Review Sheet for BIOL 240W Exam II: Kearn Kaur
1. Definition of Osmoregulation: General term for processes by which animals control solute concentrations and
balance water gain/loss. Organisms which live in different environments must maintain a solute concentration in
their cells that maintain life while preventing dehydration or flooding/cell explosion.
2. Why do organisms omsoregulate: They do because it balances out the uptake/loss of water and solutes. Cells
balance water gain and loss through osmoregulation, a process based on the controlled movement of solutes between
internal fluids and the external environment and on the movement of water, which follows osmosis.
3. Differences between an osmoconformer and osmoregulator –
Osmoconformers:Are isoosmotic with their surroundings, no tendency to lose/gain water, and do not regulate
- Only marine organisms, tend to live in environments that are fairly stable in solute concentration, many
Osmoregulators: Expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic
- Must discharge or take in water depending on the osmolarity of the environment
- Osmoregulation allows organisms to live in a wide range of habitats including freshwater and terrestrial
Main Difference:An osmoconformer do not regulate their osmolarity; there is an equal movement of water
between the animal and its environment.An osmoregulator uses energy to control the amount of water it gains
and loses; there is an unequal movement of water between the animal and its environment.
4. Environments where conforming is beneficial and why –
5. Meaning of Stenohaline and Euryhaline –
Stenohaline –Animals that cannot tolerate a wide range of changes in external osmolarity
Euryhaline –Animals which can survive fluctuations in external osmolarity
Example organisms –
Cod – Osmoregulator, Stenohaline, Saltwater, Ocean is hyperosmotic to internal environment, and
constantly lose water to the environment and gain salt from diffusion and food.
Regulation: Drink large amounts of seawater, chloride ions are actively transported out through
gills and sodium ions passively follow, and kidneys remove other waste products
Perch – Osmoregulator, Stenohaline, Freshwater, Environment is hypoosmotic to internal environment,
constantly gain water by osmosis and loss salt via diffusion, and body fluids generally have lower solute
concentrations than those of saltwater fish.
Regulation: Excrete large amounts of dilute urine, salt lost by diffusion and via urine are
replaced by foods and by uptake across gills (have spec. cells)
Salmon – Osmoregulator, Euryhaline, Freshwater and Saltwater, Environment is hypoosmotic to
internal environment and the opposite in saltwater.
Regulation: Drink lots of seawater and excrete excess salt from gills, to prevent drying out
(ocean environments). Stop drinking and produce large amounts of dilute urine, gills start to
take up salt from environment, to prevent cells from shriveling (freshwater environments)
6. Adaptations for regulation of solute concentrations in osmoregulators
Animals in wet and dry environments: Anyhydrobiosis – the ability to survive in a dormant state when the
organism’s environment dries up (ex: water bears). Land Animals: Prone to drying out, they have to reduce water loss. Done by body coverings that prevent
dehydration, nocturnal behavior to reduce evaporative water loss, drinking and eating moist foods, using
metabolic water, and very concentrated excretions
Tissues to regulate solute movements: Transport epithelia, one or more layers of specialized cells that regulate
salt movement (salt glands in seabirds contain transport epithelia)
7. Three types of excretory substances and organisms that use each
Ammonia: Very soluble, very toxic, only tolerated in low concentrations, common in aquatic species because it
requires high water intake and lots of excretion, lost through diffusion (gills and body surface) and kidneys
Urea: Lower toxicity, good for land animals because they can carry it around with them and requires less water
(more concentrated solutions are tolerated), requires energy to produce it from ammonia
Examples: mammals, most adult amphibians, sharks, and some marine bony fishes and turtles
Uric Acid: Low toxicity, not very soluble in water so can be excreted as a paste with little water loss; most
energy is expended in this
Examples: Land snails, insects, birds, and many reptiles
8. How excretory substances are suited to an animal’s environment –
Ammonia:Alot of water is needed, good for fish. Not suitable for land animals, very toxic and lots of water
Urea: Good for land animals, less water needed. Energy needs to be expended to produce it from ammonia
Uric acid: Most energy expended, requires less water loss
9. Benefit of uric acid in egg-laying animals –
Uric acid precipitates out of solution and can be stored within the egg as a harmless solid left behind when the
animal hatches, not very toxic, is tolerable
10. The four main excretory processes –
Filtration: The excretory tubule collects a filtrate from the blood. Water and solutes are forced by blood pressure
across the selectively permeable membranes of a cluster of capillaries and into the excretory tubule.
