Ch45 Lecture(pop Eco)

Population Ecology

Population Ecology Certain ecological principles govern the  growth and sustainability of all  populations­­including human  populations  

Ecological Principles Apply to All Species

Humans, Palms, Crabs, Seagulls, algae, etc.

Limits to Growth A

population’s growth depends on

the resources of its environment  Deer

introduced to Angel Island

– Population outstripped resources

Angel Island

Angel Island 1 A. Angel Island is a game reserve in San Francisco Bay near Sausalito  B. In the early 1900's well-meaning nature lovers introduced deer to the island  C. With no natural predators to control them the population quickly rose to a level much higher than the island could support  D. Well meaning people brought food to the island to feed the deer, causing the population to further increase 

Angel Island 2  E.

Eventually the population grew to over 300, much too large for the island to support  F. As the deer began to starve they ate most of the native vegetation. Without vegetation the soil started washing away and the island environment rapidly deteriorated

Angel Island - 3 G. It was proposed that hunters kill some of the deer and/or that coyotes, the deer’s natural predators, be introduced to the island. However many people objected because they viewed both alternatives as cruel  H. Eventually two thirds of the population was rounded up and moved to the mainland, at a cost of $3,000 per deer 

Angel Island - 4 

I. However, tracking studies revealed that the majority of the deer moved to the mainland were killed by cars, dogs, coyotes and hunters within 60 days



J. The story of Angel Island illustrates a basic ecological principle: a population's growth is dependent on the resources of its environment. Human intervention could only postpone, not prevent the inevitable

Angel Island - 5 

K. Many environmental problems are simply the result of a lack of understanding of basic ecological principles by politicians, lawyers, economists, the general public and even well intentioned "environmentalists". Human ignorance of simple ecological principles often leads to disastrous results



From: http://arnica.csustan.edu/boty1050/Ecology/ecol ogy.htm

Human Population Problems  Over

6 billion people alive

 About  Most

2 billion live in poverty

resources are consumed by the

relatively few people in developed countries

Population Growth  For

most of human history, humans have not been very numerous compared to other species. – It took all of human history to reach 1 billion. – 150 years to reach 3 billion. – 12 years to go from 5 to 6 billion.  Human

population tripled during the twentieth century.

Human Population History

U.S. POPClock Projection 

  

According to the U.S. Bureau of the Census, the resident population of the United States, projected to 03/21/05 at 17:04 GMT (EST+5) is 295,707,750 COMPONENT SETTINGS One birth every.................................. 7 seconds One death every.................................. 11 seconds One international migrant (net) every............ 24 seconds Net gain of one person every..................... 12 seconds

Population 

A group of individuals of the same species  occupying a given area during a particular  period of time



Can be described by demographics – Vital statistics such as size, density,  distribution, and age structure  

Population Age Structure  Divide

population into age

categories  Population’s

reproductive base

includes members of the reproductive and pre-reproductive age categories

Population Age Structure Diagram

Question 1 1. How did the community respond to the Angel Island deer problem?

Answer 1 1.

How did the community respond to the Angel Island deer problem? The community demanded that the deer be moved to the mainland, rather than be killed by hunters.

Question 2  2.

Ultimately what happen to most of the deer?

Answer 2  2.

Ultimately what happen to most of the deer?

They died from car impacts, dogs, coyotes, and hunters.

Question 3  3.

What is there to be learned from the Angel Island experience?

Answer 3  3.

What is there to be learned from the Angel Island experience?

Answers will vary….. But many will include an element of “unexpected consequences”….

Question 4 4. Define the term, population.

Answer 4 4. Define the term, population.    A group of individuals of the same  species occupying a given area during  a particular period of time.

Question 5 5. What is a population age structure diagram?

Answer 5 5. What is a population age structure diagram? A demographic analytic method that divides a population into age categories (often by gender) and displays it as a graph.

Question 6 6. A population’s ______ _____ includes members of the reproductive and pre-reproductive age categories.

Answer 6 6. A population’s reproductive base includes members of the reproductive and pre-reproductive age categories.

Density & Distribution 

Number of individuals in some specified area of habitat



Crude density information is more useful if combined with distribution data

clumped nearly uniform

random

Figure 45.2 Page 808

Clumped Distribution (STOPPED)

Determining Population Size  Direct counts are most accurate but 

seldom feasible

 Can sample an area, then extrapolate  Capture­recapture method is used for 

mobile species

Population Estimate  How

could you determine the population size of the students in Robinson Hall?

