Transcript strategies in thermal regulation - Evans Laboratory: Environmental

GLOBAL CHANGE BIOLOGY
BIOL 3999: Issues in Biological Science
Dr. Tyler Evans
Email: [email protected]
Phone: 510-885-3475
Office Hours: M,W 10:30-12:00 or by appointment
Website: http://evanslabcsueb.weebly.com/
PREVIOUS LECTURE
• linear relationship
between temperature and
CO2
• Ocean and atmospheric
temperature is
increasing and will
continue to increase
over the next century
TODAY’S LECTURE
•
establish basic principles regarding the effects of elevated
temperature on function across levels of biological
organization
•
provide background information that will assist in
understanding mechanistic basis for vulnerability to heat
stress and global warming
EFFECTS OF TEMPERATURE ON
BIOLOGICAL SYSTEMS
• multi-cellular life (metazoans) is confined to a narrow temperature range
100°C
hot springs bacteria
hot springs algae
80°C
50°C
desert maximum
desert insects
camels, some birds, some turtles
most birds, mammals
30°C
shore animals
majority of life
0°C
-80°C
Antarctic minimum (few mammals, birds)
EFFECTS OF TEMPERATURE ON BIOLOGICAL
SYSTEMS
• plants and animals are drastically affected at all levels of biological
organization by any change in their thermal environment
• reflected in global patterns of species richness
• majority of species concentrated to a narrow band of latitudes where
temperature is most conducive to life
e.g. MARINE ENVIRONMENT
TEMPERATURE HAS A DOMINANT EFFECT ON
BIOLOGICAL PROCESSES
BIOCHEMICAL: (a) ENZYMES
• temperature is measure of the molecular motion of within a material. At higher
temperatures there is more molecular vibration
• if molecules are moving sufficiently fast, they can react when collide with each other
• enzyme reaction rate rises sharply with temperature as substrates react with enzyme
catalysts (within certain functional limits)
• temperature
increases enzyme
rate until the
enzyme itself
becomes denatured
(unfolded) and no
longer functional
THERMAL STABILITY OF ENZYMES IN MARINE
ANIMALS FROM DIFFERENT HABITATS
• range of temperature that enzymes are functional under is related to temperature
regimes experienced in their native habitats
Antarctic (-2 to 2°C)
enzyme stability
North Sea (2 to 18°C)
Mediterranean
(5 to 25°C)
Indian Ocean
(20 to 28°C)
East African Lake
(25 to 28°C)
temperature
BIOCHEMICAL: (b) MEMBRANES AND CELL STRUCTURES
•
•
•
•
membranes are essential to cellular function
lipids in membranes exist as a “liquid crystal”: not quite solid, not quite liquid
this delicate balance can be easily disrupted by temperature
as temperature increases, membranes become more fluid. As temperature
decreases membranes become more rigid
BIOCHEMICAL: (b) MEMBRANES AND CELL STRUCTURES
• altering the lipid composition of membranes can help organisms maintain
function over a specific range of temperatures
• longer and saturated fatty acids (without carbon double bonds) are more rigid
and maintain membrane function at relatively higher temperatures
• choline lacks carbon double bonds and its proportion increases in species that
inhabit warmer environments
RATIO OF SATURATED: UNSATURATED FORMS OF SOME FATTY ACIDS
Species
Body Temp
(°C)
Choline
Ethanolamine
Serine inositol
Arctic Sculpin
0
0.59
0.95
0.81
Goldfish
5
0.66
0.34
0.46
Goldfish
25
0.82
0.51
0.63
Desert Pupfish
34
0.99
0.57
0.62
Rat
37
1.22
0.65
0.66
• changes are catalyzed by DESATURASES, controls formation of double bonds
BIOCHEMICAL: (c) STRESS PROTEINS
• temperature change can induce the production of a class of proteins called heat
shock proteins (Hsp’s)
• induction of these proteins is again related to typical thermal regimes experienced
in nature
• organisms in warm environments produce Hsp’s at higher temperatures than those
inhabiting colder environments
• assist in folding denatured proteins and thus maintaining their function
• is a metabolically costly response: re-folding requires ATP