Reabsorption: The transport epithelium reclaims valuable substances (glucose, certain salts, vitamins, hormones,
and amino acids) from the filtrate and returns them to the body fluids
Secretion: Other substances (nonessential solutes and wastes) such as toxins and excess ions are extracted from
body fluids and added to the contents of the excretory tubule.
Excretion: The altered filtrate (urine) leaves the system and the body
11. Overview of protonephridia, metanephridia, Malpighian tubules, and kidneys –
Protonephridia: In flatworms, form a network of dead-end tubules, which are connected to external openings,
branch throughout the flatworm body, lacks a coelom (body cavity). Are capped by a flame bulb with a tuft of
cilia that draws water and solutes from the interstitial fluid, through the flame bulb, and into the tubule system.
Metanephridia: Most annelids (earthworms), is another tubular excretory system, consist of internal openings
that collect body fluids from the coelom through a ciliated funnel, the nephrostome, and release the fluid to the
outside through the nephridiopore.
Malpighian tubules: Insects and other terrestrial arthropods have these organs that remove nitrogenous wastes
and also function in osmoregulation. These open into the digestive system and dead-end at tips that are
immersed in the hemolymph.
Kidneys: In Vertebrates, are compact, non-segmented organs containing numerous tubules arranged in a highly
organized manner. The vertebrate excretory system includes a dense network of capillaries intimately associated
with the tubules, along with ducts and other structures that carry urine out of the tubules and kidney and
eventually out of the body.
12. Definition and examples of anhyrobiosis –
Dehydration dooms most animals, but some aquatic invertebrates living in temporary ponds and films of water
around soil particles can lose almost all their body water and survive in a dormant state, called anhydrobiosis,
when their habitats dry up.
- The sugar, Trehalose, is an adaptation in water bears that allows them to keep their cell membrane intact, it
seems to protect cells by replacing water associated with membranes and proteins.
1. Define trophic hormones –
Are hormones that regulate the function of endocrine glands.
2. Hormonal cascade –
Signals to the brain stimulate the hypothalamus to secrete a hormone that stimulates or inhibits release of a
trophic hormone for a specific gland
3. Know in detail the form and function of at least 3 human endocrine glands –
A. Hypothalamus: Role in maintaining homeostasis in controlling temp., Cardio. Sys, regulating
food/water intake, control sleep/wake cycle (circadian cycle), moods, and libido. 1. Location: Below thalamus and above pituitary glands, allows it to control release of 8 hormones
from pituitary gland, easy access to central nervous system allowing immediate control over
metabolic processes because located near part of the brain stem
2. Hormones produced/stored: TRH, GnRH, GHRH, CRH, Somatostatin, and Dopamine
3. What their hormones do: TRH (release of thyroid stimulating hormone), GnRH (triggers sexual
development), GHRH (stimulates cells in anterior lobe of pituitary to secrete growth hormones,
CRH (acts on cells in anterior of pituitary to release adrenocorticotrophic hormone), Somatostatin
(inhibits the release of growth hormone and thyroid stimulating hormone), and Dopamine (inhibits
the release of prolactin also involved in the feeling of happiness and reward).
4. How their action is regulated: Connection to central nervous system allows it to receive signals that
set off different sensing regions, input/release mechanism responds and hormones are synthesized
5. Associated Disease: Hypothalamic disease, caused by head trauma, genetic disorders, radiation,
eating disorders, and surgery. Example if GHRH is not properly produced there is poor growth,
treated with hormonal replacement therapy
B. Pituitary (posterior and anterior):
1. Location: In the middle of the base of the brain (base of hypothalamus). Works closely with the
hypothalamus; the pituitary gland receives signals from hypothalamus which determines when to
2. Hormones produced/stored:ACTH, FSH, GH, LH, TSH, and prolactin in anterior (synthesizes and
secretes hormones). ADH and Oxytocin in posterior (doesn’t produce hormones itself, it
stores/releases neurohormones produced by hypothalamus and later secretes them).
3. What their hormones do:ACTH (stimulates secretion of glucocorticoids), FSH (stimulates
production of gametes), GH (stimulates growth, metabolic functions), LH (stimulates testes and
ovaries), TSH (stimulates thyroid gland), prolactin (stimulates milk production and secretion) in
anterior.ADH (promotes water retention in kidneys), Oxytocin (stimulates uterine contractions,
mammary gland cells) in posterior.
4. How their action is regulated: By regulating hormone production and secretion, the pituitary gland
directs certain biological processes by stimulating activity in other glands. Pituitary gland and
hypothalamus work together to control biochemical processes necessary to maintain homeostasis