Evolution of Biodiversity (Earth is home to tremendous diversity of…
Evolution of Biodiversity
Earth is home to tremendous diversity of species
We can think about
on three scales:
Ecosystem diversity- the variety of ecosystems within a given region.
Species diversity- the variety of species in a given ecosystem.
Genetic diversity- the variety of genes within a given species.
How many species?
a group that is distinct from other groups in terms of size, behavior, or biochemical properties and can interbreed to produce viable offspring.
The number of species in a given area is the most common measure of biodiversity (the quantity and variety within an ecosystem).
the number of species in a given area.
the measure of whether a particular ecosystem is numerically dominated by one species or are all represented by similar numbers of individuals.
Evolution is the mechanism underlying biodiversity
a change in the genetic composition of a population over time.
Microevolution- evolution below the species level.
Gives rise to diversity within a species.
Macroevolution- Evolution which gives rise to new species or new genera, family, class or phyla.
Gives rise to new species, genus, class, family, etc.
Creating Genetic Diversity
physical locations on chromosomes within each cell of an organism.
the complete set of genes in an individual.
- a random change in the genetic code.
First way that diversity is created.
Most mutations are detrimental.
Some mutations improve an organisms chances of survival and reproduction.
the actual set of traits expressed in an individual.
occurs as chromosomes are duplicated during meiosis and mitosis.
Second way diversity is created.
Piece of one chromosome breaks off and attaches to another chromosome.
Occurs by 3 primary mechanisms:
Evolution by artificial selection-
when humans determine which individuals breed.
Evolution by natural selection-
the environment determines which individuals are most likely to survive and reproduce.
Darwin’s theory of evolution by natural selection
Individuals produce an excess of offspring.
Not all offspring can 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.
Fitness: Ability to survive and reproduce.
Adaptation: Traits that improve an individual’s fitness.
All species produce an excess number of offspring. Only those offspring having the fittest genotype will pass their genes on to the next generation.
Evolution by Random Processes
Mutation- occur randomly and can add to the genetic variation of a population.
Genetic drift- change in the genetic composition of a population over time as a result of random mating.
Bottleneck effect- a reduction in the genetic diversity of a population caused by a reduction in its size.
Founder effect- a change in a population descended from a small number of colonizing individuals.
Speciation and extinction determine biodiversity
- Allopatric speciation
- when new species are created by geographic or reproductive isolation.
River changes course, etc.
Evolution shapes ecological niches and determines species distributions
Range of tolerance- all species have an optimal environment in which it performs well. The limit to the abiotic conditions they can tolerate is known as the range of tolerance.
Fundamental niche- the ideal conditions for a species.
- the range of abiotic and biotic conditions under which a species lives. This determines the species distribution, or areas of the world where it lives.
species that live under a wide range of conditions.
- species that live only in specific habitats.
The Fossil Record
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the evolution of one species into two species in the absence of geographic isolation, usually through the process of polyploidy, an increase in the number of sets of chromosomes.