coping with environmental variation: temperature and water
DESCRIPTION
Coping with Environmental Variation: Temperature and Water. Photo of differential drought stress tolerance in 2 genotypes of Arabidopsis thaliana from http ://www.riken.jp/en/research/rikenresearch/highlights/7320/. The Ecological Niche. Key niche dimensions include: - PowerPoint PPT PresentationTRANSCRIPT
Coping with Environmental Variation:Temperature and Water
Photo of differential drought stress tolerance in 2 genotypes of Arabidopsis thaliana fromhttp://www.riken.jp/en/research/rikenresearch/highlights/7320/
The Ecological Niche
Figure from Bruno et al. (2003) Trends in Ecology & Evolution
Key niche dimensions include: Energy availability Availability of other resources Physical conditions (e.g., pH)
Generalists & Specialists
Temperature (C)
Water Availability(resource & physical condition)
Species 1
Species 2
Two species with the same niche breadths along both niche axes
Generalists & Specialists
Species 1(Specialist)
Species 1 has a narrower niche breadth along both niche axes
Species 2(Generalist)
Temperature (C)
Water Availability(resource & physical condition)
Generalists & Specialists
Species 1
Individuals with much narrower niche breadths than their respective populations
Individual
Species 2
Specialist?
Generalist?
Temperature (C)
Water Availability(resource & physical condition)
Range of environmental tolerances helps determine potential geographic distribution
(fundamental niche)
Stress Tolerance
Photo of saguaro in Sonoran Desert and range map from Wikimedia Commons
To reduce exposure to, or consequences of, environmental stress:physiological changes, e.g., drought deciduousness
Tolerance & Avoidance of Stress
Photo of dry season Tabebuia aurea from Wikimedia Commons
Tolerance & Avoidance of Stress
Hibernating northern bat in Norway from Wikimedia Commons
To reduce exposure to, or consequences of, environmental stress:behavioral/physiological changes, e.g., dormancy (highly reduced metabolic activity), torpor (reduced met. & temp. in animals), hibernation (extended
torpor); winter sleep / denning (extended sleep with slight reduction in temp.)
Tolerance & Avoidance of Stress
Migration routes for some champion avian migrants from Wikimedia Commons
To reduce exposure to, or consequences of, environmental stress:behavior, e.g., migration
Acclimatization
Usually reversible physiological, morphological or behavioral adjustment by individuals to reduce stress
(under lab conditions = acclimation)
Photo of Mt. Everest base camp from https://studentadventures.co.uk/adventures/everest_base_camp_trek
Adaptation
Ecotypes are populations adapted to local conditions
Image re Clausen, Keck & Heisey’s (1948) classic study from http://www2.nau.edu/~gaud/bio300w/ecotype.htm
Temperature
Image from https://wikispaces.psu.edu/pages/viewpage.action?pageId=112526688&navigatingVersions=true
Enzymes have physical optima Isozymes’ optima differ Denature at high temp.
Lower activity limit -5 C
Temperature
Image of cell membrane from Wikimedia Commons
Influences the properties of biological membranes
Thermal Energy Balance (Plants)
Energy input vs. energy output determines an object’s heat energy change (and internal temp.)
Hplant
Cain, Bowman & Hacker (2014), Fig. 4.8
Boundary layer lowers convective heat loss
Thermal Energy Balance
Cain, Bowman & Hacker (2014), Fig. 4.11
Thermal Energy Balance (Animals)
Ectotherm – regulates temp. through energy exchange with environ.
