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Population
Dynamics
Chapter 35
Population Dynamics
Key concepts include:
• interactions within and among populations
including carrying capacities, limiting factors,
and growth curves;

Population: all the individuals of a
species that live together in an area
Three Key Features of Populations
 Size
 Density
 Dispersion


(clumped, even/uniform, random)
Three Key Features of
Populations

1. Size: number of individuals in an
area
Estimating Population
 Mark
– Recapture – used to
estimate animal population
Mark Recapture
 Capture
an initial sample, count
and mark them
 Release the marked individuals
 Capture and count another sample
 count marked individuals
recaptured
Formula
(1st sample x 2nd sample)
Number recaptured
Example: Mark - Recapture
 100
ants are captured, marked
and released. 90 ants are
captured in the 2nd sample. 8 of
the ants in the 2nd sample were
marked.
 100 x 90 =
9000= 1125 ants
8
8
Sample Plot
– used to estimate plant
populations
Sample Plot
Randomly
chosen plots
are selected and
populations counted and
averaged.
The average is used to
estimate the total
population
Example
8
8+4+6+3+2
= 23
23 = 4.6
5
4
6
2
4.6 x 100 =
460
3
Three Key Features of
Populations
2. Density: measurement of population
per unit area or unit volume
 Formula: Dp= N
S


Pop. Density = # of individuals ÷ unit
of space
Three Key Features of
Populations

3. Dispersion: describes their spacing
relative to each other
clumped
 even or uniform
 random

clumped
even
(uniform)
random
Population Dispersion
Exponential Growth
ideal, unregulated population growth
 Produces a J shaped curve

http://usrarecurrency.com/WebPgFl/C00015446A/1934$1000FRNSnC00015446A.jpg
After 4 days,
$ 0.16 vs. $ 20,000
After 8 days,
$ 2.55 vs. $ 40,000
9
2.56
 10
5.12
 11
10.24
 12
20.48
 Total $40.95
 13
40.96
 14
81.92
 15
163.84
 16
327.68
 Total $655.35
5,000
5,000
5,000
5,000
$60,000
5,000
5,000
5,000
5,000
$80,000
 17
655.36
120000
 18
1310.72
100000
 19
2621.44
80000
 20
5242.88
60000
 Total $10,485.75
40000
$100,000
5,000
5,000
5,000
5,000
20000
19
16
13
10
7
4
1
0
180000
160000
140000
 21
10,485.76
120000
 100000
22
20,971.52
80000 41,943.04
 23
60000
 24
83,886.08
40000
20000 $167,772.15
 Total
5,000
5,000
5,000
5,000
$120,000
22
19
16
13
10
7
4
1
0
25
 26
 27
 28
 29
 30
 Total

167,772.16
335,544.32
671,088.64
1,342,177.28
2,684,354.56
5,368,709.12
$10,737,418.23
5,000
5,000
5,000
5,000
5,000
5,000
$150,000
12000000
8000000
6000000
4000000
2000000
25
19
13
7
0
1
Dollars
10000000
Factors that affect populations
Limiting factor- any biotic or
abiotic factor that restricts the
existence of organisms in a
specific environment.
EX.- Amount of water
Amount of food
Temperature
Factors that limit populations
Density-dependent factors- Biotic
factors in the environment that have an
increasing effect as population size
increases
Ex. disease
competition (food supply)
parasites
predators
Factors that affect density
Density-independent factorsAbiotic factors in the environment
that affect populations regardless of
their density
Ex. temperature
fire
habitat destruction
drought
Carrying Capacitythe maximum population size that can
be supported by the available
resources

There can only be as many
organisms as the environmental
resources can support

Logistic Growth
Ideal growth that is slowed by limiting
factors as the population increases
 Produces an S shaped curve

Carrying Capacity
N
u
m
J-shaped curve
(exponential growth)
Carrying Capacity (k)
b
S-shaped curve
(logistic growth)
e
r
Time
Boom and Bust Cycles

Some populations fluctuate with
regularity
Life History

The series of events from birth,
through reproduction to death
2 Life History Patterns
 1.






R Strategists
short life span
small body size
reproduce quickly
have many offspring
little parental care
Ex: cockroaches, weeds,
bacteria
R strategist
These organisms produce as many
offspring as possible.
 Invest little in each offspring.
 In good conditions, populations explode
 Good strategy for unpredictable
environments

2 Life History Patterns
2. K Strategists
 long
life span
 large body size
 reproduce slowly
 have few young
 provides parental
care
 Ex: humans, elephants
K strategists
These organisms produce few offspring
and invest resources, time and their own
safety to ensure survival of offspring
 Good strategy for stability
 K= carrying capacity

Demography

the statistical study of populations,
make predictions about how a
population will change
Movement of Populations
1. Immigration- movement of
individuals into a population
2. Emigration- movement of
individuals out of a population
Factors That Affect Future
Population Growth
Immigration
Natality
+
+
Population
Emigration
-
Mortality
Key Features of Populations
Growth Rate: Birth Rate (natality) Death Rate (mortality)
 How many individuals are born vs. how
many die
 Birth rate (b) − death rate (d) = rate
of natural increase (r).

