Extreme Biology Flashcards

Question

What is the issue with RuBisCO?

Answer 1

Rubisco is not very efficient at grabbing CO₂, and it has an even worse problem. When the concentration of CO₂ in the air inside the leaf falls too low, Rubisco starts grabbing oxygen instead.

Answer 2

RuBisCO evolved when O₂ levels in the atmosphere were much lower than today – so less selection pressure at that time to discriminate.

Answer 3

Compensatory mechanisms for drought conditions Some plants have evolved a slower-acting RuBisCO with an improved ability to discriminate – but results in a 30% loss in photosynthetic efficiency. Or, evolution of CO2-concentrating mechanisms that reduce O2 concentration - as in cyanobacteria and C4 plants – higher catalytic rates, lower CO2 affinity.

Answer 4

* CO2 pumps increase concentration internally. * RuBisCO is sensitive to O2 * Generate an environment high in CO2 in bundle sheet cells. * Malate synthesised in mesophyll cells – diffuses to bundle sheath cells. * Less energy efficient than C3, but overall advantage because reduces wasteful oxygenation of RuBisCO.

Answer 5

C3 plants cannot grow in very hot areas because RuBisCO incorporates more oxygen into RuBisCO as temperatures increase. CO2 for RuBisCO drawn from malate rather than directly from the air.

Answer 6

* A form of C4 metabolism, but separates reactions by time (and space). * Stomata open at night. * CO₂ acquired and reacts with phosphoenolpyruvate. * Malic acid is stored. * During daylight, stomata are tightly closed. * CO₂ is released from malic acid. * CO₂ incorporated into Calvin cycle.

Answer 7

A plant adapted to growing in saline conditions, as in a salt marsh.

Answer 8

* Salt glands * Slat bladders

Answer 9

Shifts from C3 to C4 (CAM) metabolism when it encounters drought or excess salt.

Answer 10

They are specialized aerial roots enabling plant roots access to oxygen in waterlogged habitats.

Answer 11

_Lost all genes for:_ * Stomata formation * UV protection * Sensing far red light * Volatile turpenes _Regained genes for:_ * Cell wall components for osmotic control

Answer 12

Carnivorous plants are predatory flowering plants that kill animals in order to derive nutrition from their bodies. They share three attributes that operate together and separate them from other plants. Carnivorous plants: Capture and kill prey. Have a mechanism to facilitate digestion of the prey.

Answer 13

Plants also have adapted to the Arctic tundra by developing the ability to grow under a layer of snow, to carry out photosynthesis in extremely cold temperatures, and for flowering plants, to produce flowers quickly once summer begins. A small leaf structure is another physical adaptation that helps plants survive.

Answer 14

the two native vascular plant species, growing as small clumps, south of 58ºS are: 1. hair grass 2. pearlwort

Answer 15

* Changes in biological thermodynamic processes. * Changes in biomolecule conformation, stability, function. * Perturbation of normal cellular processes. * Reduced fluidity of cell membranes - rigidification. * Perturbation of the balance between production and neutralisation of reactive oxygen species (ROS). * Extracellular ice crystal formation depletes water in and around cells * - freezing dehydration and associated cell membrane disruption. * Large ice crystals grow at the expense of small crystals – ‘ice recrystallisation’.

Answer 16

South of tundra. Also known as boreal forest or snow forest. Biome dominated by coniferous forests comprising mostly pines, spruces and larches – only a few angiosperm (‘broadleaved’) trees and shrubs. Low species diversity – large stands of single species. Earth's largest terrestrial biome. One third of terrestrial carbon store. Taiga forest of Canada and Siberia - record temperatures range from -64°C to +36°C – spanning a full 100°C. Carbon dioxide ice sublimes at −78.5 °C! Some arctic pines needles and angiosperm buds can be cooled slowly to -30°C then into liquid nitrogen (-196°C) and recover alive.

Answer 17

Conifers are well adapted to dry, cold, and altitude. Most species are evergreen – resilient leaves, spring-ready. Autumn shut down of photosynthesis and increase concentrations of carotenoid pigments (e.g. zeaxanthin and lutein) to protect against light damage. Shed snow efficiently. Do not restart even on warm days – wait until April/May then rapid resumption of photosynthesis – forests rapidly become CO2 sinks.

Answer 18

Detection of cold and/or detection of predictive seasonal changes - temperature reduction, day length. - induction of protective cold tolerance mechanisms and components. Large central cell vaculole replaced by numerous small vesicles. Starch granules disappear. Thylakoid membranes in chloroplasts separate and become disorganised. Changes in membrane lipid composition (e.g. desaturation of fatty acids; increased phosphatidylethanolamine, decreased phosphatidylcholine; in chloroplast membranes, increased phospholipids, reduced galactolipids). High concentrations of oligosaccharides – promote vitrification or high viscosity in cytoplasm of freeze-dehydrated cells. Proteins – upregulation of … - dehydrins – bind membranes, prevent membrane-membrane interactions - antioxidant systems - heat shock proteins - pathogenesis-related proteins.

