Transcript Populations - Mrs. Bracken's Website

Populations
10-15% of your APES Exam
Populations
• Most species live in groups. This has several
advantages
– Increased protection from predators
– Increased chances of mating
– Division of labor
Factors that affect Population Viability
Increase Viability
Decrease Viability
Favorable environment
Unfavorable environmental conditions
High natality (births per 1000)
Low natality
Generalized Niche
Specialized niche
Satisfactory Habitat
Habitats not satisfactory or has been
seriously impacted
Few Competitors
Too many competitors
Suitable predatory defense mechanism
Unsuitable predatory defense
mechanisms
Adequate resistance to diseases and
parasites
Little or no suitable defense mechanisms
against diseases or parasites
Able to migrate
Unable to migrate
Flexible- able to adapt
Inflexible- unable to adapt
Sufficient food supply
Deficient food supply
Carrying Capacity (K)
• The number of organisms that can be
supported in a given area sustainable
• Varies from species to species and subject to
change over time
Regulating Factors
• Density independent factors: drought, flood,
natural disasters
• Density dependant factors: number of
resources, competition, disease
Biotic Potential
• The maximum rate at which a population can
grow.
• Its biotic potential, given optimal conditions,
occurs when resources are unlimited.
• Factors that influence biotic potential include
–
–
–
–
–
Age at reproduction
Reproductive life span
Average death rate under ideal conditions
Frequency of reproduction
Number of offspring
Populations
• If a population is left unchecked, population
growth rate can increase exponentially and
take on the look of a j-curve.
Predator Prey Populations
• Predation only removes the very old, very young and weak of
a prey population
• If the predators do not keep the prey population in balance,
the carrying capacity is exceeded and the prey may starve.
• Predator and prey populations are closely interdependent
S-shaped curves
• The s-shaped curve is uses to describe the pattern of growth over
extended periods of time when organisms move into an empty
niche.
• Growth rates are density-dependent
• Eventually the population will stabilize around the carrying capacity.
Thomas Malthus
• Political economist in the 19th century who
saw the decline on living conditions and
blamed it on the following
– Overproduction of the young
– Inability of resources to keep up with increased
human population
– Irresponsibility of the lower classes.
Thomas Malthus
• He suggested the following to combat the
problem of overpopulation.
– Lower class families should be regulated so poor
families do not produce more children than they
can support
• There should be “positive checks” such as
starvation and disease that occur naturally
• “preventative checks”- postponement of marriage
to keep the birth rate down
Reproductive Strategies
R- strategists
K-strategists
Mature rapidly
Mature slowly
Short lived
Long lived
Tend to be prey
Tend to be both predator and prey
Have many offspring and overproduce
Have few offspring
Low parental care
High parental care
Generally not endangered
Most endangered species are K-strategists
Wide fluctuation in population density (booms
and busts)
Population stabilizes near carrying capacity
Population size limited by density-independent Density-dependent limiting factors to
factors (climate, weather, natural disasters,
population growth stem from intraspecific
requirements for growth)
competition and include predation, parasitism,
and migration
Tend to be small
Then to be larger
Type III survivorship curve
Type I or II survivorship curve
Examples: most insects, annual plants,
bacteria, rodents
Examples: humans, elephants, cacti and sharks
Survivorship Curves
• Show age distribution characteristics of species, reproductive
strategies and life history.
• Reproductive success means how many organisms make it to
maturity and reproduce
Survivorship Curves
Type
Descriptions
I Late Loss
Reproduction occurs fairly early in life. Most deaths occur at the limit of
biological life span. Low mortality art birth. High probability of surviving
to advanced age. Advances in prenatal care, nutrition, disease
prevention and cures mean longer life spans for humans. Examples:
humans, annual plants, sheep and elephants.
II Constant
Loss
Individuals in all age categories have fairly uniform death rates.
Predations affecting all age categories is primary means of death.
Typical of organisms that reach adult stages quickly. Examples: rodents,
perennial plants and songbirds.
III Early Loss
Typical of species that have great numbers of offspring and reproduce
for most of their lifetime. Death is prevalent for younger members of
the species (environmental loss and predation) and declines with age.
Examples: sea turtles, trees, internal parasites, fish and oysters.
Human Population
• Rapid growth of the worlds human population
over the past 100 years as primarily been due to
a decrease in death rates
• These factors have reduced death rates:
– Increased food and more efficient distribution that
result in better nutrition
– Improvements in medical and public health
technology
– Improvements in sanitation and personal hygiene
– Safer water supply
Human Population
• Human population has had 3 surges
– The use of tools and fire
– The agricultural revolution when humans stopped being
hunter-gathers and began to raise crops
– The industrial and medical revolutions within the last 200
years.
