Download Natural Selection

Natural Selection
Darwin’s Breakthrough Theory
The Struggle for Existence
 Darwin believed that there is a constant
struggle for survival in the natural world
 The faster or “smarter” the predator the
more likely it is to capture food
 The better camouflaged, protected, or
cunning the prey the more likely it would
not be eaten
Survival of the Fittest
 Fitness – how well an individual is able to
survive and reproduce in a specific
environment
 Adaptation – an inherited trait which makes an
individual more fit in its environment
 Darwin called this natural selection because of
its similarity to artificial selection
How Natural Selection
Works
 All populations have genetic diversity
(they are not 100% identical)
 If an individual is born/produced that has
trait which make it more fit it then is more
likely to survive and reproduce
 When it reproduces there is a higher
chance that the beneficial traits will be
passed on to its offspring
Natural Selection
 Over very long periods of time this
selection can lead to the entire
population having the similar beneficial
traits which then makes the entire
population more fit
 Peppered moth activity
 Survival of the Sneakiest
Evidence of Evolution
 The fossil record
 Shows the gradual
change in species
over LONG periods of
time
Geographic Distribution of
Living Species
 The existence of
similar but different
species on different
continents leads to
two conclusions
 The species evolved
from a common
ancestor
 The continents where
once connected
(Pangea)
Homologous Body
Structures
 Structures with the same developmental
origins and internal structures but are
used for different things
Vestigal Organs
 “left over” structures from a common
ancestor
Similarities in Embryology
 The early stages of development of
animals with backbones are very similar