Hectotherm
Photos of basking snake and weasel from Wikimedia Commons
Endotherm – relies primarily on internal heat generation
Hendotherm
Thermal Energy Balance (Animals)
Cain, Bowman & Hacker (2014), Fig. 4.16 A
Properties of Water
Photo of water in 3 physical phases from Wikimedia Commons
Maximum density at 3.98 C
High heat capacity – ratio of change in heat energy to change in temperature
Universal solvent for biologically important solutes
Properties of Water
“Water is the medium in which all biochemical reactions necessary for physiological function occur”
Quote from Cain, Bowman & Hacker (2014), pg. 98; photo of bacteria grown from Lake Whillans (beneathAntarctic ice sheet) from http://www.nature.com/news/lakes-under-the-ice-antarctica-s-secret-garden-1.15729
Organismal water content for normal physiology60% to 90% of body mass
Water and Biology
Salt balance is intimately tied to water balance
Infra-red camera trap photo of bat at Peruvian mineral lick from http://news.mongabay.com/2008/0714-hance_bats_atbc.html
Flows along potential energy gradients (high to low)
Water Potential
Gravitational potential – owing to gravity
o = Osmotic potential – negative, owing to solutes
p = Pressure (turgor) potential – positive, owing to pressure (negative if under tension)
m = Matric potential – negative, owing to attractive forces on surfaces (e.g., large molecules, soil particles)
Water potential = o + p + m
Resistance – force that impedes movement of water(its reciprocal is conductance)
Daytime – decreasing water potential gradient from soil, through terrestrial plant, to atmosphere
Water Potential & Transpiration
Cain, Bowman & Hacker (2014), Fig. 4.20
Root-shoot ratio
Allocation Tradeoff
Cain, Bowman & Hacker (2014), Fig. 4.22
Water & Salt Balance in Teleost Fishes
Cain, Bowman & Hacker (2014), Fig. 4.24
seawater < teleost < freshwater
Hypoosmotic Hyperosmotic
Exchange gases in dry environment (low water potential)
Image of camels in Chad from Wikimedia Commons
Water & Salt Balance in Terrestrial Animals
Some adaptations to lower evaporative loss & water stress:High skin resistance
Habitat selection (sufficient water to replace losse)Metabolic water
High renal efficiency
Many scaling relationships can be expressed as power laws:
Y = c Xs
X is the independent variable – measured in units of a fundamental dimension; c is a constant of proportionality;
and s is the exponent (or “power” of the function)
The relationship is a straight line on a log-log plot:Log10(Y) = Log10(c) + s Log10(X)
…and by rearranging, this is the form of the familiar equation for a straight line:y = mx + b
Allometry
Area = Length2
Area Length2
Volume = Length3
Volume Length3
Surface area = 6 * Length2
Surface area Length2
Consider the scaling of squares & cubes as functions of the length of a side (the fundamental dimension)
Allometry
y = x2
0
20
40
60
80
100
120
0 2 4 6 8 10 12
Are
a
Y = X2
(accelerating function)
Length
Allometry
y = x2
0
20
40
60
80
100
120
0 2 4 6 8 10 12
Are
a
Y = X2
(accelerating function)
Length
Allometry
y = x2
0
20
40
60
80
100
120
0 2 4 6 8 10 12
Are
a
Y = X2
(accelerating function)
Length
Allometry
Etc…
y = x2
0
20
40
60
80
100
120
0 2 4 6 8 10 12
y = 2x
0
0.5
1
1.5
2
2.5
3
3.5
0 0.2 0.4 0.6 0.8 1 1.2
Log 1
0(A
rea)
Are
a
Y = X2
(accelerating function)
Y = 2X
Length Log10(Length)
Allometry
y = 6x2
0
100
200
300
400
500
600
700
0 2 4 6 8 10 12
y = 2x + 0.7782
0
0.5
1
1.5
2
2.5
3
0 0.2 0.4 0.6 0.8 1 1.2
Length Log10(Length)
Log 1
0(S
urfa
ce A
rea)
Sur
face
are
a
Etc…
Y = 2X + 0.778Y = 6 * X2
(accelerating function)
Allometry
y = x3
0
200
400
600
800
1000
1200
0 2 4 6 8 10 12
y = 3x
0
0.5
1
1.5
2
2.5
3
3.5
0 0.2 0.4 0.6 0.8 1 1.2
Log 1
0(V
olum
e)
Vol
ume
Etc…
Y = X3
(accelerating function)
Y = 3X
Length Log10(Length)
Allometry
Surface area = 4 r2
Surface area r2
Volume = 4/3 r3
Volume r3
Consider the ways in which surface area & volumeof a sphere scale with its radius
Allometry
Surface-to-volume ratio:
Surface area r2 Surface area1/2 r Volume r3 Volume1/3 r
Surface area1/2 Volume1/3 Surface area Volume2/3
Allometry
Etc…
y = 4.8352x0.6667
0
200
400
600
800
1000
1200
1400
0 1000 2000 3000 4000 5000
y = 0.6667x + 0.6844
0
0.5
1
1.5
2
2.5
3
3.5
0 1 2 3 4
Log10(Volume)
Log 1
0(S
urfa
ce a
rea)
Volume
Sur
face
are
a
Y=4.83 * X0.667
(decelerating function)
Volume increases proportionately faster
than surface area
Y=0.667 * X + 0.68
Slope = 1
Allometry
Etc…
y = 4.8352x0.6667
0
200
400
600
800
1000
1200
1400
0 1000 2000 3000 4000 5000
Volume
Sur
face
are
a
Y=4.83 * X0.667
(decelerating function)
This simple fact has myriad important
implications for biology(e.g., heat exchange)
y = 0.6667x + 0.6844
0
0.5
1
1.5
2
2.5
3
3.5
0 1 2 3 4
Log10(Volume)
Log 1
0(S
urfa
ce a
rea) Y=0.667 * X + 0.68
Slope = 1
Allometry
Allometry
Paedophryne amauensis
Image of dinosaurs and world’s smallest known vertebrate from Wikimedia Commons
Assuming ecotothermy and environmental ceteris paribus, which one warms up (or cools down) fastest?