mini mod.: animal adaptations Flashcards
stenohaline V euryhaline animals and osmoconformers
Stenohaline animals
–Can only survive in relatively constant conditions
–Narrow range of salinity
–Either marine or freshwater
*Euryhaline
–Can survive in a wide range of salinity
–Short term – estuarine & intertidal
–Long term – diadromous
–Anadromous??
–Catadromous??
Osmoconformers - Internal osmolarity matches external envt.
Explain how osmoregulation occurs in elasmobrachs (cartilagenous eg.sharks, rays and skaters)
marine elasmobrachs:
Nearly all ureotelic
–Except freshwater rays
*Marine rays use trimethylamine oxide (TMAO)
Reabsorb/retain solutes such as urea
*Serum osmolarity greater than sea water
–hyperosmotic
*Water gained is excreted by kidneys
*No need to drink
*As salinity decreases (Euryhaline spp.):
–Less TMAO produced and reabsorbed
–More urine
–More Na & Cl uptake and reabsorption (gills and kidney)
fresh water elasmobrachs:
*Ammonotelic
*Dilute Urine
*Cannot make and retain TMAO
*As salinity increases (Euryhaline spp.):
–Increase urea production and retention
–Decrease urea excretion
–Increase Na+ and Cl-
–Decrease ammonia excretion
Explain how osmoregulation occurs in teleosts (most/bony fish)
Freshwater:
Goals: to get salt in (via gills)
avoid: water/(deal with)large amount getting in
Avoid: losing salt to fresh water
producing: large volume of dilute urine –>done by specialised gill chloride cells
–Enables conserving salt and avoiding water
salt water:
Keep body at lower osmolarity to water
drink/ingest water
Actively excrete through gill-sodium/chloride
produce low vol. of urine
Try and reabsorb water from urine –>done by specialised gill chloride cells
–conserve water + excrete salt as they ingest salt water
Describe freshwater and Marine Environments
Must avoid desiccation in an aqueous envt.
*Marine
–1000 mosmol/L
–Conserve water
–Get rid of excess salts
*Freshwater
–1-10 mosmol/L
–Conserve salts
–Get rid of excess water
Define Stenohaline & Euryhaline
stenohaline-only survives in narrow range of salinity
euryhaline-survives in wide range of salinity
euryhaline-how they work
*Intertidal/Estuarine
–Both types of chloride cell systems
–Kidneys only play significant role in low salinity
*Diadromous
–Hormone mediated
–Drive adaptations
stress responce:
*Adrenaline
–Increases gill permeability
–Increases osmotic challenge
*Steps can be taken to reduce impact
–Adjust envt. to tend towards isosmotic conditions
–Dilute seawater
–Add solute to freshwater
marine mammals:
*Similar challenges to those in arid envt.
*No extra-renal salt excreting organs
*Water from Food
–Can be hypotonic or isotonic with seawater
–Elasmobranchs Vs Teleosts
*Water from seawater – variation
*Metabolic Water
*Water losses
–Cutaneous, respiration, milk, urine, fecaes
water balance during lactation + and other adaptations
*High demand for water
*Otariids (Sea Lions) Vs Phocids (True Seals)
*Otariids
–Continue feeding – Hypotonic prey
*Phocids
–Fasting
–Milk composition changes
–Reduce water, increase lipid
other adaptations
*Reduce respiratory losses
–Nasal turbinates
–Apnea
*Reduced/absent sweat glands in some species
describe: endotherm, ectotherm, poikilotherm and homeotherm.
Homeothermy-organisms that keep their body temperature stable independently of ext. env.
poikilothermy- animals where body temp. Varies with the environment
Endothermy- regulate temperature relying on internal sources of heat(metabolic rates high at extreme temps- working to keep body temp stable eg. Higher/lower)
ectothermy- regulate body temperature largely reliant on external sources of heat (temp rises-body temp rises with it - as does metabolic rate. Too cold-metabolic rate slows)
examples:
Most land mammals(human)-endotherm+hemeothermy
freshwater fish/inverterbrates - ectothermy and poikilothermy
adaptation V acclimatisation
Adaptation - The evolutionary adjustment of morphology and physiology to changing environmental conditions. Natural selection adjusts the frequency of genes that code for traits affecting fitness.
Acclimatisation - Based on the range of physiological responses present in an organism. Phenotypic plasticity gives rise to short-term changes in response to environmental disturbance.
responses to changes in environment
Avoid:
It may avoid environmental problems e.g. by migrating, or moving to unstressed micro-habitats.
