Animal Adaptations

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What are the features of Marine organisms?

They have an osmolarity of 1000 mOsm

They aim to conserve water and get rid of excess salts

What are the features of Freshwater organisms?

They have an osmolarity of 1-10 mOsm

They aim to conserve salts and to get rid of excess water

What are the features of Stenohalines?

They can only survive in constant conditions

They can only live in a narrow range of salinity

They can be either marine or freshwater organisms e.g. Haddock

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What are the features of Euryhalines?

They can survive in a wide range of salinity

They can have short term acclimation - estuarine or intertidal

Or, they can have long term acclimation - diadromous. These organisms spend portions of their life cycle in fresh water and a portion of their life in salty water. They represent Anadromous and Catadromous organisms.

What does Estuarine mean?

A habitat where fresh water from rivers and streams mixes with the salty ocean water.

What does Intertidal mean?

The area also known as the foreshore or seashore, that is above water level at low tide and underwater at high tide.

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What does Anadromous mean?

Organisms that can breed in freshwater but live in salt water e.g. salmon.

What does Catadromous mean?

Organisms that breed in salt water but live in fresh water e.g. eels.

What are Osmoconformers?

Organisms whose internal osmolarity matches the osmolarity of the external environment.

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What are some of the main features of Marine Elasmobranchs?

Almost all Ureotelic; except freshwater rays

Produce concentrated urine

Marine rays use TMAO and urea to regulate osmolarity. TMAO also protects proteins from denaturing

The serum osmolarity is greater than sea water (hyperosmotic) therefore water enters the organism by osmosis therefore they do not have to drink

The kidneys excrete water

As the salinity decreases, less TMAO and urea is produced, more urine is produced and there is greater uptake of sodium and chloride ions via the gills and kidney

What are some of the features of Freshwater Elasmobranchs?

Ammonotelic

Produce dilute urine

Cannot make and retain urea and TMAO

As salinity increases, urea production and retention is increased, urea excretion is decreased, ion uptake is increased and ammonia excretion is decreased.

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What are the roles of the Rectal Gland in Marine Elasmobranchs?

NaCl regulation via an electrochemical gradient to export salt

Use of ATP to make urea, TMAO and excrete salt

What are the functions of gills in Marine Elasmobranchs?

Makes urea in the urea cycle

Retains urea

Contains an active sodium-potassium pump to excrete salt

Phospholipid head groups are altered to lower the permeability of the membrane

What are the functions of the kidney in Marine Elasmobranchs?

Countercurrent multiplier system

90-95% of urea is reabsorbed by facilitated diffusion

Contains a urea-sodium pump

High salinity increases the number of pumps present in the wall of the collecting duct

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What mechanisms are involved in endocrine regulation in Elasmobranchs?

Natriuretic peptide system increases urine production, stimulates salt secretion from the rectal gland, inhibits drinking and relaxes blood vessels.

Arginine Vasotocin increases plasma osmolarity and reduces urine production.

Renin-Angiotensin system is antagonistic to NP system, reduces urine flow, increases drinking and constricts blood vessels.

What are the metabolic costs of endocrine regulation in Elasmobranchs?

ATP is required to produce urea

Dietary protein is required

What is the function of Gill Chloride cells in marine Teleosts?

Gets rid of excess salt

Same function as the rectal gland of a shark

Contains a sodium-potassium pump

Contains mitochondria rich cells

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What are the functions of the two different types of Mitochondria Rich Cells?

A cells pump sodium ions out until their concentration is low enough for sodium ions to diffuse in again

B cells pump chloride ions into the cell with sodium ions using a co-transport protein

What hormones influence Freshwater organisms?

Cortisol and Prolactin

What hormones influence Marine organisms?

Cortisol and Growth Hormone

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How does the Stress Response occur in fish?

Adrenaline increases gill permeability and therefore increases the osmotic challenge.

Steps can be taken to reduce the impact, for example:

Adjust the environment to tend towards iso-osmotic conditions

Dilute seawater

Add solute to freshwater

What are the features of Marine Mammals?

