Genes form blueprint for organism's traits, diversity of genes helps determine species and ecosystem
diversity.
Number of Species on Earth
Species: A group of organisms distinct from other groups in terms
of size, shape, behavior or biochemistry that can interbreed with
others in the group to produce viable offspring
The number of species is the
most common measurement
of biodiversity.
This can be hard to determine due to inaccessibility of certain
nocturnal, ocean dwelling or microscopic beings.
Current estimates of total species on Earth are between
5-100 million, most likely around 10 million.
Species Richness and Eveness
Simply the number of species
cannot accurately determine
local or regional species
diversity.
Species Richness: the
number of species in a
given area
Richness provides general sense of biodiversity.
Species Evenness: says whether
an ecosystem is numerically
dominated by one species or
whether all species have similar
abundances
Low species evenness implies low biodiversity.
Evolutionary Relationships Among Species
Scientists organize species into categories
based on how closely related they are.
Phylogenies: branching patterns of evolutionary relationships
Expressed through phylogenetic tree.
Is determined by similarity of traits.
Evolution as the Mechanism Underlying Biodiversity
Evolution: change in the genetic
composition of a population over
time, produces Earth's
biodiversity
Microevolution: evolution below the
species level, i.e. different varieties
of the same fruit
Macroevolution: genetic
changes that create new
species, genera, families,
classes or phyla- larger
categories of organisms into
which species are
organized.
Creating Genetic Diversity
Genes: physical locations on chromosomes within each
cell of an organism, determine possible traits that are
passed down to offspring.
Genotype: complete set of genes in an individual
Two Processes of Genetic Diversity
Mutation: occasional mistake in DNA copying process
that produces a random change in genetic code
Most are detrimental, but some improve chances
of survival or reproduction
Recombination: as chromosomes are duplicated during
reproductive cell division, a piece of a chromosome breaks off and
attaches to another chromosome, creating new combination of
genes producing novel traits
Can provide new immune defenses, increasing
survival rate.
Phenotype: the actual set of traits expressed in an individual's anatomy, physiology and behavior
Evolution by Artificial Selection
Artificial Selection: human induced
evolution, i.e. breeding animals to
create certain traits
Can result in unwanted
resistances (i.e. to antibiotics)
or characteristics
Evolution by Natural Selection
Natural Selection: Environment
induced evolution based on
which individuals can survive
and reproduce
Darwin's Theory of Natural Selection
Individuals produce
excess offspring
Not all offspring survive
Individuals differ in traits
Differences in traits can be
passed from parent to offspring
Differences in traits imply
differences in the ability to
survive and reproduce
Fitness: an organism's ability
to survive and reproduce
(trait that implies Natural
Selection
Adaptation: a trait that improves an individual's fitness
Evolution by Random Processes
Mutation: occurs
randomly, if not lethal,
adds to genetic variation
of population,
accumulation of
mutations in a
population becomes
evolution
Genetic Drift: change in genetic
composition of a population over
time as the result of random
mating, non- adaptive and
random process
Bottleneck Effect: reduction in
genetic diversity of a population
caused by a reduction in its size
Founder Effect: change in a population
descended from randomly chosen
colonizing individuals
Speciation and Extinction
Determine Biodiversity
Allopatric Speciation: speciation
requiring geographic isolation,
most common way new species
evolve
Geographic Isolation: when
a subset of individuals from a
larger population colonize a
new area, physically
separated from the rest of
the population.
Reproductive Isolation: Due
to physical separation over a
period of time, organisms
become to different to
reproduce viable offspring
together
Sympatric
Speciation:
evolution of
one species
into two
species
without any
geographic
isolation
Pace of Evolution
Rate of Environmental Change- how fast a
species can adapt determines its survival
Genetic Variation- species with high genetic variation contain
individuals with a wide variety of phenotypes, making it more like
for some to survive
Population Size- though small populations usually don't have much genetic
variation, if there is a mutation, it spreads quickly
Generation Time- if a species becomes reproductively mature quickly, it tends to evolve faster
Genetic Engineering: when scientists copy genes from a species with a desirable trait and insert it into
another species
Genetically modified organisms: organisms which have been genetically engineered
Evolution Shapes Ecological Niches and Species Distribution
Range of Tolerance: a species' limit to abiotic
conditions it can tolerate (i.e. temperature, pH,
salinity)
Fundamental Niche: set of ideal living conditions for a species
This includes abiotic conditions (temperature, etc) and
biotic conditions (competition, predators and disease)
Realized Niche: the
range of abiotic and
biotic conditions under
which a species
actually lives
Distribution: areas of the world in which a species lives
Niche Generalists: can
live in a variety of habitats
and feed on a variety of
species
Niche Specialists: must
live in specific habitat or
feed on small group of
species
Environmental Change and Species Distribution
As environments change (i.e. in climate,
resources) species move to different areas, their
ability to do this differs (i.e. a bird vs. a worm)
Environmental Change and Species Extinction
If a species cannot
adapt to an
environment or change
to a more suitable one,
it will go extinct
Much information on evolution has been procured through studying fossils
Fossils: the remains of organism that have been
preserved in rock.
According to fossil records there have been five periods of Global Mass Extinction
Mass Extinction: extinction of
large number of species over a
relatively short time period
The biggest mass extinction was 251
million yrs ago, 90% of marine
speciesand 70% of land vertebrates
went extinct.
Most famous mass
extinction was at the
end of the Cretaceous
Period, half of all
species (i.e. dinosaurs)
went extinct, probably
due to large meteorite
that. A squirrel sized
primate that is an
ancestor of humans,
survived.
We are currently
experiencing a sixth mass
extinction primarily due to
harmful human activities
with rapidly onset
consequences leaving
little time to move or
adapt to survive
extinction.