The number of revelers on the beach?

Does Time and Place Make a Difference?

Hilton Head

Daytona Beach

Capture-Recapture Method  Capture,

mark, and release individuals

 Return

sample

 Count

later and capture second

the number of marked individuals and use this to estimate total population

Example: Capture - Recapture 

In 1970, naturalists wanted to estimate the number of pickerel fish in Dryden Lake in central New York State. They captured 232 pickerel, put a mark on their fins, and returned the fish to the lake. Several weeks later, another sample of 329 pickerel fish were captured. Of this second sample, 16 had marks on their fins. (Chaterjee in Mosteller et al. Statistics by Example: Finding Models).

Chain Pickerel

How Many Pickerel Were in the Lake? N = total number of pickerel in lake  NM = total number of marked pickerel (232)  RC = Number of recaptured pickerel (16)  NS = number of fish in sample (329) 

NM/N = RC/NS  N = (NM x NS)/RC 

Solution N

= (232 x 329)/16

N

= 4770 pickerel in the lake (estimate)

 This

is an example of how the “Capture/Recapture” method works.

Assumptions The sampling is random  The marked organisms will not be harmed by the capture and markings  The marked organisms will not avoid recapture  The samples are statistically large enough to avoid problems with sampling error  No significant emigration/immigration occurs  The sampling is done promptly 

Question 7 (Stopped here 3/4/2008) 7. Define crude population density.

Answer 7 7. Define crude population density. The number of individuals in some specified area of habitat. It does not take into consideration the distribution of organisms.

Question 8 8. What are two distribution patterns (there are three)?

Answer 8 8. What are two distribution patterns (there are three)? Clumped Random Uniform (Any two will do….)

Question 9 9. State two methods of determining population size (there are three).

Answer 9 9. State two methods of determining population size (there are three).  Direct counts   Can sample an area, then extrapolate  Capture­recapture method

Changes in Population Size  Immigration adds individuals  Emigration subtracts individuals  Births add individuals  Deaths subtract individuals

Zero Population Growth  Interval

in which number of births

is balanced by number of deaths  Assume

no change as a result of

migration  Population

size remains stable

Per Capita Rates (Stopped )  Rates  Total

per individual

number of events in a time

interval divided by the number of individuals  Per

capita birth rate per month = Number of births per month Population size

r  Net

reproduction per individual per

unit time (Intrinsic rate of natural increase) a constant the units are inverse time  Variable

combines per capita birth

and death rates (assuming both constant)  Can

be used to calculate rate of

Exponential Growth Equation G = rN G

is population growth per unit time  r is net reproduction per individual per unit time  N is population size

Exponential Growth (STOPPED) 

Population size expands by ever increasing increments during successive intervals



The larger the population gets, the more individuals there are to reproduce

Figure 45.4 Page 810

(r) Strategies            

Short life Rapid growth Early maturity Many small offspring. Little parental care. Little investment in individual offspring. Adapted to unstable environment. Pioneers, colonizers Niche generalists Prey Regulated mainly by extrinsic factors. Low trophic level.

Weedy Species – “r Strategists” 



Opportunistic Species - Quickly appear when opportunities arise. – Many weeds. Pioneer Species - Can quickly colonize open, disturbed, or bare ground.

Effect of Deaths 

Population grows exponentially as long as per capita death rates are lower than per capita birth rates 25% mortality between divisions

 

Figure 45.5 Page 811

Question 10 10. What are two rates that increase population size?

Answer 10 10. What are two rates that increase population size? Birth rate Immigration rate

Question 11 11. When is a zero population rate attained?

Answer 11 11. When is a zero population rate attained? When: births + immigration = deaths + emigration

Question 12 12. State the Exponential Growth Equation.

Answer 12 12. State the Exponential Growth Equation.

G = rN

Question 13 13. Given G = rN, what do the symbols represent?

Answer 13 13. Given G = rN, what do the symbols represent?

G

is population growth per unit time  r is net reproduction per individual per unit time  N is population size

Question 14 14. What type of organisms are “r strategists”?

Answer 14 14. What type of organisms are “r strategists”? Weedy species and pioneer species

Question 15 15. State three characteristics of “r strategists”.

Answer 15 15. State three characteristics of “r strategists”.  Short life  Rapid growth  Early maturity  Many small offspring.  Little parental care.  Little investment in individual offspring.      

