What is the significance of the evolution of Hox gene clusters during vertebrate evolution?
-Duplication of Hox genes made increased morphological complexity possible.
-Duplicate Hox genes triggered the formation of neural crest cells and allowed them to disperse throughout the body, forming a variety of structures.
-Novel Hox genes coded for novel vertebrate features, such as jaws, limbs, and large brains.
answer
Duplication of Hox genes made increased morphological complexity possible.
-As a result of gene duplication, craniates possess two or more sets of Hox genes (lancelets and tunicates have only one). Other important families of genes that produce signaling molecules and transcription factors are also duplicated in craniates. The additional genetic complexity due to duplication of Hox genes may have made it possible for craniates to develop more complex morphologies than those of lancelets and tunicates. Read about Hox gene clusters as derived characters of craniates.
question
What evidence suggests that vertebrates are more closely related to echinoderms than are any other invertebrate phyla?
-Shared patterns of development
-Shared DNA sequences
-Shared morphology
answer
Shared DNA sequences
-The clade Deuterostomia comprising chordates (including vertebrates) and echinoderms is defined primarily by DNA similarities. Read about deuterostomes.
question
Internal fertilization, leathery amniotic eggs, and skin that resists drying are characteristics of which extant vertebrate group?
-amphibians
-mammals
-non-bird reptiles
-chondrichthyans
-birds.
answer
non-bird reptiles
question
The earliest known mineralized structures in vertebrates are associated with which function?
-reproduction
-locomotion
-respiration
-defense
-feeding
answer
feeding
question
The most ancient branch point in animal phylogeny is that between having
-radial and bilateral symmetry.
-a body cavity and no body cavity.
-true tissues and no tissues.
-a well-defined head and no head.
answer
a body cavity and no body cavity.
question
Whatever its ultimate cause(s), the Cambrian explosion is a prime example of
-a large meteor impact.
-adaptive radiation.
-mass extinction.
-evolutionary stasis.
answer
adaptive radiation.
question
Which of the following animal groups is entirely aquatic?
-Platyhelminthes
-Crustacea
-Echinodermata
-Nematoda
-Mollusca
answer
Echinodermata
question
Which of the following are the most abundant and diverse of the extant vertebrates?
-amphibians
-mammals
-birds
-ray-finned fishes
answer
ray-finned fishes
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