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Chapter 12Biodiversity
Biodiversity- the diversity to genes, species and
ecosystems in a region
-the more different species in an area, the more
biodiversity
Extinction- death of a species, elimination of all of a
particular species
As species become extinct, they decrease the
biodiversity of an area
Major factors of extinction:
1. low population density
(successful reproduction of a small number is
less likely as compared to a larger number ex.
cheetah)
2. found in only a small area
(if something happens in that area such as a
natural disaster, then the species will die)
3. specialized niche
(ex. If eat only a certain type of food, then if
that food is gone they will die)
Extinction due to human activity:
• Exploit minerals and resources
(ex. Space)
• Damage the environment
(ex. As humans used fire, they
burned many ecosystems)
(ex. cutting down of timber
damaged habitats)
(ex. Farming, eat many animals
and plants)
Types of diversity:
• Genetic diversity
• Species diversity
• Ecosystem diversity
Genetic diversity
Term used to describe the
number of different kinds
of genes present in a
population or species
High genetic diversity
means there are many
genes present and the
individuals have different
structures and abilities
Factors that affect genetic
diversity:
1. Mutations- changes in
the genetic information of
an organism
• They introduce new genetic
information into a
population by modifying
genes (DNA)
• It changes characteristics
of offspring
Factors that affect genetic
diversity continued:
2. migration- movement of
individuals from one
population to another
ex. An animal takes characteristics
from the old environment to the
new one/he may not have
characteristics that allow him to
thrive in the new environment
Genetic diversity factors continued:
3. Sexual reproductioncontributing of different traits
causes new genetic
combinations resulting in new
characteristics
4. Population size- the smaller the
population the few variations of
genes
5. Selective breeding- certain
desired characteristics are
passed on (lowers genetic
diversity)
Species diversity:
• Measure of the number of different species in
the same area
• Example: tropical rainforest has high species
diversity
Measure of species diversity:
• Species richness- count the number of
the different kinds of species
• Taxonomic richness- the number of
different taxonomic groups in an area
ex. Number of frogs (all types)
Factors that affect species
diversity:
• Drastic change in
the ecosystem
such as disaster or
human activity
• Introduction of new
species/migration
• Size of the area
Ecosystem diversity
Measure of the number
of kinds of ecosystems
in an area
Topography has a lot to
do with the type of
ecosystem
4 Major Human Threats to
Biodiversity:
•
•
•
•
Habitat loss
Overexploitation
Introduction to exotic species
Persecution of pest organisms
Habitat loss:
-Conversion of natural ecosystems to
human dominated ecosystems
-main human activities are farming,
grazing of livestock, modification of
aquatic habitats, conversion of
landscapes
-These activities reduce
the number of existing
species because it
damages their habitat
-80-90% of species lost
are due to this
Means of habitat removal
(clearing of land):
• Agriculture- about 40% of the
world’s land has been converted
to cropland and pasture
– Desertification- over use of land
for things such as grazing of
pastures
• Deforestation- removal of
forests for building materials,
clear land for fields
– Clear-cutting- removal of all trees in
a large area (it causes a lot of erosion)
– Selective harvesting- choosing the
trees that they want to harvest (ex.
Mahogany)
Urban habitat loss:
• About 4.3 percent of US land is used for urban
centers, industrial sites, transportation
infrastructures
• These areas are mostly covered with
impermeable surfaces (no plant growth)
• It diverts rain to local stream and rivers
Overexploitation
-Occurs when humans harvest
organisms faster than
they reproduce
-causes 30% of endangered
animals (ex. Overfishing)
-illegal trade of wild animals produces $2 to 30.5 billion per
year (meat from wild animals is called “bush meat”
Introduction of exotic species:
-Exotic species- species
brought from areas outside
of the ecosystem (not native)
-Competes with native
species for resources
such as food and space
Control of pest organisms (affect
on biodiversity)
• When you kill one species,
it will affect other species
• Example: killing large
predators such as the
grizzly bear and mountain
lion because they kill
livestock has reduced their
population drastically.
• This leads to more prey in
an area (overpopulation of
animals like rodents)
species in danger of extinction:
Endangered species- species
that has such a small number that they
are in immediate jeopardy of extinction
– Their survival is unlikely of the
conditions threatening them continue
Threatened species- could
become extinct if a critical factor in
their environment changes
The method to stop extinction is to
preserve the habitat
This is why we try to preserve the
wilderness- a place that is
unaltered by man
ex. yellowstone
How to insure survival of
animals?
• Provide a suitable habitat and protect the
animals and habitat (wildlife management)
Preserving biodiversity:
• Understand the life history of the organism
and its significance so that effective
measures can be taken
• Protect species that are endangered or
threatened legally
(Convention of Biological
Diversity treaty)
• Reduce the impact
of human activity