Problem 1 - Biology: The Dynamic Science

Question

Which of the following statements about osmoregulation is true? a. In freshwater invertebrates, salts move out of the body into the water because the animal is hypoosmotic to the water. b. A marine teleost has to fight gaining water because it is isoosmotic to the sea. Most land animals are osmoconformers. d. Vertebrates are usually osmoregulators. Terrestrial animals can regulate their osmolarity without expending energy.

Step-by-Step Solution

Answer

The correct statement is d. Vertebrates are usually osmoregulators.

Step 1: Understanding the Terms

Firstly, understand the following key terms. Osmoconformers are organisms that maintain their body fluids in equilibrium with the environment while osmoregulators regulate their body fluids, which can have a different concentration compared to their environment. Hypoosmotic means the concentration of solutes is greater inside the cell than outside, isoosmotic means there is no net movement of water since the concentration of solutes is the same inside and outside, while hyperosmotic means that the concentration of solutes is greater outside the cell.

Step 2: Analyzing Each Statement

Next, analyze each of the given statements in relation to the defined terms. Evaluate whether each statement accurately represents the osmoregulatory behavior of the specified species or group of animals.

Step 3: Evaluating the Options

Go through each option one by one. 'a' and 'b' are incorrect as freshwater invertebrates are hyperosmotic to the water and they maintain their salt balance by actively taking in salts via their gills, not losing them. Marine teleosts are however hypoosmotic to the sea water, and they constantly lose water by osmosis. 'c' is also wrong as most land animals are osmoregulators. They need to regulate their internal environment versus their external environment. For option 'e', terrestrial animals cannot regulate their osmolarity without expending energy as they need it for active processes of osmoregulation like secretion of waste. Therefore, 'd' which states that vertebrates are usually osmoregulators, is true since vertebrates actively regulate their internal environment to maintain homeostasis.