Conform:
It may change its internal state so that it is more similar to the imposed external state e.g. by hibernating or entering torpor.
Regulate:
The animal tries to maintain its internal environment (homeostasis) irrespective of external conditions. This usually requires the use of metabolic energy and/or external resources such as food and water.
Strategies for cold(freezing) environments
4 strategies in cold-adapted ectotherms:
i.Anhydrobiosis/cryptobiosis – e.g. cysts and eggs
ii.Vitrification
iii.Freeze tolerance – FT
iv.Freeze avoidance – FA (i.e. freeze intolerance)
sensing body temperature
Responses Include:
*Metabolic Rate (Thyroid)
*Behavioural e.g. Avoidance, Eating, Huddling
*Vasoconstriction
*Vasodilation
*Shunts
*Sweating
*Arrector pili muscle
thermogenesis
Exercise induced thermogenesis
Diet induced thermogenesis
Shivering thermogenesis
Non shivering thermogenesis ->Heat generated without shivering
Futile cycling
(BAT)Brown adipose tissue
Explain the process of non-shivering thermogenesis in BAT
brown adipose tissue(BAT)
Who has brown adipose tissue
*Neonatal humans have well developed Brown Adipose Tissue
*Adult humans have less
*Some more than others
–Less with age
–More in women
–Less in obese
*Hard to detect in diabetics
*Cold responsive
*Inducible?
Dinitrophenol:
*2,4-dinitrophenol
*Crosses the inner mitochondrial membrane
*Carries H+
*Uncouples Oxidative Phosphorylation
*Proton motive force dissipated
*Increased O2 & NADH consumption
Used in:
Herbicides & Fungicides
*Explosives manufacture
*Weight loss – side effects?
Describe the evolutionary development of locomotion in fishes
structure of fins:
aquatic vertebrates,
modern fish,
types of paired fins
lobe finned fish
locomotive mechanisms in an aquatic environment
Aquatic vertebrates
Fins usually occur singly (dorsal, anal, caudal)
or in pairs (pectoral and pelvic fins)
Paired fins are the phylogenetic source of the tetrapod limbs
modern fish:
Basal pterygiophores (Proximal) : 3 large elements that articulate the fin to the pelvic or pectoral girdle
Radial pterygiophores (Middle): Smaller more distal elements
Dermal fin rays (Distal)
–Slender rods
–Keratinised in elasmobranchs
–Ossified or chondrified in bony fishes
types of paired fins:
Ray fins - very flexible with thin base (Actinopterygii)
Fin Fold Fins – very broad based (Chondrichthyes)
Lobed fins - fleshy muscular lobe at base – makes them more flexible (Sarcopterygii )
lobe finned fish:
Class Sarcopterygii
Only a few living representatives
Coelacanth and six species of lungfish
Unlike other fish, sarcopterygian fish have a central appendage in their fins containing many bones & muscles.
The fins are very flexible and potentially useful for supporting the body on land.
locomotive mechanisms in an aquatic environment:
Forward propulsion in fish
–Achieved by lateral flexion of vertebrae caused by axial musculature
–This results in lateral undulations
–Caudal fin (tail) sweeps from side to side
–Movement of tail exerts a forward and lateral force against the resistance of the water
The forward component of resistance propels fish forward
–Lateral component will tend to make the body of the fish move sideways but this is minimised by the fact that the body is large and its inertia is more difficult to overcome
terrestrial locomotion and movements that could be used on land
Lateral undulations of fish on to land
–Muscles of primitive crossopterygians were too weak to support body out of water (no buoyancy)
–However, the slight musculature was sufficient to fix the fins on the body like pegs
–Lateral undulations and peg like fins act as pivots around which the body could rotate
–“bottom-walking” of today’s lungfish use fins as pivot points about which buoyant body moves
IN WATER:
Propulsion through lateral undulations;
Horizontally held fins ->LIFT
Vertically held fins ->THRUST
ON LAND:
Same lateral undulations place fins as pivot points; body rotates around pivot; limbs not as strong as tetrapods (not carrying body weight, no real locomotory function)
moving to land - function and evolution of limbs
Function of limbs:
Locomotion
Tool eg. Mole, cat, baboon
evolution:
One of the two major groups of sarcopterygians, either the coelacanths or the lungfishes, was responsible for giving rise to tetrapods. The question is, which one?
