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.

A group of individuals of the same

species that inhabits a specific area

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

The number of new individuals that are

produced by a population in a period

The number of individuals that die in a

given period

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 slowdown in population growth that

occurs as a population approaches its

carrying capacity

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 number of deaths per 1,000 people

per year

The number of deaths per 1,000 people

per year

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

Distribution of a population among the

three age classes determines its age

structure

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

School age more schools had to be

built, but years later many schools closed

due to low enrollment

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

Just beginning demographic transition

Death rates already have dropped and

birthrates are dropping

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/