Pre AP Biology -EVO 1.2 Classifying Evolutionary Relationships - MCQ Exam Style Questions -New Syllabus
Pre AP Biology -EVO 1.2 Classifying Evolutionary Relationships – MCQ Exam Style Questions – New Syllabus 2025-2026
Pre AP Biology -EVO 1.2 Classifying Evolutionary Relationships – MCQ Exam Style Questions – Pre AP Biology – per latest Pre AP Biology Syllabus.
▶️ Answer/Explanation
The correct answer is a. Cnidaria.
A medusa is one of the two primary body forms found in the phylum Cnidaria.
It is characterized by a bell-shaped, free-swimming body with tentacles hanging downward.
Common examples of the medusa form include jellyfish.
The other primary body form in this phylum is the sessile polyp, such as sea anemones.
Phyla like Arthropoda, Echinodermata, and Porifera do not exhibit the medusa body plan.
▶️ Answer/Explanation
The correct answer is d. $4$.
Basal phyla are those that diverged early from the main animal lineage.
Scientists generally identify $4$ distinct basal animal phyla.
These include Porifera (sponges) and Cnidaria (jellyfish and corals).
They also include Ctenophora (comb jellies) and Placozoa.
These groups lack the complex bilateral symmetry found in Bilateria.
They represent the most primitive branches of the animal phylogenetic tree.
▶️ Answer/Explanation
The correct option is b.
Key innovations refer to traits that evolved within the animal lineage to drive diversification.
Heterotrophy and multicellularity are ancestral traits shared with fungi or protist ancestors.
The evolution of symmetry (radial and bilateral) allowed for directed movement and cephalization.
The development of specialized tissues enabled complex organ systems and physiological division of labor.
These two features distinguishes Parazoa (sponges) from Eumetazoa (true animals).
Therefore, symmetry and tissue differentiation are the primary evolutionary “milestones” listed.