Endothermy and Ectothermy

Endothermy and Ectothermy

Ch. 6.7, Bush

Outline

v Effects of temperature on life

v Thermoregulation

v Ecological aspects of thermoregulation

Outline


v Thermoregulation


Effects of extreme temperatures

v Cold -- the effects of freezing– physical damage to structures caused by the formation of

ice; the membrane bound structures are destroyed or damaged.

v Heat– inadequate O2 supply for metabolic demands (especially in

areas where O2 is low, such as water)

v Heat and Cold– reduced activity or denaturation of proteins -- the inactivation

of certain proteins with the result that metabolic pathways are distorted.

Optimal temperature for enzyme functioning Body Temperature

v Law of Tolerance:– for most requirements of life, there is an

optimal quantity, above and below which the organism performs poorly

v There is much variation in the range of temperatures that a species can tolerate

Outline


v Thermoregulation


Thermoregulation

vmaintenance of internal temperature within a range that allows cells to function efficiently

v Two main types– ectothermy – endothermy

Endothermy versus ectothermy Ectothermy

v an animal that relies on external environment for temperature control instead of generating its own body heat

v “cold-blooded”

v e.g., invertebrates, reptiles, amphibians, and most fish

v the majority of animals are ectotherms

Metabolism and temperature

v ectotherms cannot move very much unless the ambient temperature allows

v roughly, for each 10 degree increase in temperature, there is a 2.5 increase in metabolic activity

Ectothermy

Desert iguanas are active only when ambient temperature is close to optimal for them

Ectothermic animals Endothermy

v a warm-blooded animal that controls its body temperature by producing its own heat through metabolism

v evolved approximately 140 mya

v E.g., birds, mammals, marsupial, some active fish like the great white shark and swordfish

Endothermic animals Outline

v Endothermy versus ectothermy

v Behavioural adaptations to thermoregulation

v Physiological adaptations to thermoregulation

Behavioural adaptations for thermoregulation

v animals often bathe in water to cool off or bask in the sun to heat up

Shivering, sweating, and panting

v honeybees survive harsh winters by clustering together and shivering, which generates metabolic heat

v Inefficient – 75% of energy is lost in mechanical movement

Torpor

v metabolism decreasesv heart and respiratory

system slow downv body temperature

decreases

v conserves energy when food supplies are low and environmental temps are extreme

E.g., hummingbirds on cold nights

Hibernation

v Long-term torpor

v adaptation for winter cold and food scarcity

v E.g., ground squirrels

Aestivation

v summer torpor

v adaptation for high temperatures and scarce water supplies

v E.g., mud turtles, snails

Endothermy and the evolution of sleep?

v evolutionary remnant of torpor of our ancestors

v the body needs sleep in order to offset the high energy costs of endothermy: – When animals fall asleep their metabolic

rates decrease by approximately ten percent

Colour and Posture

v Change coloration (darker colors absorb more heat)– E.g., lizards, butterflies,

crabs

v Posture:– Change shape (flatten

out to heat up quickly)– Orientation changes

Chemical adaptations

v Many Canadian butterflies overwinter here and hibernate

v they produce sugar-like substances as antifreeze

v E.g., Mourning Cloak butterfly

Outline


v Thermoregulation


Advantages & Disadvantages of Endothermy

v Advantages:– external temperature does not affect their

performance– allows them to live in colder habitats – muscles can provide more sustained power

– e.g., a horse can move for much longer periods than a crocodile can

v Disadvantage:– energy expensive

– an endotherm will have to eat much more than an ectotherm of equivalent size

Where can endotherms thrive?

v Higher latitudes and deserts

v Terrestrial environments have more variation in daily and seasonal temperature which contributes to more endotherms in terrestrial environments

v endotherms (mammals and birds) generally outcompete ectotherms if they are after the same food source

Size and thermoregulation

v Small mammals (such as mice and shrews) have a greater dependence on internally-generated heat than big mammals (such as elephants and hippos)

v leads to:– presence of insulation (fur - large mammals

generally have less hair) – voracious appetites of small mammals (a shrew

eats more per unit body weight than an elephant does)

Surface area to volume ratios Ectothermy vs. endothermy

v Many more ectotherms are small in size versus endotherms

v Ectotherms typically have no insulation

v Posture is different

Where do ectotherms thrive?

v Where food items are:– scarce

– small

v In environments low in O2

Ecosystem functioning and ectothermy

v Production Efficiency:-can be seen as the ratio of assimilation between

trophic levels

= biomass of predatorbiomass of food species

v Ectotherms are more efficient than endotherms(up to 15% versus 7%)

Thermoregulation and food chains

v Endotherms are often the top predator in food chains

v Food chains with lots of ectothermsare often longer in length

Summary

v Endothermic animals regulate their body heat to stay within the optimal range for performance while the temperature of ectothermic animals fluctuates with that of the surrounding environment

v Both endotherms and ectotherms have a variety of behavioural and physiological adaptations to deal with environmental extremes

Climate

Ch. 4, Bush

Outline

v Climate and ecology

v Solar energy and air circulation

vOceanic influences

v Cycles of climate change

Outline



vOceanic influences


Climate affects ecology Temperature and precipitation

Outline



vOceanic influences


Solar energy

v Solar energy distribution is not balanced across the globe in– intensity– constancy

v Together, these differences explain the distribution of tropical and temperate climates

