Parasitology Lec 2: Environmental Considerations

of the 30 invertebrate phyla, almost how much of them are entirely marine

half

members of the remaining phyla are primarily marine, and to a lesser extent, occur in

freshwater habitats

*know! of the invertebrates, only the ____ have been successful in terrestrial environments

Arthropods

an aquatic environment affects morphology and physiology: since aquatic organisms are not in danger of drying out, they do not need

thick body walls

*the body walls of aquatic invertebrates are

*thin

what do these thin body walls allow for

gas exchange across the general body surface (O2, CO2)

aquatic inverts therefore do not need

specialized respiratory organs

*are the gills that occur on aquatic invertes like fish fills

*no

aquatic invert gills are vascularized extensions of what

the body wall and there mainly to increase the surface area for gas exchange

in water, the gametes, embryos and larvae are not subject to

dehydration and osmotic stress

what can be completed entirely in the water

fert. and development

many aquatic species freely

disperse sperm and eggs into the water

ammonia is the byproduct of what

amino acid and protein break down

ammonia is also very ____ to organisms

toxic (especially in higher concentrations)

how can aquatic organisms get rid of ammonia

they can simply release ammonia into the water across the body wall as it is produced (terrestrial organisms cant do that because they can’t donate water to dilute it)

What must terrestrial organisms convert ammonia to

urea or uric acid in small amounts of water.

*know! Urea and uric acid are ____

*less toxic

this conversion uses what

energy, takes time and requires a complex excretory system

water is ____than air

denser

there is no need for a rigid skeletal support system because why

the water is supportive

animals can move with ____ in water

greater efficiency

Animals can be ____ because free-floating food (phytoplankton and zooplankton) will move through the area

sessile

*know for exam! Water has greater ____ than air

*thermal stability

water is ___to heat up and ____ to cool down

slow; slow

the metabolism of invertebrates is directly related to what

the temperature

environments, like water, that vary less in temperature are what to the invertebrates

less stressful

*Some disadvantages of living in water: *oxygen diffuses ____ in water than in the air

*more slowly

how much slower does oxygen diffuse in water than in the air

300,000 times more slowly

a sessile organism must live where

in the current or have a means of creating water flow over respiratory surfaces to obtain enough oxygen

water is viscous which means

movement of it or through it causes friction on organisms living in water

a unique difficulty of a freshwater habitat: most freshwater animals are ___ in comparison to the water

hyperosmotic

hyperosmotic in other words, they have a ____ concentration of solutes in them than does the freshwater that surrounds them

greater

therefore, water tends to diffuse ____ along the osmotic concentration gradient

inward

as a result of all this, all freshwater animals must be able to

constantly expel large volumes of freshwater

*important idea: the freshwater habitat is ___ in salts and this makes it difficult for the freshwater organisms to obtain salts

low

therefore, the freshwater animals must have a sophisticated physiological system to ____

expel large amounts of water while reclaiming salts from the urine for their bodies

many invertebrates such as flatworms use a ____ as their excretory organ

nephridium

Nephridium:

a blind-ended tubule that expels waste through an excretory pore

at the end of each blind tubule of the nephridium is a what

a ciliated flame cell