Answer 19

Temperate winter or tropical dry seasons. Abscission layer forms between the leaf petiole and the stem. Forms in the spring during active new growth of the leaf. Layers of cells that can separate from each other. The cells are sensitive to auxin produced by the leaf. Sufficient auxin à abscission layer cells remain connected. In autumn, or when under water stress, auxin from the leaf decreases or stops à cellular elongation within the abscission layer. Elongation of these cells break the connection between the different cell layers à leaf breaks away. Abscission layer cells seals the break, plant does not lose sap. Meanwhile – production of sticky, sugar-protected buds ready for spring

Answer 20

If a lot of cold wind blows past your rhododendron in the winter, it will curl its leaves inward so less leaf surface is exposed; the plant’s trying to keep water from evaporating out of its leaves.

Answer 21

Crown drag – strongest in broad-leaved trees – advantage to be deciduous. Oak-type tree – dense, heavy trunk, limited sway, broad, stiff root base. Pine-type tree – lighter trunk, more sway, deep tap root.

Answer 22

Most rainforest soil is nutrient-poor. Nutrients available largely near soil surface. Rainforest trees therefore tend to have very shallow roots. * Buttress roots

Answer 23

Leaves need to protect themselves and the tree’s crown by reducing drag. They twist, curl and fold. Small leaves and flexible branches help.

Answer 24

* Distant colonisation * Devastated land * (fire, vulcanism) * Wide separation

Answer 25

An ecosystem type that occurs between approx. latitudes 28 º N or S of the equator. More biodiverse than anywhere else on land (compare with tundra). How does a tree find a mate in a tropical rainforest? Conspecifics and potential plant mates are usually far away. Need to synchronise flowering. But how? What cues to use? In temperate and polar regions plants can use seasonal daylength and/or temperature changes.

Answer 26

Extremophile prokaryotes have their origins in the Archean Aeon (Eon)

Answer 27

* pH * High temperatures * Radiation * Pressure * Salinity * Freeze Tolerance * Desiccation

Answer 28

Most life is underground. With the No. of microbes on earth being around 4 x 10³⁰ at least.

Answer 29

* ‘Worms from Hell’ South African mines. * Deep subsurface biosphere \> 3 km into the Earth’s crust. * Detected at 0.9–3.6 km deep - Halicephalobus mephisto. * Tolerate high temperatures - Reproduce asexually - Feed upon subsurface bacteria. * 14C data - nematodes reside in 3,000–12,000-year-old palaeometeoric water. * Such nematode species should be found in other deep hypoxic settings. * May control the microbial population by grazing on fracture surface biofilm patches. * Multicellular life in the deep subsurface of the Earth has implications for the search for subsurface life on other planets in our Solar System. * (anhydrobiosis dauer larvae)

Answer 30

_Chemoautotrophs_ * Convert the heat, methane, and sulphur compounds provided by black smokers into biochemically useful energy through chemosynthesis. * More complex life forms, such as clams and tubeworms, feed on these organisms.

Answer 31

Cyanobacterium

Answer 32

Atacama is the driest place on earth

Answer 33

“Water bears”, “space bears”, or “moss piglets” Kingdom Animalia; Phylum Tardigrada Some can withstand – * temperatures down to 1°K (−272°C). * temperatures up to 420°K (150°C) for several minutes. * pressures about 6x greater than found in the deepest ocean trenches. * ionizing radiation doses hundreds of times higher than lethal for humans. * vacuum of outer space. * can go without food or water for \>30 years, * drying out to the point where they are 3% or less water, * successfully rehydrate, forage, and reproduce.

Answer 34

* Acidophile - Growth at pH \< 3 * Alkaliphile - Growth at pH \>9 * Anaerobe - An organism that doesn't require O₂ * A facultative anaerobe * An obligate anaerobe * Cryptoendolith - Microscopic spaces within rocks * Halophile - Requiring \> 0.2M NaCl for growth * Hyperthermophiles - Thrives \>80ºC, {hydrothermal systems} * Hypolith - An organism that lives underneath rocks in cold deserts * Lithoautotroph - CO₂ sole C source; energy - reduced minerals. * Metallotolerant - Tolerant of soluble heavy metals like copper argon and zinc. * Oligotroph - Growth in nutritionally limited environments * Osmophile - Growth in low water potentials * Piezophile - (aka barophile) requires high pressures - deep oceans / underground * Polyextremophile - Tolerant of several extreme conditions * Psychrophile/Cryophile - Growth \< -15 °C (permafrost, ice, cold ocean, snowpacks) * Radioresistant (ophile?) - Resistant to high levels of ionizing radiation, (UV, nuclear radiation) * Thermophile - An organism that can thrive at temperatures between 45–122 °C * Thermoacidophile - Thermophile plus acidophile features \>70–80 °C and pH 2 - 3 * Xerophile - Dry, desiccating conditions; e.g. soil microbes of deserts

Answer 35

They need to be able to fix carbon and acquire nitrogen for growth.

