Question

which of the statements is true of saltwater and freshwater animal waste management systems?
a) freshwater-based animals must have mechanisms to prevent water from trying to diffuse into their bodies.
b) saltwater-based animals must have a mechanism to prevent water from trying to diffuse into their bodies
c) both saltwater and freshwater animals dont need to eliminate waste, as it diffuses out of their bodies naturally
d) no saltwater or freshwater animals urinate.
question 8 (5 points)
listen
which of the following set of characteristics accurately describes the phylum cnidaria?
a) cylindrical bodies with bilateral symmetry and two digestive openings
b) radial symmetry with only two germ layers and one digestive opening
c) asymmetric and porous body plans

Explanation:

First Question (about saltwater and freshwater animal waste management systems)

• For option A: Freshwater has a lower solute concentration than the inside of freshwater animals' bodies. By osmosis, water will tend to diffuse into their bodies, so they need mechanisms (like osmoregulatory organs) to prevent excessive water intake.
• For option B: Saltwater has a higher solute concentration than the inside of saltwater animals' bodies. So water tends to diffuse out of their bodies, and they need mechanisms to prevent water loss, not prevent water from diffusing in.
• For option C: All animals need to eliminate waste (like nitrogenous waste), and waste does not just diffuse out naturally in a way that meets their metabolic needs. They have specialized excretory systems.
• For option D: Many saltwater and freshwater animals do urinate (or have equivalent excretory processes) to eliminate waste and regulate osmotic balance.

Second Question (about phylum Cnidaria)

• For option A: Cnidarians have radial symmetry (not bilateral) and one digestive opening (not two). Organisms with bilateral symmetry and two digestive openings are more advanced, like annelids or arthropods.
• For option B: Cnidarians (e.g., jellyfish, corals) have radial symmetry, are diploblastic (have two germ layers - ectoderm and endoderm), and have a gastrovascular cavity with one opening (serving as both mouth and anus).
• For option C: Asymmetric and porous body plans are characteristic of poriferans (sponges), not cnidarians.

Answer:

A) Freshwater - based animals must have mechanisms to prevent water from trying to diffuse into their bodies.