Question

If humans had evolved to live in an aquatic freshwater environment rather than evolving to live in terrestrial environments, what evolutionary adaptions would be necessary to maintain water and salt balances, and how would the osmoregulatory and excretory systems have to change?

Write a brief description of the osmoregulatory and excretory systems of a human that adapted for an aquatic freshwater environment, and why it would look the way it does. Consider the following:

• What would be required to maintain water and salt balances, and how the osmoregulatory and excretory systems would have to change to compensate? You are encouraged to look up other (non-human; can be non-mammalian) animals that share these habitats for ideas.
• What if humans had evolved and were adapted to live in very specific habitats? In other words, it would still look *basically* like a human but would have some important differences related to its circulatory and/or breathing systems.
• What would these systems of a human that adapted to a different environment look like, and why would it look like this?
• You should consider the following parts and functions of the osmoregulatory and excretory system in your answer: Kidney – size, activity, Bladder - size, Water retention, Nitrogenous waste type (ammonia, urea, uric acid), Anything else you think is important to osmoregulatory and excretory systems.

Answer 1

Osmoregulation is the process of maintaining salt and water balance across membranes within the body.

surrounding cells have fluids inside and are composed of water, electrolytes, and nonelectrolytes.

The fluids inside the body include blood plasma, the fluid that exists within cells, and the interstitial fluid that exists in the spaces between cells and tissues of the body.

The membranes of the body are semipermeable membranes.

To maintain osmotic balance Excess water, wastes and electrolytes are transported to the kidneys and excreted.

Insufficient fluid intake results in fluid conservation by the kidneys.

Without a mechanism to regulate osmotic pressure, or when a disease damages this mechanism, there is a tendency to accumulate toxic waste and water, which can have dire consequences.

Excretory System

its function is to remove waste from the body through the skin as sweat, the lungs in the form of exhaled carbon dioxide, and through the urinary system in the form of urine.

All three of these systems participate in osmoregulation and waste removal.

kidney plays a very large role in human osmoregulation by regulating the amount of water reabsorbed from glomerular filtrate in kidney tubules, which is controlled by hormones such as antidiuretic hormone (ADH), aldosterone, and angiotensin

The difference in kidney structure between marine and terrestrial mammals suggests that the ‘specialized’ kidneys of marine mammals allow them to occupy habitats with a broad range of salinity since the kidneys are the principal organs of water and electrolyte regulation

the structures identified in cetacean kidneys that are lacking in those terrestrial mammalian kidneys studied are (i) specialized glycogen stores in the proximal convoluted tubule epithelial cells, (ii) highly concentrated bundles of medullary blood vessels (iii) the presence of a sports perimedullaris musculus, a layer of collagen, elastic fibers and smooth muscle separating the cortex from the medulla