Population Change
• CRUDE: per 1,000
• Crude birth rate: births per 1,000 people
• Crude death rate: deaths per 1,000 people
Population change= (crude birth rate + Immigration) – (crude death rate + emigration)
Practice Problem- Population Change
• In 1950, the population of Devinville was
20,000. The birth rate was measured at 25 per
1,000 population per year. Immigration was
measured at 600 per year. Death rate was
measured at 7 per 1,000 per year. While
emigration was measured at 200 per year. By
how much did the population increase or
decrease in that year.
Practice Problem- Population Change
ANSWER
Population change= (crude birth rate + Immigration) – (crude death rate + emigration)
=
(25(20) + 600)
(7(20) + 200)
= + 760
The population grew from 20,000 to 20,760
Why multiply by 20?? Remember that CRUDE means per 1,000… in this problem we
started with 20,000 people…
Human Population- Actual Population
rate
• The actual population rate is calculated by the
following formula
Actual Growth rate (%)= birth rate- death rate
10
Practice Problem- Actual Growth Rate
• The United states had a birth rate of 14.6 live
births per 1,000 population in one year,
compared to India’s birth rate of 22.2 in that
same year. The death rate in that year for the
United States was 8.3 deaths per 1,000
population compared to India’s rate of 6.4 –
Calculate the population growth rates (%) for
both the United States and India for that year.
Practice Problem- Actual Growth Rate
ANSWER
Actual Growth rate (%)= birth rate- death rate
10
United States: 14.6-8.3 = 0.6%
10
India: 22.2- 6.4 = 1.6%
10
Human Population
• The current growth rate of the world is 1.4%,
this would add 80 million people to the 7.3
billion people on planet every year
Human Population Distribution
• Between 2000 and 2030 most growth will
occur in less developed countries in Africa,
Asia and Latin America.
• More developed countries in Europe and
North America will have growth rates less than
1%.
• Some countries such as Russia, Germany, Italy
and Japan will experience negative growth
Fertility Rates
• Replacement Level Fertility: a couple only has
enough kids to replace themselves = 2.1
• RLF rates are lover in moderately developed
countries and higher in less developed
countries
• Total Fertility Rate: the number of children a
woman will have in her lifetime.
• The country of Niger in Africa leads the
world’s TFR at 7.46
Fertility Rates
• Despite half of the worlds population being below RLF
the population will still grow quickly. This is because of
nations with above RLF levels and the large numbers of
younger females who have not yet had children.
• Declines in fertility rates can be attributed to the
following:
– Urbanization- reduces the need for child workers, higher
cost of living
– Personal and government acceptance of family planning
– Increased numbers of females in the workplace or getting
an education (female empowerment)
– Postponing marriage and having careers.
Fertility Rates
• Effects of RLF (without looking at
immigration): population decline and
population aging.
• The greatest TFR in the United States
happened after WWII (baby boomers)
• New immigrants and their descendants are
projected to contribute to 66% of the
expected growth by 2050.
Fertility Rates
Rule of 70- Doubling Time
• If you are given a percent of population
increase and asked to find how many years it
will take that population to double. Take off
the percentage and put it under 70.
• Example: Growth rate of 2%
70 = 35 years
2
Demographic Transition
Age Structure Diagrams
• Determined by birth rate, generation time,
death rate and sex ratios.
Age Structure Diagrams
Strategies for Sustainability
• Provide economic incentives for having fewer children
• Empower women- Low status of women is the number one
problem
• Education usually leads to higher incomes. Higher incomes
decrease the need for extra children to take care of older
parents.
• More education leads to having children later in life
• Provide government family planning.
• Improve prenatal and infant health care. Women would not
need to have more children if their children survive
• Increase economic development in less developed counties
through free trade and private investment with tax
incentives
Case Study and National Policy- China
• Between 1972 and 2000 China cut it’s crude birth rate in half
(TFR dropped from 5.7 to 1.8)
• Most effective and strictest programs in the world
• Incentives such as extra food, larger pensions, better housing,
free medical care, free tuition, and salary bonuses for parents
who limit their number of children
• Couples are encouraged to postpone marriage and only to
have 1 child
• If the first is a female they are able to have one more child
and keep their incentives
• Physicians receive a bonus for sterilization procedures
• Couples pushed to terminate unplanned pregnancy
• Penalties include fines, loss of land , less food, decrease in
farm supplies, loss of government benefits, discharge from
Communist Party.