Answer 36

Diazotrophs\* are bacteria and archaea that fix atmospheric nitrogen gas into a more usable form such as ammonia (cyanobacteria, green sulphur bacteria, eubacteria) Examples include: * Legumes (Fabaceae) – Rhizobia bacteria - nitrogen-fixing nodules * Cannabaceae – hops, cannabis, hackberries - Rhizobia - nitrogen-fixing nodules * Alder and bayberry - Frankia bacteria - nitrogen-fixing nodules

Answer 37

Nitrosomonas, Gram-negative, chemoautotrophic bacterium. pH range of 6 – 9; 20–30 °C Oxidizes ammonia into nitrite (nitritation). Increases the bioavailability of nitrogen to plants. Power-generating membranes - long, thin tubes inside the cell. Use electrons from oxidation of ammonia to produce energy. Fixes carbon from the atmosphere – but not like plants … Uses energy from oxidation of ammonia to fix gaseous carbon dioxide into organic molecules. Must consume large amounts of ammonia before cell division can occur - cell division slow. Photophobic - forms a biofilm matrix, or clumps with other microbes, to avoid light.

Answer 38

Membrane lipids are made mainly of glycerides

Answer 39

Saturated fatty acids have no C=C double bonds in their hydrophobic tail and thus have a higher boiling point compared to unstaurated fatty acids which do. As the C=C causes a kink within the membrane layer widening the distance to another fatty acid chain, weakening the london dispersion forces.

Answer 40

* When exposed to stress the heterogeneous mixtures (rafts) of different lipids can phase separate to form pools of a single class * Can lead to a physical change in the bilayer structure * Inverted micelles and Hexagonal II (HexII) can form → leakage . Inverted micelles – head groups face inwards

Answer 41

* When membrane lipids become more unsaturated - * introduces kinks in the fatty acid chains * reducing attractive van der Waal’s forces between the chains * reducing the temperature of the liquid crystalline-to-gel phase transition (Tm)

Answer 42

* Cholesterol, an important constituent of cell membranes, has a rigid ring system and a short, branched hydrocarbon tail. * Cholesterol is largely hydrophobic. * But has a polar head group that orientates it in the membrane * But it has one polar group, a hydroxyl, making it amphipathic.

Answer 43

* Interaction with the relatively rigid cholesterol decreases the mobility of hydrocarbon tails of phospholipids. * Cholesterol interferes with close packing of fatty acid tails. * Phospholipid membranes with a high concentration of cholesterol have a fluidity intermediate between the liquid crystal and crystal states.

Answer 44

At low temperatures: Increase the number of cis double bonds in fatty acids (unsaturated fatty acids) At high temperatures: Decrease the number of cis double bonds in fatty acids (àsaturated fatty acids)

Answer 45

First classified in 1977 by Woese & Fox – in 1990 Three Domains Evidence from: Gene sequence – particularly ribosomal RNA Metabolism - broad range of energy sources - Organic, NH3, Metals, H2, etc., Membranes comprise ether lipids not ester lipids Reproduce asexually (binary fission / budding / fragmentation – do not form spores Originally considered extremophiles’ but found in most habitats (hot springs, salt lakes, marshland, mammalian and insect guts, mouth, skin, ocean. Now recognised as key organisms in carbon and nitrogen cycles on the planet No pathogenic species found to date – mutualism / commensalism e.g. methanogens Major interest from biotech Industry for sewage & waste treatment, novel enzymes Archaea are more closely related to Eukaryotes than (Eu)Bacteria – clearer in marine Archaea

Answer 46

Archaea have branched isoprene side chains in their lipid membrane which can: - can be joined together between phopholipids - can form carbon rings. This increases structural stability of the membrane

Answer 47

Most archaea possess a cell wall. The wall is assembled from surface-layer proteins, which form an “S-layer”. An S-layer is a rigid array of protein molecules that cover the outside of the cell (like chain mail). This layer provides both chemical and physical protection, and can prevent macromolecules from contacting the cell membrane.

Answer 48

Bacteriorhodopsin is a protein used by Archaea, most notably by haloarchaea, a class of the Euryarchaeota. It acts as a proton pump; that is, it captures light energy and uses it to move protons across the membrane out of the cell. The resulting proton gradient is subsequently converted into chemical energy

Answer 49

(Thermo)acidophiles _E.g. Picrophilus torridus_ ## Footnote * Picrophilus torridus grows best pH 0.5 – 1.5 and \>60˚C! * Thick Extracellular protein mucilage * Cytoplasmic pH ~ 4.5 * 1.5 Mb genome (E coli ~4.5 MB) * 12% genes are transporters * Like all Archaeans, Cell Membrane consists of ether lipids * Cell wall has S-Layer * Oxidises sugars via modified glycolysis pathway

Answer 50

Protein 3-D structure depends on … Intra- and inter-molecular forces and bonds - disulphide bridges - charge interactions (e.g. ‘salt bridges’) Van der Waals forces hydrogen bonds hydrophobic interactions

Answer 51

* Primary – the order of amino acids in the polypeptide chain. * Secondary – how the chain forms into structures such as alpha-helix or beta sheets (also called pleated sheets). * Tertiary – how these secondary structures come together to form the overall fold of the protein. * Quaternary – how separate folded proteins associate into larger structures either by non-covalent interactions and/or covalent cys-cys disulphide bonds (as in antibody molecules).

Answer 52

Taq polymerases are similar in structure to other polymerases. But they have more inter- and intra-molecular interactions which hold the protein’s structure together.

Answer 53

Isolated from an Archean, Thermococcus litoralis.

