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Ecology
• Study of how organisms interact with each other and with their environment
Levels of Ecological Organization• Populations
– groups of individuals of the same species living together in one area
• Communities– populations of different species living together
in one area
• Ecosystems– communities and the non-living parts of the
environment with which they interact
Population Structure
Key aspects:
• Population Size
• Population Density
• Population Dispersion
Population Size
• Affects populations ability to survive
• small populations - more likely to go extinct
Population Density
• Number of individuals per unit area
• low density can be problem too
Population Dispersion
• Spacing of individuals within the population
• Random, uniform or clumped
• Clumped dispersion is when individuals aggregate in patches.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 52.2a
• By contrast, uniform dispersion is when individuals are evenly spaced.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 52.2b
• In random dispersion, the position of each individual is independent of the others.
• Overall, dispersion depends on resource distribution.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin CummingsFig. 52.2c
Survivorship Curves
• Graphical representation of the survivorship (opposite of mortality) at each age
Survivorship Curves
• Type I– increased risk of dying when old
• Type II– equal chance of dying at all ages
• Type III– increased chance of dying when young
Fig. 56.10
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0 25
Pro
port
ion
Sur
vivi
ng1.0
0.1
Human (type I)
Hydra (type II)
Oyster (type III)
0.01
0.00150
Percent of Maximum Life Span10075
Fig. 56.11
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
3 6 9 12 15 18 21 24 27
0.0020.0030.0040.005
0.01
0.020.030.040.05
0.1
0.20.30.40.5
1.0
Age (months)
Pro
port
ion
Sur
vivi
ng
Poa annua – most like Type II
Population Growth
• Biotic Potential– r– the rate a population would grow at with no
limits– intrinsic rate of increase
Exponential Growth
dN/dt = rN
r = (b - d) + (i - e)
Fig. 56.16-1Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
0 5 10Number of Generations (t)
Pop
ulat
ion
Siz
e (N
)
15
1250
1000
750
= 1.0 N
500
250
0
dNdt
Carrying Capacity
• populations eventually reach a limit to their growth
• K = number of individuals that the environment can support
Logistic Growth
dN/dt = rN ((K - N)/ K)
• growth rate slows as the carry capacity is approached
• sigmoid growth curve (S-shaped)
• most populations remain constant in size
Fig. 56.16Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
0 5 10Number of Generations (t)
Pop
ulat
ion
Siz
e (N
)
15
1250
1000
750
= 1.0 N
500
250
0
= 1.0 N
Carryingcapacity
1000 – N1000
dNdt
dNdt
Fig. 56.17
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
N = K
Below K Above K
Population Size (N)
Pop
ulat
ion
Gro
wth
Rat
e (d
N/d
t)
0
NegativeGrowthRate
PositiveGrowthRate
CarryingCapacity (K)
Fig. 56.18 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
1915 1925 1935 1945
a. b.
200 10 30 5040
10
8
6
4
2
0 Num
ber
of C
lado
cera
ns (
per
200
mL
)
500
400
300
200
100
0
Num
ber
of B
reed
ing
Mal
eF
ur S
eals
(th
ousa
nds)
Time (years) Time (days)
Logistic Growth
Fig. 56.24
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
4000B.C.
2
1
3
4
5
6
3000B.C.
2000B.C.
1000B.C.
Bil
lion
s of
Peo
ple
0 1000 2000
Significant advancesin public health
IndustrialRevolution
Bubonic plague“Black Death”
Year
Limits to Population Growth
• Resource limitation- competition
• predation
Community Ecology
• Study interactions among populations
• Niche– total of all the ways an organism uses resources
in its environment– food consumption, space utilization, temp
range, etc...
• Habitat– physical location
Competition
• struggle between organisms to utilize the same resource when the resource is limited
• niches overlap and resources are limited
Fig. 57.4Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
High tide
Low tideLow tide
C.stellatus fundamental and realized niches are identical whenS.balanoides is removed.