They have no extra renal salt-excreting organs

They obtain their water from food (pre-formed water) or produce metabolic water.

They can be elasmobranchs or teleosts

They often lose water through respiration, lactation, excretion of urine and faeces

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How can Marine Mammals minimise their water loss?

Have a reniculate kidney rather than lobulate which increases the surface area of the medulla

What adaptations do Otariids (sea lions) and Phocids (true seals) have to maintain water balance during lactation?

Otariids continue feeding on hypotonic prey

Phocids fast instead of continuing with feeding, their milk composition changes, they increase the concentration of lipid and reduce the volume of water in the milk.

Both species also reduce respiratory losses by nasal turbinates and apnea

Some species have reduced/absent sweat glands

What is Endothermy?

An organism that relies on internal sources of heat.

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What is Ectothermy?

An organism that relies in external sources of heat.

What is Homeothermy?

Maintaining a constant temperature.

What is Poikilothermy?

Maintaining a variable temperature.

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What is Adaptation?

Evolutionary adjustment of morphology and physiology to changing environmental conditions. Natural selection adjusts the frequency of genes that code for traits affecting fitness.

What is Acclimatisation?

Based upon a range of physiological responses present in an organism. Phenotypic plasticity gives rise to short term changes in response to environmental disturbance.

What does an animal do when it's confronted with a change in its environment?

Avoid e.g. migrate

Conform e.g. hibernation

Regulate e.g. homeostasis

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What are four strategies used by cold-adapted ectotherms?

Anhydrobiosis - dehydrate themselves

Vitrification

Freeze tolerance - ECM freezes

Freeze avoidance

What is the Thermoneutral zone?

Where the basal metabolic rate is constant.

What responses are involved in sensing body temperature?

Metabolic rate

Behavioural e.g. avoidance, eating, huddling

Vasoconstriction

Vasodilation

Shunts

Sweating

Arrector pili muscle

Central and peripheral sensors lead to hypothalamus

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What is Thermogenesis?

Adapting to temperature changes

Often exercise induced - we get warmer the more we exercise

Often diet induced - we get warmer the more we eat

Shivering is essentially muscle contraction that generates heat

What is the importance of UCP-1?

The sympathetic nervous system activates Uncoupling Protein 1 via adrenaline signalling

UCP1 uncouples oxidative phosphorylation

Lipids are used in beta oxidation to power the electron transport chain

PKA breaks down the triglycerides and the fatty acids undergo beta oxidation

Alters gene expression in cells to make more UCP-1, heat, neoplasia and mitochondrial genesis

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What is Oxidative Phosphorylation?

The electron transport chain pumps protons across the outer mitochondrial membrane into the intermembrane space from the cytoplasm

This creates a voltage potential

Protons flow through ATPase to generate ATP

Energy can be converted into heat

What organisms use brown adipose tissue and UCP-1 to generate heat?

Mice, bats and potatoes use brown adipose or UCP-1 whereas pigs cannot because they have a deletion in the UCP-1 gene.

What is the Brown Adipose Tissue recruitment diet?

High fat

Low protein

High carbohydrate

Induces obesity

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Who is likely to have Brown Adipose Tissue?

Some adult humans have BAT

It is used to detect fast growing tumours via radioactive glucose

The younger you are, the more likely you are to have BAT

Women are more likely to have BAT than men

More overweight people are less likely to have BAT

Neonates have well developed BAT

BAT is cold responsive so uses more glucose

What is Dinitrophenol?

2,4-DNP carries protons across the inner mitochondrial membrane

Uncouples oxidative phosphorylation

The proton motive force is dissipated

Increases oxygen and NADH consumption

Herbicides often contain 2,4-DNP to kill and stop production of ATP

Caused fevers and weight loss in women manufacturing explosives in WW1 which damaged the kidneys, caused malignant hyperthermia and death.

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What are the different types of fins?

