GOOD MORNING!!! (APES Review, 3/7/12, CAPT Week) Our Plan for This Wednesday Morning…• 1) EAT! EAT! EAT! • 2) Lab Activity: Estimating Population Size• 3) Lecture: Introduce Population Biology• 4) Activity: Population Growth Activity• 5) Calculation Practice – Growth Rate• 6) Lecture: Human Population Dynamics• 7) Activity (Computers): Age Structure Diagram• HW: • prb.org activity• Quiz/Test, TBD

POPULATION BIOLOGY Chapter 6

HUMAN POPULATION DYNAMICS

(Chapter 7 – See other PPOINT)

What Limits the Growth of Populations?

Intrinsic factors - Operate within or between individual organisms in the same species.

Extrinsic factors - Imposed from outside the population.

Biotic factors - Caused by living organisms. Abiotic factors - Caused by non-living

environmental components.

Populations Have Certain Characteristics (2)

Why Do Population Sizes Change?• Temperature• Presence of disease organisms or harmful

chemicals• Resource availability• Arrival or disappearance of competing species

Populations Can Grow, Shrink, or Remain Stable (1)

Population size governed by• Births• Deaths• Immigration• Emigration

Population change =

(births + immigration) – (deaths + emigration)

Fig. 5-B, p. 110

Fig. 5-11, p. 111

Bioticpotential

Po

pu

lati

on

siz

e

Time (t)

Carrying capacity (K)

Environmentalresistance

Population stabilizes

Exponentialgrowth

No population can continue to increase in size indefinitely. Exponential growth (left half of the curve) occurs when resources are not limiting and a population can grow at its intrinsic rate of increase (r) or biotic potential. Such exponential growth is converted to logistic growth, in which the growth rate decreases as the population becomes larger and faces environmental resistance. Over time, the population size stabilizes at or near the carrying capacity (K) of its environment, which results in a sigmoid (S-shaped) population growth curve. Depending on resource availability, the size of a population often fluctuates around its carrying capacity, although a population may temporarily exceed its carrying capacity and then suffer a sharp decline or crash in its numbers.. Question: What is an example of environmental resistance that humans have not been able to overcome?

Boom and Bust Cycles

r-Adapted Species

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

K-Adapted Species

Long life Slower growth Late maturity Fewer large

offspring High parental care

and protection. High investment in

individual offspring.

Adapted to stable environment.

Later stages of succession.

Niche specialists Predators Regulated mainly

by intrinsic factors. High trophic level

Fig. 5-12, p. 111

1925

Nu

mb

er o

f sh

eep

(m

illi

on

s)

.5

1.0

1.5

2.0 Populationovershootscarryingcapacity

Carrying capacity

Population recoversand stabilizes

Exponentialgrowth

Populationruns out ofresourcesand crashes

18251800 1850 1875 1900Year

Fig. 5-13, p. 112

2,000

Carryingcapacity

1910 1920 1930 1940 1950

Nu

mb

er o

f re

ind

eer

Populationovershootscarryingcapacity

Populationcrashes

0

500

1,000

1,500

Year

Fig. 5-14, p. 112

Carrying capacity

r species;experiencer selection

K species;experienceK selection

K

Time

Nu

mb

er

of

ind

ivid

ual

s

Fig. 5-15, p. 114

No Population Can Grow Indefinitely: J-Curves and S-Curves (1)

Biotic potential• Low • High

Intrinsic rate of increase (r)

Individuals in populations with high r • Reproduce early in life• Have short generation times• Can reproduce many times• Have many offspring each time they reproduce

No Population Can Grow Indefinitely: J-Curves and S-Curves (2)

Size of populations limited by• Light• Water• Space• Nutrients• Exposure to too many competitors, predators or

infectious diseases

Density Dependent Factors

Higher proportion of population is affected as population density increases.• Predation• Parasitism• Infectious disease• Competition for resources

Tend to reduce population size by decreasing natality or increasing mortality.• Interspecific Interactions

• Predator-Prey oscillations• Intraspecific Interactions

• Territoriality• Stress and Crowding

• Stress-related diseases

Density Independent Factors

Constant proportion of the population is affected regardless of population density.

