Coping with Environmental Variation: Temperature and Water

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?