Transcript Patterns of Evolution

Patterns of Evolution
Sec 17-4
Microevolution
• Refers to small-scale evolutionary patterns
that occur in a population over short
periods of time, such as generations
• Change in genes of populations
Examples of Microevolution
• Natural Selection
• Migration
• Mate Choice
• Mutation
• Genetic Drift
Natural Selection and Migration
• As you have learned, natural selection can
cause an increase or decrease in certain alleles
in a population
• Migration: is the movement of individuals into,
out of, or between populations
• Population: a group of organisms of the same
species that live in a specific geographical area
Mate Choice
• If parents are paired up randomly in a
population a random assortment of traits
will be passed on to the next generation
• If parents are limited or selective in their
choice of mates, a limited set of traits will
be passed on (artificial selection)
• Larger male iguanas on the Galapagos
islands are more favorable
Mutation and Genetic Drift
• Mutation- any change in DNA
• Mutation can change the numbers and
types of alleles from one generation to the
next
• However changes are rare
• Genetic Drift: the random change in allele
frequency in a population
Macroevolution
• Refers to large scale evolutionary patterns and
processes that occur over long periods of time
• Includes
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Extinction
Adaptive radiation
Convergent evolution
Coevolution
Punctuated equilibrium
Changes in developmental genes
Extinction
• If all members of a lineage die off or
simply fail to reproduce, the lineage is said
to be extinct
Natural selection did not allow them to evolve
to new environments
Mass Extinctions
• Periods of time when entire ecosystems were
destroyed
– Causes collapse of food chains and food webs
– Extinction was due to environments collapsing rather
than natural selection
• Ice ages, asteroids,…
• Large loss of life leaves many holes for new
organisms to evolve into
Adaptive Radiation
• The evolution of several different species
from one common species
– EX: Darwin’s 13 finches all evolved from one
common species of finch
• A side effect is that these radiations can
produce unrelated organisms that look
similar
Convergent Evolution
• When unrelated organisms come to
resemble one another
Due to natural selection working on the raw
materials of organisms that live in similar
environments
• EX: fish and sea mammals
– All adapt a streamlined figure, appendages to move
through water,…
Coevolution
• Organisms that are closely connected to
one another by ecological interactions may
evolve together
When one organism changes, the other
organism will change as well
• Example: Pollination
Gradualism/Punctuated
Equilibrium
• Gradualism is the idea that evolution
occurs slowly and steadily over time
• Punctuated equilibrium is the idea that
long, stable periods of “organism
equilibrium” are interrupted by brief
periods of rapid change
Gradualism
Punctuated
Equilibrium