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)