BIOL 3999: Issues in Biological Science

GLOBAL CHANGE BIOLOGY

Dr. Tyler EvansEmail: tyler.evans@csueastbay.eduPhone: 510-885-3475Office Hours: M,W 10:30-12:00 or by appointmentWebsite: 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

• 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

TODAY’S LECTURE

EFFECTS OF TEMPERATURE ON BIOLOGICAL SYSTEMS

• multi-cellular life (metazoans) is confined to a narrow temperature range

100°C

50°C

0°C

-80°C

hot springs bacteria

hot springs algae

desert insects

30°C

camels, some birds, some turtles

most birds, mammals

shore animals majority of life

Antarctic minimum (few mammals, birds)

desert maximum80°C

EFFECTS OF TEMPERATURE ON BIOLOGICAL SYSTEMS

• 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

• plants and animals are drastically affected at all levels of biological organization by any change in their thermal 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

enzy

me

stab

ility

temperature

Antarctic (-2 to 2°C)

North Sea (2 to 18°C)

Mediterranean(5 to 25°C)

Indian Ocean(20 to 28°C)

East African Lake(25 to 28°C)

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

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

• altering the lipid composition of membranes can help organisms maintain function over a specific range of temperatures

BIOCHEMICAL: (b) MEMBRANES AND CELL STRUCTURES

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

• 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

• 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

Temperature

Rate

of p

roce

ss

rate enhancing effects

destructive effects

PHYSIOLOGICAL: BI-PHASIC RESPONSE• a number of physiological processes show this two phase responses

e.g. HEART RATE• heart rate a various

temperatures for intertidal porcelain crabs

temperature (°C)

• 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

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

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

50°C

0°C

-80°C

hot springs bacteria

hot springs algae

desert insects

30°C

camels, some birds, some turtles

most birds, mammals

shore animals majority of life

Antarctic minimum (few mammals, birds)

desert maximum80°C

TERMINOLOGY IN THERMAL BIOLOGYENDOTHERM: 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 REGULATION1.) MIGRATION (AVOIDANCE)• location and use of appropriate climatic conditions in time and space

• Monarch butterflies cannot survive the Northern winter so migrate great distances to warmer habitats in Mexico

e.g. LONG DISTANCE MIGRATION

STRATEGIES IN THERMAL REGULATION1.) 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 REGULATION1.) MIGRATION (AVOIDANCE)• only works if you can move!

• plants and trees • barnacles in the intertidal

STRATEGIES IN THERMAL REGULATION2.) 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 GRADIENTSe.g. SEASONAL GRADIENTS e.g. ALTITUDINAL 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

STRATEGIES IN THERMAL REGULATION2.) ACCLIMATIZATION/ACCLIMATION (TOLERANCE)e.g. LATITUDINAL GRADIENTS

• the purple sea urchin (Strongylocentrotus purpuratus) inhabits nearshore marine environments from Alaska to Mexico

• 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 10-30% in small birds

• increased reliance on fats to fuel sustained shivering in winter relative to summer

STRATEGIES IN THERMAL REGULATION2.) ACCLIMATIZATION/ACCLIMATION (TOLERANCE)e.g. SEASONAL GRADIENTS

Black capped chickadeePoecile atricapillus

STRATEGIES IN THERMAL REGULATION2.) 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

• 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

2.) ACCLIMATIZATION/ACCLIMATION (TOLERANCE)

• 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 REGULATION2.) ACCLIMATIZATION/ACCLIMATION (TOLERANCE)

• Area of the tolerance polygon describes phenotypic plasticitySPECIES 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 REGULATION3.) 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 REGULATION3.) ADAPTATION (EVOLUTION)e.g. CHANGES IN PROTEIN STABILITY

Mytilus galloprovincialis Mytilus trossulus

Warm-adapted Cold-adapted

• 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.

temperature

LDH

enzy

me

activ

ity M. galloprovincialis M. trossulus

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 INFORMATIONBIOLOGICAL 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 EXTINCTIONYadong Sun et al. (2012) Lethally hot temperatures during the early Triassic greenhouse. Science. 338: 366.

NEXT LECTURE:INTERTIDAL-PORCELAIN CRABS