Chapter 5 Populations - Science with Mrs....
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Chapter 5 Populations Essential Questions: What factors influence population growth? You should be able to: 5-1 How Population Grow Describe the characteristics of a population and factors that affect population size Distinguish between exponential and logistic growth. 5-2 Limits to Growth Identify density dependent and independent limiting factors of population growth 5-3 Human Population Growth Describe factors that have impacted human population growth over time
Transcript of Chapter 5 Populations - Science with Mrs....
Chapter 5 Populations
Essential Questions: What factors influence population growth?
You should be able to:
5-1 How Population Grow
Describe the characteristics of a population and factors that affect
population size
Distinguish between exponential and logistic growth.
5-2 Limits to Growth
Identify density dependent and independent limiting factors of population
growth
5-3 Human Population Growth
Describe factors that have impacted human population growth over time
Remember our sea otters?
Change in sea otter populations around the Aleutian Islands
Killer whale prey in the Aleutians
Year
1950 1960 1970 1980 1990 2000
Pro
port
ion o
f m
axim
um
0.0
0.2
0.4
0.6
0.8
1.0
HarborSeals
Steller Sea Lions
SeaOtters
GreatWhalesGrey Whales
So who cares if sea otters go extinct?
With your partners, make a prediction about what will happen to the kelp forests of the Aleutian Islands habitat if the sea otters become extinct
What’s next?With your partners, sum everything
up. What will eventually happen to all the members of this ecosystem if the sea otters become extinct?
ESSENTIAL QUESTION:WHAT FACTORS INFLUENCE
POPULATION GROWTH?
Chapter 5
5 – 1 How Populations Grow
Describe the characteristics of
a population and factors that
affect population size
Distinguish between
exponential and logistic growth.
Characteristics of PopulationsThe four important characteristics used to describe a population are:
1. geographic distribution –area inhabited by a population
2. density - # of individuals per unit area
3. growth rate – how fast the population grows
4. age structure – the distribution of individuals among
age classes
Population GrowthThe three factors that can affect population growth are:
1. The # of births
2. The # of deaths
3. The # of individuals migrating
Immigration (coming IN)
Emigration (EXITING)
What will happen to a population if the birthrate is greater than the death rate?
What will happen to a population if the birthrate equalsthe death rate?
What will happen to a population if the death rate is greaterthan the birth rate?
When hunting of sea otters by people stopped,what do you think happened to the sea otter population?
What have killer whales done to the sea otter population?
IDEAL CONDITIONS FOR
GROWTH
What happens when there are…
Under ideal conditions with unlimited resources, a population will grow exponentially - when the individuals in a population reproduce at a constant rate.
Exponential Growth
So, why haven’t bacteria and elephants taken over the planet?
Logistic Growth
• Occurs when a population’s growth slows or stops because things run out!
Eventually a lack of food, water, air,
or space to live or reproduce will
determine a population’s size.
Carrying Capacity – the largest number of individuals that an environment can support.
What is the growth rate when a population is at carrying capacity?
ESSENTIAL QUESTION:WHAT FACTORS INFLUENCE
POPULATION GROWTH?
Chapter 5
5-2 LIMITS TO GROWTH
Identify density dependent and independent limiting factors of
population growth
Surprise ! they’re called:
Limiting Factors –
a factor that causes population growth to decrease.
2 forms:
– density dependent
– density independent
What factors limit population growth?
Limiting Factor
• A factor that causes population growth to decrease
Ex.) Parasitism, disease, drought, extreme weather
• A resource base that is limited can also affect the long term survival of a species
Density – dependent Factors
• Limiting factors that depend on population size
• Density dependent factors include:
- competition (interspecific and intraspecific)
- predation
- parasitism and disease
Can be among members of the same species (intraspecific) –every individual in a population will be competing for the same food and nesting sites.
Competition
Puffins
Can also be between members of different species (interspecific).
Predation - predator/prey relationships
*Remember the killer whale/sea otter and the sea otter/sea urchin relationships
Parasitism and Disease
A tomato hornworm is covered
with cocoons of pupating braconid
wasps. The braconid wasp causes
the hornworm to die as it pupates.
