Part 1 How do organisms evolve? - Coggle Diagram
How do organisms evolve?
11.1 Genetic Variation Within Population
1)Genetic variation in a population increases the chance that some individuals will survive.
To have different phenotype, a population must have genetic variaton
leads to phenotypic variation
Phenotypic variation is necessary for natural selection
Genetic variation is stored in a population's gene pool
made up of all allele in a population
allele combinations form when organisms have offspring
alleles of all of the individuals in a population.
Allele frequencies measure genetic variation
measures how common allele is in population
can be calculated for each allele in gene pool
2)Genetic variation comes from several sources.
Mutation is a random change in the DNA of a gene.
can form new allele
can be passed on tooffspring if in reproductive cells.
Recombination forms new combinations of alleles
usually occurs during meiosis
parents' alleles arranged in new ways in gametes
Hybridization is the crossing of two different species.
occurs when individuals can't find mate of own species.
topic of current scientific research
other mechanisms of revolution
1.less likely to have some individuals that can adapt
harmful alleles can be become more common due to chance
1.common i small populations2.causes a loss of genetic diversity 3.change in allele frequencies due to chance
a few individual start a new population
occurs after start of new populations
drastically reduces population size
effect is genetic drift that occurs after a population has been reduced in size
1.the is movement of allele between population2.increases the chance that two population will evolve into different species3.when individual new population and reprodce
1.when certain trait increase mating success 2.it occurs due to higher cost of reproducing for females
11.2 Natural Selection in Population
1) Natural selection acts on distributions of traits.
This type of distribution, in which the frequency is highest near the mean value and decreases toward each extreme end of the range, is called a normal distibution
When these frequency values are graphed, the result is a bell-shaped curve
highest frequency near mean value
frequencies decrease toward each extreme value
Traits not undergoing natural selection have a normal distribution
2) Natural selection can change the distribution of a trait in one of three ways.
Microevolution is evolution within a population
observable change in the allele frequencies
can result from natural selection
Natural selection can take one of the three paths
Directional selection favors phenotypes at one extreme
left or right
An extreme phenotype that was once rare in a population becomes more common.
example: The rise of drug-
Stabilizing selection favors the intermediate phenotype
example: The gall fly and its
bell shape is broken
Disruptive selection favors both extreme phenotypes
example: feather color in male lazuli buntings, a bird species native to North America
he provide a frame work for understanding how population evolve and is a type of model
if five condition are met
1.very large population, no genetic drift2.no immigration ,no gene flow 3, no mutations , no new alleles added to gene pool
4, random mating, no sexual selection 5, no natural selection .all traits aid equally in survival
p2 + 2pq +q2 =1
p=dominant allele q=recessive allele pq=heterozygous p2=dominant homozygous q2=recessive dominant 2pq=heterozygous genotype
there are five factors that can lead to evolution
genetic drift gene flow mutations produce. sexual selection natural selection
11.5 Speciation Through Isolation
New species can arise when populations are isolated
B. Populations can become isolated in several ways.
can cause isolation.
2.Geographic barriers can cause isolation.
can cause isolation.
A. The isolation of populations can lead to speciation.
Reproductive isolation occurs when members of different populations can no longer mate successfully.
is the final stage of
Speciation is the rise of two or more
species from one existing species.
11.6 Patterns in Evolution
Evolution occurs in patterns.
Evolution through natural selection is
1.Convergent evolution describes evolution toward similar traits in unrelated
2.Divergent evolution describes evolution toward different traits in closely
Species can shape each other over time.
Coevolution is the process in which two or more species evolve in response
to changes in each other.
Coevolution can occur in beneficial relationships.
Evolutionary arms races:
Coevolution can also occur in competitive relationships, sometimes called evolutionary.
Species can become extinct.
Extinction is the permanent loss of species
1Background extinctions occur continuously
at a very low rate.
2Mass extinctions are rate but much more
Speciation often occurs in patterns.
punctuated equilibrium, which states that episodes of speciation occur suddenly in geologic time and are followed by long periods of little evolutionary chances.
Adaptive radiation is the rapid evolution of diverse species from ancestral species.