Download 11.6 Patterns in Evolution TEKS 7B, 7D, 7E, 7F The student is

11.6 Patterns in Evolution
TEKS 7B, 7D, 7E, 7F
The student is expected to:
7B analyze and evaluate scientific
explanations concerning any data of
sudden appearance, stasis, and sequential
nature of groups in the fossil record;
7D analyze and evaluate how the elements
of natural selection, including inherited
variation, the potential of a population to
produce more offspring than can survive,
and a finite supply of environmental
resources, result in differential
reproductive success;
11.6 Patterns in Evolution
TEKS 7B, 7D, 7E, 7F
(continued)
7E analyze and evaluate the relationship
of natural selection to adaptation and to
the development of diversity in and
among species;
7F analyze and evaluate the effects
of other evolutionary mechanisms,
including genetic drift, gene flow,
mutation, and recombination
11.6 Patterns in Evolution
KEY CONCEPT
Evolution occurs in patterns.
TEKS 7B, 7D, 7E, 7F
11.6 Patterns in Evolution
TEKS 7B, 7D, 7E, 7F
Evolution through natural selection is not random.
• Natural selection can have direction.
• The effects of natural selection add up over time.
11.6 Patterns in Evolution
• Convergent evolution describes
evolution toward similar traits in
unrelated species.
TEKS 7B, 7D, 7E, 7F
11.6 Patterns in Evolution
TEKS 7B, 7D, 7E, 7F
• Divergent evolution describes evolution toward different
traits in closely related species.
kit fox
red fox
ancestor
How do convergent and divergent
evolution illustrate the directional
nature of natural selection?
11.6 Patterns in Evolution
TEKS 7B, 7D, 7E, 7F
Species can shape each other over time.
• Two or more species can evolve together through
coevolution.
– evolutionary paths become connected
– species evolve in response to changes in each other
11.6 Patterns in Evolution
TEKS 7B, 7D, 7E, 7F
• Coevolution can occur in beneficial relationships.
11.6 Patterns in Evolution
TEKS 7B, 7D, 7E, 7F
• Coevolution can occur in competitive relationships,
sometimes called evolutionary.
11.6 Patterns in Evolution
TEKS 7B, 7D, 7E, 7F
Species can become extinct.
• Extinction is the elimination of a species from Earth.
• Background extinctions occur continuously at a very low
rate.
– occurs at roughly the same
rate as speciation
– usually affects a few species
in a small area
– caused by local changes in
environment
11.6 Patterns in Evolution
TEKS 7B, 7D, 7E, 7F
• Mass extinctions are rare but much more intense.
– destroy many species at global level
– thought to be caused by catastrophic events
– at least five mass extinctions in last 600 million years
11.6 Patterns in Evolution
TEKS 7B, 7D, 7E, 7F
Speciation often occurs in patterns.
• A pattern of punctuated equilibrium exists in the fossil
record.
– theory proposed by Eldredge and Gould in 1972
– episodes of speciation occur suddenly in geologic
time
– followed by long periods of little evolutionary change
– revised Darwin’s idea that species arose through
gradual transformations
11.6 Patterns in Evolution
TEKS 7B, 7D, 7E, 7F
• Many species evolve from one species during adaptive
radiation.
– ancestral species diversifies into many descendent
species
– descendent species
usually adapted to
wide range of
environments