Answer 54

Deep-sea hydrothermal vents, shallow submarine thermal springs, oil wells. Anaerobic organotroph, hyperthermophile. Grows at between 55 and 100 °C. Unlike many other thermococci, T. litoralis is non-motile. Cell wall consists of a single S-layer that does not form hexagonal lattices. Many thermococcales obligately use sulphur as an electron acceptor in metabolism, but T. litoralis only needs sulphur to help stimulate growth, and can live without it. Vent polymerase has a lower error rate than Taq polymerase due to its proofreading 3’-5’ exonuclease abilities.

Answer 55

* Heat shock proteins (Hsp) * Synthesis induced by stresses such as heat, infection, inflammation, exercise, exposure of the cell to toxins (ethanol, arsenic, trace metals, UV), starvation, hypoxia, nitrogen deficiency (in plants), water deprivation. * Hsps can: * Assist re-folding of proteins. * Target damaged proteins for degradation and recycling. * But also - some are important chaperones that assist proper folding of proteins into the correct conformation (shape) as they emerge from ribosomes, and prevent aggregation.

Answer 56

Proteasomes are protein complexes which degrade unneeded or damaged or misfolded proteins by proteolysis (enzymatic cleavage at peptide bonds). Proteasomes are found inside all eukaryotes and archaea, and in some bacteria. Found in the cytoplasm and nucleus

Answer 57

Damaged or misfolded proteins are first labelled for destruction by ubiquitination. A sequence of three enzymes targets causes covalent attachment of ubiquitins to a lysine in the protein. A target protein must be labelled with at least four ubiquitin monomers (in the form of a polyubiquitin chain; “polyubiquitination”) before it is recognized by the lid proteasome. Inside the proteasome a protein is cleaved by an enzyme with a threonine in its active site.

Answer 58

* Methanogenic Archaea breakdown lignocellulose to simple sugars – NH4 (Biogas) is the byproduct (Shale Gas) * Cattle typically emits around 250 L of CH4 /Day - ~ 25% of anthropogenic methane emissions * Also key organisms in decomposition * Anaerobic Respiration; O2 is toxic to Methanogens * Organic C (CO2, Ethanoate) + 4 H2→ CH4 + 2H2O * Humans ~10% ‘flatulus’ is NH3 produced by gut Archaea! Bacteria produce the ‘Sulphide smell’ * Most natural gas has resulted from Archaeal methanogens and organic detritus

Answer 59

The three groups are: 1. Evaders 2. Evaporators 3. Endurers There is a correlation between the rat of evaoporation and body mass.

Answer 60

Some animals reduce the amount of surface area they ahve in contact with hot surfaces. Spiders roll down dunes to quicken the amount of time it takes to reach one point to another.

Answer 61

Rather than moving in the direction of the head as do other snakes (A), sidewinding snakes move sideways both on level ground (B) and up slopes (C). Marvi et al. show that when snakes sidewind up a slope, they increase the body length that is in contact with the ground, thereby reducing slip.

Answer 62

Antelope Ground Squirrels burrow to avoid raising their internal body temperature. Like other mammals, this species cannot survive body temoeratures \> 43 degrees celsius but can tolerate 42.3 with no ill effects.

Answer 63

It effectively cools and reduces CO2 in the burrows.

Answer 64

They produce latherin which is the sweat protein of horses that has strong detergent (surfactant)-like activity to enhance movemment of sweat water from skin to the surface of the pelt for evaporative cooling.

Answer 65

Birds do not have sweat glands so they use the gular fluttering ability instead. Dogs also do not sweata dn opt to pant.

Answer 66

The kangaroo rat has a small body ad will die at 10-20% water loss, so it opts to avoid heat in burrows. Camels have large bodies and can't evade the heat. Their water expenditure for cooling is limited. Hence thick insulation and body temperature tolerance. Graph represents evaporative cooling necessary to maintain body temperature steady for 1 hour.

Answer 67

Shaving a camel would be detrimental because it will lose 50% more water if you do.

Answer 68

Camels will essentially tolerate fluctuations in body temperature when dehydrated. Soley relying on the breakdown of fat from the humps in its back to produce water which goes into the bloodstream for hydration.

Answer 69

The brainm - v. sensitive to overheating The way to prevent heating of brain. Animals inhale trhrough the nasal area. So the nasal surfaces have been cooled by evaporation. That evaporation is also useful because the moist air enters the lungs. The veins from the nasal area mix with arteries going towards the brain and lower the temp of the brain. It is essentially a counter-current system called Rete Mirabile.

Answer 70

Desert animals have a much longer loop of henle than ordinary animals.

Answer 71

Rattkesnakes Which shake the rattle

Answer 72

To survive in the arid wilderness of southwestern Africa, the Namib Desert beetle harvests water from thin air. The blueberry-size, long-legged insect leans its bumpy body into the wind, letting droplets of fog accumulate and drip down its wing case into its mouth.27 Nov 2019

Answer 73

There is a dense layer of under down which helps insulate the bird from extremes of heat and cold. The feathers of the belly are specially adapted for absorbing water and retaining it, allowing adults, particularly males, to carry water to chicks that may be many miles away from watering holes.