Tend to be abiotic components. Do not directly regulate population size. EXAMPLES:

Sample Problem: A population of birds was measured to be 1500 birds. Over the course of a year, there were 300 births and 200 deaths. 100 birds entered the population by migration, 50 birds left population by emigration.How to Calculate Change in Population Size

How to Calculate Growth Rate of a Population:

Calculating R from CBR and CDR

How to Calculate Doubling Time of a Population:

No Population Can Grow Indefinitely: J-Curves and S-Curves (3)

Environmental resistance

Carrying capacity (K)

Exponential growth

Logistic growth

Genetic Diversity Can Affect the Size of Small Populations

Founder effect

Demographic bottleneck

Genetic drift

Inbreeding

Minimum viable population size

Under Some Circumstances Population Density Affects Population Size

Density-dependent population controls• Predation• Parasitism• Infectious disease• Competition for resources

Several Different Types of Population Change Occur in Nature

Stable

Irruptive

Cyclic fluctuations, boom-and-bust cycles• Top-down population regulation• Bottom-up population regulation

Irregular

Survivorship Curves

Humans Are Not Exempt from Nature’s Population Controls

Ireland• Potato crop in 1845

Bubonic plague• Fourteenth century

AIDS• Global epidemic

Case Study: Exploding White-Tailed Deer Population in the U.S.

1900: deer habitat destruction and uncontrolled hunting

1920s–1930s: laws to protect the deer

Current population explosion for deer• Lyme disease• Deer-vehicle accidents• Eating garden plants and shrubs

Ways to control the deer population

Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction?

Habitat

Hunted: early 1900s

Partial recovery

Why care about sea otters?• Ethics• Keystone species• Tourism dollars

LOOK NO FURTHER…

ALL OF THE INFORMATION ON the SLIDES FOLLOWING THIS ONE WILL NOT BE ON THE POPULATION TEST!

5-1 How Do Species Interact?

Concept 5-1 Five types of species interactions—competition, predation, parasitism, mutualism, and commensalism—affect the resource use and population sizes of the species in an ecosystem.

Species Interact in Five Major Ways

Interspecific Competition

Predation

Parasitism

Mutualism

Commensalism

Most Species Compete with One Another for Certain Resources

Competition

Competitive exclusion principle

Most Consumer Species Feed on Live Organisms of Other Species (1)

Predators may capture prey by• Walking• Swimming• Flying• Pursuit and ambush• Camouflage• Chemical warfare

Most Consumer Species Feed on Live Organisms of Other Species (2)

Prey may avoid capture by• Camouflage• Chemical warfare• Warning coloration• Mimicry• Deceptive looks• Deceptive behavior

Science Focus: Why Should We Care about Kelp Forests?

Kelp forests: biologically diverse marine habitat

Major threats to kelp forests• Sea urchins• Pollution from water run-off• Global warming

Predator and Prey Species Can Drive Each Other’s Evolution

Intense natural selection pressures between predator and prey populations

Coevolution

Some Species Feed off Other Species by Living on or in Them

Parasitism

Parasite-host interaction may lead to coevolution

In Some Interactions, Both Species Benefit

Mutualism

Nutrition and protection relationship

Gut inhabitant mutualism

In Some Interactions, One Species Benefits and the Other Is Not Harmed

Commensalism

Epiphytes

Birds nesting in trees

5-2 How Can Natural Selection Reduce Competition between Species?

Concept 5-2 Some species develop adaptations that allow them to reduce or avoid competition with other species for resources.

Some Species Evolve Ways to Share Resources

Resource partitioning

Reduce niche overlap

Use shared resources at different• Times• Places• Ways