AP BIOLOGY

Detailed explanation-1: -The invertebrates, or invertebrata, are animals that do not contain bony structures, such as the cranium and vertebrae. The simplest of all the invertebrates are the Parazoans, which include only the phylum Porifera: the sponges (Figure 4.3.

Detailed explanation-2: -The phylum Porifera includes animals called Sponges. The said animal (sponges) has a body that contains several channels and pores. They possess unspecialized cells that do not form any tissue or organ. Thus, they lack any true tissue.

Detailed explanation-3: -They are multicellular but do not have tissues or organs. The name porifera means ‘pore bearer’ in Latin.

Detailed explanation-4: -The simplest animals include the sponges (Porifera) and the Cnidaria. Sponges are unsymmetrical or radially symmetrical, with many cell types but no distinct tissues; their bodies contain numerous pores and sharp protective spicules.

Detailed explanation-5: -This is because sponges evolved much earlier than other animals. In fact, sponges do not even have true tissues. Instead, their bodies are made up of specialized cells (cell-level organization) that do specific jobs.