Download Evolution and Natural Selection

EVOLUTION AND
NATURAL SELECTION
Theory of Evolution
•Evolution = Change in a population over time
•Theories = explanation of a natural phenomenon
• Theories can be either supported or disproved but
never proven
•What phenomenon does evolution explain?
•Every organism is different (diversity)
•All organisms have things in common (Genetic
code)
Theory of Evolution
2 Views of evolution:
•Microevolution = Small changes over short periods
of time
• Supports improvements in existing species
•Macroevolution = small changes accumulating
over long periods of time resulting in major
changes
• Supports the formation of new species
Three Types of Evolution
1. Divergent – similar
Organisms become
increasingly different
because of different types
of environments (ex.
Darwin’s Finches)
Three Types of Evolution
2. Convergent – different
organisms become
increasingly similar
because of similar
types of environments
(ex. Sharks and
dolphins)
Three Types of Evolution
3. Coevolution (Parallel) two non-related species
change because of
their close interactions
(ex. Predator/prey or
plant/pollinator)
Cladogram
•Cladogram = tree showing evolutionary
relationships based on similar characteristics
• Shows divergent evolution
What trait separates rodents from
birds?
Which two species are more
related, crocodiles and birds or
crocodiles and rabbits?
Natural Selection
•Natural Selection = organisms adapt to their
environment (“survival of the fittest”)
History of Natural Selection Theory
•Jean-Baptiste Lamarck
(1700s) = first person to state
organisms change over time
and new organisms are
modified from descendants
of older organisms
• Theory of Acquired Traits
History of Natural Selection Theory
•Charles Darwin (1800s) – sailed on the H.M.S.
Beagle and gathered data from organisms
(fossils, finches, etc.)
Charles Darwin
•From his data, Darwin hypothesized that all
species descended from one or few original
types of life
•He concluded that the way species/organisms
change over time was by natural selection
Process of Natural Selection
• Must have a variation in traits of a
population (different genes)
• Must have environmental pressures
that favor one variation of that trait
over the other
• Organisms with better traits survive
better and longer, reproduce, and
pass those good traits to offspring
• Result = population better suited for
environment
What causes evolution to happen?
1. Natural Selection
2. Geographic Isolation
• Organisms become isolated by
geographic barrier
• If they are no longer able to
reproduce, they may become
two separate species
(speciation)
3. Artificial Selection
• Humans choose which traits to
select for (ex. Dog breeding,
genetic engineering, etc.)