Transcript Theory of Evolution - Solon City Schools

Theory of
Evolution
Chapter 15
What is Evolution?
• Change over time
• The process by which modern organisms have
descended from ancient organisms
2 Competing Theories:
Darwin and Lamarck
Darwin and Lamarck agreed on a
few things…
• Life is still changing
• Living things become better suited to their
environment
• All organisms are related
• Simple  Complex
Lamarck
• Organisms can change the shape or size
of organs depending on how they use
them
• Acquired characteristics could be
inherited.
– If an animal altered its body during its lifetime,
that change will pass to offspring
• Organisms have a tendency toward
perfection
Darwin
Inherited Variation and Artificial
Selection
• Artificial Selection: nature provides the
variation and humans select those
variations they find useful
• Darwin had no idea how heredity actually
worked
Evolution by Natural Selection
• Darwin wanted to compare processes in
nature to artificial selection
– The struggle for existence
– Survival of the fittest
– Descent with modification
The Struggle for Existence
• High birth rates and shortage of basic
needs would force organisms to compete
• Struggle for Existence: each species
compete regularly to obtain food, living
space, and other necessities of life.
Survival of the Fittest
• How well suited is an organism to its
environment?
• Fitness: the ability of an individual to survive
and reproduce in its specific environment
• Darwin proposed that fitness is a result of
adaptations
• Individuals that are better suited to their
environment survive and reproduce most
successfully
Natural Selection
• Only certain individuals of a population
reproduce
• In natural selection, traits being selected
contribute to fitness in the environment
• Natural selection results in changes in
inherited characteristics in a population
Lamarck-
why was he wrong??
– Lamarck did not know how traits were
inherited
– He did not know that an organism’s behavior
has no effect on the traits it passes down
– Acquired characteristics are not passed on to
offspring,
– Organisms do not get what they "need"
through "inner wants" or through "use and
disuse” Individual intentions do not play a
role.
– Instead, the animals well suited survive and
reproduce while those ill suited die