• three Hsp’s interacting with an
unfolded client protein (red)
TEMPERATURE HAS A DOMINANT EFFECT ON
BIOLOGICAL PROCESSES
PHYSIOLOGICAL: BI-PHASIC RESPONSE
• biological processes generally exhibit a two phase response to increases in temperature:
1.) activity increases as a consequence of the of the rate-enhancing effects of
temperature on enzymes
2.) at higher temperatures the destructive effects of temperature take over and
rates of activity decline
Rate of process
rate enhancing effects
destructive effects
Temperature
PHYSIOLOGICAL: BI-PHASIC RESPONSE
• a number of physiological processes show this two phase responses
e.g. HEART RATE
temperature (°C)
• heart rate a various
temperatures for intertidal
porcelain crabs
CELLS AND ORGANISMS: “WEAKEST LINKS”
• effects of temperature on cells and organisms is the result of “weak links”, essential
processes that are more vulnerable to heat stress than others
• weak links establish functional limit for cells and organisms beyond which death
occurs
• in the crayfish, first sign of heat stress is
breakdown of normal permeability of gill
membranes, so that ion gradients critical
to survival are disrupted
UPPER CRITICAL TEMPERATURE
• weakest links in responses to temperature will determine the UPPER CRITICAL
TEMPERATURE, the maximum tolerable temperature for the whole organism
100°C
hot springs bacteria
hot springs algae
80°C
50°C
desert maximum
desert insects
camels, some birds, some turtles
most birds, mammals
30°C
shore animals
majority of life
0°C
-80°C
Antarctic minimum (few mammals, birds)
TERMINOLOGY IN THERMAL BIOLOGY
ENDOTHERM: body temperature principally dependent
on internally generated metabolic heat
• birds and mammals
ECTOTHERM: body temperature principally dependent
on external heat sources
(almost exclusively the sun)
• everything else: insects, reptiles, amphibians,
fish, marine invertebrates
EURYTHERMAL (‘eury’ = greek for wide)
• tolerates and is active within a wide range of temperatures
• temperate insects and reptiles function between 8-38°C
STENOTHERMAL (‘steno’ = greek for narrow)
• tolerates and is active within a very narrow range of temperatures
• most mammals and birds and some organisms from very stable environments
STRATEGIES IN THERMAL REGULATION
1.) MIGRATION (AVOIDANCE)
2.) ACCLIMATIZATION/ACCLIMATION (TOLERANCE)
3.) ADAPTATION (EVOLUTION)
STRATEGIES IN THERMAL REGULATION
1.) MIGRATION (AVOIDANCE)
• location and use of appropriate climatic conditions in time and space
e.g. LONG DISTANCE MIGRATION
• Monarch butterflies
cannot survive the
Northern winter so
migrate great
distances to warmer
habitats in Mexico
STRATEGIES IN THERMAL REGULATION
1.) MIGRATION (AVOIDANCE)
• location and use of appropriate climatic conditions in time and space
e.g. SMALL-SCALE USE OF MICROCLIMATES
• for very small
organisms like ants
environment is very
“fine-grained”, with
conditions varying
widely in time and
space. These
creatures may have
access to a range of
microclimates
STRATEGIES IN THERMAL REGULATION
1.) MIGRATION (AVOIDANCE)
• only works if you can move!
• plants and trees
• barnacles in the intertidal
STRATEGIES IN THERMAL REGULATION
2.) ACCLIMATIZATION/ACCLIMATION (TOLERANCE)
• plants and animals vary considerably in their tolerance of temperature
• biochemical, cellular and/or physiological processes are adjusted to
compensate for variations in their thermal environment
• referred to as ACCLIMATIZATION when occurring in nature and ACCLIMATION
when it occurs in the lab.
• act to keep biological processes operating at roughly the same rate across a
range of temperatures
e.g. LATITUDAL GRADIENTS
e.g. SEASONAL GRADIENTS
e.g. ALTITUDINAL GRADIENTS
STRATEGIES IN THERMAL REGULATION
2.) ACCLIMATIZATION/ACCLIMATION (TOLERANCE)
e.g. LATITUDINAL GRADIENTS
• some species of marine invertebrates occupy have biogeographic ranges that extend
across a wide temperature gradient.