Answer 74

Foot pads & long legs - & chest callus. High speed and stamina & one-sided gait. Anti-dust eyelashes & sealable nostrils. Thick pelt reflects sunlight and insulates (a shaved camel loses 50% more water to avoid overheating). Great dehydration tolerance (a human dies at 10-12% body weight of water loss, camels can cope with twice that) Concentrated, viscous urine & ultra-dry faeces, but dilute milk (unlike small burrowing desert mammals, e.g. kangaroo rats). Body temperature flexibility. Water loss from tissues, not blood (little change in blood viscosity). Metabolic water? Yes, but not the function of the hump. Hump for localised fat storage – using it for metabolic water would cost too much water loss from extra respiration. Forestomach & saliva inflow. Robust, oval erythrocytes, strengthened cytoskeleton, altered lipids (protein-to-lipid ratio very high, 3:1, vastly increased number of intramembranous particles relative to the human erythrocyte ghost).

Answer 75

One of the hottest terrestrial environments on Earth. Ecological niche - “thermophilic scavenger”. Search for heat-killed insects and other arthropods. Can forage when temperatures of the desert surface are 60° to 70°C. But “operative environmental temperatures” are 48° to 51°C. To unload excess heat they pause on top of stones or dry vegetation, where, because of the steep temperature gradient above the sand surface, they encounter considerably lower temperatures. Under the midday Sun the ants do this up to 70% of their entire foraging time. Must keep their temperature below their critical thermal maximum of 53.6°C. Need to reduce heat absorption and efficiently dissipate excess heat - to minimize the amount of time spent in thermal refuges.

Answer 76

1. Total internal reflection - the hairs enhance reflectivity in the visible and near infrared. 2. Where solar radiation becomes negligible for wavelengths \>2.5 mm, the hairs act as an anti-reflection layer enhancing emissivity and thus increase the ability to offload excess heat via blackbody radiation. 3. The ants’ bare undersides reflect IR radiation from the hot desert floor more efficiently than if it were covered by hairs.

Answer 77

Sand can reach 60°C The ants can run across hot sand at 0.855 m/second (= 108 times their length per second) Not just running, but gallop – all six feet off the ground simultaneously.

Answer 78

Common in salt lakes Tolerate varying levels of salinity from 5-250 g/L or more (seawater ~3.5%; 35 g/L). Their eggs are metabolically inactive. Remain in total stasis for two years in dry oxygen-free conditions. Cryptobiotic. Cryptobiosis - "hidden life". While in cryptobiosis, brine shrimp eggs can survive temperatures of −190 °C and a small percentage can survive above boiling temperature of 105 °C for up to two hours.

Answer 79

Inhabit temporary rainy season pools that vanish before the fish can complete their life cycle. Eggs marooned sealed from oxygen for weeks or months. Enter “diapause,” or dormancy. 25°C - stop developing and hearts stop Europe’s crucian carp and North America’s Western painted turtle can live without oxygen just as long as the killifish. Some organisms experience anoxia when the lakes they live in freeze – the cold allows survival by slowing metabolism. Killifish survive anoxia at tropical temperatures – a harder task.

Answer 80

Many animals migrate seasonally to avoid winter cold that will make them physiologically unable to survive, or that will eliminate their food supplies until spring. The greatest migrators in terms of distances are bids and cetaceans. But we will deal with those animals that do not migrate because the distances are too great for them, or there are physical barriers, or that they have found ways to continue feeding or coping in other ways.

Answer 81

Bar-tailed godwits shrink their internal organs to lighten the load on long flights. Photograph: Juan Carlos Martinez Salvadores/Alamy

Answer 82

Subnivean habitats are where animals shelter within or under a snow pack, using its protection from wind chill outside, and the insulation that snow can provide through the air it holds keeps the temperatures higher than outside. This allows small mammals such as lemmings to feed under the snow all winter such that they do not need to hibernate, and can create insulated nest shelters within the snow. Global climate change is, however, causing unusual warm periods in winter that cause the snow either to be too thin, or that it thaws and re-freezes to create a hard ice layer that is not conducive to survival of the lemming - this limits the lemmings’ population growth resulting in fewer so-called ‘lemming plagues’. This effect also causes problems for the reindeer on Svalbard that rely on being able to paw their way through the snow layer to get to their food, but if a hard ice layer forms then they starve.

Answer 83

_Thermal conductivity_ Large mammals cannot shelter easily from the cold, and if they cannot spend winters in a protective den as bears do, then they rely heavily on insulation to reduce heat loss. This chart illustrates how good fat, fur and feathers can be as insulators. The effect for fur and feathers is due to a considerable extent to the air they hold.

Answer 84

Layers of fur can be adjusted seasonally so that winter fur is much denser and longer than for summer pelts.

Answer 85

Some sea animals such as penguins and fur seals have an external layer of insulation (feathers or fur), but most species of sea mammal (such as whales and dolphins) do not. Instead they rely on a thick layer of internal insulation that doubles as a food store and streamlining. Here is a cross section of a frozen seal showing the depth of the fat-rich blubber layer, amounting to about one third of the radius from the core of the animal. And even there the composition of the blubber layer changes from inside to outside in order to retain the physical properties of the lipids in cell membranes throughout, as explained in the slide. Incidentally, the blubber layer of seals that are preyed upon by polar bears are crucial to the survival of the bears – fat is a high energy store per gram of tissue, and the bears need to acquire it to fuel the heat production they need to survive in the sea or in land or ice environments that will be below freezing for several months.