Adapted to unstable environment. Pioneers, colonizers Niche generalists Prey Regulated mainly by extrinsic factors. Low trophic level.

Biotic Potential  Maximum

rate of increase per

individual under ideal conditions  Varies  In

between species

nature, biotic potential is rarely

reached

Limiting Factors  Any essential resource that is in 

short supply  All limiting factors acting on a 

population dictate sustainable  population size

Carrying Capacity (K)  Maximum

number of individuals that

can be sustained in a particular habitat  Logistic

growth occurs when

population size is limited by carrying capacity

Logistic Growth Equation G = rmax N ((K-N)/K) 

G = population growth per unit time



rmax = maximum population growth rate per unit time



N = number of individuals



K = carrying capacity

Logistic Growth 

As size of the population increases, rate of reproduction decreases



When the population reaches carrying capacity, population growth ceases

Logistic Growth Graph initial carrying capacity

new carrying capacity

Figure 45.6 Page 812

K Strategists  Long

life  Slower growth  Late maturity  Fewer large offspring.  High parental care and protection.  High investment in individual offspring.

More on K Strategists  Adapted

to stable environment.  Later stages of succession.  Niche specialists  Predators (often, but not always)  Regulated mainly by intrinsic factors.  High trophic level.

Top Predators

Question 16 16. Define biotic potential.

Answer 16 16. Define biotic potential.  Maximum

rate of increase per

individual under ideal conditions

Question 17 17. What is “K”?

Answer 17 17. What is “K”?  Maximum

number of individuals

that can be sustained in a particular habitat (carrying capacity)

Question 18 18. State the logistic equation.

Answer 18 18. State the logistic equation. G = rmax N ((K-N)/K)

Question 19 19. Given the logistic equation, G = rmax N (K-N/K) What do the symbols stand for?

Answer 19 19. Given the logistic equation, G = rmax N (K-N/K) What do the symbols stand for? 

G = population growth per unit time



rmax = maximum population growth rate per unit time



N = number of individuals



K = carrying capacity

Question 20 20.Refering to the former equation, what happens to G as N approaches K?

Answer 20 20.Refering to the former equation, what happens to G as N approaches K? G (growth rate) approaches zero. The population stops growing.

Overshooting Capacity 

Population may temporarily increase above carrying capacity



Overshoot is usually followed by a crash; dramatic increase in deaths Reindeer on St. Matthew’s Island Figure 45.6 Page 812

Density-Dependent Controls  Logistic

growth equation deals

with density-dependent controls  Limiting

factors become more

intense as population size increases  Disease,

competition, parasites,

toxic effects of waste products

Density-Independent Controls  Factors

unaffected by population

density  Natural

disasters or climate changes

affect large and small populations alike

A Hurricane is an Example of a Density Independent Factor

Earth Quakes and Tsunamis

Life History Patterns  Patterns of timing of reproduction 

and survivorship  Vary among species  Summarized in survivorship 

curves and life tables

Life Table  Tracks

age-specific patterns

 Population

is divided into age

categories  Birth

rates and mortality risks are

calculated for each age category

Survivorship Curves Graph of age-specific survivorship

Figure 45.8 Page 815

Type I  Large

animals, few offspring, much parental care, live to an old age

Type II Birds are good examples…… Intermediate number of offspring, some parental care, fairly constant survival rate over a life time.

Type III These are typical “r strategists”, weedy species, pesky….. Short life, many offspring, little parental care, high mortality of the young…

Predation and Life History   Guppy populations vary in life history 

characteristics and morphology  Differences have genetic basis  Variation seems to be result of directional 

selection by predators

Human Population Growth  (STOPPED 3/25)   Population now exceeds 6 billion  Rates of increase vary among countries  Average annual increase is 1.26 percent  Population continues to increase 

exponentially

Human Population History

Side-Stepping Controls  Expanded

into new habitats

 Agriculture

increased carrying

capacity; use of fossil fuels aided increase  Hygiene

and medicine lessened

effects of density-dependent controls

Future Growth  Exponential

growth cannot continue

forever  Breakthroughs

in technology may

further increase carrying capacity  Eventually,

density-dependent

factors will slow growth

Fertility Rates   Worldwide, average annual rate of 

increase is 1.26%  Total fertility rate (TFR) is average 

number of children born to a woman  Highest in developing countries, lowest 

in developed countries

Age Structure Diagrams Show age distribution of a population Figure 45.14 Page 821

Rapid Growth

Slow Growth

Zero Growth

Negative Growth

Population Momentum  Lowering

fertility rates cannot immediately slow population growth rate

 Why?

