Post on 26-Dec-2015
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
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. 5-11, 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?
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
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
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.