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Multiple Choice
Which of the following statements about bilaterian animals is true?
A
Bilaterian animals have bilateral symmetry and three germ layers.
B
Bilaterian animals are characterized by having a single body cavity.
C
Bilaterian animals include only invertebrates.
D
Bilaterian animals have radial symmetry.
Verified step by step guidance
1
Understand the term 'bilaterian animals': Bilaterian animals are a group of animals that exhibit bilateral symmetry, meaning their body can be divided into two mirror-image halves along a single plane.
Identify the characteristics of bilaterian animals: They possess three germ layers during embryonic development, which are the ectoderm, mesoderm, and endoderm. This is known as being triploblastic.
Clarify the concept of body cavities: Bilaterian animals typically have a coelom, which is a body cavity completely lined with mesoderm. However, not all bilaterians have a single body cavity; some may have more complex structures.
Differentiate between invertebrates and vertebrates: Bilaterian animals include both invertebrates (animals without a backbone) and vertebrates (animals with a backbone), so they are not limited to invertebrates.
Contrast bilateral and radial symmetry: Bilateral symmetry is distinct from radial symmetry, which is found in animals like jellyfish and starfish, where body parts are arranged around a central axis. Bilaterians do not have radial symmetry.