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• Evolution
• Gradual change in the genetics of a
species/population over time; how
descendants differ from their ancestors.
Types of Selection
• Artificial Selection
• Selection by humans for breeding of useful
traits from the natural variation among
different organisms, Ex. Dog Breeding
Types of Selection
• Natural Selection
• Process by which individuals that are
better suited to their environment
survive and reproduce successfully
How to Survive
• Struggle for Existence
• Competition among members
of a species for food, living
space, and the other
necessities of life
• Fitness
• Ability of an organism to
survive and reproduce in its
• Adaptation
• Inherited characteristic
that increases an
organism’s chance of
Do you think that
there is a struggle for
existence between
Example of natural selection,
adaptations, fitness and the struggle for
Peppered Moth
Peppered Moth Evolution 2:04
• Descent with Modification
• Principle that each living species has descended, with changes, from other
species over time
• Common Descent
• Principle that all living things have a common ancestor
NOVA Embryo
Natural Selection - "Stated
Clearly“ 9:18
• Homologous Structures
• Structures that have different mature
forms in different organisms but
develop from the same embryonic
tissues; common ancestor
• Analogous Structures
• Structures that appear the same but
do not develop because of similar
ancestry; same selective pressures
• Vestigial Organs
• A structure or organ that is useless
today but an ancestor used
• Gene Pool
• Combined genetic information of all
the members of a particular population
• Relative Frequency
• Number of times an allele occurs in a
gene pool compared with the number of
times other alleles occur
Who is represented in
the gene pool?
• Genetic Drift
• Random change in allele frequencies
that occurs in small populations
• Founder Effect
• Loss of genetic variation that occurs when
a new population is established by a very
small number of individuals from a larger
population Founder Effect 2:55
• Genetic Equilibrium
• Situation in which allele
frequencies remain constant
How do we get separate species?
• Speciation
• Formation of new species
• Reproductive Isolation
• Separation of a species or populations so that they
cannot interbreed and produce fertile offspring
• Behavioral Isolation
• Form of reproductive isolation in which two
populations have differences in courtship rituals or
other types of behavior that prevent them from
interbreeding. Ex. Albatross 1:04, Ex. Birds of Paradise
How do we get separate species?
• Geographic Isolation
• Form of reproductive isolation in which two
populations are separated physically by
geographic barriers such as rivers, mountains,
or stretches of water
• Temporal Isolation
• Form of reproductive isolation in which two
populations reproduce at different times
CC - Big History "Evolution“ 15:04
What Darwin Never Knew 1:54:08 start @ 2:17