Document 15573406

• 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
• 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
Evolution - "Stated Clearly"
• 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
• Genetic Equilibrium
• Situation in which allele
frequencies remain constant
Founder Effect
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, 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"
What Darwin Never Knew - Part 1