Fall 2010 IB Workshop Series sponsored by IB academic advisors
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Transcript of Fall 2010 IB Workshop Series sponsored by IB academic advisors
Fall 2010 IB Workshop Seriessponsored by IB academic advisors
Winning Resumes for IB Students
Wednesday, Sept. 224:00-5:00pm 161 Noyes Lab
Career Center staff will discuss the basics of writing a resume including format and objectives. Cover letters and special
situations are also addressed.
ASSIGNMENT FOR THURSDAY
1) Complete Problem Set 3: 223-226 in
lab manual
2) Go to:
Course website for Sept. 24
Read article BEFORE class
‘Human Population Explosion’
3) No LO or PPT for Thursday; only ICA.
This lecture Ch 10 + 12:Population Dynamics and StructureRead LO Major Concepts
Objectives• Temporal dynamics: fluctuations through time• Density-dependent vs. independent regulation• Types and causes of fluctuations• Models with time delays
• Population abundance• How to estimate?• Age and sex structure
• Spatial structures• Distribution (range)• Density• Dispersion
What determines the abundance and distribution of populations?
Read LO I + II
What controls population size?
time
time
time
N
density-dependent
change in environment
density-independent
K
Chance??
Logistic equation assumes:• Instantaneous (d-d) feedback of K onto N• If time lags in response --> fluctuation of N
around K• Longer lags---> more fluctuation; may crash.
N
K
time
How well do populations fit the logistic growth model?
Density-dependent factors drive populations toward equilibrium (stable population size),
• BUT
• they also fluctuate around equilibrium due to:
1) changes in environmental conditions
2) chance
3) intrinsic dynamics of population
responses
• Fluctuation is the rule for natural populations.• Less fluctuation for large animals with • long life span because of: • greater homeostasis• many overlapping generations--> high intrinsic stability
• Fluctuations greater if small/short lifespan– little homeostasis– populations turn over rapidly--> – low intrinsic stability
Population cycles synchronized among species in a region. Periodic cycles with peaks separated by same number of years.
Other species may vary in their response to changes in the environment --> asynchronized cycles.
Environmental fluctuations (extrinsic factors) (and organism responses) tend to be irregular, not periodic.
But many populations change with periodic, non-random frequency. *** Is an extrinsic or intrinsic factor likely to be responsible? Explain.
Some populations exhibit regularfluctuations (cycles) in size.
What density-dependent factor causes grouse populations to cycle? Consider abiotic and biotic interactions…
What factor causes grouse populations to cycle? ICA 1• Hypothesis: Density-dependent infections by a
parasitic roundworm cause the cycles.• Prediction: Populations treated with anti-
roundworm drugs will not crash following treatments, but control populations will.
• Graph the prediction. Label axes.
Control:no drugs
Control:
No drugsQuickTime™ and a
TIFF (LZW) decompressorare needed to see this picture.
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
Experimental #
Control #
Drug Drug
What is conclusion?Is hypothesis proven?
Time
Results
An intrinsic mechanism for population cycles?
• ‘Momentum’ by high birth rate at low density --> overshoot K.
• Low survival at high density--> overcompensate and decrease below K.
• Population cycles result from time delays in the birth and death rates of populations in response to their own densities.
Discrete-time models with density-dependence:• Built-in time delay ---> can’t continually adjust• Patterns of oscillations depend on value of R• (per capita growth rate)
>>2 chaos
Population dynamics reflect a complex interaction of biotic and abiotic influences, and are rarely stable.
Population: all individuals of a species in an areaSubpopulations: in different habitat patches*** What are structures (traits) of populations?• Size (abundance)• Age structure• Sex ratio
• Distribution (range) • Density (#/unit area)• Dispersion (spacing)
• Genetic structure
Population size may be estimated by several methods, e.g. mark-recapture
Aerial censuses
Censusing a population
• Number of individuals
• Sex ratio
• Age structure
• complex if:
• can’t age
• size does not = age (plants)
• Long-term vs. short-term
Size classes of individuals of same age.
***What’s the ‘take-home message’ = main conclusion?
Temporal variation in recruitment of new individuals affects age structure --->
long-term implications on population growth.
Species distributions (ranges): are they really continuous? Read LO II
What must happen for species to extend range at periphery?
What prevents it from doing so?
***What factors limit the (geographic) distribution (+ range) of organisms?
• Phenology• Dispersal• Behavior (habitat selection)• Biotic factors (other species)• Abiotic factors (chemical / physical)• Human introductions• Chance• History
Geographic distributions are discontinuous. Within itsrange, only suitable habitatsare occupied. What factor determines this distribution?
•Transplant 2 species to range of elevations --> measure fitness components.
What is the main result :for lowland species on L?for highland species on R?
What is the main conclusion?
LOW HIGH
ICA 2
Geographic range includes all areas occupiedduring entire life history; must include migration.
Geographic ranges with migration - know nopolitical boundaries…adds complexity to protection.
Are ranges stable through time?
Introducedstarlings
Population density declines as body size increases.
ICA 3 Summarize the major result in Fig. 1.
Fig. 1
Summarize major result in Fig. 2
Range
Summarize major result in Fig. 3
Within its range, population density (#/area) varies with differences in habitat quality.
ICA 4 What accounts for this owl’s distribution?
Owl location‘Old growth’ forest
Density and reproduction success are dependent on amount of suitable habitat for prey.
Older forest (%)
Numberper km2
Contrasting patterns of dispersion
Dispersion = spacing of individuals with respect to others in a population
• Which is most common in plants? animals?
(Even)
***What factors influence dispersion of individuals within populations?
• habitat heterogeneity
• dispersal limitation• reproductive mode• social interactions
Dispersal mode of plants affects their spatialdispersion.
ICA 5 What type of dispersion is shown here? Hypothesize what causes the pattern.
A B