Bell-ringer: What is carrying capacity? Go over...
Transcript of Bell-ringer: What is carrying capacity? Go over...
Bell-ringer: What is carrying
capacity?
Go over exam
Finish working on
packet/questions
Ted Talk: The Earth is Full
Wrap-up: Do you think
humans have reached
carrying capacity? Why or
why not?
Bell-ringer: What
factors play into
carrying capacity?
Carrying Capacity
Notes
Wrap-up: What is an
invasive species?
A plant, fungus, or animal species that is
not native to a specific location (an
introduced species), and which has a
tendency to spread to a degree
believed to cause damage to the
environment, human economy or
human health.
An organism whose presence, absence or abundance reflects a specific environmental condition
Indicator species can signal a change in the biological condition of a particular ecosystem, and thus may be used to diagnose the health of an ecosystem
Sensitive to heavy metals or acids in
precipitation and therefore may be
indicators of air pollution
A keystone species is
a plant or animal that plays
a unique and crucial role in the way
an ecosystem functions.
Without keystone species, the ecosystem
would be dramatically different or cease
to exist altogether.
Prairie dogs contribute to the soil and
water quality in their plains ecosystem.
Their foraging retains water in the soil
and forces fresh new grasses to
continually grow.
Young grasses have more nutrients for
species such as bison and elk.
The rate at which the number of these
individuals changes from one period to
the next
Equal to the number of births minus the
number of deaths
dN/dt = birthrate – death rate
When birthrate is less than death rate the
population shrinks
When birthrate is greater than death rate
the population grows
1. Geometric Population Growth
› Occurs in populations that produce a single
batch of offspring in a year
› Population increases by a constant ratio from one generation to the next (ex. Insect)
2. Exponential Population Growth
› Continuous population growth
› Only possible under ideal conditions
Low population density number of
individuals per unit area
Colonization of new areas
Sudden increase in food supply
Implementation of new protection
regime
Bell-ringer: When birthrate is greater than death rate what happens to the population?
Tiny bit of notes
Begin invasive species project
Wrap-up: What is a density-dependent factor?
The factor that is in least supply relative
to the needs of the population
Similar to a limiting nutrient
Divided into two categories:
1. Density-dependent factors
2. Density-independent factors
Factors that affect population growth
but are not related to the size of the
population
Often are associated with weather
› Not related to population size
Density-independent factors are
determined by chance
Factors that are related to population
size
The size of a population affects the rate
at which it grows or shrinks via factors
such as predation, disease, and
reproduction
Ex.) Disease spreads more rapidly when
individuals are crowded together.
Bell-ringer: What is a
density-
independent
factor?
Go over rubric
Work on project
Wrap-up: What is
your invasive
species?
Bell-ringer: What is
carrying capacity?
Invasive Species
presentations
Review for quiz
tomorrow
Wrap-up: What is a
keystone species?
Give an example.
Bell-ringer: What is an example of a keystone species?
Quiz
Collect any backwork no work after today
Reading
Wrap-Up: What do you think would happen if we rid the world of mosquitoes?
Bell-ringer: Draw exponential growth vs. geometric growth.
Go over/grade hw
Collect BRs
Notes
Wrap-up: What is overshoot?
REMINDER: LAST DAY FOR ANY BACKWORK!!!
States that the change in population is
determined by two factors:
1. The maximum potential growth rate
2. The importance of density-dependent
factors
The maximum number of individuals of a
population that can be maintained
indefinitely by the environmental goods
and services that are generated by a
given area of the environment
Determined by the balance between
the amount of environmental goods and
services that are required by each
individual and the quantity of these
goods and services that are provided by
the environment
Critical to the notion of carrying
capacity because the availability of
environmental goods and services varies
with the type of ecosystem
Carrying capacity for a particular
population depends on the conditions
that are unique to a local ecosystem
The ability of an ecosystem to provide the
same quantity and quality of environmental
goods and services over time
A population cannot use environmental
goods or services faster than the
environment provides them
Use of environmental goods or services
within this limit ensures that the environment
can sustain the population indefinitely
Exceeding carrying capacity
Populations may overshoot their carrying capacity because of time lags in the relationship b/t population size and density-dependent factors
Overshoot is temporary b/c the negative feedback loop will regulate population
The average number of children that
each woman in her childbearing years
will bear over her lifetime
The total fertility rate at which a
population remains constant.
Each couple will bear the number of
children needed to replace themselves.
Replacement fertility must be greater
than 2 because some children die
before they reach reproductive age and
some women have no children.
The number of males and females in an
age group
Generally are divided into three groups:
1. Pre-reproductive: 0-14 years old
2. Reproductive: 15-44 years old
3. Post-reproductive: 45 and older
Population histograms: diagrams that represent the number of males and females in various age groups
Population momentum is the built-in potential for growth › Ex.) People in the bottom of
the pyramid move into their reproductive years, the crude birthrate may rise significantly
Provide important insights into the
socioeconomic conditions of the past
and present
Ex.) More than a decade of very high
total fertility rates in the US at the end of
WWII produced a large cohort of
children known as the BABY BOOMERS
Born between 1946 and 1964
Generated a bulge in the age structure
pyramid for the US that has influenced
culture at every stage
Currently make up nearly half of the US
adult population
Dominate the job market
Buy most of the goods and services
Cast the most votes in elections
Will cause changes in the age-dependency ratio: › the number of people under the age of 15 plus
the number of people of 65 divided by the number of people between these ages
People between 15 and 65 hold most of the jobs, earn most of the income, and support the youth and elderly
Fewer people will work to support a large group of retired baby boomers problematic to SS trust fund
Baby boomers have been paying into
the fund to support their parents
When they retire, this large bulge of older
Americans will draw their checks from a
relatively small group of workers (YOU
GUYS!)
