Comparative anatomy Exam 3 (new material) review

Provide 3 functions of the muscular system

• Movement of the body and internal organs

• Maintenance of posture

• Heat production through muscle contraction

What mechanism drives the aspiratory ventilation in
most amniotes? What group does not possess this
mechanism of ventilation and why?

• Most amniotes use aspiratory ventilation, which involves expanding the thoracic cavity (using ribs and/or diaphragm) to draw air into the lungs via negative pressure.

• Amphibians lack this mechanism; they use buccal pumping, which is less efficient and relies on positive pressure generated by the mouth

Briefly define evolution

Evolution is the change in allele frequencies in a population over time, leading to descent with modification.

Provide 2 groups which possess both the right and
left systemic arches?

• Amphibians

• Reptiles (excluding birds and some derived lineages)

What are the two functions of the urinary system
of vertebrates?

• Removal of nitrogenous wastes from the body

• Regulation of water and electrolyte balance

Provide 2 modifications to the axial skeleton found
in tetrapods that aid in the transition from aquatic
to more terrestrial lifestyles.

• Development of a stronger vertebral column to support body weight out of water

• Presence of a neck (cervical vertebrae) to allow head movement independent of the body

How does the respiratory system of mammals differ
from the remaining amniotes and why is this a
more efficient form of respiration than the
plesiomorphic condition of amniotes?

• Mammals use a diaphragm to create negative pressure for ventilation.

• They also have alveolar lungs with a vast surface area for gas exchange.

• This is more efficient than the faveolar lungs seen in other amniotes (like reptiles) because alveoli increase the surface area and reduce diffusion distance.

Provide 2 types of osmoregulation in vertebrates
and a group which possesses that type of
osmoregulation

• Osmoconformers: Maintain internal conditions similar to the environment (e.g., marine hagfish).

• Osmoregulators: Actively regulate internal salt and water levels (e.g., freshwater teleosts).

What are the three components of the
cardiovascular system in vertebrates?

• Heart (pump)

• Blood vessels (tubing)

• Blood (carriers)

Provide 3 types of connective tissue we talked
about this semester.

• Cartilage

• Bone

• Adipose tissue

Briefly explain ventilation via the buccal pump and
why it is not as efficient as the other two methods of
ventilation.

• The buccal pump involves the animal forcing air into the lungs using muscular movements of the mouth.

• It is less efficient because it doesn’t fully empty the lungs and relies on positive pressure, limiting gas exchange compared to negative pressure breathing (aspiratory).

Provide two trends of the muscular system
observed in the evolutionary history of vertebrates

• Increase in muscle specialization and complexity

• Transition from segmental muscles to more regional, function-specific muscles

What are 3 synapomorphies of amniotes?

• Amniotic egg with specialized membranes (amnion, chorion, allantois)

• Keratinized skin that reduces water loss

• Costal (rib-based) ventilation of the lungs

In which group of vertebrates do we first see a
complete separation of the atrium into right and
left chambers? Provide the same for the ventricle?

• Amphibians show partial separation, but reptiles (e.g., turtles and lizards) begin to show a more complete division.

• Crocodilians, birds, and mammals have a completely divided atrium and ventricle.

A connection between the nasal opening and the
pharynx is a synapomorphy of which two groups of
vertebrates?

The connection between the nasal cavity and pharynx (internal nares or choanae) is a synapomorphy of:

• Rhipidistians (a group of lobe-finned fishes)

• Tetrapods

What is a secondary palate? Provide a group which
possesses a secondary palate

• A secondary palate separates the nasal and oral cavities, allowing breathing while chewing.

• Found in mammals and crocodilians

What are the 3 different types of blood vessels in
vertebrates?

• Arteries (carry blood away from the heart)

• Veins (carry blood to the heart)

• Capillaries (site of gas and nutrient exchange)

Provide 2 trends in the evolution of the muscular
system of vertebrates

• Increased regionalization of muscles

• Shift from myomeric segmentation to more individualized muscles

Provide 2 bones in the jaws of fishes that become
incorporated into the middle ear. Also, provide
their homologous counterpart in the middle ear

• Hyomandibula → Stapes (columella)

• Quadrate and Articular → Incus and Malleus, respectively (in mammals)

What are Darwin’s 4 postulates?

• Individuals in a population vary.

• Variation is heritable.

• More offspring are produced than can survive (struggle for existence).

• Individuals with advantageous traits are more likely to survive and reproduce

What is the plesiomorphic condition of the aortic
arches and heart in Gnathostomes?

• Six pairs of aortic arches

• Single-circuit heart (sinus venosus → atrium → ventricle → conus arteriosus)

What is the major organ and structural unit of the
urinary system?

• Kidney is the major organ.

• Nephron is the functional unit.

What are two characteristics of Chondrichthyes?

• Skeleton made of cartilage

• Possession of placoid scales and internal fertilization

Briefly define agonist and fixator as they relate to
the classification of muscles.

• Agonist: Primary muscle responsible for a movement.