• acclimatization is used to ensure proper function at a range of temperatures
• the purple sea urchin
(Strongylocentrotus purpuratus)
inhabits nearshore marine
environments from Alaska to
Mexico
STRATEGIES IN THERMAL REGULATION
2.) ACCLIMATIZATION/ACCLIMATION (TOLERANCE)
e.g. SEASONAL GRADIENTS
• small birds that are resident in cold climates generally show marked winter increases in
THERMOGENIC CAPACITY (overall capacity for heat production) that are accompanied by
winter increases in cold hardiness
• winter triggers an increases in pectoralis
muscle mass, generally ranging from 1030% in small birds
• increased reliance on fats to fuel sustained
shivering in winter relative to summer
Black capped chickadee
Poecile atricapillus
STRATEGIES IN THERMAL REGULATION
2.) ACCLIMATIZATION/ACCLIMATION (TOLERANCE)
e.g. ALTITUDINAL GRADIENTS
• decreased oxygen concentration at high altitudes stimulate the production of red
blood cells in humans
• this increases the capacity for oxygen transport to cells and tissues
• reason why many athletes train at altitude
STRATEGIES IN THERMAL REGULATION
2.) ACCLIMATIZATION/ACCLIMATION (TOLERANCE)
• the capacity to acclimatize or acclimate is often referred to as an organisms PHENOTYPIC
PLASTICITY, essentially how much an organisms can modify processes to function in a
new environment
• phenotypic plasticity can be captured in TOLERANCE POLYGONS
• survival may be possible
over a range of
temperatures (i.e.
resistance), but certain
physiological functions like
growth and reproduction
are limited to specific
temperatures windows
STRATEGIES IN THERMAL REGULATION
2.) ACCLIMATIZATION/ACCLIMATION (TOLERANCE)
• Area of the tolerance polygon describes phenotypic plasticity
SPECIES
AREA OF TOLERANCE POLYGON
HABITAT
Goldfish
1220
Freshwater, widespread
Bullhead trout
1162
Freshwater, widespread
Lobster
830
Marine, widespread
Greenfish
800
Marine, widespread
Silverside
715
Marine, widespread
Flounder
685
Marine, temperate
Trout
625
Freshwater/marine, temperate
Puffer fish
550
Marine, temperate
Chum salmon
468
Freshwater/marine, temperate
Rock Perch
47
Antarctic
STRATEGIES IN THERMAL REGULATION
3.) ADAPTATION (EVOLUTION)
• permanent changes in an organisms DNA that alters the function of particular proteins
that happens to prove beneficial in new environment
STRATEGIES IN THERMAL REGULATION
3.) ADAPTATION (EVOLUTION)
e.g. CHANGES IN PROTEIN STABILITY
Mytilus galloprovincialis
Mytilus trossulus
Warm-adapted
Cold-adapted
LDH enzyme activity
• lactate dehyrodgenase (LDH), an important enzyme in anaerobic metabolism contains an
amino acid substitution in M. galloprovincialis that confers additional stability to the
enzyme at high temperature. This contributes to the increased heat tolerance of this
species.
M. trossulus
M. galloprovincialis
temperature
EXTINCTION
• lethally hot temperatures exerted a direct effect on the end-Permian mass extinction
(250 million years ago)
• also inhibited the ability of remaining animals to proliferate following the extinction
event
• a role for temperature stress in Earth’s most severe extinction
• inverse relationship between the temperature and biodiversity during this period
• temporary loss of both marine and terrestrial vertebrates
• reduced size of the remaining invertebrates.
96% of marine life
70-80% of terrestrial life
LECTURE SUMMARY
• Temperature has a dominant effect on biological systems
• biochemical level
• enzyme activity
• membrane fluidity
• stress proteins (Hsp’s)
• physiological
• bi-phasic response: rate-enhancing followed by destruction
• heart rate
• cells and organisms
• “weakest links”
• Strategies in thermal regulation
• migration (avoidance)
• acclimatization/acclimation (tolerance)
• adaptation (evolution)
• Temperature and Permian Mass Extinction
MORE INFORMATION
BIOLOGICAL EFFECTS OF TEMPERAURE
Wlimer, Stone & Johnson. (2005)
Environmental Physiology of Animals
(2nd edition). Blackwell Publishing
Company, Oxford, UK.
CHAPTER 8: Temperature and its
effects (pp 175-222)
TEMPERATURE AND TRIASSIC EXTINCTION
Yadong Sun et al. (2012) Lethally hot temperatures during the early Triassic
greenhouse. Science. 338: 366.
NEXT LECTURE:
INTERTIDAL-PORCELAIN CRABS