Transcript 4 & 5 short Biodiversity

How fast do populations grow?
• Populations of organisms, do not experience
linear growth. Rather, the graph of a
growing population starts out slowly, then
begins to resemble a J-shaped curve.
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Population Ecology
Human Population Growth
 The study of human population size, density,
distribution, movement, and birth and death rates
is demography.
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Population Dynamics
• Under normal
conditions, with
limiting factors,
populations show an
S-shaped curve as
they approach the
carrying capacity of
the environment
where they live.
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Trends in Human Population Growth
 Population
trends can
be altered
by events
such as
disease and
war.
 Human
population
growth is not the same in all countries.
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Age Structure
 A population’s
age structure
is the number
of males and
females in
each of three
age groups:
pre-reproductive stage, reproductive stage, and
post- reproductive stage.
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Zero Population Growth
 (ZPG) occurs when the birthrate equals
the death rate.
 The age structure eventually should be
more balanced with numbers at prereproductive, reproductive, and postreproductive ages being approximately
equal.
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Carrying capacity
• The number of organisms of one species that
an environment can support indefinitely is its
carrying capacity.
Click image to view movie.
• When a population
overshoots the
carrying capacity,
then limiting factors
may come into
effect.
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Section 4.1 Summary – pages 91-99
Carrying capacity
• Deaths
begin to
exceed
births and
the
population
falls below
carrying
capacity.
Critical miminum
number- the number
below which the species
is destined for extinction.
Carrying capacity
It is different for each
organism.
A variety of population
growth patterns, also
called its life-history
pattern are possible in
nature.
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Rapid life-history patterns
• Rapid life-history patterns are common
among organisms from changeable or
unpredictable environments.
• Rapid life-history
organisms have
• a small body size
• mature rapidly
• reproduce early
• have a short life span.
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Slow life-history patterns
• Slow life-history
organisms
• live in more stable
environments
• reproduce and mature
slowly, and are longlived.
• They maintain
population sizes at or
near carrying capacity.
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Density factors and population growth
• How organisms are dispersed can be
important.
• Three patterns of dispersal are random,
clumped, and uniform.
Random
Clumped
Uniform
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Density factors and population growth
• Density-dependent factors include disease,
competition, predators, parasites, and food
Density-independent factors can affect all
populations, regardless of their density.
• Most density-independent
factors are abiotic factors,
such as temperature,
storms, and major habitat
disruption.
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Predation affects population size
Number of organisms(in thousands)
Lynx and Hare Pelts Sold to the Hudson’s Bay Company
Hare
Lynx
Times (in years)
•Competition
•is a density-dependent factor.
•When a population increases and the
demand for resources exceeds the supply,
the population size decreases.
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Doubling time
• Doubling time is the time needed for a
population to double in size.
• 70 divided by % growth = doubling time
• a 3.5% growth rate represents a doubling
time of 20 years.
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Age structure
Population Distribution Per Age Range for Several Countries
Stable growth
Rapid growth
Male
Slow growth
Reproductive years
Age
Female
Population (percent of total for each country)
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Where is biodiversity found?
• Tropical regions contain two-thirds of all land
species on Earth.
• The more energy (sunlight) generally, the
more organisms live there.
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Biodiversity brings stability
• the loss may have consequences for other
living things in the area.
• Biodiversity can bring stability to an
ecosystem.
• A pest could easily destroy all the corn in a
farmer’s field, but it would be far more
difficult for a single type of insect or disease
to destroy all individuals of a plant species in
a rain forest.
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Section 5.1 Summary – pages 111-120
Biodiversity- Importance to people
• Humans depend on other organisms for
• Food
• medicine.
• Agriculture (source of genetic material)
• aesthetic
Section 5.1 Summary – pages21
111-120
Loss of Biodiversity
• Extinction is the disappearance of a species
when the last of its members dies.
• Extinction is a natural
process and Earth has
experienced several
mass extinctions
during its history.
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Section 5.1 Summary – pages 111-120
Loss of Biodiversity
• A species is endangered species when extinction is
possible.
• threatened species-is likely to become endangered
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Habitat loss
• One of the biggest reasons for decline
in biodiversity is habitat loss.
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Habitat fragmentation
• .
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Habitat fragmentation
Habitat
fragmentation
is the
Habitat fragmentation has been
separation of
found to contribute to:
wilderness
• increased extinction of local species areas from
other
• changes in overall biodiversity
wilderness
• new opportunities for invasions by
areas
unwanted or exotic species.
•
increased risk of fire
• disruption of ecological processes.
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Habitat fragmentation
• The smaller the fragment, the less
biodiversity the area can support.
• Geographic isolation can lead to genetic
isolation (causes inbreeding).
• makes it difficult for species to reestablish
themselves in an area.
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Edge and size
• The edge of a habitat or ecosystem is where one
habitat or ecosystem meets another.
• The different conditions along the boundaries of
an ecosystem are called edge effects.
• Different organisms might live
along the edge of a forest instead
of in the interior of the forest.
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Habitat
• the damage to a habitat
degradation by pollution
• Pollutants -including
volcanic eruptions and
forest fires.
• Acid precipitation—rain
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Exotic species
• People sometimes
introduce a new species
into an ecosystem,
either intentionally or
unintentionally.
• These species can
cause problems for
the native species.
Kudzu
•Graph compares the number of
native vs. alien species in FL.
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Conservation biology is the study and
implementation of methods to protect
biodiversity.
• Preserving habitats
•Establishing parks and
other protected regions
has been an effective
way to preserve
ecosystems and the
communities of species
that live in them.
Saguaro National Park, Arizona
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Legal protections of species
The US Endangered Species Act (ESA) is Federal legislation that aims
to conserve the ecosystems upon which endangered and threatened
species depend. The ESA was signed into law by President Nixon in
December, 1973.
The ESA protects plant and animal species and is jointly administered
by the US Fish & Wildlife Service and NOAA Fisheries. Its aim is
twofold: to provide protection for species that are in danger of
extinction and to conserve the habitats on which those species
depend.
Organisms placed on the list are provided critical resources and their
habitats are protected. Any activity that endangers them, even on
private land is prohibited.
• This law made it illegal to harm any species (catch, dig up,
move, kill, or use parts of the organism) on the endangered or
threatened species lists.
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Habitat corridors
• Research shows that separate
wildlife populations may be
resulting in inbreeding
•Habitat corridors are protected
strips of land that allow the
migration of organisms from
one wilderness area to another
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• Reintroduction programs
• release organisms into where they once lived.
• The most successful are when organisms are
taken in the wild and transported to a suitable
habitat
• Animals kept in captivity may lose the
necessary behaviors to survive and reproduce
in the wild.
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Captivity
• Some species no
longer exist in the wild,
but a small number of
individual organisms is
maintained by humans.
Protecting plant species
seeds can be cooled
and stored for long
periods of time in a
seed banks
Reintroduction is
possible if needed in
the future
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