Endotherms 7-8

Question 1

What are the three functions of a skeleton?

Answer 1

Support (providing a framework to maintain shape as well as respiration)
Attachment of things such as muscles
Movement by providing a rigid objects for muscles to work against

Question 2

What are the three types of skeleton?

Answer 2

Hydrostatic, exoskeletons and endoskeletons

Question 3

What are the features of the vertebrate skeleton?

Answer 3

This consists of fused and free bones with there being more than 200 in mammals
Split into two parts the axial part which contains the skull, vertebral column and ribs
And the appendicular part which contains limbs, pelvic and pectoral
The majority of the muscle load (ability to resist gravity) in terrestrial birds and mammals is carried by muscles and tendons rather than the skeleton

Question 4

How do modes of locomotion depend on the environment?

Answer 4

In the water, swimming requires movement through a dense medium which requires energy to move through but provides resistance and has less gravitational effect terrestrial
Air has a high gravity energy cost but there is almost no friction
In terrestrial forms of movement the effect of gravity is large and there is moderate friction

Question 5

What are the different forms of joints?

Answer 5

These are immovable joints which are sutures found in the bones of the skull
Slightly movable joints where the bones are bridged by cartilage such as in the spine
Freely movable joints like synovial joints where the ends are capped with cartilage and strengthened by ligaments
The movement is dictated by the structure of the joint

Question 6

What are the actions of the skeletal muscles?

Answer 6

They will produce movement of the skeleton when they act and attach via tendons at the origin and insertion with the insertion being the bit that moves during contraction
There are synergists and antagonists as well as flexors and extensors
There is also different forms of contraction including isotonic (muscle shortens when applying force), isometric (muscle acts but does not shorten) and eccentric contractions where the muscle lengthens under load

Question 7

When has flight evolved?

Answer 7

It has evolved independently four times in pterosaurs, insects, birds and bats
The form of birds is variable but more uniform than mammals showing how the form is limited by retaining the ability to fly

Question 8

What are the four key characteristics of birds linked to their ability to fly?

Answer 8

Rigidity (lots of bone fusion), reduction (loss of weight), redistribution of weight and limb modifications for flight

Question 9

What are the features of the avian skeleton?

Answer 9

Not lighter in relation to body mass than similar sized mammal but different weight distribution
Bones are filled with air (pneumaticity) and the skull is light, leg bones are heavier than mammals so more mass is found in the hind-limb area
Power-output per unit mass of pectoral muscles is 10-20 times more than that of most muscles
Extensive fusion of the skeleton to strength and rigidity, pelvis is fused to form strong attachment for the legs
Thoracic vertebrae tightly bound together to resist twisting and bending during flight
Lateral braces on ribs for extra support
Large keel like sternum for attachment of large flight muscles

Question 10

What is the wing structure of birds?

Answer 10

Bones of the hands are fused and there is a large amount of pneumaticity

Question 11

Where do the feathers in birds come from?

Answer 11

These develop from pits and follicles in the skin and arranged in tracts called pterylae
These are species such as penguins and ratites have lost these however

Question 12

What are the different types of contour feathers found in birds?

Answer 12

Contour feather which can be divided into secondary feathers which are close into the body, control wing shape and generate lift as well as primary/hand feathers which are towards the end of the wing and are for power generation
These feathers are linked together which is important for maintaining shape so the wing is capable of generating lift

Question 13

What are the five types of feathers found in birds?

Answer 13

Contour feathers which are for body and flight
Semiplumes which are for thermal insulation
Down which is for insulation
Bristles which are tactile filters around the bill and eyes
Filoplumes which are sensory to help keep contour feathers in place

Question 14

What are the anatomical features of a feather?

Answer 14

There are the rachius which is the central “stalk” of the feather, projecting out from this stalk there is the vanes and at the end of the feather where it inserts into the body we see the calamus

Question 15

What are the features of bat flight?

Answer 15

The trunk is rigid through vertebral fusion however when they are not fused they have limited mobility and the bones are not hollow
The pelvis is fused and the shoulder girdle is more complex than in birds allowing them to have 3 facets so 17 flight muscles rather than just two can be attached as well as not having their hand bones fused
There is a variable sternal ridge with the muscles being supported by ligamentous sheet for attachment of flight muscles

Question 16

What are the adaptations for flight seen in the bat?

Answer 16

There is a wing camber with an increased camber increasing lift
There are wing flaps which can allow adjustment of leading edge of the wing bats can increase lift during slow flight
They have energy saving elastic with elastin in wing stores kinetic energy from up/downstroke allows efficient change in direction allowing a 56% saving on energy

Question 17

What are the different types of swimming mammals?

Answer 17

Semiaquatic mammals have evolved several times and use paraxial swimming or doggy paddling this is highly inefficient due to high drag and low power
Fully aquatic mammals have only evolved twice in the cetacean and sirenia these use axial swimming which is dorso-ventral flexion as opposed to lateral flexing seen in reptiles and fish

Question 18

What is pinniped use in swim?

Answer 18

This is where the limbs are used for swimming, there are pectoral oscillations where the forelimbs are used for power while the hindlimbs are used for direction
There may be pelvic oscillation where the hindlimb and forelimb are used

Question 19

How do the cetacean and sirnenians swim?

Answer 19

They use a modification of the flexion of the vertebral column used by terrestrial mammals this is a energetically costly system though not as much as the energetic cost of pinniped swimming

Question 20

What are the problems of terrestrial locomotion?

Answer 20

There is a lower drag or friction but there is a need for support so energy must be expended both moving and resisting gravity

Question 21

What are the basic modes of mammalian locomotion?

Answer 21

Bounding and scrambling this is dependent on the flexed spine and limbs and involves key articulations at the shoulder and hip

Question 22

What is cursorial movement?

Answer 22

This is running and is about speed which is achieved through either stride length or stride rate there are mutually exclusive due to the outlever arm principal the balance of other factors will determine the balance of stride rate and stride length

Question 23

What are the features of forelimbs?

Answer 23

These carry 60% of static body weight catching the weight as it is thrown forward by the pelvic limbs
They can improve gait efficiency by storing it as potential energy in stretched ligaments
The anatomical features of forelimbs include being shorter and straighter than the pelvic limbs, connected to the trunk only by muscle and ligamentation they also commonly have a broader more rounded hoof

Question 24

What are the features of the hind limbs?

Answer 24

These are the motors of locomotion which drive the trunk forward and propel the body up/over obstacles during limbs
Anatomical features of these include being longer and more angular than the forelimb and having a narrower more pointed hoof

Question 25

What are the locomotive features of the horse?

Answer 25

There is extreme elongation of the lower portion of the limbs not the upper
There is a less flexible vertebral column, muscles are limited to the proximal part of the limb to reduce weight end of lever
Force of muscles transmitted through long tendons
Ligaments and the hoof can store potential energy during change in gate phase

Question 26

What are the adaptions for locomotion seen in carnivores?

Answer 26

These require a multipurpose limb required for both running and manipulation
There is a reduction in the number of toes but they are not fused
There are shorter legs but increased stride frequency
There is a flexible trunk

Question 27

What is fossorial locomotion?

Answer 27

These are diggers of tunnelers which have elongated bodies and short limbs the limbs are optimised for power with the limb anatomy depending on the type of digger
All 5 digits are retained
There are stout claws
Large projections on limb bones for muscle attachment
Strengthened pelvis for bracing while digging