First dorsal fin

Second dorsal fin

Finlets

Caudal fin

Anal fin

Pelvic fin and Pectoral fin are paired (phylogenetic source of tetrapod limbs)

What are the functions of fins?

Stability - streamlining, prevent pitch, roll and yaw

Braking - by paired fins

Steering - rudders control direction of movement

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What is the general structure of fins in modern fishes?

Basal pterygiophores are three large elements that articulate the fin to the pelvic (where the leg connects) or pectoral (where the arm connects) girale

Radial pterygiophores are smaller more distal elements

Dermal fin rays are slender rods which are keratinised in elasmobranchs or ossified or chondrified in bony fishes

What are the types of paired fins?

Ray fins - very flexible with a thin base

Fin Fold Fins - very broad based

Lobed fins - fleshy muscular lobe at base to make them more flexible

What are Lobe-finned fish?

Belong to the class sarcopterygii

Includes Coelacanth and six species of lungfish

They have a central appendage in their fins containing many bones and muscles

The fins are flexible and potentially useful for supporting the body on land

Lobed fins are a precursor to the tetrapod limb

The fins are connected to the girdles by a continuous chain of bones that are homologous to tetrapod limbs

Sarcopterygii are divided into two groups: Coelacanths and the lungfishes

They have lobed pectoral and pelvic fins

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How is Forward Propulsion achieved in fish?

Lateral flexion of the vertebrate caused by axial musculature results in lateral undulations (body moves from side to side)

The movement of the tail exerts a forward and lateral force against the resistance of water

The forward component of resistance propels fish forward

The lateral component tends to make the body of the fish move sideways but this is manufactured by the fact that the body is large and its inertia is more difficult to overcome

Horizontally held fins provide lift

Vertically held fins provide thrust

What adaptations of fish could lead to terrestrial locomotion?

Lateral undulations of fish lead to the possibility of getting onto land

The muscles of primitive crosspterygians were too weak to support the body out of water due to no buoyancy however, the slight musculature was sufficient to fix the fins on the body line 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 to move the buoyant body

Some trunk undulations in swimming could be used for short journeys across land

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What is the evolution of limbs from fins?

It is generally accepted that early tetrapod limbs evolved from lobe-finned coelacanths due to similarities between their appendicular skeletons.

What are features of early Tetrapods?

Short limbs

First segment almost horizontal

Second segment perpendicular to first

Toes tend to point laterally

What are features of Terrestrial Locomotion?

Lifting of limb introduced axial torque of vertebral column

Primitive gait

Extra stability gained by: buoyancy, tail on ground and belly walking

Lateral sequence gait also increases stability

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What are the features of inefficient locomotion?

Sprawled posture

Body weight supported by adductor muscles

Overarm swing with each step

How is the efficiency of locomotion improved?

Limbs are drawn under the body

Change in limb posture

Bipedalism

Four-footed gait

What is Bipedalism?

Hind limbs are strengthened and lengthened

Knees are rotated anteriorly to a position beneath the body

Front legs are hardly modified (initially)

Seen in dinosaurs and birds

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What is a Four-footed gait?

Characteristic of mammals

Knees are rotated anteriorly

Elbow is rotated posteriorly and brought closer to the body

What are the advantages of changed limb posture?

Body weight is supported by rigid bones which leads to decreased energy expenditure

Increased efficiency of limb swing

Change in flexion of vertebral column from lateral flexion to vertical flexion which increases the stride length

What is Cursorial locomotion?

Fast running e.g. cheetah.

Running is mainly about speed

A full cycle of running/walking is called a stride.

The faster the rate of limb oscillation, the faster the animal travels - the rate of stride

Speed = length of stride x rate of stride

Rate and length are antagonistic

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What is Fossorial locomotion?

Digging e.g. rabbits

What is Saltatorial locomotion?

Hopping e.g. kangaroo

What is Arboreal locomotion?

Locomotion of an organism who lives in the trees.

Scansorial involves climbing with claws e.g. squirrels.

Brachiation involves hand gripping branch and swinging beneath e.g. monkeys.

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What methods of locomotion do not involve limbs?

