Question

Question 1: Homeostasis, Common Ancestry, and Divergence

a) One problem that all respiring organisms share is the need for biological structures that allow efficient uptake of oxygen and removal of carbon dioxide. Two types of structures that have evolved for carrying out gas exchange are gills and lungs. The table below lists organisms according to the type of structure they use for gas exchange.

Organisms with gills Organisms with lungs fish rabbit lobster frog squid lizard clam eagle some salamanders species some salamander species

• Describe the general process of gas exchange that occurs between a gill or lung and the surrounding environment.

• Describe three similarities in the structures of gills and lungs that help ensure high efficiency of gas exchange.

• Explain why one group of organisms evolved to have gills while the other group evolved to have lungs. Include in your explanation a discussion about the two groups of salamanders shown in the table.

• Describe the probable characteristics of the gas exchange structure present in a common ancestor of all of the organisms listed in the table. Explain how evolution played a role in the development of the gill and the lung.

b) All animals must solve the problem of nitrogen waste excretion in order to maintain homeostasis. There are three basic types of nitrogen waste products that animals produce: ammonia, urea, or uric acid. Aquatic animals tend to produce ammonia, whereas terrestrial animals tend to produce either urea or uric acid.

• Explain why nitrogen excretion is an important aspect of animal homeostasis.

• Explain how the types of nitrogen excretion, their energy requirements, and habitat are related.

• Explain how the three animals listed in the table above provide an example of how a group of animals can show continuity due to common ancestry as well as divergence due to adaptation to different environments.