the theory of evolution. what is evolution? change over time fossil evidence shows that living...
TRANSCRIPT
The Theory of Evolution
What is Evolution?
• Change over time• Fossil evidence
shows that living things have not always been the same as today
History of the theory…
• James Hutton (1785)– Earth formed very slowly, earth is old – Forces beneath the earth’s surface act to form
mountains, rocks, and valleys
History of the theory…
• Thomas Malthus (1798)– Predicted that the human population would
grow faster and larger than the space and food supplies will allow
– Predicted there would be a great struggle for survival, leading to wars and famine
History of the theory…
• Jean-Baptiste de Lamarck (1809)– Was the first to propose a mechanism for
evolution– Hypothesized that the environment influenced
the development of traits– Inheritance of acquired traits
Lamarck’s Theory
• Acquired traits are developed as needed– Example:
• long neck of giraffe• Fins and tail of a dolphin
Lamarck’s Theory-problems…
• Acquired traits are passed on to offspring– We know that only traits that are controlled by
genes can be passed down to future generations
• A trait that is not needed will be lost– We know that an organism cannot “lose” a
trait it had at the start of its life, because traits are controlled by its genes
History of the theory…
• Charles Lyell– His book, Principles of Geology, explained
that earth continues to change just as it has for millions of years
– And processes that have shaped (and continue to shape) the earth are very slow
History of the theory…
• Charles Darwin (1832)– Set sail as ship’s naturalist on the HMS
Beagle– Read the works of Malthus, Hutton, and Lyell
while sailing around the world– Collected evidence that would be used to
support his developing theory
History of the theory…
• Alfred Wallace (1858)
– Wrote to Darwin speculating on evolution by natural selection
Darwin’s Theory
• On the Origin of Species (1859)• Individuals differ and some of the variation is
inheritable• Many more offspring are born than can survive• There is competition for resources• Each individual has advantages and
disadvantages in the struggle to survive• Those most adapted to the environment will
survive and pass their traits on
Evidence to support Darwin’s Theory
• Fossil record
Evidence to support Darwin’s Theory
• Fossil record• Geographic
distribution of living species
Evidence to support Darwin’s Theory
• Fossil record• Geographic
distribution of living species
• Homologous body structures
Evidence to support Darwin’s Theory
• Fossil record• Geographic
distribution of living species
• Homologous body structures
• Embryological similarities
Weaknesses of the theory…
• Cannot explain how the first life began– First single cell– First multi-cellular
organism
Weaknesses of the theory…
Relies on random mutation as the explanation for change– Most mutations are
harmful
Weaknesses of the theory…
• A “missing link” is not known for any two species– All species seem to have come into being
independently of any other
More like a lizard or a bird?
• Theory changes as more evidence is found– Dinosaur theory