Answer 86

Heat is lost in several ways in animals – evaporation of water from mouth, nostrils, lungs, and evaporation, conductance, and radiation from their surfaces. So, reducing the surface:volume ratio reduces heat loss. The perfect way to retain heat is probably to be spherical. But animals have to move, which requires limbs, and need slender surfaces such as ears, snouts, tails that will have high surface area:volume ratios. To reduce heat loss form these structures, animals may reduce the temperature of them whilst retaining a high core body temperature. This reduction in the temperatures of peripheral structures whilst retaining higher temperatures in their cores and other structures that will fail at low temperatures (such as the brain) is termed “regional heterothermy”.

Answer 87

Possession of good insulation can present the problem of overheating when the external temperature changes or excess heat is produced internally through exercise, as with migrating, hunting or escape. Polar bears, for instance, can overheat if forced to engage in a long chase. But, insulation layers can be tuned by reducing or increasing the dept of fur or feather layers using erector muscles in the skin – such as in goose pimples or goose bumps in humans, which are contracted erector muscles attached to hairs (not much use in humans now). Alternatively, peripheral blood flow can be increased to heat the external surface and thereby lose heat, or reduced to conserve heat. This works by muscular contraction or relaxation of blood vessels to open or close peripheral blood vessels or shunts as illustrated in the slide.

Answer 88

One means by which heat can be conserved to create regional heterothermy is with countercurrent heat exchangers. In these, the arteries leading from the heart to a peripheral structure are closely apposed to the veins returning from that structure. Heat is exchanged between them, warming the venous blood returning to the heart (which can prevent it stopping), and cooling the arterial blood moving to the periphery such that heat loss will be reduced. This also means that surfaces that are routinely cold (penguins’ feet, polar bear paws) usually have higher levels of polyunsaturated fatty acids in their membrane lipids to keep their cell membranes fluid enough to function properly.

Answer 89

Birds tend to have very thin legs, so have a very high surface to volume ratios. They consequently exhibit highly efficient countercurrent heat exchangers as illustrated here in a cross section of a bird’s leg, with the central artery with its muscular wall apposed to the thin-walled veins.

Answer 90

Marine mammals, being endotherms living in water colder than their cores, have a similar problem to cold-living land animals. And the solution is again countercurrent heat exchangers in their limbs, flukes, and dorsal fins.

Answer 91

Countercurrent exchangers are also used in poikilohermc animals (so-called “cold-blooded”; those that do not produce heat internally as do homeotherms in order to create a higher body temperature) to retain heat generated by muscles to make them more active. Here, for example, is the tuna – a fast marine hunter – their swimming muscles have high levels of myoglobin, a haemoglobin-like oxygen-carrying protein enriched in highly active muscles such as in the tuna, and also in many diving mammals. A rete mirabile is a complex interweaving of arteries and veins as illustrated in one of the previous slides.

Answer 92

Countercurrent exchangers allow some species of fish to be effectively endothermic by reducing the loos of heat they generate metabolically. The regionally endothermic tunas (family Scombridae), and lamnid sharks (family Lamnidae) (which warm their aerobic swimming musculature as well as other regions in some species), and the billfishes (families Istiophoridae and Xiphiidae, which warm the eye and brain region only), are often termed “high-performance” fishes because of their increased physiological function associated with regional heat retention. However, these fishes fall far short of whole-body endothermy because much of the body (including vital organs such as the heart) remains at ambient temperature, which ultimately puts limits on aerobic performance in cold water.

Answer 93

Gigantothermic Counter-current heat exchangers allow the leatherback turtle to be the only reptile capable of surviving and hunting in cold temperate, even subpolar, or deep waters. They have thick layers of fat and oil insulation, and counter-current heat exchangers at the base of their limbs that also retain heat in their muscles. They are also the largest species of marine turtle, a feature that reduces their surface:volume ratio – hence they are termed to be “gigantotheric” (which might also have applied to large dinosaurs.

Answer 94

As with tuna and the other fish mentioned in previous slides, bumblebees use countercurrent exchangers to retain heat I their flight muscles and not lose it via the blood circulation to the abdomen. This contributes to the ability of bunblebees to fly at cooler ambient temperatures than other bees and insects, and also be more active earlier in the spring and at higher altitudes.

Answer 95

Animals (and plants) that cannot keep themselves warm and have to survive in cold or even sub-freezing temperatures can protect themselves against the destructive freezing of their tissues. Ice crystals are sharp and can puncture cell membranes and damage tissues, and will also dehydrate cells. They can reduce the freezing point of their body fluids by producing certain sugars or anti-freeze proteins. Here, an Arctic beetle that can survive at freezing temperatures by producing produces high levels of glycerol and sorbitol that are cryo-protective. (Glycerol, incidentally, was the first effective cryoprotectant found for freezing and storing viable human sperm.) But, the insects need to produce these cryoprotectants in advance of their need. So, in advance of the freezing times, they respond to lowering temperatures with the approaching winter by producing these sugars.