POSTREPRODUCTIVE
REPRODUCTIVE
PREREPRODUCTIVE
Population of a Stable Country
Demographic Transition

The movement from high birth and high
death rate to low death rate then lower
birth rate
Human Population Growth
Human Population Growth
Births
Deaths
Natural
increase
Year
130,013,274
56,130,242
73,883,032
Month
Day
10,834,440
4,677,520
6,156,919
356,201
153,781
202,419
6,408
8,434
Time unit
Hour
14,842
Minute
247
107
141
Second
4.1
1.8
2.3
************************************
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*******************
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Chapter 36
Ecosystem Structure and Dynamics
Biodiversity

The number of different species in a
community
Competition

Interspecific competition – two species
compete for the same resource
Niche

is how an organism makes its living, or
how it uses resources
 What
it eats
 Its habitat
Competitive Exclusion

When two species occupy the same
niche, one is displaced
Resource partitioning

In order for two species to inhabit the
same area, they divide resources
Symbiotic Relationships
Symbiosis- two species living together
3 Types of
1. Commensalism
2. Parasitism
3. Mutualism
Symbiotic Relationships
Commensalismone species benefits
and the other is
neither harmed nor
helped
Ex. orchids on a tree
Symbiotic Relationships
Commensalismone species benefits
and the other is
neither harmed nor
helped
Ex. polar bears and
cyanobacteria
Symbiotic Relationships
Parasitismone species benefits (parasite) and
the other is harmed (host)
 Parasite-Host
relationship
Symbiotic Relationships
ParasitismEx.
lampreys,
leeches,
fleas,
ticks,
tapeworm
parasite-host
Symbiotic Relationships
Mutualismbeneficial to
both species
Ex. cleaning birds
and cleaner
shrimp
Symbiotic Relationships
Mutualismbeneficial to both species
Ex. lichen
Type of
Species
relationship
harmed
Commensalism
Species
benefits
Parasitism
Mutualism
= 1 species
Species
neutral
Trophic Levels
 Each
link in a food chain is known
as a trophic level.
 Trophic levels represent a feeding
step in the transfer of energy
and matter in an ecosystem.
Herbivores – eat only producers
Cows, Deer, Horses,
Grasshoppers
Carnivores – eat only the flesh
of other animals
Wolves, Tigers, Bass, Orca
Detritovores – eat only dead
organisms or wastes
Vultures, Carrion Beetles
Omnivores – eat both animals
and plants
Bears, Pigs, Humans
Trophic Levels
Biomass- the amount of organic matter
comprising a group of organisms in a
habitat.


As you move up a food chain, both
available energy and biomass
decrease.
Energy is transferred upwards but is
diminished with each transfer.
Energy Lost
90% is lost as heat
10% is passed on to the next
level
Trophic Levels
E
N
E
R
G
Y
Tertiary
consumers- top
carnivores
E
Secondary consumerssmall carnivores
Primary consumers- Herbivores
Producers- Autotrophs
E
E
Trophic Levels
Food chain- simple model that
shows how matter and energy
move through an ecosystem
Trophic Levels
Food web- shows all possible
feeding relationships in a
community at each trophic level
 Represents
a network of
interconnected food chains
Food chain
(just 1 path of energy)
Food web
(all possible energy paths)
Nutrient Cycles
 Cycling
maintains homeostasis
(balance) in the environment.
 3 cycles to investigate:
 1. Water cycle
 2. Carbon cycle
 3. Nitrogen cycle
Water cycle-
Evaporation – liquid to gas
 Transpiration- evaporation through
leaves of plants
 Condensation- gas to liquid
 Precipitation- snow, rain, etc.

Water cycle-
Carbon cycle-

Photosynthesis and respiration cycle
carbon and oxygen through the
environment.
Carbon cycle-
 Photosynthesis
Energy + CO2 + H2O  C6H12O6 + O2
 Cellular
Respiration
C6H12O6 + O2  Energy + CO2 + H2O
Nitrogen cycleAtmospheric nitrogen (N2) makes up
nearly 78%-80% of air.
 Organisms can not use it in that form.
 Lightning and bacteria convert nitrogen
into usable forms.

Nitrogen cycleOnly in certain bacteria and industrial
technologies can fix nitrogen.
 Nitrogen fixation -convert atmospheric
nitrogen (N2) into ammonium (NH4+)
which can be used to make organic
compounds like amino acids.

N2
NH4+

Nitrogen cycleNitrogen-fixing
bacteria:
 Some live in a
symbiotic
relationship with
plants of the
legume family
(e.g., soybeans,
clover, peanuts).

Some nitrogen-fixing bacteria live free
in the soil.
 Nitrogen-fixing cyanobacteria are
essential to maintaining the fertility of
semi-aquatic environments like rice
paddies.

Lightning
Atmospheric
nitrogen
Nitrogen Cycle
Denitrification
by bacteria
Animals
Nitrogen
fixing bacteria
Decomposers
Ammonium
Nitrification
by bacteria
Plants
Nitrites
Nitrates
Toxins in food chainsWhile energy decreases as it moves up
the food chain, toxins increase in
potency.
 This is called biological magnification

Succession
a series of changes in a
community in which new
populations of organisms
gradually replace existing ones
Primary succession
colonization of new sites by
communities of organisms – takes
place on bare rock
Primary succession New
bare rock comes from 2
sources:
1.
volcanic lava flow cools
and forms rock
Primary succession New
bare rock comes from 2
sources:
2.
Glaciers retreat and expose
rock
Pioneer species
the first organisms to colonize
a new site
 Ex:
lichens are the first to
colonize lava rocks
Primary SuccessionRock
Climax community
a stable, mature community that
undergoes little or no
succession
Primary succession-
Secondary succession
sequence of community changes
that takes place when a
community is disrupted by
natural disaster or human
actions – takes place on
existing soil
Secondary succession
Ex:

fire
Secondary succession
Ex:
 farming
Secondary succession-
Secondary succession-