ZOO Chapter 11

Living on Land

tetrapods evolved features that function on land, where water is more scarce and the body must move and be supported without the buoyancy and density of water.

Bones, muscles,

kidneys, lungs,

cardiovascular

system, sensory

systems,

reproductive system

are all modified.

Sarcopterygian fishes characteristics

Epaxial muscles

Hypaxial muscles- Internal and external oblique

Basal amniotes characteristics

Epaxial muscles- Transversospinalis, Longissimus, Iliocostalis

Hypaxial muscles- Subvertebralis, Transversus/ Recus abdominus, Internal/ External oblique

Structure of bone and joints

Bone is a composite material with mineral crystals of hydroxyapatite that resist compression and collagen fibers that resist tension. Calcium, a metal, is a major component.

resist compression

mineral crystals of hydroxyapatite

resist tension

Collagen fibers

The _________ resists compression and the pull of gravity

vertebral column

appeared in early tetrapods, and link neighboring vertebrae, allowing the vertebral column to resist vertical loading from gravity.

Zygapophyses- Pre and Post

the __________ (inferior process) of the higher vertebra fits onto the ___________ (superior process) of the lower vertebra.

postzygapophysis; prezygapophysis

Tetrapod forelimb is derived from _________ bones of the fin, while the pectoral girdle is derived from _______ bones of the head/operculum.

endochondral; dermal

Evolution of the neck of tetrapods- Clavicle, Humerus, Cleithrum

A) Eusthenopteron- retains a rigid, fish-like arrangement where the clavicle and cleithrum (dermal bones of the shoulder girdle) are firmly sutured to the posttemporal and supracleithrum bones of the skull. The humerus (endochondral bone) articulates with the scapulocoracoid inside this anchored girdle.

B) Tikaalik- humerus became larger, flattened, and more robust to support weight and push off the substrate

C) Acanthostega- clear gap between the skull and the cleithrum confirms a well-defined neck region.

D) Proterogyrinus- As an advanced, highly mobile stem tetrapod capable of terrestrial locomotion, its clavicle is reduced and refined, while the humerus is exceptionally robust with complex muscle attachments to lift the chest off the ground.

Clavicle

Dermal bones of shoulder girdle

Cleithrum

(Dermal bones of shoulder girdle)

Humerus

(Endochondral bone)

are more elaborated in tetrapods as compared with fishes,

forming familiar muscles, e.g. biceps, pectoralis.

muscles of the pectoral girdle

-This allows greater range of motion and force production to lift and propel the body.

Muscles of pectoral girdle tetrapods

Triceps brachii, Biceps Brachii, Pectoralis

Tetrapod skeleton can be divided into

axial (cranium, vertebrae, ribs) and appendicular (girdles and limbs).

axial skeleton

skull, vertebral column, ribs, and sternum- forms the long axis of the body

appendicular skeleton

Bones of the pectoral girdle, pelvic girdle, and limbs are the appendicular skeleton.

allow movement of the head relative to the trunk. In

extant tetrapods, the first cervical vertebra is the atlas, which allows the

nodding movement, as in “yes”. In amniotes, the second cervical vertebra,

the axis, rotates on the atlas, allowing shaking the head, as in “no”.

Cervical vertebrae

often bear ribs. In mammals, ____ vertebrae are

thoracic vertebrae with ribs and lumbar vertebrae without ribs.

Trunk vertebrae

In mammals, trunk vertebrae are

_______ vertebrae with ribs and _______ vertebrae without ribs.

thoracic; lumbar

articulate tightly with the pelvic girdle in tetrapods and

allow the hindlimbs to transfer force to the axial skeleton. These are often

fused together, as in humans.

Sacral vertebrae

support the tail and are usually structurally simpler

than trunk vertebrae.

Caudal vertebrae

are paired, curved bones that extend from vertebrae and support and

enclose the body cavity and function in ventilation. In mammals, ribs

enclose just the thoracic cavity.

Ribs

or breastbone, is a midventral endochondral element found

only in tetrapods.

sternum

Different stances are associated with differences in sizes of arm muscles and regions of the pectoral girdle, as well as different forms of locomotion.

Sprawling- ‘basal’ amniote

Upright/ Parasagittal- therian mammal, such as opossum

Early tetrapod locomotion in a modern analogue, the salamander

bondy bends to right; left hindlimb and right forelimb move together.