Answer 96

Arctic and Antarctic fish can live in waters that are colder than the temperatures at which their blood would freeze. This is because teleosts (body fish) have body fluids with lower salt concentrations than the surrounding sea water, so could freeze before the water around the does so. They therefore need some form of cryoprotectants to keep their body fluids from freezing. One way to do so is to produce anti-freeze proteins, which act to inhibit the growth of ice crystals, and also accumulate to prevent the growth of sharp-pointed crystals. Anti-freeze proteins tend to have faces enriched in serine and threonine amino acid sidechains, the hydroxyls of which interact directly with ice. Remarkably, Arctic and Antarctic fish have evolved quite different anti-freeze proteins since they evolved from different ancestors, as separated by waters in which such proteins are not needed.

Answer 97

Hibernation is a prolonged reduction in body temperature and metabolism. Deep torpor. Winter dormancy. Animals that undergo torpor include squirrels, bats and hedgehogs.

Answer 98

Period of inactivity, often with reduced temperature and metabolism. Short term, overnight/diurnal – temperature or food supply fluctuation.

Answer 99

Period of torpor to avoid heat and drought – usually summer.

Answer 100

* Dramatically reduced metabolic rate. * Core temperature 5-15ºC (some even lower, -2.9ºC!), * so, as little as 1ºC above ambient. * Ground squirrels – core \<0ºC, head and neck 0ºC * Core temperature still controlled to a few * degrees above freezing. * Heart rate ~10% of normal; stroke volume ~ normal. * Head and brown fat receive more blood than other organs. * Cellular lipid composition altered. * Extra types of lipid transporter proteins in heart muscle cells. * Membranes of organelles in nervous system cells organise into protein-free * domains – temperature-induced phase changes?

Answer 101

Arousal from hibernation is not a simple process. The organs of the thorax (heart) and head warm first, followed by other tissues. Heat is produced by two main mechanisms – shivering to produce heat form muscle activity, and by activation of brown fat that directly generates heat though activation of mitochondria. Brown fat is so-named because it possesses very high concentrations of mitochondria which are rich in cytochromes (“cell colour”).

Answer 102

As one goes from small to large animals then their metabolic rate per gram of tissue goes down. So, less expenditure of body reserves is required to maintain their body temperatures. Also, large animals have small surface:volume ratios, so lose less heat, such that they can survive a winter living on their stores of fat – brown bears, for instance, can double their body weights in a feeding frenzy before winter. And, yes, when bears den for the winter their body temperatures do not fall to the levels achieved by hibernating ground squirrels or hamsters.

Answer 103

Large mammals do not enter full low-temperature hibernation, and are rouseable because … * Less energy per gram required to maintain body temperature (though female bears lose ~50% body weight during winter confinement). * Low surface:volume ratio – less heat loss per gram. * Arousal energetically too costly for such large masses. * Bears in temperate regions - "denning" or "winter lethargy" * Female bears have it tough – no food or drink, delayed implantation, lactation and neonatal care during winter.

Answer 104

Well, yes. The temperatures of denning bears do fall to low levels, though not below 30 oC, and nowhere near the 10 oC of small hibernators. Meanwhile their breathing and heart rates fall considerably. This all means that their metabolic rates are within the same range as that of a small mammal in hibernation – remember that the latter animals still have to control their body temperatures and keep their hearts, brain, and so on active. So, now bears are accepted to be hibernators.

Answer 105

Fat storage – insulation and winter survival (50% weight loss). Average body core temperature for a mammal. Running & overheating problem. Compact ears and tail. Hollow hairs – insulation, light pipes, buoyancy. (Algae.) Black skin – UV absorbance. PUFAs on cold contact areas. Sleep covering snouts. Pregnant/nursing females are deep sleepers, 31-35ºC, but demands for birthing \>\>\>

Answer 106

* Fertilized ovum undergoes delayed implantation. * Cubs born soon after implantation occurs in early winter. * Cubs are tiny, typically 30 cm long and weighing 700 g (mothers 300 kg). * Helpless, blind cubs open their eyes after about a month. * Milk contains approximately 33% fat - higher than that of any other species of bear and comparable to that of other marine mammals. * The female can control urea cycling so she can endure a long fast which can be up to nine months. * Their muscular walls of their hearts need to be modified.

Answer 107

* Increased pressure: * 1 atm pressure increase per 10 m depth * Sperm whale at 3,000 m =\> 300 atm Gas-filled spaces crushed, tissue damage * Gasses absorbed/dissolved at high pressure * O2 toxicity. * N2 narcosis. * Embolism risk. * Difficulty regulating temperature as it gets colder the deeper an animal dives. * Difficulty with sensory perception the deeper you dive. * Energy metabolism

Answer 108

* Bradycardia * Vasoconstriction * Changes in organ perfusion patterns * Changes in blood pH, PO2 and oxygen content. * Anaerobic metabolism * In humans - apnoea, bradycardia, reduced cardiac output, reduced blood supply to extremities, gradual increase in mean arterial blood pressure.

Answer 109

“the dive duration after which there is an increase in post-dive concentration of lactate in the blood”. * Weddell seals - 90% of dives are less than 20 min (feeding dives). * Only a few are longer (exploratory dives). * During short dives seals remain aerobic with little lactate accumulation. * ADL can be calculated from the size of the oxygen stores and the animal’s metabolic rate. Can indicate (very approximately) the maximum dive duration. * Usefulness debated.

