Evolution of Biodiversity

Evolution of Biodiversity

1. Scales of biodiversity2. Species richness vs. Species evenness3. 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 equilibrium7. Types of Speciation8. 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 species?– 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 tree.

Species richness vs. Species evenness

Richness• Number of species in a

given area.

Evenness• 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 tolerantb. AIDS immunityc. 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

selection

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 breed. – 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

offspring.– 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.

Genetic equilibrium- Population 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 population.

• Over time, the divided populations may become two species that may no longer interbreed, even if reunited.

Allopatric Speciation

• Geographic isolation- Occurs whenever a physical barrier divides a population.

• 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

Allopatric 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

Sympatric Speciation

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• Light• Temperature• Nutrients (nitrogen)• Gases• Habitat space• Water• Wind• Latitude• Altitude• Soil type• Population size• Genetic diversity

Niche= where an organism is the most fit.

Fundamental Niche• Full potential role of an

organism

Realized Niche• What it can realistically

fulfill when taking into account predation and competition

What happens when resources run out?

Resource partitioning: the evolutionary change in species in response to selection

pressures (usually from competition)

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)– Scales– 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