12.14.4 The Nervous System: A Phylogenetic Perspective

Question 1

The Nervous System: A Phylogenetic Perspective

Answer 1

• In order to maintain homeostasis, multicellular organisms have developed nervous systems for communication between tissues and organs.
• The most primitive animal is the sponge (Phylum Porifera), which has no nervous system. Cnidarians (Phylum Cnidaria) have the most primitive nervous system, which is a network of nerves between its two cell layers.
• Cephalization, the accumulation of ganglia and sensory organs in the head of animals, had important implications for the evolution of many systems.
• The evolution of a central nervous system, facilitating communication between the brain and body, provided a great homeostatic advantage to animals.

Question 2

note

Answer 2

• Systems within a multicellular organism must be able to communicate with each other in order to maintain
  homeostasis. Cells communicate with each other through cell junctions and membrane receptors. The nervous system allows for communication between cells, tissues, and organs.
• The most primitive animal is the sponge (Phylum Porifera). Sponges have no true organ systems and therefore no nervous system. They function by filtering water and trapping food particles.

Question 3

cnidarians

Answer 3

• The most primitive nervous system in animals is found in Cnidarians (Phylum Cnidaria). Cnidarians have a network of nerves between two cell layers. This nervous system allows Cnidarians to detect and respond to stimuli.

Question 4

cephalization

Answer 4

• Cephalization is the aggregation of nerves and brain tissue in the anterior portion of an animal. Cephalization had important implication for the evolution of many systems including the digestive system, the circulatory system and especially the nervous system.
• Aggregations of ganglia developed into brains. A
  central nervous system (CNS) is made up of a brain along one or two longitudinal nerve cords

Question 5

Which of the following have no nervous system?

Answer 5

• Phylum Porifera

Question 6

The most primitive nervous system in animals is found in phylum _______________.

Answer 6

• Cnidaria

Question 7

Which of the following organisms shows cephalization?

Answer 7

• tape worm

Question 8

Clusters of nerve cell bodies are referred to as _______________.

Answer 8

• ganglia

Question 9

True or false?

Sponges have the most primitive nervous system.

Answer 9

• false