Download NATURAL SELECTION

Bell ringer
1. A species of mockingbird lives in the Apalachicola National
Forest. One year, a few of the mockingbirds were born
with very long beaks. Over the next several years, the area
experienced particularly cold winters. The weather forced
the insects in the area to burrow deeper into the ground.
Surveys of the mockingbird population showed that the
number of long-beaked mockingbirds had increased.
What would account for this increase in the number of
long-beaked mockingbirds?
A.
B.
C.
D.
Short-beaked mockingbirds migrated to warmer climates.
Short-beaked mockingbirds became food for other animals.
Long-beaked mockingbirds were able to reach food and survived.
Long-beaked mockingbirds were able to stay warmer during the
cold winters.
NATURAL SELECTION
SC.912.L.15.13 Describe the
conditions required for natural
selection, including:
overproduction of offspring,
inherited variation, and the
struggle to survive, which result in
differential reproductive success.
Essential Question: How
can a change in the
environment initiate a
change in a population?
– Discuss mechanisms of
evolutionary change other than
natural selection such as
genetic drift and gene flow
– Describe how mutation and
genetic recombination increase
genetic variation.
NATURAL SELECTION
• WHAT YOU NEED TO KNOW
• You need to know the conditions required for
natural selection to occur. These include:
overproduction of offspring, inherited variation,
and the struggle to survive, which result in
differential reproductive success.
• You need to understand genetic drift and gene
flow.
• You need to know how mutation and genetic
recombination increase genetic variation.
NATURAL SELECTION:
• The process by which forms of life having traits that better
enable them to adapt to specific environmental pressures,
as predators, changes in climate, or competition for food or
mates, will tend to survive and reproduce in greater
numbers than others of their kind, thus ensuring the
perpetuation of those favorable traits in succeeding
generations.
• Sometimes called survival of the fittest.
• Individuals with favorable traits are more likely to leave
more offspring better suited for their environment.
Natural Selection
CHARLES DARWIN
• Proposed Evolution Resulting from Natural
Selection:
– Organisms Produce Many Offspring
– Competition for Food, Territory, Mates, etc.
– Those With Best Traits Survive
– Organisms Change Over Many Generations
• Time Frame: Millions of Years
OVERPRODUCTION OF OFFSPRING
• Overproduction of offspring: In any given
generation, populations tend to create more
progeny than can survive to reproductive age.
INHERITED VARIATION
• Variations of genomes between members of
species, or between groups of species thriving
in different parts of the world as a result of
genetic mutation.
STRUGGLE TO SURVIVE
1. To remain alive or in existence.
2. To carry on despite hardships or trauma;
persevere: families that were surviving in tents
after the flood.
3. To remain functional or usable.
REASONS:
Not enough resources (food, water, shelter,
mate, etc.)
DIFFERENTIAL REPRODUCTIVE SUCCESS
• When one group has more viable offspring than
another. If two populations are similar but one
has a variation that leads to fewer births and
more deaths, you will see differential
reproductive success between the populations.
GENETIC DRIFT
• Genetic drift is a mechanism of evolution that
occurs by random chance rather than natural
selection.
• In genetic drift, a population experiences a
change in the frequency of a given allele,
prompted by random luck rather than a need for
adaptation.
• This differs from natural selection, in which allelic
frequency is altered based on the fittest genes
surviving to reproduce and the weaker genes
dying off.
GENETIC DRIFT
Genetic drift tends to be a phenomenon amongst smaller populations, while
natural selection holds sway in larger populations.
GENETIC DRIFT
GENE FLOW
• the alteration of the frequencies of alleles of
particular genes in a population, resulting
from interbreeding with organisms from
another population having different
frequencies.
GENE FLOW
GENE FLOW
GENETIC VARIATION
• Without genetic variation, some of the basic
mechanisms of evolutionary change cannot
operate.
• There are two sources of genetic variation,
which we will learn more about:
GENETIC VARIATION
• Mutations are changes in the DNA. A single
mutation can have a large effect, but in many
cases, evolutionary change is based on the
accumulation of many mutations.
• Genetic Recombination is the process of
forming new allelic combination in offspring
by exchanges between genetic materials (as
exchange of DNA sequences between DNA
molecules).
MUTATION
A permanent, heritable change in the nucleotide
sequence in a gene or a chromosome; the process in
which such a change occurs in a gene or in a
chromosome.
GENETIC RECOMBINATION
We Do
• Natural selection worksheet
Bell ringer
A species of mockingbird lives in the Apalachicola National
Forest. One year, a few of the mockingbirds were born with
very long beaks. Over the next several years, the area
experienced particularly cold winters. The weather forced the
insects in the area to burrow deeper into the ground. Surveys
of the mockingbird population showed that the number of
long-beaked mockingbirds had increased. What would
account for this increase in the number of long-beaked
mockingbirds?
A.
B.
C.
D.
Short-beaked mockingbirds migrated to warmer climates.
Short-beaked mockingbirds became food for other animals.
Long-beaked mockingbirds were able to reach food and survived.
Long-beaked mockingbirds were able to stay warmer during the
cold winters.
Bell ringer
A species of mockingbird lives in the Apalachicola National
Forest. One year, a few of the mockingbirds were born with
very long beaks. Over the next several years, the area
experienced particularly cold winters. The weather forced the
insects in the area to burrow deeper into the ground. Surveys
of the mockingbird population showed that the number of
long-beaked mockingbirds had increased. What would
account for this increase in the number of long-beaked
mockingbirds?
A. Short-beaked mockingbirds migrated to warmer climates.
B. Short-beaked mockingbirds became food for other animals.
C. Long-beaked mockingbirds were able to reach food and
survived.
D. Long-beaked mockingbirds were able to stay warmer during the
You Do
A subspecies is a different group within a species that is able to
interbreed but is usually prevented from doing so by geographical
isolation. The Florida Panther is a subspecies of the American
Cougar, and there are very few (less than 100) remaining in its
population. When populations get this small, inbreeding results in
low genetic diversity. The result is fewer beneficial adaptations
that might help the animals survive environmental change, as well
as an increase in the occurrence of genetic abnormalities. How can
this subspecies of cougar be saved from extinction?
A. Keep the existing population in a controlled environment until their
population increases.
B. Increase the genetic diversity by introducing other subspecies of
cougar to the population.
C. Relocate remaining Florida Panthers to the larger populations of
cougar subspecies in Texas and California.
D. Remove all the panthers with genetic abnormalities from the
environment and leave only the healthy ones.
Florida Panthers are an endangered species. Because the
remaining population of Florida Panthers is quite small and fairly
closely related, there are concerns that there is not enough
genetic variability within the population. How does greater
genetic variability within the population affect the Florida
Panthers' reproductive success?
A. It reduces the need to keep Florida Panthers alive in
captivity.
B. It increases the rate of mutations that create helpful
adaptations.
C. It reduces the expansion of harmful traits that result
from inbreeding.
D. It increases the chance that the Florida Panther will be
able to survive sea level rise.
Natural selection is a process that results in change within
a species over time. Which of the following is NOT a
condition required for natural selection to result in
speciation?
A.
B.
C.
D.
overpopulation of the species
genetic equilibrium of the species
genetic variation within the species
competition for survival within the species