●It is generally accepted that early tetrapod limbs developed from lobe-finned crossopterygians (coelacanths)
●Appendicular skeleton of both similar:
similarities between classes - early tetrapods
Tetrapoda includes four classes: amphibians, reptiles, mammals, and birds
All tetrapod limbs have same basic plan
Despite superficial differences - legs, wings, flippers, etc.
early tetrapods:
●Short limbs
●First segment almost horizontal
●Second segment perpendicular to first (vertically down)
●Toes tended to point laterally
●This condition found today in urodeles and some primitive reptiles
terrestrial locomotion
●Same method used by early amphibians in order to lift and plant foot ->then tetrapod vertebral column rotates about the pivot point
●Today’s urodeles, lizards, turtles, etc. still use this method
●Lifting of limb brought in new factor: axial torque of vertebral column
●Primitive gait used here = trot (simultaneous placement of diagonally opposite feet on the ground)
●Inherently unstable as C of G balanced on thin line between supports
–Extra stability gained by:
»Buoyancy (in water)
»Tail on ground
»Belly walking (ventral surface remains in contact with ground)
inefficient locomotion, and improving efficiency of locomotion
advantages to changed limb posture
●Sprawled posture employed by urodeles and some reptiles (e.g., crocodiles) is ok at rest (body weight on ground) but inefficient in terms of energy expenditure
improving efficiency
●Bipedalism (dinosaurs, birds, bipedal reptiles)
–Front legs (initially) little modified
–Hind limbs lengthened and strengthened
–Knees rotated anteriorly to a position essentially beneath body
●Four-footed gait (characteristic of mammals, also some dinosaurs)
–Knees rotated anteriorly (as above)
–Elbow rotated posteriorly and brought closer to body
advantages to change:
●1. Body weight now supported by rigid bones ->decreased energy expenditure
●2. Increased efficiency of limb swing ->limb movement in sagittal plane - easy pendulum swing beneath body
●3. Change in flexion of vertebral column from lateral flexion to vertical flexion (and extension) -> increase in stride length
● = Quadrupedal gait!
modes of terrestrial locomotion and locomotion without limbs(snakes)
Cursorial
–Fast running e.g., antelope, horse, cheetah, some lizards
–Carnivores
Fossorial
–Digging
–e.g., moles, rabbits, sand snake, some rodents
Saltatorial (ricochetal)
–hopping e.g., kangaroo, frog, hare
Arboreal (life in trees)
–Scansorial (climbing with claws) e.g., squirrel, nuthatch
–Brachiation (hand grips branch and body swings beneath) e.g., monkeys, chimpanzees
Lateral undulation
Most common
Large dorsal muscles are activated sequentially along the body (Unilaterally)
Rectilinear
Straight line movement.
Large snakes such as large vipers, boas, and pythons. The belly scales are alternately lifted slightly from the ground and pulled forward, and then pulled downward and backward.
locomotion without limbs(snakes):
–Lateral undulation / serpentine
–Rectilinear
–Concertina
–Sidewinder
–Unique modes of terrestrial locomotion!
cursorial locomotion: structural adaptations
●Full cycle of running or walking animal = stride
●The faster the rate of limb oscillation, the faster the animal travels = rate of stride
●Speed = length of stride x rate of stride
●But…rate and length are antagonistic, i.e., enhancing one compromises the other
increasing length of stride
●Lengthen the limb
●Highly cursorial: lengthen distal limb elements
●Radius and tibia usually longer than proximal segment
●Light and slim (tendons rather than muscles)
●Change in foot posture:
PLANTIGRADE
DIGITIGRADE
UNGULIGRADE
●Highly mobile shoulders
●Absent or reduced clavicle
●Increase the distance through which the limbs move while they are off the ground
●Scapula more mobile in mammals (fixed in amphibians)
●Scapula oriented to side, not over back, so rotates in same plane as limb
Flexibility of the spine
–Lateral flexion in lizards and amphibians
–Vertical flexion and extension in fast quadrupedal mammals
–Back muscles flex the spine bring hindquarters under the body just before the hind legs reach the ground
increasing rate of stride
●Speed also depends on the rate at which the limbs are moved
●Larger & more efficient muscles increase rate
●Shortening the limb would increase rate (but shorten stride length)
●Strength vs. speed of muscle
–optimum leverage for speed
●Lighten distal end of limb ( inertia that must be overcome)
–Reduced muscle mass
–Reduced digits
●More easily and efficiently moved with less energy
Define and describe types of gait
walk, amble, trot, pace, canter, gallop, pronk
walk - 4 independant footfalls-3point support
amble - sped up walk
trot - 2-beat gait diagonals alternate
pace - 2 beat (like swimming)
gallop - 4 beat gait legs gather under then stretch out
pronk - 4 feet on ground, then period of suspension, abruptly jars/decelerated the animal
