Transcript The Ecosystem

CONSERVATION AND
BIODIVERSITY
4.1 Biodiversity in ecosystems
Assessment Statements
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4.1.1 Define the terms biodiversity, genetic
diversity, species diversity, and habitat diversity
4.1.2 Outline the mechanism of natural selection as
a possible driving force for speciation.
4.1.3 State that isolation can lead to different
species being produced that are unable to
interbreed to yield fertile offspring.
4.1.4 Explain how plate activity has influenced
evolution and biodiversity.
4.1.5 Explain the relationships among ecosystem
stability, diversity, succession and habitat.
4.1.1 Define the terms biodiversity, genetic diversity, species
diversity, and habitat diversity
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Biodiversity – amount
of biological or living
diversity per unit area.
Consists of species,
habitat, and genetic
diversity
Species diversity – the
variety of species per
unit area; includes the
number of species
present and their
relative abundance.
4.1.1 Define the terms biodiversity, genetic diversity, species
diversity, and habitat diversity
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Habitat Diversity –
the range of
different habitats in
an ecosystem
Genetic Diversity –
Range of genetic
material present in a
gene pool or
population of a
species.
4.1.2 Outline the mechanism of natural selection as a possible
driving force for speciation.
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Evolution is the cumulative,
gradual change in the
genetic characteristics of
successive generations of
a species or race of an
organism, ultimately
giving rise to species or
races different from the
common ancestor.
Evolution reflects changes
in the genetic composition
of a population over
time.
4.1.2 Outline the mechanism of natural selection as a possible
driving force for speciation.
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Natural Selection
(Evolution) comes down to
a species adapting to
their surroundings over
time. A species with only
plants to eat, will adapt
to eating plants. A
species with only animals
to eat, will adapt to
eating animals.
4.1.2 Outline the mechanism of natural selection as a possible
driving force for speciation.
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Darwin’s theory of evolution by
natural selection comes down to
the following points:
Species show variation.
All species over-produce.
Despite over-production,
population levels remain the same.
Over-production leads to
competition for resources.
The fittest, or best adapted
organisms, survive.
The survivors reproduce and pass
on their adaptive genes to the
next generation.
Over time, the population’s gene
pool changes and new species
emerge.
4.1.3 State that isolation can lead to different species being
produced that are unable to interbreed to yield fertile offspring.
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Isolation is the process by
which two populations
become separated by
geographical, behavioral,
genetic, or reproductive
factors. If gene flow
between the two subpopulations is prevented,
new species may evolve.
Geographical isolation is
prominent by the fact that
the species being physically
divided stops the gene flow
and therefore makes
speciation more likely.
4.1.3 State that isolation can lead to different species being
produced that are unable to interbreed to yield fertile offspring.
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Behavioral isolation is where
changes to the appearance or
behavior of the populations
may result in there no longer
being attraction among the
two types, and therefore no
longer breed.
Reproductive isolation is where
two populations can no longer
physically breed due to
changes to reproductive
organs.
Finally genetic isolation is
where there are too many
genetic differences for the two
populations to produce fertile
young.
4.1.4 Explain how plate activity has influenced evolution and
biodiversity.
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The Earth’s crust (lithosphere) is
divided into many different
plates. These plates are
carried on the mantle
(asthenosphere), which can
flow like a liquid on a
geological time scale. Edges
of adjacent plates can either
move parallel to one another,
push one under the other, or
collide.
During the Paleozoic and
Mesozoic eras all land mass
was combined as the
supercontinent Pangaea.
However over time the land
mass split apart into Laurasia
and Gondwana.
4.1.4 Explain how plate activity has influenced evolution and
biodiversity.
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The movement of the
major and minor plates in
relation to one another is
called plate tectonics.
Movement of tectonic
plates can produce
barriers such as mountain
ranges, oceans and rift
valleys that can lead to
isolation of gene pools
and then speciation.
4.1.4 Explain how plate activity has influenced evolution and
biodiversity.
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Land bridges can form
from previously
unconnected plates
allowing species to
spread.
The movement of plates
through different climatic
zones allows new habitats
to present themselves,
and allow for different
adaptations.
4.1.5 Explain the relationships among ecosystem stability,
diversity, succession and habitat.
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Organisms can colonize isolated
land using several methods:
Air – By flying or passive
transport
Sea – By swimming or floating
on a log
Animal – By traveling inside or
attached to animals that swim or
fly
Colonization can be thought of
as a type of dispersal as the
organisms are dispersed to a
new area
4.1.5 Explain the relationships among ecosystem stability,
diversity, succession and habitat.
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Jump dispersal – Long-distance
dispersal to remote areas by
one or a few organisms.
Explains wide distributions.
Diffusion – Slower than jump
dispersal and involves
populations, rather than
individuals. Explain spread of
species along edge of territory
to new areas
Secular Migration – Dispersal
over geological timescales.
Takes place so slowly that the
diffusing species undergoes
evolutionary changes during the
process.
4.1.5 Explain the relationships among ecosystem stability,
diversity, succession and habitat.
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Remember that succession is
when an ecosystem is formed
from bare rock. As plants and
animals arrive in a new area,
they can get succession started.
The succession will continue from
there through a number of seres,
which are sets of communities
that succeed one another over
the course of succession. If left
uninterrupted, it will eventually
lead to a climax community in
this new locale. Species and
genetic diversity increase
through a succession.
4.1.5 Explain the relationships among ecosystem stability,
diversity, succession and habitat.
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If there is a disturbance, the
ability for the ecosystem to
recover is based on three
factors:
Inertia(persistence) – resistance
to being altered
Resilience – ability of a system
to recover after a disturbance
Diversity – the number and
proportions of species present
The higher these are, the more
likely they are to recover