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Ecology Shapes Evolution
The study of interaction between an organism
and its environment and to one another.
• Defined as the change that occurs in the characteristics of
the living things over time.
– It may be change in the form and behavior of organisms
between generations
– It may be genetic changes in a population of organisms over
time.
• Evolutionary solution
• a genetically determined characteristics that improves
an organism’s ability to survive and reproduce in a
particular environment.• Behavioral, morphological or physiological.
• Ecology for the most part ignores evolution because
organisms are treated as constants," said David Reznick,
an evolutionary biologist at the University of California
• the general assumption is that ecological interactions
happen on such a short time scale in comparison to
evolution that evolution can be ignored
• refers to diversity in gene frequencies.
• is a term used to describe the variation in the DNA
sequence in each of our genomes
The basic evolutionary unit is
Population.
• Population
– A group of individuals of the same species that live in the same
area and interbreed.
• Gene pool– Consist of all the genes in all the individuals making up a
population.
• Mutations
• Gene flow (migration)
• Genetic Drift
• Natural Selection
• Sex
• A heritable change in the kind, structure, sequence or
number of the component parts of DNA.
– Produce new alleles and new genes.
• Original source of genetic variation that serves as raw
material for evolution.
• Are random
• Effects depends upon on how it changes the structure, function
or behavior of the individual.
– may be beneficial, neutral, or harmful to the individuals that inherit
them.
Chemicals, radiation, copying errors
• Mutations do not try to supply what the organism
needs.
– These mutations are not likely to account for a change in allele
frequency.
– These good mutations bring new genetic information into the
genetic pool.
• The movement of alleles between
populations as a result of movement of
individuals from one population to
another.
• A change in allele frequency that can occur
when mating with members from another
population occurs.
• Tends to reduce differences between
populations over time
• Chance events that cause allele frequencies to fluctuate
unpredictably from one generation to the next.
• Chance determine reproductive success.
• Tends to reduce genetic variation
If there is a drastic change (disease or natural catastrophe) in the
survival of a large population, there is little change in the frequency of
that population's alleles. In a smaller population, drastic change can
result in loss of an entire allele.
Genetic Drift
Genetic Drift: Bottleneck effect
• The change in allele frequency in a population due to
chance following a sharp reduction in the population size.
• When a small portion of a population migrates to another area,
starting a new population.
• The allele frequencies in their gene pool may be different than the
original population.
Genetic Drift: Founder effect
Natural Selection
• is the process by which individual organisms with
favorable traits are more likely to survive and reproduce.
Natural Selection
• traits determine reproductive success;
• Alleles that confer “success” are more likely to be passed on to future
generations and will increase their % relative to other alleles over time.
Technical term for “success” is differential reproductive success
• Natural selection is the primary mechanism of
adaptive evolution• Accumulates and maintains favorable genotypes in a
population
• Natural selection increases the frequencies of
certain genotypes, fitting organisms to their
environment over generations
Sexual Selection
• a form of natural selection in which individuals with certain
traits are more likely than other individuals to obtain
mates.• Is a direct competition among individuals of one sex for mates of the
opposite sex
• Sexual Dimorphism
– Distinction in the appearance between male and female
Intersexual selection
Intrasexual selection
2 Processes Involved In Evolution
• Adaptation
– traits that confer an advantage to those individuals who leave
more offspring
• Speciation
– The smallest independently evolving unit.
What is a Species?
A species is a group of individuals capable of interbreeding to
produce fertile offspring.
This is the biological
species concept. Like all
attempts to define a
species, it has a problem.
Biological species concept
• defined as a group of individuals that actually or potentially interbreed in nature.
• Focus on similar characteristics AND the ability of organisms to interbreed in
nature and produce viable, fertile offspring
• ADVANTAGE:
• It is widely used by scientists
• DISADVANTAGE:
• Can’t be applied for species the reproduce asexually
• Uncertain for populations that are physically separated and don’t have the
opportunity to breed naturally
• Can’t be applied to fossil species, which are no longer reproducing
Morphological Species Concept
• Focus on the morphology of an organism.
• It refers to the body size, shape and other structural features.
• Advantage:
• This can be applied to asexual organisms and fossils
• Does not require information on possible interbreeding.
• Disadvantage
• Too much variation within a species
• Approach relies on subjective criteria, and researchers may disagree on which features
distinguish a species.
Speciation
http://scienceblogs.com/evolvingthoughts/2007/03/11/basic-concepts-allopatry-and-s/
The key to speciation is the evolution of
genetic differences between incipient
species.
Reduction to gene flow plays a critical
role in speciation.
Allopatric Speciation: The Great Divide
Speciation by geographic isolation
Two models of allopatric speciation
• Dispersal model: colonization of remote islands by mainland organism
Vicariance may be due to a variety of factors:
• Changes in courses of rivers
• Mountain-building events
• Volcanism
•Environmental changes
Two models of allopatric speciation
• Vicariance model
Allopatric Speciation: A change in the environment
Two species of ground squirrel are believed to have descended from a
common ancestral population that was separated by formation of the Grand
Canyon.
Harris’ antelope squirrel White-tailed antelope squirrel
Sympatric Speciation
Does not require large scale geographic distance
to reduce gene flow between parts of population.
• A new species arises within the same
geographic area as its parents.
• Occur when mating and resulting gene flow
between populations are reduced by factors
such as polyploidy, habitat differentiation, and
sexual selection.
Sympatric Speciation
• Industrial Melanism
Sympatric Speciation
Some key insights:
-Mating occurs on the host plant
-The adult female selects the host
-Host selection is under genetic control
-Reproductive isolation by different factors
Domestication
Extinction
Causes of Extinction: Habitat Alteration
Hunting
Predator control
Mutation
Immigration
Individual Selection
Individual Selection VS Group Selection
ALTRUISM
• may be explained by the
natural instinct to improve
the chances of passing on
one's genes.
• Behavior that benefits others
at a personal cost to the
behaving individual.
Evolution of Evolution: Mimicry