• Fixator: Stabilizes the origin of the agonist to ensure efficient movement.

What aortic arches are homologous to the
pulmonary, right systemic and left systemic arteries
in Sauropsids?

• Arch VI → Pulmonary arteries

• Arch IV (right) → Right systemic arch

• Arch IV (left) → Left systemic arch (may be reduced or lost in birds)

What are the 3 phyla that make up the
“protochordates”?

• Hemichordata

• Cephalochordata

• Urochordata

Compare and contrast osmoconformers and
osmoregulators in general. (1 similarity and 1
difference)

• Similarity: Both regulate internal fluid environments in response to external changes.

• Difference: Osmoconformers match their body fluids to the environment (e.g., marine invertebrates), while osmoregulators maintain internal conditions regardless of external salinity (e.g., freshwater fish)

Provide 4 synapomorphies of mammals

• Hair

• Mammary glands

• Three middle ear bones

• Neocortex in the brain

Explain the complete circulation of blood flow
through the cardiovascular system in mammals,
i.e., which chambers and organs it flows through in
which order.

• Body →

• Vena cava →

• Right atrium →

• Right ventricle →

• Pulmonary arteries →

• Lungs →

• Pulmonary veins →

• Left atrium →

• Left ventricle →

• Aorta →

• Body

The nephron is the functional unit of the kidney.
Provide the two major components of a nephron
and their subcomponents.

• Renal corpuscle

  • Glomerulus

  • Bowman’s capsule

• Renal tubule

  • Proximal tubule

  • Loop of Henle

  • Distal tubule

  • Collecting duct

Provide two types of kidneys found in vertebrates
and how do they differ from one another?

• Opisthonephros (found in fish and amphibians; extends along much of the body)

• Metanephros (found in amniotes; more compact and located toward the rear

How do the aortic arches of mammals and birds
differ?

• Birds: Only the right systemic arch remains.

• Mammals: Only the left systemic arch remains

What are the 5 chordate characteristics?

• Notochord

• Dorsal hollow nerve cord

• Pharyngeal slits

• Post-anal tail

• Endostyle or thyroid gland

What are the three types of muscle tissues and
how can they be distinguished histologically?

• Skeletal muscle: Striated, multinucleated, voluntary control

• Cardiac muscle: Striated, branched, single nucleus, intercalated discs, involuntary

• Smooth muscle: Non-striated, spindle-shaped, single nucleus, involuntary

What would happen to a freshwater teleost (hyper-
osmoregulator) if it were to be placed in saltwater?
Explain why

• It would lose water and gain salts via osmosis and diffusion.

• This could lead to dehydration and ion imbalance, potentially fatal without regulatory mechanisms.

What are the two types of temporal fenestration
observed in vertebrates and which two groups
possess them?

• Synapsid (one temporal fenestra): Mammals

• Diapsid (two temporal fenestrae): Reptiles, including birds

What is unique about the respiratory system of
archosaurs and how could this have helped them to
become the dominant lineage of vertebrates on the
planet during the Mesozoic Era?

• Unidirectional airflow using air sacs (also in birds)

• Allows continuous oxygenation even during exhalation — very efficient, supporting high activity and likely contributing to their Mesozoic dominance

Provide 3 of the 5 stages of embryonic
development?

• Cleavage

• Gastrulation

• Neurulation
  (also: organogenesis and growth)

Provide the three ways in which vertebrates
remove nitrogenous waste and a group that is
capable of each

• Ammonotelic (ammonia): Fish

• Ureotelic (urea): Amphibians and mammals

• Uricotelic (uric acid): Reptiles and birds

Provide the 3 functions of the circulatory system in
vertebrates.

• Transport of gases, nutrients, hormones

• Protection (immune cells and clotting)

• Regulation of temperature and pH

What are characteristics of amphibian integument
that facilitates cutaneous respiration?

Thin skin, highly vascularized, often covered in mucus to maintain moisture — all facilitate gas exchange

What is the difference between the jaws of
Chondrichthyes and osteichthyes?

• Chondrichthyes: Cartilaginous jaws, often protrusible, supported by hyomandibula

• Osteichthyes: Bony jaws, usually more rigid, complex with many bones

What is the difference between red and white
muscle in vertebrates and why is this classification
not the best way to classify muscles?

• Red muscle: High myoglobin, slow-twitch, endurance

• White muscle: Low myoglobin, fast-twitch, quick bursts

• Classification is incomplete — muscle function varies by more than just colo

Lungfishes, Squamates/Turtles and Crocodilians all
have unique modifications to the heart and aortic
arches. Choose one of these groups and describe
the modifications that they possess

• Four-chambered heart with foramen of Panizza connecting left and right aortic arches

• Allows shunting of blood depending on whether the animal is diving or on land

What are the two functions of the gas bladder of
Osteichthyes and which one is likely to be
plesiomorphic? Explain why

• Buoyancy control

• Respiration (lung-like function)

• Respiration is likely plesiomorphic, as seen in primitive forms and lungfish — gas bladder derived from ancestral lung