This means higher taxes from you!
By the year 2030 more than 20% of the
population will be over 65
This will increase the demand for health
care
Additional cost of health care will fall on
a smaller proportion of the population
who will be working and paying taxes
Can we calculate an upper limit on the
size of the human population?
No….the relationship between people
and the environment is far more
complex than it is for frogs and other
nonhuman populations
But people have tried anyway…
Economist-philosopher Thomas Malthus
was the first to try and quantify carrying
capacity for the human population
1787 wrote an Essay on Population which
described how the environment limited
the size of the human population
Like other animals, human populations
grow exponentially.
However, food production, the factor
that ultimately limits the size of the
human population grows linearly.
Population and food production were
on a collision course because of a simple
mathematical truth:
› Exponential growth eventually catches up and surpasses linear growth
Implies that the human population will
eventually exceed food production
Applied his theory to the English
population and predicted that it was on
the verge of collapse
Argued that England should slow its
population growth through voluntary means sound familiar?
If not disease, starvation, economic
misery, etc. would involuntarily slow
population growth
Malthus’ prediction of collapse did not
occur
Perhaps because people are so different
than animals and plants that there is no
perfect predictor
Pattern of dropping death rates and
later birthrates
› Eventually birthrates drop to equal death
rates and the population is no longer growing
› Once they have passed through this
transition, most developed nations have low
birthrates, low death rates, and low or
negative rates of population growth
Short lag between the drop in death
rates and birthrates will stabilize the
human population at 9-10 billion
Lack of natural resources, environmental
degradation, or other forces prevent the
income gains that slow birthrates,
population may reach much higher
levels
Resources are determined by the
environment in which organisms inhabit
Plants and animals can’t significantly
increase the types or quantities of
environmental goods or services
available
As a result, the max. number of
organisms is determined by the
characteristics of the environment
Local environment doesn’t determine quantities and types of resources available to humans
People CAN and DO modify their environment to increase the quantities and types of goods and services provided
We can move goods over long distances
These strategies INCREASE carrying capacity
Until about 12,000 years ago people
obtained their food by hunting and
gathering
Quantity of food available was determined
by the rate at which the local ecosystem
produces edible plants and animals
› Imposes upper limit on population size in that
area
12,000 years ago people started to modify the environment through agriculture
They replaced the natural ecosystem with one that supports the plants and animals of people’s choosing
Converted grasslands and forests to wheat fields and pastures, people increased the mount he food that can be produced in a given area
This raises carrying capacity!
People expand livable areas of the
world
Use natural resources, waste assimilation,
and ecosystem services from distant
environments
Ex.) NYC covers 780 square kilometers
but it uses much larger area to obtain
resources and assimilate wastes
Japan: Densely populated with few natural resources draw environmental goods and services from ecosystems scattered across the planet
Canada: Imports bananas from Colombia because banana trees cannot grow in Canada
Development that meets the needs of the present without compromising the ability of future generations to meet their own needs
Definition does not provide a specific criterion by which society can determine whether its actions compromise the ability of future generations to meet their own needs
For human actions to be sustainable,
they cannot degrade the environment
or use environmental goods or services
faster than they are generated by the
environment.
If economy was managed using strong
sustainability, the use of oil
(nonrenewable) would be forbidden
Only 6 million barrels of oil are generated
yearly
Divided equally among 6 billion people
that leaves each person with only .001
barrel per year (1.5 liters)
Comes from three sources:
1. Goods and services that are produced by the environment
2. Goods and services that are produced by
economic forms of capital (machines)
3. Goods and services that are produced by
social institutions (education and justice)
States that an action that degrades the
environment or uses a natural resource
or a waste-processing service faster than
it is generated by the environment can
be sustainable if these losses are offset
by an increase in another source of well-
being (economic capital or social
institutions)
Human actions diminish ocean’s ability
to produce fish
Humans farm fish which makes up for
some of the reduction from the ocean
Human well-being does not depend
solely on the environment, as is the case
for nonhuman species
Material standard of living is growing exponentially exponential population
growth will eventually outrun the
environment’s ability to provide goods
and services
Use computer simulations to analyze the
relationships among population growth,
economic growth, and the environment
Accept the fact the population is
growing exponentially
Disagree that the supply of
environmental goods and services grows
linearly
Argue that improved technology can
help goods and services keep up with
the population
https://www.ted.com/talks/paul_gilding_
the_earth_is_full?language=en
Lab:
http://www.mhhe.com/biosci/genbio/vir
tual_labs_2K8/labs/BL_19/