Animal Biology

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homeotherm

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temperature regulator which maintains an internal temperature within a tolerable range

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poikilotherm

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temperature conformer whose body temperature changes with the environment- upper limit is 52'C, lowered freezing point

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endotherm

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body heat comes from active metabolism. Has better endurance and can be active for longer, but it is energetically expensive so needs more food.

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ectotherm

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body heat comes from the surroundings, is less energetically expensive but has less endurance

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characteristics of chordates

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pharyngeal slits, notochord, muscular post anal tail, hollow dorsal nerve cord

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characteristics of arthropoda

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hard exoskeleton, jointed limbs, segmentation, open circulatory system

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4 lines of evidence on which fact of evolution is based

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macroevolution, microevolution, imperfections (vestigial organs) and molecular evidence

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thermoregulation in mammals/birds

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increased heat production by increased muscle contraction and non-shivering thermogenesis. Heat loss reduced by feathers/fur, vasoconstriction, counter-current heat exchange. Heat loss increased by vasodilation, sweating, panting, saliva and urine

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thermoregulation in fish

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generally ectothermic, but some produce heat through swimming muscles and lost to water through gills. they have adaptations to decrease heat loss which increases activity by keeping swimming muscles warm

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thermoregulation in amphibians

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evaporative cooling (controlled secretion of mucus) and behavioural adaptations like seeking cooler or warmer microclimates

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thermoregulation in reptiles

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ectotherms so warm themselves by behaviour- basking, burrowing, moving to damp areas. some endothermic (shivering) for periods

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thermoregulation in invertebrates

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mostly thermoconformers- adjust behavioural or physiological mechanisms

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hyperosmotic

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higher concentration of solute inside the cell, so water flows in

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hypoosmotic

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higher concentration of solute outside the cell, so water flows out of cell

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osmoconformers

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Stenohaline- can't tolerate large changes in external osmolarity

They are isoosmotic and so don't adjust their internal osmolarity

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osmoregulators

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Euryhaline- can tolerate large fluctuations in external osmolarity.

They expend energy to control water uptake or loss, and require an osmotic gradient

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control of osmolarity in Hagfish

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osmoconformers

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control of osmolarity in marine teleosts

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they are hypoosmotic

Osmoregulators- constantly lose water through gills and so constantly drink and urinate little. They actively pump water out through their gills and kidneys to distill seawater (specialised Cl cells in kidneys to dispel ions)

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control of osmolarity in cartilaginous fish

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they are isoosmotic with seawater

Osmoconformers

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control of osmolarity in freshwater teleosts

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Hyperosmotic

Osmoregulators- constantly take in water through osmosis, so excrete large quantities of dilute urine, actively take up salts across epithelium to replenish salt conc.

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control of osmolarity in land animals

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avoid dehydration by...

protective layers, behavioural adaptations, drinking and eating moist foods

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Protonephridia

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found in flatworms

network of dead-end tubules connected to external openings. smallest branches capped by flame bulb, into which beating cilia draw interstitial fluid

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Metanephridia

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found in earthworm

each segment has pair of open ended metanephridia. tubules collect coelomic fluid and produce dilute urine for excretion. filtrate modified between capillaries and tube

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Malpighian Tubules

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found in insects and other terrestrial arthropods

tubules remove nitrogenous waste from haemolymph and produce dry waste matter. water reabsorbed between mid and hind gut

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Vertebrate kidneys

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have long loop of Henle to maximize water conservation. Urine more concentrated than fluids because of urea and NaCl.

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Respiration through gills

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outfoldings of body with large surface area to maximize gas exchange area, and so uptake of oxygen from the water. Fish use counter-current exchange so that the water encountering the gills always has more oxygen than the blood

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Respiration through tracheal systems

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tiny branching tubules which penetrate body and directly supply body cells with oxygen. large insects ventilate their tracheal system to meet oxygen demand

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Respiration through lungs (example of birds)

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localised respiratory organ- circulatory system transports gases to rest of body.

Bird lungs needs very efficient lungs for flight, so have 8-9 sac system which act as bellows for ventilation. Air passes in one direction, 2 cycles of in/exhalation needed for one breath to pass through

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open circulatory system

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insects, arthropods, most molluscs

haemolymph bathes organs dircetly.

lower hydrostatic pressure so less costly

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closed circulatory system

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blood confined to vessels, separate to interstitial fluid. high pressure is more energy-costly, but has more effective delivery of oxygen to tissues.

controllable capillaries aid thermoregulation

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single circulation

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blood not repressurised at heart before travelling to other tissues

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double circulation

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blood repressurised at heart, maintains higher blood pressure in organs

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challenges of low pressure for bar headed goose

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cold wind and low partial pressure of oxygen

adaptations include...

large wing span (energy saving), increased heart mass during migration, deep breathing to increase oxygen capacity, Hb variant binds O2 better, behavioural

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challenges of high pressure

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Pressure increases with depth, and as pressure decreases, the pressure of gases in lungs increases- causes the bends.

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sperm whale adaptations to high pressure

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reduces N2 in tissues by breathing out before dive, completely collapses air sacs and upper airways at 50m depth, reduces blood flow to lungs so gas doesn't enter bloodstream

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how is buoyancy achieved?

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buoyancy saves energy by matching water density

swimbladder- adjustable to maintain neutral buoyancy- restricts to zone of neutral buoyancy

Nautilus shell- divided into chambers of gases at atmospheric pressure.

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if food is less that 50m away, a bee will...

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perform a round dance

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if food is over 50m away and towards the sun, a bee will

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perform a waggle dance up the honeycomb. length of straight=distance away, angle of straight= direction of food

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polarised light is...

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light which only vibrates in one direction

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degree of polarisation

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the amount of light which is polarised- unpolarised light vibrates in all directions, less polarised light will vibrate in fewer directions

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angle of polarisation

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the angle at which polarised light vibrates

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detection of polarised light

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Bees have photosensitive pigement called RHODOPSIN in their photoreceptor cells (ommatidia), which is arranged horizontally along the microvilli of the ommatidia. this maximizes the absorption of polarised light in that axis, and each ommatidia is stimulated by different angles of polarised light. to work out where the sun is, the bee turns its head to see which ommatidia is maximally stimulated.

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why can't humans see it?

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rhodopsin in human photoreceptor cells is randomly arranged in order to block out damaging UV light, and so we can't detect polarised light patterns

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patterns of polarisation in the sky

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maximum polarisation at 90 degrees from sun along sun-antisun axis. sun is area of least polarisation.

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Infrared detection in snakes

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pit organs are responsible for detecting infrared radiation. they allow the snake to build a thermal image of its prey using point to point mapping by comparing the strength of stimuli to each receptor. moves head round to compare images from each pit organ.

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structure of pit organs

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air filled cavities on either side of pit membrane, which is innervated by many sensory receptor neurons. the membrane has many TRP channels, which open in response to heat and allow cations to flow into receptor, depolarising it and creating an action potential.

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constant frequency calls

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bats use these calls, which are higher energy and so travel far, to determine direction of a target. they use Doppler shift- if echo=CF, object is stationary. if echo frequency > CF, object is approaching. if echo frequency < CF, object is retreating

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Frequency modulated calls

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compare time between emitted call and returning echo. the calls are very short, and only pass through each frequency once.

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Moth-bat coevolution

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moths have evolved ears which open in the body cavity under the wing. they allow the moth to respond to the very high frequency calls of bats by mimicking a leaf fall flight pattern when the calls are frequent enough.