U9 : Undersea world

of thermoregulation.Endothermic is the ability of some creatures to control their body temperatures through internal means such as muscle shivering, fat burning, drawing and panting.. I

of thermoregulation.

Endothermic is the ability of some creatures to control their

body temperatures through internal means such as muscle

shivering, fat burning, drawing and panting

Homoeothermic is thermoregulation that maintains a stable

internal body temperature regardless of external influence This temperature is often higher than the immediate

environment The opposite is poikilothermy

Tachymetabolism is the kind of thermoregulation used by

creatures that maintain a high resting metabolism

Tachymetabolic creatures are, essentially, "on" all the

time Though their resting metabolism is still many times slower than their active metabolism, the difference is often not as large as that seen in Brady metabolic creatures

Tachymetabolic creatures have greater difficulty dealing with

a scarcity of food

WARM-BLOODED AND COLD BLOODED ANIMALS

Generating and conserving heat

 The creatures traditionally regarded as warm-blooded have a larger number of mitochondria per cell, which enables them

to generate heat by increasing the rate at which they "burn" fats and sugars This requires a much greater quantity of food than is needed by cold-blooded animals in order to replace the fat and sugar reserves

Avoiding over-heating

 In equatorial climates and during temperate summers heating is as great a threat as cold In hot conditions many warm-blooded animals increase heat loss by panting and or flushing (increasing the blood flow to the skin) Hairless and short-haired mammals also sweat, since the evaporation of sweat uses a lot of heat

over-WARM-BLOODED AND COLD BLOODED ANIMALS

Advantages of a fast metabolism

 The overall speed of an animal's metabolism increases by a factor of about 2 for every 10 C° rise in temperature (limited

by the need to avoid hyperthermia) Warm-bloodedness does not provide greater speed than cold-bloodedness - cold-blooded animals can move as fast as warm-blooded animals of the same size and build But warm-blooded animals have much greater stamina than cold-blooded creatures of the same size and build

Advantages of homeothermy

 Enzymes have strong temperature preferences and their efficiency is much reduced outside their preferred ranges A creature with a fairly constant body temperature can

therefore use enzymes which are efficient at that temperature Another advantage of a homeothermic animal would be its ability to maintain its constant body temperature even in freezing cold weather

WARM-BLOODED AND COLD BLOODED ANIMALS

 Shivering and fat-burning to maintain temperature are very energy-intensive, for example:

1 in winter many small birds lose one third of their body weight overnight

2 in general a warm-blooded animal requires 5 to 10 times as much food as a cold-blooded animal of the same size and build, so cold-blooded animals are better at surviving famines and barren environments

WARM-BLOODED AND COLD BLOODED ANIMALS

Ectothermy - This refers to creatures that control body

temperature through external means , such as the sun, or flowing air/water

Poikilothermy - This refers to creatures whose internal

temperatures vary, often matching the ambient temperature of the immediate environment

Bradymetabolism - This term refers to creatures with a high active

metabolism and a considerably slower resting metabolism

Bradymetabolic animals can often undergo dramatic changes in metabolic speed, according to food availability and temperature Many bradymetabolic creatures in deserts and in areas that

experience extreme winters are capable of "shutting down" their metabolisms to approach near-death states, until favourable conditions return

WARM-BLOODED AND COLD BLOODED ANIMALS

Types of temperature control

Examples of temperature control include:

 Snakes and lizards sunning themselves on rocks

 Fish changing depths in the water column to find a suitable temperature

 Desert animals burrowing beneath the sand during the day

 Insects that warm their flight muscles by vibrating them in place

 Dilating or constricting peripheral blood vessels to adapt more

or less quickly to the ambient temperature

WARM-BLOODED AND COLD BLOODED ANIMALS

 This energy difference also means that a given niche of a given ecology can support three to ten times the number of

poikilothermic animals as homeothermic animals However, in a given niche, homeotherms often drive poikilothermic

competitors to extinction because homeotherms can gather food for a greater fraction of each day

 Poikilotherms succeed in some niches, such as islands, or distinct bioregions (such as the small bioregions of the Amazon basin) These often do not have enough food to support a

viable breeding population of homeothermic animals In these niches, poikilotherms such as large lizards, crabs and frogs supplant homeotherms such as birds and mammals

WARM-BLOODED AND COLD BLOODED ANIMALS

WARM-BLOODED AND COLD BLOODED ANIMALS

Thermal image of a cold-blooded tarantula on a human hand

 Some other "cold-blooded" creatures use internal mechanisms

to maintain body temperatures significantly above the ambient level:

Tuna and swordfish fish have long been thought to be cold blooded Tuna and swordfish dive deep into the ocean where the water is very cold Swordfish are able to raise the

temperature of their brains and eyes, which allows faster eye movements when hunting Tuna are able to warm their entire bodies through a heat exchange mechanism called the rete mirabile, which helps keep heat inside the body, and minimizes the loss of heat through the gills They also have their

swimming muscles near the center of their bodies instead of near the surface, which minimises heat loss

WARM-BLOODED AND COLD BLOODED ANIMALS

 Large sea turtles exhibit inertial homeothermy (Gigantothermy) - their low ratio of surface area to volume minimises heat loss

WARM-BLOODED AND COLD BLOODED ANIMALS

Luong Toan Hoang Long

Phan Ngoc Anh

Vu Le Khoa

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