Case Study and National Policy- India
• In 1952 India began its first
involving vasectomies.
family planning program
• Reasons for India’s failures
(population of 400 million)
– Poor planning
• In 2000, India’s population
– Low status of women
was 1 billion or 16% of the
– Favoring male children
worlds population.
– Insensitivity to cultures
• 1/3 of the population earns
• Tubal Ligation is preferred
less than 0.40 a day.
today
• Cropland has decreased by
• Condoms are free although
used by less than 10%
50% per capita since 1960
• Other birth control methods
• In the 1970’s India
only used by upper class
implemented a mandatory
sterilization program
Impacts of Human Population Growth
• A large portion of the world is malnourished (25%)
• Areas with the greatest malnutrition are; Africa, Asia and
parts of Latin America (also areas with highest TFR)
• Factors contributing to malnutrition:
– Poverty
– Droughts, which will only increase as the impact of global
warming becomes more severe
– Populations that have surpassed their carrying capacity
– Political instability and wars that will cause mass migrations
– Pestilence (fatal epidemic diseases)
– Foreign investors who own large landholdings and whose sole
motivation is money (selling food to highest bidder; exploiting
it)
Impacts of Human Population GrowthAIDS- United States
• In the United States, more than half a million people have died of
AIDS or complications of it since 1981.
• 15,000 US citizens die annually
• 1 million people live with the virus
• 40,000 become infected each year
• African Americans (13% of US population) account for ½ of new
infections and 1/3 of all AIDS-related deaths
• African American males are 7X more likely to get the HIV infection
than Caucasian males
• African American females are 20X more likely to get the HIV
infection than Caucasian females
• The fastest growing population of new infections are 15-24 year
olds.
Impacts of Human Population GrowthAIDS- Worldwide
• 25 million people have died from AIDS and 2.8 million
died in 2006 alone.
• WHO says AIDS could kill 31 million people in India and
18 million people in China by 2025.
• The toll from AIDS over the next 25 years will go far
beyond the 34 million people thought to have died
from the Black Plague or the 20-40 million people who
died of the Spanish Flu
• AIDS is the leading cause of death in Africa, which has
accounted for nearly half of all the global AIDS deaths.
• In some countries AIDS reduces life expectancy to less
than 40 years
Impacts of Human Population GrowthSmoking
• WHO estimates by 2020, tobacco-related
illnesses will be the worlds leading killer. And
will be responsible for more deaths than AIDS,
TB, road accidents, murder and suicide
combined.
Impacts of Human Population GrowthOther Health Effects
• Tuberculosis is the leading cause of death in
many poorer countries and its economic impact
on global economies is estimated at 12 billion
dollars.
• Each year 500 million people are infected with
Malaria- leading to 1 million deaths. 75% of the
infected are children in Africa. Developments of
new strains of Malaria are more common and
they are less reactive to drug therapy
Impacts of Human Population GrowthPandemics
• Spanish Flu of 1918-1919 killed between 2040 million. 28% of Americans were infected.
Most devastating pandemic in the recorded in
world history.
• Bird Flu (H1N1) could kill as many as 7 million
people and infect 1/3 of the population if it is
passed person to person
Net Primary Productivity
• NPP: the total amount of solar energy converted into
biochemical energy through photosynthesis minus the
energy needed by those plants for their functions.
• It is a quantifiable measure f resources available on earth
• Estimated that there is 150 billion tons of organic matter
per year (without human activity)
• Humans have cause a 12% decline in NPP through
deforestation alone
• Humans use about 27% of the NPP for their own purposes.
• In theory, using 100% NPP would support about 15 billion
people.
Factors that Affect Resource Utilization
Factor
Description
Energy Resources
One average American consumes as much
energy as 500 Ethiopians or 35 people
from India
Environmental Degradation
Increased population size = increased
erosion, desertification, pollution, impact
on ozone layer, gases that contribute to
global warming
Exploitation of natural resources as a
function of GDP
The richest 20% of the world’s population
contribute to resource depletion of
energy and raw materials. This leads to
Pollution. The poorest 20% are being
forced to cut down trees and land for
their own personal use
Factors that Affect Resource Utilization
Factor
Description
Extinction of animal and plant species.
Close to 50% of all species on earth could
be on the path to extinction within the
next 100 years.
Political unrest
Affects employment, food distribution and
standard of living- thus affecting
utilization of resources
Population Density
Density, more than population size, has a
greater effect on pollution and use of
energy.
Population size
Large numbers of people lead to large
numbers of habitat destruction
Poverty
20% of the worlds richest countries
control 80% of the worlds wealth. The
poorest 20% only control 1.8% of the
wealth.