Evolution of Biodiversity

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Transcript Evolution of Biodiversity

Evolution of Biodiversity
1. Scales of biodiversity
2. Species richness vs. Species evenness
3. Biodiversity in individuals
• Biodiversity in populations (4. artificial selection
vs. 5. natural selection)
**you may want to put in two boxes**
6. Random changes in genetic equilibrium
7. Types of Speciation
8. Rate of natural selection
Three different scales of diversity
• Ecosystem diversity
• Species diversity
• Genetic diversity
Just for fun…
• How many species are found on Earth?
– Scientists have named 2 million but are estimating
around 5-100 million out there.
• Which group of organisms has the most
– Insects (total number of tropical insects could be
30 million.
– Scientists found that perhaps 8 million beetles
species in the tropics that feed on one type of
Species richness vs. Species evenness
• Number of species in a
given area.
• Tells whether a particular
ecosystem is numerically
dominated by one species
or whether all of its species
have similar abundances.
So what creates biodiversity?
In individuals?
• Mutations: change in DNA
• Which of the following is a real mutation
found in humans?
a. Lactose tolerant
b. AIDS immunity
c. Blue eyes
• Mutations
– Genetic change
– Can occur by chance
– Many are lethal
• Quickly eliminated
– Some are useful
• Become part of gene pool by the process of natural
In populations?
Population Genetics and Evolution
• Populations, not individuals, evolve,
• Evolution occurs as a population’s genes and
their frequencies change over time.
• This can happen by artificial selection or
natural selection
Artificial Selection
• When humans determine which individuals
– GMO’s and genetic engineering
Natural Selection
• Nature decides the most fit organisms.
• A random process
• Charles Darwin’s theory of Evolution
Individuals produce an excess of offspring
Not all offspring survive
Individuals differ in their traits
Differences in traits can be passed on from parents to
– Differences in traits are associated with differences in
the ability to survive and reproduce.
• Gene Pool- All of the
alleles of the
population’s genes are
together like being
together in a large pool.
equilibriumPopulation in which the
frequency of alleles remains the
same over generations.
Random Changes in Genetic Equilibrium
• Genetic drift- the alteration of allelic
frequencies by chance events.
– Greatly affect small populations
– Genes of the original ancestors represent only a
small fraction of the gene pool
– Result in an increase of rare alleles
Child has six fingers due to
genetic drift.
This child belongs to an
Amish Community in PA.
They are an isolated
population due to religious
and belief system.
One of the original
ancestor’s have the
recessive allele.
Because of the small gene
pool, many individuals
inherited the recessive
allele over time
Random Changes in Genetic Equilibrium
• Gene Flow- The transport of genes by
migrating individuals.
– In other words movement of individuals in and
out of a populations.
• When an individual leaves a population, its genes are
lost from the gene pool.
• When an individual enter a population, their gene are
added to the gene pool.
Random Changes in Genetic Equilibrium
• Bottle-neck effect: if a population experiences
a drastic decrease in size some genotypes will
be lost and the genetic composition of the
surviors will differ from the composition of the
original group.
Evolution of Species
• Speciation- occurs when
members of similar
populations no longer
interbreed to produce
fertile offspring.
• The formation of a river
may divide the frogs into
two populations. A new
form may appear in one
• Over time, the divided
populations may become
two species that may no
longer interbreed, even if
Allopatric Speciation
• Geographic isolationOccurs whenever a
physical barrier divides
a population.
Allopatric Speciation
• Reproductive isolation- occurs when formerly
interbreeding organisms can no longer mate
and produce fertile offspring.
– Genetic material of the population becomes so
different that fertilization can not occur
– Behavioral
• An example would be mating at different seasons
Sympatric Speciation
• Change in Chromosome Numbers
– Polyploid- Any individual or species with a
multiple of the normal set of chromosomes.
– Flowering plants and important crop plants
• Wheat
• Cotton
• Apples
5. Speciation Rates
• Gradualism- is the idea that species originate
through a gradual change of adaptations.
• Punctuated equilibrium- hypothesis that
argues that speciation occurs relatively
quickly, in rapid bursts, with long periods of
genetic equilibrium .
How does evolution shape niches
and determine species distribuation.
Limiting Factors
Nutrients (nitrogen)
Habitat space
Soil type
Population size
Genetic diversity
Niche= where an organism is the most
Fundamental Niche
• Full potential role of an
Realized Niche
• What it can realistically
fulfill when taking into
account predation and
What happens when resources
run out?
Resource partitioning: the evolutionary
change in species in response to
selection pressures (usually from
Things that can cause this…
• Invasive species: species that are not native to
a area and have no natural predators.
As a review…
• Value of Ecosystems
• Changes to ecosystems
– Resistance vs. resilience
– Intermediate disturbance hypothesis
– Succession (primary vs. secondary)
• Biodiversity (results from changes)
Species richness vs. species evenness
Biodiversity in individuals = mutations
Biodiversity in populations = evolution
• Artificial vs. Natural Selection
Changes in genetic equilibrium
Types of speciation
Rates of natural selection
Things that effect natural selection
Limiting factors
Fundamental niche vs. realized niche
Invasive species
Resource partioning