Population Ecology

Chapter 53 Campbell & Reece

Population group of a single species

in the same area

Density

Dispersion

Video of GYE bears

Density

• Dynamic (immigration, emigration, birth death)

• Mark-recapture method

• Index of population size (scat, burrows,etc “sign surveys”)– Glacier NP DNA study podcast or MSNBC

Patterns of Dispersion

• Clustered– Environmental factors unevenly distributed– Mating– Defense/predation

• Uniform– Territoriality– Absence of strong attraction/repulsion– Key environmental factors evenly distributed

• Random – not that common

• Image from Wikipedia, http://en.wikipedia.org/wiki/File:Population_distribution.svg

Table 53.1 Belding's Ground Squirrel Survivorship

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1 2 3 4 5 6 7 8 9 10

Age (years) at end of year

Pro

po

rtio

n a

live

female proportion alive

male proportion alive

Table 53.1 Belding's Ground Squirrel Survivorship

0.001

0.01

0.1

1

1 2 3 4 5 6 7 8 9 10

Age (years) at end of year

Pro

po

rtio

n a

live

female proportion alive

male proportion alive

Survivorship Curves

http://www.bio.miami.edu/dana/pix/survivorship.gif

Tioga Pass, California (3,031m)home of the Belding’s ground

squirrel• _3,031 m

Reproductive Output

• “Big-bang” reproduction – “semelparity”– Reproduce 1x in life

then die– Favored with poor

survival of either parent or offspring

– Often occur with highly variable, unpredictable environments

Image from scienceblogs.com

Repeat reproduction (iteroparity) –

* common in more dependable, predictable environments

High parental care, low numbers of offspring, high survival

Tasmanian Devil, from http://news.mongabay.com/2008/0714-hance_devils.html

Trade-offs

• Ideal = many offspring, well-cared for, repeatedly over lifespan

• This does not exist

• Reproduction is costly (increased maternal mortality)

Growth Curves

• Exponential growth (geometric)– Ideal, limitless growth– Must be temporary– J-shaped curve– Exponential Growth Simulator

http://nortonbooks.com/college/biology/animations/ch34a01.htm

• Logistic GrowthCarrying capacity – There are limits to

growth!– S-curve (sigmoid)– Logistic Growth Simulator:

http://nortonbooks.com/college/biology/animations/ch34a02.htm

Limiting Factors Carrying Capacity

• FWARPS

• Carrying Capacity (K) = max # of individuals of a species that can occupy a certain habitat

• Lag time, Boom & bust (rough transition)

Kaibab Plateau, Arizona

http://depts.alverno.edu/nsmt/youngcc/research/kaibab/story3.html

Rule of 70

• 70 / growth rate = doubling time!

• Learn this, avoid massive debt

K-selection

• Sensitive to population density

• More successful in crowded environments

• Often iteroparous

http://z.about.com/d/healing/1/0/7/N/gtotem_koala.jpg

R-selection

• Maximize reproductive success in uncrowded environments

• Density-independent

• Often semelparous

• Disturbed habitats

http://www.hot-screensaver.com/wp-myimages/cockroach.jpg

Reproductive Strategies• r- Selected (maximum

growth rate, below carrying capacity)– Early reproduction

– Short life span– High mortality rate– Little or no parental care– Large investment in

producing large numbers of offspring

– Below carrying capacity– Examples:

• Bony fish• Grasshoppers

• K-Selected (maximizes population size near carrying capacity)– Late reproduction– Long life span– Low mortality rate– Extensive parental care– Greater investment in

maintenance and survival of adults

– At or near carrying capacity

– Examples:• Sharks• Elephants

BioEd Online

Slide adapted from BioEd Online

Limits on Population Growth

• Density Dependent Limits– Food– Water– Shelter– Disease

• Density Independent Limits– Weather – Climate

Water and shelter are critical limiting factors in

the desert.

Fire is an example of a

Density independent

Limiting factor.BioEd Online Slide adapted from BioEd Online

Limiting Factors

• Density Independent– Fires, floods, drought, etc– Can be exacerbated by density

Density Dependent

Disease, territoriality, competition, predation, toxic waste, intrinsic factors (physiological)

Population Dynamics

• Isle Royale Moose and Wolves

Human Population• Look at 53.22…seriously look at it

http://economicedge.blogspot.com/2009_05_17_archive.html

Demographic Transition

• HIGH birth rate, HIGH Death Rate

• HIGH Birth Rate, Low Death Rate

• Low Birth Rate, Low Death Rate

Age Structure Pyramids

http://www.census.gov/ipc/www/idb/country.php

Ecological Footprint

• footprint as homework