Answer 110

Longer dives need longer surface recovery times to repay oxygen debt

Answer 111

Total O₂ Percentage of total (ml/kg-1) Lungs Blood Muscle Human 20 24 57 19 Weddell seal 87 5 66 29 Cetaceans and manatees can renew 90% of air in the lungs in a single breath, human at rest, only 10%

Answer 112

Blood oxygen stores: * Increased blood volume * Increased haematocrit (but that risks increased blood viscosity and overall oxygen carrying capacity) Muscle myoglobin: * Highest concentrations in deep divers. Higher affinity for O2 than haemoglobin, so would strip O2 from blood. Muscles tolerant to hypoxia. Withdrawal of blood from muscles (and gut, kidneys) protects essential organs (e.g. brain) from damage. Lung oxygen stores: * But, danger of crushing and hazardous gas absorption during dives. Retia mirabilia Spleen and other sites

Answer 113

A marine mammal of the order Cetacea ; a whale, dolphin, or porpoise.

Answer 114

Tissue masses with extensive contorted blood vessels, usually on inner dorsal wall of thoracic cavity, also in periphery. Sperm whale has the most.

Answer 115

* Pinnipeds (phocids (true seals), otariids (sea lions, eared, fur seals), odobenids (walrus)) * Have a venous system enlarged and increased in complexity * Adaptations combined in phocids (true seals) * Spleen storage – diving capacity correlated with spleen size (~4.5% of body mass; more in elephant seals) * {Cetaceans – very small spleens – proportionally smaller than in land animals!}

Answer 116

* No larger in cetaceans and pinnipeds than in land mammals. (Sea otters – larger lungs – buoyancy?) * Less lobed and have increased cartilaginous support. * Very small residual volumes. * Cetaceans – diaphragm oblique – allows viscera to move forward under compression. * Tracheae short and well-reinforced with rings – collapses in baleen whales, rigid in toothed whales. * Ribs modified to allow lung collapse - air expelled into bronchioles and tracheae. * Cetaceans dive with full lungs - pinnipeds typically exhale.

Answer 117

Diving mosasaurs, plesiosaurs, and humans develop dysbaric osteonecrosis from end-artery nitrogen embolism ("the bends") in certain bones. Progressive, erosive, and remodeling development of dysbaric osteonecrosis in sperm whale subarticular rib bone surfaces. The top to bottom panels show a progression from calf to mature adult. Scale bar 2 cm top panel, 1 cm rest. Dark areas indicate the vascular channels, which appear normal in the calf and increasingly eroded and enlarged in larger animals.

Answer 118

The Bajau, or ‘‘Sea Nomads,’’ have engaged in breath-hold diving for thousands of years. Natural selection on genetic variants in the PDE10A gene have increased spleen size in the Bajau, providing them with a larger reservoir of oxygenated red blood cells. Evidence of strong selection specific to the Bajau on BDKRB2, a gene affecting the human diving reflex.

Answer 119

* Amphibians are positive pressure breathers. * Most non-avian reptiles, birds and mammals are negative pressure breathers, using rib ventilation. * Mammals have elaborate, alveolated lungs to increase surface area for gas exchange, but are still essentially simple bags. * Birds have a flow-through system in their lungs so that only fresh/unused air passes over absorptive surfaces.

Answer 120

* Seen at up to 10,175 m (Mt Everest 8,840 m) (though debated) * Slightly larger wing area for its weight than other geese. * Breathe more efficiently under low oxygen conditions and are able to reduce heat loss. * Haemoglobin - higher oxygen affinity than that of other geese. * Sustain the 10–20-fold increase in O2 consumption rate necessary to fuel flapping flight. * Flight muscle – * Increases in bulk prior to migration time – captive or not. * Mitochondria show no special respiratory capacities, O2 kinetics or phosphorylation efficiencies. * Mitochondrial volume densities of each fibre type are not unusual. * But … * Mitochondria are distributed towards the subsarcolemma and adjacent to capillaries. * Higher proportion of oxidative fibres. * More capillaries per muscle fibre than expected * Higher capillary densities and more homogeneous capillary spacing. * Differences exist without prior exercise or hypoxia exposure.

Answer 121

_Tibetans, Andeans, Ethiopians_ Tend to have: * Larger hearts and lungs. * Altered cerebrovascular responses. * But no change in amino acid sequence of haemoglobins or myoglobins. * Higher oxygen level in placental blood. * ‘Natural’ experiment - Native versus Han in Tibet.

Answer 122

Compared with Andean populations living in similar high-altitude conditions, Tibetans exhibit a distinct suite of physiologic traits - decreased arterial oxygen content, - increased resting ventilation, lack of hypoxic pulmonary vasoconstriction, - lower incidence of reduced birth weight, - reduced hemoglobin (Hb) concentration (on average, 3.6 g/dl less for both males and females). Neighboring Han Chinese individuals and other non-adapted lowland visitors to high-altitude regions - develop increased Hb concentration to compensate for the hypoxic high-altitude environment, and this response is associated with adverse effects.