A model organism is a species that researchers study to better understand certain biological processes. Mollusks and arthropods are commonly used as model organisms for studying mechanisms of learning and memory, while sponges and jellyfish are not. This is because mollusks and arthropods can respond to changes in their environment, while jellyfish and sponges cannot.
Answer:
D. Mollusks and arthropods exhibit cephalization, while jellyfish and sponges do not.
Explanation:
The processes of learning and memory are functions of brain. Cephalization is the process of concentration of sensory structure and development of head in organisms. Jellyfishes (cnidarian) and sponges (poriferan) are the radially symmetrical organisms with no cephalization. Flatworms were first organisms to exhibit some cephalization. Mollusks and arthropods are among the animals that exhibit high degree of cephalization and hence are used as model organisms to study the mechanisms of learning and memory.