There are already many future parents alive

 If

every couple had just two children, population would still keep growing for another 60 years

Projected Human Populations

Life Expectancy and Income

Slowing Growth in China  World’s

most extensive family

planning program  Government

rewards small family

size, penalizes larger families, provides free birth control, abortion, sterilization  Since

5.7

1972, TFR down to 1.8 from

Population

Each Dot Represents 5,000 Persons

Cities 1 2 3 4 5 6

Chongqing Shanghai Beijing Chengdu Harbin Tianjin

15,300,000 13,100,000 12,200,000 9,900,000 9,200,000 9,000,000

7

Shijiazhuang

8,600,000

8 9 10 11 12

Wuhan Qingdao Changchun Guangzhou Hong Kong

7,200,000 7,000,000 6,800,000 6,700,000 6,700,000

Total

111,700,000

http://www.paulnoll.com/China/Population/population-cities.html

0--4

Percent of Total 9.30%

5--9

9.07%

10-14

10.39%

15--19

11.95%

20--24

11.38%

25--29

6.96%

30--34

8.40%

35--39

6.68%

40--44

4.40%

45--49

4,40%

50--54

4.32%

55--59

3.70%

60-64

2.99%

65--69

2.27%

70--74

1.61%

75--79

0.95%

80-84

0.47%

85-89

0.15%

90-94 95-99

0.03% 0.01%

Age

Male 4.87 % 4.69 % 5.35 % 6.10 % 5.69 % 3.56 % 4.29 % 3.43 % 2.29 % 2.29 % 2.24 % 1.92 % 1.52 % 1.10 % 0.74 % 0.40 % 0.17 % 0.05 % 0.01 % -

4.43%

Sex Ratio Male: Female 109.95 to 100

4.38%

107.19 to 100

5.04%

106.18 to 100

5.89%

103.66 to 100

5.68%

100.19 to 100

3.40%

104.70 to 100

4.11%

104.27 to 100

3.26%

105.13 to 100

2.11%

108.45 to 100

2.11%

108.45 to 100

2.08%

107.32 to 100

1.78%

107.48 to 100

1.47%

102.84 to 100

1.17%

94.15 to 100

0.87%

84.74 to 100

0.55%

71.43 to 100

0.30%

57.89 to 100

0.10%

45.61 to 100

0.02% -

38.18 to 100 36.80 to 100

Female

C hin a's Po pul atio n by Ag e and Sex fro m the 198 7 Ce nsu s F act ors in the dis pro por tion ate rati o of mal e/fe mal e A nu mb er of fact ors cau se the dis pro por tion ate nu mb er of mal es to fem ale s. In rur al are as the mal es are mu ch mo re val uab le tha n fem ale s. The rea son is that wh en the you ng peo ple get mar rie d the ne w cou ple goe s to the hou se of the mal e and that fam ily gai ns the fem ale to wor k whi le the hou se wit h the fem ale los es the one wor ker that the y had . Als o the old cou ple wit

Effects of Economic  Development   Total fertility rates (TFRs) are highest in 

developing countries, lowest in  developed countries  When individuals are economically 

secure, they are under less pressure to  have large families

Sweat Shop, India

Shop size = 2m x 5m. How many people can you count? http://www.mcps.k12.md.us/curriculum/socialstd/grade7/india/Sweatshop.html

Population Sizes in 2001 Asia

3.7 billion

Europe

727 million

Africa

816 million

Latin America

525 million

North America

316 million

Oceania

31 million

Human Population Growth

 http://www.youtube.com/watch?v=Atnu  An

Animated History of Human Population Growth

Demographic Transition Model  Based

on historical data from

western Europe  Postulates

that as countries become

industrialized, first death rates drop, then birth rates drop

Demographic Transition Model Stage 1 Preindustrial

Stage 2 Transitional

Stage 3 Industrial

Stage 4 Postindustrial

relative population size births deaths

low

Figure 45.16 Page 822

increasing

very high

decreasing

low

zero

negative

Resource Consumption  United

States has 4.7 percent of the world’s population

 Americans

have a disproportionately large effect on the world’s resources

 Per

capita, Americans consume more resources and create more pollution than citizens of less developed nations

Population Ecology The End