By the time the wasps undergo
metamorphosis, all of the hosts
insides have been digested, thus
by the time they are ready to
pupate, the caterpillar will die.
While this may be detrimental to
the tomato hornworm, it is
considered beneficial for
gardeners...as the tomato
hornworm can be a significant
pest. Parasitism usually connotes a
negative feeling; however as seen
in this case, it can be considered
beneficial.
Tomato hornworm
Density – Independent Factors
• Affect all populations in similar ways regardless of the population size
• Density independent factors include:- drought and other climate extremes- human disturbances
Unusual Weather
Human Disturbances
ESSENTIAL QUESTION:WHAT FACTORS INFLUENCE
POPULATION GROWTH?
Chapter 5
http://www.census.gov/main/www/popclock.html
According to the U.S. Bureau of the Census, the resident
population of the United States, projected to 09/20/12 is
314,412,871COMPONENT SETTINGS FOR SEPTEMBER 2012
One birth every 7 seconds
One death every 13 seconds
One international migrant (net) every 44 seconds
Net gain of one person every 12 seconds
Current U.S. Population
5 -3 Human Population Growth
• How has the size of the human population changed over time?
• Why do population growth rates differ in countries throughout the world?
WHAT FACTORS INFLUENCE THE GROWTH OF HUMAN POPULATIONS IN ANY GIVEN REGION?
Brainstorm
Studying the Human Population
• What do we call the study of human population characteristics?
Demography
• Why is it important?
Demography
• Studying the characteristics of human population growth
– Birth Rates
• # of individuals born / amount of time
– Death Rates
• # of deaths / amount of time
– Age Structure of the target population
Demographic Indicators
• Total fertility rate (TFR)
– the average number of children each woman
has over her lifetime
• more than 2 = growth
• less than 2 = decline
• Reason?
Age Structure
• Population growth
– Depends on how many people of different ages make up a given population
• Age structure diagrams
– show populations broken down by
• gender
• age group
Age-Structure Diagrams
U.S. has equal numbers of people in each age group = relatively stable population (zero growth). Rwanda has lots of young people = rapid population growth.
How does
economic status
influence
population growth?
Rich vs. Poor
The United Nations divides countries into 2
categories by income
1. High income, highly developed,
industrialized countries (MDC’s)
2. Low-to-Middle income countries,
moderately developed (LDC’s)
MDC’s versus LDC’s
High-income, more developed, industrialized countries have– 21% of the world
population
– 80% of the world money
90% of the population can afford– food
– shelter
– clothing
– medical help
Low-income, less developed countries have
– 79% of the world population
– 20% of the world money
10% of the population can afford– food
– shelter
– clothing
– medical help
MDC’s
LDC’s
Population Change Over Time
MDC’s
Total fertility rate (TFR)1.7
years to double the population 264
LDC’s
Total fertility rate (TFR)3.2
years to double the population 43
lots of time before the
population doubles –
very slow growth
very little time before
the population doubles
– very fast growth
Demographic Transition
• Stage 1
– Pre-industrialized countries
• Stage 2
– Less-developed countries
• Stage 3
– More-developed countries
Predicting World Population
Growth
Should we be concerned?
“The raging monster upon
the land is population
growth.”
E.O. WilsonHarvard Professor of Biology
“Anyone who believes
exponential growth
can go on forever
in a finite world
is a madman.”
Kenneth Boulding
07/01/07 6,602,274,812
08/01/07 6,608,818,475
09/01/07 6,615,362,139
10/01/07 6,621,694,717
11/01/07 6,628,238,381
12/01/07 6,634,570,959
01/01/08 6,641,114,623
02/01/08 6,647,658,287
03/01/08 6,653,779,780
04/01/08 6,660,323,443
05/01/08 6,666,656,022
06/01/08 6,673,199,685
07/01/08 6,679,532,264
Difference of
+ 77,257,452
In one year!
Monthly World population figures:
Source: http://www.census.gov/ipc/www/popclockworld.html
Human Population
Will probably reach 9 billion in your lifetime
Increases at a rate of 3 people every second
9 people were born while you read this
By the end of the day
259,200 people will be born
Let’s Go Back and Look!
http://www.census.gov/main/www/popclock.html
