Biodiversity

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Biodiversity

• Sections 18.4. 16.4, and 30.1

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• The word diversity is used in many contexts.
• What is genetic diversity within a species?
• What is meant by species diversity within an
  ecosystem?
• Can there be genetic diversity within an
  ecosystem?

W O R K T O G E T H E R
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Biodiversity is

1. The number of species in a region.
2. The types of alleles found in the gene pool.
3. The number of individuals found in an ecosystem.
4. The number of individuals in a population.

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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.

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Different areas of the world differ in their
relative amounts of biodiversity. Why?
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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!
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Estimates vary about the number of species yet to
be discovered and named, but its clear that we
have a long way to go!
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How do scientists estimate how many species have
not been discovered yet?

1. They count known species, then multiply by 10 as
   a guess.
2. They base the number on sampling methods that
   determine species richness.
3. They dont. Its just too hard.

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• 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.

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• 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.

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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?
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High species diversity is found in tropical
rainforests and coral reefs. Why?
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Extinction Risks

• Specialization and resource partitioning increase
  diversity.
• However, the tradeoff is that organisms become
  more vulnerable to extinction if the environment
  drastically changes.

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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 Devils Hole Pupfish lives in a single
waterhole in Nevada.
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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.

Fenders Blue Butterfly feeds only on Kinkaids
Lupine.
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Interactions

• Isolation reduces competition and predation.
• If a new predator or competitor is introduced, a
  formerly isolated species may be hunted or
  out-competed to extinction.

Many Hawaiian birds were driven to extinction by
introduced predators.
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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.
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Species are at LEAST risk for extinction if they

1. Are highly specialized for their niche.
2. Have a widespread distribution.
3. Are losing their habitat.
4. Must compete with invasive species.

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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.

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• 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.

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Ecosystem services
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
Directly used substances food plants and
animals building materials fiber and fabric
materials fuel medicinal plants oxygen
replenishment
Ecosystem services are direct and indirect
benefits humans receive from the environment.
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Humans have directly benefitted from biodiversity.
Drugs derived from plants and animals.
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Forest mushrooms
Tropical fruits
Andean Potatoes
A diverse ecosystem yields a diversity of foods.
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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.
25
Permaculture and mixed-crop agriculture supports
a diverse soil food web, which supports the
crops. These methods tend to be more
labor-intensive.
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• It is estimated that the Native Americans on the
  east coast used over 200 different plants and
  several dozen different animals for food. By
  comparison, how diverse is our food supply?
• What grains do you eat regularly? List as many as
  you can think of.
• What other plants have you eaten in the past
  week? List as many as you can think of.
• What animals and animal products (milk, eggs)
  have you eaten in the pats week ,if any? List as
  many as you can think of.

W O R K T O G E T H E R
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Humans also benefit indirectly from intact,
diverse ecosystems.
Natural rivers meander, creating a richly diverse
wetland ecosystem.
28
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.
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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.
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The term ecosystem services refers to

1. Direct and indirect benefits humans receive from
   the ecosystem.
2. How the ecosystem supplies our needs even when we
   extract resources at a high rate.
3. When humans do service projects to help restore
   ecosystems.

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E.O. Wilson on Biodiversity
TED Presentation
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• According to E.O. Wilson, what is the importance
  of discovering and naming all the species on
  Earth?
• Have we named all or nearly all of the species on
  our planet?

W O R K T O G E T H E R
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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.