S.balanoides and C.stellatus competing
Chthamalus
Chthamalusrealized niche
Chthamalusfundamentalniche
Semibalanus
Semibalanusrealized niche
Semibalanusfundamentalniche
J.H. Connell’s classical study of barnacles
Competition
• “fighting” = interference competition
• consuming shared resources = exploitative competition
Competition
• Interspecific competition– between individuals from different species
• Intraspecific competition– between individuals from same species
One Possible Result of Competition
• Competitive exclusion– no species can occupy the same niche
indefinitely– one species will be outcompeted and be driven
to extinction locally
Fig. 57.5Gausse’s
Experiments
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0
50
100
150
200
40 8 12 16 20 24 40 8 12 16 20 24 40 8 12 16 20 24
a.
Days Days Days
Paramecium caudatum
Paramecium aureliaParamecium bursaria
Popu
latio
n D
ensi
ty(m
easu
red
by v
olum
e)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
200
150
100
50
040 8 12 16 20 24
Days
Paramecium caudatum
Paramecium aurelia
Paramecium bursaria
Pop
ulat
ion
Den
sity
(mea
sure
d by
vol
ume)
b.
Competitive Exclusion
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
c.
0 20 24161284
Days
Paramecium caudatum
Paramecium aureliaParamecium bursaria
Pop
ulat
ion
Den
sity
(mea
sure
d by
vol
ume) 75
50
25
0
Coexistence…Resource Partitioning
Fig. 57.5
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
0
50
100
150
200
40 8 12 16 20 24 40 8 12 16 20 24 40 8 12 16 20 24
a.
c.
200
150
100
50
00 20 2416128440 8 12 16 20 24
Days Days Days
Days Days
Paramecium caudatum
Paramecium aureliaParamecium bursaria
Popu
latio
n D
ensi
ty(m
easu
red
by v
olum
e)Po
pula
tion
Den
sity
(mea
sure
d by
vol
ume)
Popu
latio
n D
ensi
ty(m
easu
red
by v
olum
e)
b.
75
50
25
0
Other Results of Competition
• Niche overlap can lead to...– Resource partitioning– character displacement
– Resource partitioning is the differentiation of niches that enables two similar species to coexist in a community.
Fig. 53.2Fig. 53.3
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Character displacement is the tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populationsof the same two species.– Hereditary changes
evolve that bringabout resourcepartitioning.
Fig. 53.4
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Predation
• Predator uses prey for food
• prey evolves defenses, predator evolves adaptations to overcome…arms race
Predation
Plant defenses against herbivores:
• morphological - thorns, spines, plant hairs
• chemicals - secondary compounds
Animal defenses against predators:• Behavioral defenses include fleeing,
hiding, self-defense, noises, and mobbing.
Predation
• Camouflage includes cryptic coloration,
Leaf mimic katydid from the Ecuadorian Amazon
• Deceptive Markings: eyespots
http://discovermagazine.com/photos/11-the-calculating-beauty-of-butterflies
http://www.flickr.com/photos/ladyoftheflowers/2386058994/
• Mechanical defenses include spines & shells.
african-safari-pictures.com
http://www.animalpictures1.com/r-sea-urchin-112-sea-urchin-1958.htm
• Chemical defenses include odors and toxins – may get them from the plants they eat (ex: monarch butterfly & milkweed)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Aposematic coloration is indicated by warning colors, and is sometimes associated with other defenses (toxins).
Fig. 53.6
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Mimicry is when organisms resemble other species.– Batesian mimicry is where a harmless species mimics
a harmful one.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• Müllerian mimicry is where two or more unpalatable species resemble each other.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 53.8
Fig. 57.14
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Heliconius melpomene
Papilio glaucusBattus philenor
a. Batesian mimicry: Pipevine swallowtail butterfly (Battus philenor) is poisonous; Tiger swallowtail (Papilio glaucus) is a palatable mimic.
Heliconius erato
Heliconius cydnoHeliconius sapho
b. Müllerian mimicry: Two pairs of mimics; all are distasteful.
Predation
• Can promote species diversity
• predator eats superior competitor
• Keystone speciesexert an importantregulating effecton other speciesin a community.
Fig. 53.14
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
• If they are removed, community structure is greatly affected.
Fig. 53.15
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Coevolution & interspecific interactions– Coevolution refers to reciprocal evolutionary
adaptations of two interacting species.• When one species evolves, it exerts selective
pressure on the other to evolve to continue the interaction.
Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
The Oogpister Beetle Video
http://www.snotr.com/video/4732