7.19 Comparative Anatomy & Physiology 2

Thirty question-and-answer flashcards reviewing key concepts of osmoregulation, excretory organs, nitrogenous wastes, and digestive system structure and adaptations.

What is osmoregulation in animals?

The process of maintaining internal water and salt balance so that body fluids remain isotonic to cells.

Why must animal cells remain in an isotonic environment?

To prevent swelling or shrinking that would disrupt cell shape and function.

Around what osmolarity are vertebrate extracellular fluids kept?

Approximately 300 milliosmoles (mOsm).

In a hypotonic environment, what happens to water movement and the cell?

Water moves into the cell, causing it to swell or possibly burst.

How do freshwater fish maintain osmotic balance?

They produce large amounts of dilute urine and actively pump salts into their bodies via the gills.

State two osmoregulatory adaptations of marine (saltwater) fish.

They drink seawater, excrete salts out through the gills, and produce smaller volumes of isotonic urine.

How do terrestrial vertebrates offset water loss to evaporation?

Using keratinized skin, obtaining water in the diet, and adjusting urine volume/concentration through the kidneys.

What structures allow marine birds and reptiles to excrete excess salt?

Specialized salt glands near the eyes or nasal cavity that actively pump out electrolytes.

List the four key processes occurring in a nephron.

Filtration, reabsorption, secretion, and excretion.

Which excretory structures are characteristic of flatworms?

Flame cells.

Define nitrogenous waste.

Nitrogen-containing metabolic waste produced mainly from protein and nucleic-acid catabolism.

Why is ammonia typically excreted directly by aquatic animals?

It is highly toxic but very water-soluble, and the surrounding water immediately dilutes it.

Into which compound do mammals convert ammonia, and why?

Urea; it is less toxic than ammonia and needs less water to eliminate.

Which animals convert ammonia into uric acid, and what is the advantage?

Birds, reptiles, and insects; uric acid is insoluble and can be excreted as a semi-solid paste, conserving water.

What is the energetic trade-off for producing urea or uric acid?

Both conversions require additional metabolic energy compared with excreting ammonia directly.

Name the three primary functions of all digestive systems.

Digestion of macromolecules, absorption of nutrients, and elimination of indigestible wastes.

Differentiate between incomplete and complete digestive systems.

Incomplete systems have one opening serving as both mouth and anus; complete systems (alimentary canals) have separate mouth and anus openings.

Give two animal groups possessing incomplete digestive systems.

Cnidarians and flatworms.

What structures increase surface area in the vertebrate small intestine?

Folds called villi and microscopic projections called microvilli.

How are carnivore and herbivore teeth specialized for diet?

Carnivores have large, sharp canines for tearing flesh; herbivores have broad molars for grinding plant material.

What do birds possess instead of teeth to handle diverse diets?

Beaks whose shapes are adapted to specific food sources.

What is the function of the rumen in ruminant mammals?

It houses large microbial populations that ferment cellulose from plant material.

What behavioral adaptation helps rabbits extract maximum nutrients from fiber?

Coprophagy—re-ingesting their feces to further digest plant material.

Describe the cecum and its size in herbivores versus carnivores.

A pouch off the large intestine that contains cellulose-fermenting microbes; it is large in herbivores and small in carnivores/omnivores.

Define a milliosmole (mOsm).

A unit expressing the number of milliequivalents of solute per kilogram of solvent, accounting for electrolyte dissociation.

Why do marine fish drink seawater?

To replace water lost osmotically to their hypertonic environment.

Which hormone allows the human kidney to vary urine concentration from ~100 to 1,200 mOsm?

Antidiuretic hormone (ADH).

How do marine iguanas rid themselves of excess salt?

They excrete concentrated salt from nasal salt glands and often "sneeze" it out.

Define an alimentary canal.

A complete digestive tract with two separate openings—mouth for ingestion and anus for egestion.

What are salt glands in marine birds?

Specialized exocrine glands near the eyes or nostrils that excrete hyper-saline solutions to remove excess salt from the bloodstream.