Lateral undulation

Rectilinear

Concertina

Sidewinder

What is Lateral Undulation?

Large dorsal muscles are activated sequentially along the body (unilaterally).

What is Rectilinear?

Straight line movement

Belly scales are alternately lifted slightly from the ground and pulled forward, downward then backward

Occurs in large snakes

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What is Concertina locomotion?

Alternately pulling the body into bends and then straightening the body out forward from the bends.

What is Sidewinder locomotion?

Muscle activity during sidewinding is similar to that in lateral undulation except that some muscles are also active bilaterally in regions of trunk lifting.

What are Fossorial adaptations for digging/burrowing?

Fusiform body

Reduction of tail

Loss of eyes

Disappearance of ears of pinnae

Digging mechanisms: fore limbs, short and stout build, long claws suitable for loosening the earth, foot serves to drive the creature ahead and to resist the backward thrust received from the hands.

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What are the features of movement on land?

Propulsion with limbs

Exert forces on ground

The human skeleton is not a good design for movement over uneven terrain

How is the length of a stride increased?

Lengthen the limb

Lengthen distal limb elements - highly cursorial

Radius and tibia usually longer than proximal segment

Light and slim body

Tendon rather than muscles

Change in foot posture from plantigrade to unguligrade

Highly mobile shoulders

Absent or reduced clavicle

Scapula more mobile

Scapular re-orientated to the side so as to rotate in the same plane as the limb

Flexibility of the spine

Increased back flexion and extension

Increased rotation of girdles

Increase swing of legs

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How is the rate of stride increased?

Larger and more efficient muscles

Shorter limbs

What are the two insertions which determine strength and speed?

Proximal insertion determines speed. The moving part swings through a large distance.

Distal insertion determines strength. The moving part swings through a small distance.

Reducing the weight of the distal end of the limb decreases the inertia that must be overcome. A reduced muscle mass and reduced digits provides easier and more efficient movement with decreased energy expenditure.

Describe various mammals with different numbers of digits.

Rodents, rabbits and carnivores all walk on four digits.

Rhinos and tapirs have three digits

Pigs, sheep and camels have two digits

Primitive horses have four digits but the modern horse has one

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What is the Gait?

The pattern of foot falls

A regularly repeated sequence

Includes: walk, amble, trot, pace, canter, etc.

What is a Walk?

Four independent footfalls

Three point support

Footfall sequence is: R hind, R front, L hind, L front, Repeat

What is an Amble?

A sped-up walk

Transitional between a walk and a trot

This is what animals do when constrained to walking but they want to move fast

This is what animals do when they are very large and cannot trot

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What is a Trot?

A two-beat gait

Two point support

Right and left diagonals alternate in supporting weight

Usually in animals with a broader body e.g. horse

What is a Pace?

A two-beat gait

Two point support

The two lateral limbs are used alternately for weight support

Seen in long-legged animals

E.g. camel or giraffe

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What is a Gallop?

A four-beat gait

The fastest gait

Has a period of suspension when the legs are gathered under the animal, the legs are stretched out fore and hind or both

What is an Equine Transverse Gallop?

A horse derives momentum and speed mostly from its hind limbs

Cheetah derives momentum and speed mostly by its forelimbs

What is a Pronk?

All four feet on the ground simultaneously

Has a period of suspension

Abruptly jars and decelerates the animal

Great four-footed stability

Social display of defensive behaviour

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Describe Human Locomotion.

Bipedalism

Walk to a run

Upright posture is very unstable

There are only two supports

A large part of the body weight is about the centre of gravity

How is posture improved in humans?

The front of the body is lifted 30 degrees

The upper part of the pelvis is tilted back; rotating the vertebral column another 30 degrees

Lumbar region of vertebral column curves the last 30 degrees

What is Lordosis of the spine?

Exaggerated lumbar curve

Arched lower back

Lower back pain

Pelvis tilts forward

Weak buttock muscles

Bottom sticking out

Hard to stand up straight

Front of hips are tight