Nov 8 - University of San Diego

butterbeanscubaBiotechnologie

12 déc. 2012 (il y a 8 années et 7 mois)

355 vue(s)

I.
Biodiversity


Factors


E.
Exotic Species

2.
Mongoose


Predator in Hawaii


Introduced in 1883 to combat rat population


Prey on native birds

3.
Lionfish


Venomous predator


Introduced in Caribbean/W Atlantic
ca.

early/mid
1990’s


Preys on 65+ spp. of fishes


No natural predators


Nile perch


Lake Victoria

Brown tree snake
-

Guam

Argentine ants
-

California

Caulerpa taxifolia

-

California

II.
Biodiversity


Value


A.
Value to Humans


Economic


Ex



Lomborg: $3
-
33 trillion annually


Biodiversity loss could lead to
removal of species

that benefit humans but aren’t currently known to do
so


Ex



Chapin et al. suggest increased frequency of
Lyme
disease

in 20
th

century may have been related to
increase in abundance of tick
-
bearing mice (once
controlled by food competition with passenger pigeons)


Species extinction
reduces potential pool

of species
containing chemical compounds with pharmaceutical
or industrial applications


Counter



Many pharmaceutical companies now use
directed design

to search for new drugs

II.
Biodiversity


Value


A.
Value to Humans



Problem



Benefits may not be obvious


Difficult to convince people that it’s important to
preserve something with no immediately apparent
intrinsic value to them (
charisma?
)


Ex



Economic value of viral resistance added to
commercial strains of perennial corn through
hybridization with teosinte (Mexican wild grass) is ~
$230
-
300 million


Ex



Weedy tomatoes from Peru


Discovered in 1962 during search for potatoes


Seeds sent to researcher at UC Davis who used plants
to breed with other tomatoes


In 1980 after nearly 10 generations of crossing and
backcrossing, new strains were produced with larger
fruit, improved pigmentation and increased
concentrations of sugars and soluble solids

II.
Biodiversity


Value


B.
Ecosystem Value


Biodiversity can have large effects on ecosystem
stability and productivity

1.
Benefits of biodiversity

a.
Productivity


Halving species richness reduces productivity by
10
-
20% (Tilman)


Average plot with one plant species is less than half
as productive as a plot with 24
-
32 species


Question



Can these results be extrapolated to
other systems and time/space scales?

b.
Nutrient retention


Loss of nutrients through leaching is reduced when
diversity is high


Caveat



Studies to date have focused on low
diversity communities (
Why?
); can those results be
generalized?

II.
Biodiversity


Value


B.
Ecosystem Value

1.
Benefits of biodiversity

c.
Ecosystem stability


Mechanism


Multiple species compete for resources


If abundance of one species declines due to perturbation,
competing species may increase in abundance


Individual species abundances may vary, but community
as a whole is more stable with more species


Consequences


High diversity doesn’t guarantee that individual
populations won’t fluctuate


Ex



Higher diversity (unfertilized) plots of native plant
species maintained more biomass during drought than
lower diversity (fertilized) plots


High diversity may confer greater resistance to pests and
diseases


Ex



Higher diversity plots of native plant species had
greater resistance to fungal diseases, reduced predation
by herbivorous insects and reduced invasion by weeds

II.
Biodiversity


Value


B.
Ecosystem Value

2.
Considerations

a.
Species richness vs. Species evenness


Simple species richness may be deceptive as an indicator of
biodiversity and ecosystem stability


Evenness usually responds more rapidly to perturbation
than richness and may have important ecosystem
consequences


Richness is typical focus of studies and policy decisions

b.
Importance of individual species


Charismatic megafauna:
What about non
-
charismatic species?


Different species affect ecosystems in different ways (keystone
species
vs.

non
-
keystone species)


Ex



Sea otters/Sea urchins/Kelp forests in eastern Pacific
Ocean


Question:

How many species are required to maintain “normal”
ecosystem function and stability?


No magic number


Losing one ant species in a tropical forest may have less
immediate impact than losing one species of fungus that
is crucial to nutrient cycling in the soil

III.
Biodiversity


Management



Strategies outlined in Convention on Biological
Diversity


Developed between 1988 and 1992


Opened for ratification at UN Conference on
Environment and Development (Rio “Earth Summit”)


Ratified by 168 nations; went into force in Dec 1992


Objectives


“…the conservation of biological
diversity, the sustainable use of its components and
the fair and equitable sharing of the benefits arising
out of the utilization of genetic resources…”


Articles 8
-
9 specify a combination of
in situ

and
ex situ

conservation measures


Primary use of
in situ

conservation


Use of
ex situ

measures as a complement

IV.
Genetic Engineering


A.
Background


Concept based on idea that organisms share
same basic genetic material (DNA)


Functionally similar units (genes)


Same basic mechanisms of
gene expression


Theoretically possible to transfer genes
between organisms and expect traits to be
transferred faithfully


Insertion of a foreign gene into a species’
genome creates a
transgenic

organism


Inserted gene may or may not be expressed


Theoretically, no limits on what can be inserted


Ex



Insulin gene inserted into bacteria


Ex



UCSD researchers inserted bacterial
luciferin/luciferase genes into tobacco plant


Technology offers potential to create novel
organisms with unusual and potentially
beneficial attributes

IV.
Genetic Engineering


A.
Background


Concept based on idea that organisms share
same basic genetic material (DNA)


Functionally similar units (genes)


Same basic mechanisms of
gene expression


Theoretically possible to transfer genes
between organisms and expect traits to be
transferred faithfully


Insertion of a foreign gene into a species’
genome creates a
transgenic

organism


Inserted gene may or may not be expressed


Theoretically, no limits on what can be inserted


Ex


Insulin gene inserted into bacteria


Ex


UCSD researchers inserted bacterial
luciferin/luciferase genes into tobacco plant


Technology offers potential to create novel
organisms with unusual and potentially
beneficial attributes

IV.
Genetic Engineering


B.
Purposes

1.
Accelerate and refine selection process


“Normal” hybridizing limited by


Generation time


Combining entire genomes, not just traits of interest

2.
Create otherwise unattainable hybrids


Ex



Arctic flounder and strawberry or tomato


Bottom line

-

Genetic engineering of organisms is
intended to benefit humans, not modified organisms


Proponents stress
potential benefits

to
humankind and the environment


Opponents emphasize
potential risks

and
concerns


Conversation with Hugh Grant


IV.
Genetic Engineering


C.
Advantages

1.
Greater agricultural yields


More food production per acre could


Reduce area needed to support existing population


Support future population growth


Ex



European corn borer destroys 7% of annual corn harvest worldwide


Modified corn resistant to ECB could eliminate this loss


Extra corn =

7
-
10 mmt (enough to feed 60 million people)

2.
Reduced herbicide use


Wheat, corn, soybeans, cotton, sugar beets, alfalfa, etc. engineered to be
resistant to certain herbicides (e.g. Roundup)


Farmers can spray crops with less herbicide to kill weeds


Ex



Soybeans


Reduction of herbicide use by 10
-
40% from 1996
-
1997

3.
Reduced pesticide use


Crop plants can be engineered for resistance to certain pesticides


Ex



Insect resistant cotton planted in Alabama led to an 80% reduction in
use of insecticides on cotton from 1996
-
1997

4.
Environmentally beneficial tasks


Ex



Bacteria engineered to degrade petroleum rapidly can be used to
clean up oil spills

5.
Novel properties


Ex



Phytase maize (approved in China, 2009)


Enzyme makes phosphorus more available to livestock


Enhances animal growth, reduces P content of waste (up to 60%)