Supporting feet are those that stay on the ground while the other two feet move. Right front/ left back or Left front/ right back

Elephants always have

at least one foot on the ground when locomoting.

Archosaurs may have been _______ ancestrally.

bipedal

_______________ has evolved many times, but never in

birds or mammals.

Limbless locomotion

Ricochetal locomotion

kangaroo

Upright bipedal striding

humans

Bipedal running

some lizards

Jumping locomotion

anurans

Bipedal ancestry

is evident in the limb proportions of sauropod

Elephants, sauropods, and other large tetrapods with column-like leg posture are considered

graviportal.

This posture requires less relative muscle force to support body weight.

Joints in the elephant leg are _______ to the axis of support than they are in the cat leg.

closer

Scaling Principles:

length, area and volume grow at different rates, even if shape is the same.

Doubling the length of a cube increases the area by four times and the volume by eight times. Why does this matter to animals?

Body mass is proportional to volume, while muscle and bone

strength is proportional to area (cross section).

Body size influences the locomotor gait.

Larger mammals stagger their footfalls (gallop) while small mammals often pair them (bound)

Body size also affects the function of the axial skeleton in locomotion.

Larger mammals have less flexibility of the spine.

Cheetahs and other fast mammals (e.g. greyhounds) have two aerial suspension phases

one with gathered limbs and one with extended limbs.

Horses only have limbs tucked when airborne.

They are never airborne while their legs are extended. When a horse extends its limbs, it is firmly planted on the ground, actively pushing off. The moment it launches into flight, its legs immediately tuck inward

Mammals and archosaurs have a completely divided heart and

two circuits:

a high-pressure systemic circuit and low-pressure pulmonary circuit.

High pressure in the lung would be bad,

causing blood plasma to enter the alveoli via ultrafiltration.

have a single circuit and undivided heart and relatively low blood pressure.

fishes

The heart and aortic arches in jawed fishes and lungfishes

Fishes have a single circuit and undivided heart and relatively low blood pressure.

Lungs, when present, inject oxygen into the circulation before the heart.

Gills inject oxygen into the system after the heart.

The lung is modified into a swim bladder and does not function in respiration in

many bony fishes.

have a single circuit, incompletely divided heart and low blood pressure.

Lissamphibians

The heart and aortic arches in Lissamphibians

Lissamphibians have a single circuit, incompletely divided heart and low blood pressure.

Lungs inject oxygen into the left heart, and the skin provides oxygen to the right heart.

Some mixing of blood occurs in the conus arteriosus as blood leaves the heart.

have an incompletely divided heart and some mixing of oxygenated and deoxygenated blood as it leaves the heart.

Amniotes, such as lizards

why your vision is (more) blurry under water.

Focusing of images takes place in different parts

of the eye in water vs air.

focusing takes place in the lens, which is often spherical and

moved back and forth to focus the image on the retina.

In water

focusing takes place mainly in the cornea, and the lens can fine

tune the image by changing shape

in air

convert incoming light into electrical nerve signals and transmit them to the brain so you can see

retina

How does LASIK laser vision correction work?

corrects blurry vision by using precision lasers to permanently reshape the cornea—the clear, dome-shaped outer window of the eye—so that light rays focus sharply onto the retina at the back of the eye

Thermoregulation is more challenging in air vs water because

air is less conductive to heat, so temperature can vary spatially.

Heat can be transferred to and from an animal by four mechanisms.

Convection, Conduction, Evaporation, Radiation

Convection

is bulk movement of a fluid such as air or water, which can carry heat. Wind chill is the removal of heat from your body by convection of air, and why a fan can cool you.

Radiation

is transfer of heat by infrared rays, such as from the sun, a warm rock or body nearby, or a campfire.

Conduction

is direct heat transfer by contact between two objects, such as a lizard sitting on a warm rock. If you touch a hot object, heat flows into you, but if you touch a cold object, heat flows out of you.

Evaporation and condensation

causes heat to be transferred when the heat energy causes a liquid such as water to change phases. We lose heat through evaporation as water in our lungs takes energy from our body to change from liquid to gaseous phase, or from our skin when we sweat. Your bathroom mirror gains heat from the humid air as condensation forms.