Intensity of Solar energy

v Solar energy is more intense at lower latitudes (that is, closer to the equator) because:

• the “footprint” of the beam of energy is smaller at tropical latitudes

• beams have shorter passage through the atmosphere

Intensity of solar energy

more energy per square meter in the tropics than at the poles

Differences in daylength Differences in Day Length

v caused by the constant tilt of Earth as it orbits around the sun

v the reason why temperate environments have four seasons while tropical environments do not

Heat and air circulation

v The disparity in energy input across the globe drives all our weather systems

v This is because heat energy must flow from warm to cold

Hadley cells – the effect of heat transfer

v Hot air rises and, as it rises, it cools

v Cool air cannot hold as much moisture as heated air, so it rains

v This cool, dry air must go somewhere so it pushes towards the poles, where it slows and descends

v As it descends, it is warmed

Hadley cells Hadley cells and climate

v The downdraft of hot dry air causes the formation of the desert regions of Earth:

E.g., SaharaSonoranAustralianGobiAtacama

Equatorial rainforest

v Average temp:– 20-34 ° C

v Average rainfall:– 124-660 cm

Deserts – caused by downdrafts of hot, dry air

v Average temp:– 20 to 25° C

v Average rainfall:– under 15 cm a year

Movement of the thermal equator Hadley cells

Intertropical convergence zone (ITCZ) Movement of the ITCZ

v responsible for wet and dry seasons of the tropics

Seasonality and ITZC

v In temperate latitudes, seasonality is closely related to day length

v In tropical latitudes, seasonality is closely associated with rainfall.

v Tropical rainfall influences:– Germination, flowering, and fruiting in plants

– Breeding, feeding, migration, and life history strategies in animals

Movement of the ITCZ

v hurricanes are spawned at the most northerly edge of the ITCZ

Outline



vOceanic influences


Ocean and heat transfer

v water takes more energy to heat than land or air

Water moderates climate

The ocean makes coastal regions havemilder climates

Intertropical convergence zone (ITCZ)

Gulf Stream

v Gulf Stream comes up from Gulf of Mexico, across Atlantic Ocean, to moderate climate of Western Europe

Effects of the Gulf Stream

v The Gulf Stream makes snow rare in London but common in Toronto:

Altitude Ave. Temp (Jan)

London 51 οN 6 οCToronto 43 οN -4 οC

Earth’s rotation causes the Coriolis effect

v Both objects A and B make one rotation on the Earth’s axis per day

v An object located at the equator is rotating faster than an object at the pole

Coriolis Effect

v Earth rotates eastward making all object deflect in this direction

v http://www.eoascientific.com/campus/earth/multimedia/coriolis/view_interactive

Coriolis Effect and air circulation Trade winds and the Gulf Stream

Major water currents Outline



vOceanic influences


Cycles of Climate Change

v There are two main cycles of climate change that are natural:

– El Nino Oscillation

– Glaciation

Gulf Stream

v Gulf Stream comes up from Gulf of Mexico, across Atlantic Ocean, to moderate climate of Western Europe

Gulf Stream causes ocean currents

v Warm water evaporatesv Ocean becomes more saltyv Loses heat as it moves towards polev Water becomes more dense as it becomes

more salty and/or loses heatv This dense, cold, salty water sinking off the

coast of Greenland sets in motion an immense flow of water through the oceans

Ocean currents

El Nino Southern Oscillation (ENSO)

v A decrease in wind speed of the Trade Winds off Tahiti is observed every 3-7 years

v causes less warm surface water being piled up around Indonesia

v Instead, warm surface water piles up off Peru in South America

El Nino Southern Oscillation (ENSO)

El Nino Effects El Nino and Hurricane Pauline

El Nino and ecology

v Evidence indicates that Galapagos marine iguanas actually shrink during El Nino events

v El Nino reduces food supply (green and red algae)

El Nino and Insect outbreaks

v In a dry lowland forest near Panama's Pacific coast, moth larvae devoured 250 percent more leaf material than usual

v Bartonellosis, an insect-borne disease highly fatal to humans, are closely related to the climate event El Niño

Glacial and Interglacial periods

v In the last 4 million years there have been at least 22 ice ages (= glacial periods)

vWarm periods between glacial periods (interglacial) periods have been brief

In general…

v Interglacial periods – mild in temperature and with more precipitation--

periods of diversification and range expansion in organisms adapted to warmer conditions

v Glacial periods – fragmentation of plant and animal ranges (except

for arctic or cold-desert adapted organisms)

Glaciation and water level changes

v About 3 million years ago, a major Ice Age began when the sea level dropped enough to expose the Isthmus of Panama

v The Panama land bridge made possible one of the great events in biology-the interchange of species of two continents.

Glaciation and land changes

v Moving into South America were:– fox; deer; tapir;

spectacled bear; spotted cat; llama.

v Moving into North America were: – parrot; toucan,

armadillo; giant sloth; howler monkey; anteater; and capybara

Last glacial period ended 11,000 years ago

v 90% of last 2 million years has been glacial

v For the last 10,000 years, plants and animals have been living in an unusually warm environment

Summary

v Most weather patterns are ultimately caused by the fact that equatorial regions receive more solar energy than polar regions

– Location of tropical, temperate and desert ecosystems

– Wind and water currents– Seasonality of the tropics

v Weather and climate fluctuate over relatively short time frames and relatively long ones

Documents

Endothermy and Ectothermy