Download Species Concept

Biodiversity
Sections 18.4. 16.4, and 30.1
Biodiversity
• The total number of species in a region
is known as biodiversity.
• Besides the number of species, the
numbers within each species is
important. If one population grows in size
and dominates an ecosystem, that
ecosystem can lose biodiversity.
Different areas of the world differ in their relative
amounts of biodiversity. Why?
E.O. Wilson on Biodiversity
TED Presentation
Studying Biodiversity
• The number of
named species falls
far behind the
estimated number
of actual species.
• Some groups, such
as insects are
studied far more
than others. Why?
Notice this is just
Eukaryotes!
Estimates vary about the number of species yet to be
discovered and named, but it’s clear that we have a
long way to go!
• Species richness:
the number of
species in a given
area.
• A species area
curve plots the
number of species
encountered as a
function of
sampling area
size.
• Species richness:
Often used to
describe species
within the same
trophic level.
• In many ecosystems,
most species are
present in small
numbers of
individuals. Only a few
species are present in
high numbers of
individuals.
Species equitability: another measure of evenness of
distribution of individuals among the species in a
community.
Both of these “ecosystems” are equally diverse.
Which is more equitable?
High species diversity is found in tropical rainforests
and coral reefs. Why?
Extinction Risks
• Specialization and resource partitioning
increase diversity.
• However, the tradeoff is that organisms
become more vulnerable to extinction if
the environment drastically changes.
Localized Distribution
• By living in a limited
area, a population
avoids competition
with other
populations.
• The risk is that a
natural disaster will
destroy the limited
habitat.
The Devil’s Hole Pupfish lives
in a single waterhole in
Nevada.
Overspecialization
• Organisms that have
specialized feeding
habits reduce
competition with
other species.
• If the limited food
source goes extinct,
so does the species
feeding on it.
Fender’s Blue Butterfly feeds
only on Kinkaid’s Lupine.
Interactions
• Isolation reduces
competition and
predation.
• If a new predator or
competitor is
introduced, a formerly
isolated species may
be hunted or outcompeted to
Many Hawai’ian birds were driven
extinction.
to extinction by introduced
predators.
Habitat Loss
• The greatest cause
of extinction is
habitat loss.
• Organisms with
highly specialized
habitat needs may
avoid competition,
but risk extinction if
their habitat is
threatened.
Tropical rain forests are being
logged at an alarming rate, mostly
for grazing cattle.
Humans and Biodiversity
• Humans change ecosystems:
deforestation, use of land for farming,
pollution, altering rivers, and more.
Habitat destruction reduces biodiversity.
• Ecosystems also impact humans: Loss
of forests, farmland, clean water, flood
protection, and more can directly impact
human life.
• Habitat destruction
worldwide threatens –
or may have
destroyed – many
species that have not
even been named.
• Recent discoveries of
new mammal species
have found the
animals already on
the brink of extinction.
Ecosystem services
Directly used substances
• food plants and animals
• building materials
• fiber and fabric materials
• fuel
• medicinal plants
• oxygen replenishment
Indirect, beneficial services
• maintaining soil fertility
• pollination
• seed dispersal
• waste decomposition
• regulation of local climate
• flood control
• erosion control
• pollution control
• pest control
• wildlife habitat
• repository of genes
“Ecosystem services” are direct and indirect benefits
humans receive from the environment.
Humans have directly benefitted from biodiversity.
Drugs derived from plants and animals.
Forest mushrooms
Tropical fruits
Andean Potatoes
A diverse ecosystem yields a diversity of foods.
Modern agriculture relies on vast monocultures of
crop plants; the exact opposite of diversity.
Monocultures are easier to harvest, but more
vulnerable to diseases and pests than mixed crops.
Permaculture and
mixed-crop agriculture
supports a diverse soil
food web, which
supports the crops.
These methods tend to
be more labor-intensive.
Humans also benefit indirectly from intact, diverse
ecosystems.
Natural rivers meander, creating a richly diverse
wetland ecosystem.
Channelizing rivers, reducing
wetlands, and cutting down
trees along rivers changes
the ecosystem.
Loss of wetland diversity
means loss of species.
Sediments that would be
deposited along the river
system and in islands
around the mouth of the
river flows straight out to
sea.
New Orleans was once
protected by the many
islands in the
Mississippi Delta.
Much of the sediment
that built those islands
now runs out to the sea.
The islands have
eroded, leaving less
protection against
hurricanes.
Recap
• Biodiversity refers to the number of
different species in an ecosystem.
• Measures of biodiversity also take into
account the relative population sizes of
different species.
• Humans have a powerful effect on the
biodiversity of many ecosystems. Loss of
biodiversity can affect humans in turn.