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UNI101Y1 Study Guide - Intertidal Zone, Interspecific Competition, Limiting Factor


Department
University College Courses
Course Code
UNI101Y1
Professor
Spencer Barrett

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BIO120H © Lisa Zhao 2011 | Page 4
ASYMMETRIC COMPETITI ON CAN OCCUR WHEN DIFFERENT FACTORS LIMIT
THE POPULATIONS OF C OMPETITORS
a
as
sy
ym
mm
me
et
tr
ri
ic
c
c
co
om
mp
pe
et
ti
it
ti
io
on
n: a competitive relationship b/w 2 species in which each has an
adv. w/ respect to diff. limiting factors in the envmt
ex. one may exploit more resources, other better at tolerating stressful conditions or
avoiding consumers
research study
J
Jo
os
se
ep
ph
h
C
Co
on
nn
ne
el
ll
l
(asymmetric
competition)
barnacles
Chthalamus
stellatus and
Balanus balanoids
barnacles are sessile, form dense continuous pop. on rocky
shores, feed on plankton filtered from water
food isn’t a limiting resource b/c feeding can’t reduce the vast
# of plankton
they are limited by space for settling and growth
Chthalamus are at higher regions of intertidal zone than Balanus
he demonstrated that adult C are restricted to upper regions b/c
of interspecific competition (not limited by tolerance)
removed B from rock C thrived in lower regions
these species compete for space
B have heavier shells and grow faster than C
their shells edge under C’s shells and pry them off the rock
C more resistant to desiccation than B
B don’t invade upper regions even when there is no C
win each region of the intertidal zone, one of the barnacle species is the superior
competitor
the superior competitor for resources is always more strongly limited by another factor
ex. envmtal stress/ predators i.e. Balanus
trade-off b/w stress tolerance and competitive ability
coexist b/c limited by diff. factors
HABITAT PRODUCTIVITY CAN INFLUENCE COMPET ITION BETWEEN PLANT
SPECIES
plant competition depends on nutrient levels in soil (controls growth and its ability to
shade competitors)
Grubb-Tilman vs. Grime- Keddy
P
P.
.
J
J.
.
G
Gr
ru
ub
bb
b and D
Da
av
vi
id
d
T
Ti
il
lm
ma
an
n
plants compete more intensely when mineral nutrients are less abundant in soil
o high levels are less likely to limit plant pop., thus interspecific competition is
weaker
J
J.
.
P
P.
.
G
Gr
ri
im
me
e and P
Pa
au
ul
l
K
Ke
ed
dd
dy
y
plants compete less intensely when water and mineral nutrients are less abundant
o competition for light is more imp. than competition for soil nutrients
o lack of water and nutrients limit pop. to the point that indic. plants are widely
spaced and don’t compete for light
S
S.
.D
D.
.
W
Wi
il
ls
so
on
n and D
Da
av
vi
id
d
T
Ti
il
lm
ma
an
n: 3 species of prairie grasses
plants competed primarily below ground for nutrients on low-nutrient plots and
primarily above ground for light on high-nutrient plots
thus, intense competition at all nutrient levels
little relationship b/w nutrient levels and competition
N
Na
an
nc
cy
y
E
Em
me
er
ry
y et al.: manipulated soil salinity and saturation (stressful) in marshes
plant species were zoned according to tolerance
when fertilizer was added to junctions of the zones, the more stress-tolerant species
was released from nutrient limitation and outcompeted the other species
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