Theory of EvolutionChapter 13 – Sect. 3: Examples of
Evolution
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Natural Selection at Work Environment dictates
the direction and amount of change in evolution
If the environment changes in the future, the set of characteristics that most help an individual reproduce successfully may change
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Factors in Natural Selection(pg. 288 1-4)
All populations have genetic variations. The environment presents challenges to
successful reproduction. Individuals tend to produce more offspring than
the environment can support. Individuals that are better able to cope with the
challenges presented by their environment tend to leave more offspring.
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Examples of Natural Selection
Strains of lung disease tuberculosis (TB) becoming resistant to certain antibiotics DNA in each strain is different = evolution &
natural selection Darwin’s finches developed different size
and shape beaks based on food sources Finches with proper beak for food survive =
evolution & natural selection
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Formation of New Species
Divergence – accumulation of differences between groups Leads to the formation of new species
Subspecies – populations of the same species that differ genetically because of adaptations to different living conditions Can become so different that can no longer
interbreed successfully Speciation – the process by which new species
form