Chapter 4
Biodiversity: the variety of earth’s species, the genes they
contain, the ecosystems in which they live and the
ecosystem processes and energy flow that sustain all life
•
the variety of different species living in a particular area
provides us with food, energy, medicine, air and water
quality, population control and other “free” ecosystem
services
estimated 8-100 million species on earth, we have identified
about 1.9 million different species
most species located in the tropical rain forests.
Insects are the most prolific
species diversity
number of species living in an ecosystem
genetic diversity
diversity in genes that allows differential survival and
reproduction in changing ecosystems (ability to adapt)
ecosystem diversity
different terrestrial (biomes) and aquatic ecosystems
functional diversity
processes such as energy and matter cycling through
ecosystems (food webs, keystone predators, nutrient cycles etc.)
•
Biological Evolution by Natural Selection
•
Charles Darwin in 1859
• evidence from observations (adaptations to environments)
and fossil evidence
•
•
struggle for survival gives organisms an advantage to
survive and reproduce, allowing them to pass
advantageous traits on to the next generation
• “survival of the fittest”
evolution: process whereby life changes over time through
changes in the genetic characteristics of populations in
response to environmental pressures.
• all species descended from an earlier ancestral species
relies on genetic variation within populations
occurs via mutations (random changes in DNA sequences)
may result from mistakes during DNA replication or protein
synthesis or exposure to mutating agents--chemicals (mutagens)
only mutations in reproductive cells will be passed on (heritable
traits)
populations may also experience genetic drift, genetic
bottlenecks and the founder effect
environmental conditions favor some individuals (traits) over others
some individuals have an advantage (adaptation) that allow them
to survive and reproduce under specific environmental conditions
must lead to differential reproduction (those with the trait have
more offspring than those without)
Geologic processes
tectonic plates drift and move slowly
earthquakes and volcanoes (isolate populations, or
eliminate entire populations)
location of continents and oceans influence climate
allow species to move and adapt to new environments,
thus allowing speciation to happen
Climate change
glaciation and warming periods (raising sea levels)
affects locations/types of ecosystems
a species is a group of individuals in a population
that mate and produce fertile offspring
speciation is a process where one species splits into
two groups and can no longer produce fertile
offspring together
geographic isolation: physical isolation for a long period of time
reproductive isolation: mutations and changes in genetic
information result in populations not being able to reproduce
successfully with original population (last step in speciation)
when an entire species ceases to exist either globally
(biological) or in a specific region (local)
species must either adapt, move or face extinction during
environmental changes
mass extinction: large, catastrophic and widespread loss
of species (20-25%) in a few million years
earth has had 3-5 mass extinctions, some argue we are
currently undergoing another mass extinction that is human
caused
usually followed by a large period of speciation as new
species fill available ecological niches
balance between speciation and extinction determines earth’s
biodiversity
Species Diversity
•
•
species richness: number of species present
• highest in tropics and decreases as move toward poles (rain
forests, coral reefs, tropical lakes, islands and ocean-bottom
are highest)
•
more diverse an ecosystem is the more productive it will be
(more producers=more biomass=more consumers
supported)
•
complex ecosystems (high richness) will be better able to
withstand disturbances, disease and infestations
• more ways to respond to environmental stresses and
changes
• high net primary productivity
ecological niche: role a
species plays in a specific
ecosystem
includes everything that will
affect its survival and
reproduction
generalist species: broad niches
(live everywhere, eat anything)
specialist species: narrow niche
(live in specific habitat, eat
specific food, tolerate narrow
range of environmental
conditions)
endemic species: species found only in one area, vulnerable to
extinction
native species: species that normally thrive in a particular ecosystem
non-native (invasive) species: species that migrate or are introduced to
an ecosystem
kudzu vine and feral pigs in the southwest
indicator species: provide early warnings of damage to an ecosystem
amphibians sensitive to chemical changes and pollutants
keystone species: roles have large effect on types and abundance of
other species in an ecosystem.
large predatory fish on coral reefs keep other fish populations from
exploding
foundation species: creating and enhancing their habitats in a way that
benefit other species
beavers building dams to flood areas and create wetlands
•
increasing rate of speciation through artificial selection
and genetic engineering
•
habitat destruction and fragmentation
•
overfishing and poaching
•
climate change
•
disruption of ecosystems
•
introducing invasive species
A region of high
biodiversity
that is under
direct threat
from humans
Targeted
areas where
protection
needs to
happen first
(lost 70%+)
of original
habitat
High number
of endemic
species (not
found
anywhere
else in world)
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