ZoologyLesson 2 of 6 in the course Vertebrates

Fish Diversity: Jawless, Cartilaginous, and Bony Fishes

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

This lesson explores the earliest fishes and the two living groups of jawless fishes: hagfishes and lampreys. Comparing them shows how vertebrate features appeared and diversified over evolutionary time.

Fishes were the earliest vertebrates, and jawless forms appeared before jawed fishes. Living jawless fishes belong to the superclass Agnatha. Their defining traits include a lack of jaws and a lack of paired lateral appendages, such as pectoral and pelvic fins. They also lack scales and internal ossification, though those traits are not defining features of the group.

All flashcards

What is Agnatha?
A superclass of jawless fishes. Living members lack jaws and paired lateral appendages and include hagfishes and lampreys.
What were ostracoderms?
An assemblage of extinct jawless fishes covered in bony armor; they may not form one natural evolutionary group.
How do hagfishes locate and eat food?
Sensory barbels help them find food by smell and touch; keratinized teeth on a movable cartilaginous plate rasp flesh.
How does hagfish slime help it survive?
Glands release mucus that becomes slippery in water, helping hagfishes escape predators.
What is an ammocoete?
A lamprey larva that lives in streams or rivers as a suspension feeder for three to 15 years.

Quiz questions

  1. Jaws in early gnathostomes probably evolved from which structures?Answer: The first pair of gill arches.
  2. Which description best characterizes the skeleton of Chondrichthyes?Answer: It is primarily cartilaginous, with some parts strengthened by calcium carbonate.
  3. What do the ampullae of Lorenzini help sharks detect?Answer: Electrical fields produced by living organisms.
  4. What distinguishes a heterocercal tail?Answer: Its upper lobe is larger and contains an extension of the vertebral column.
  5. Which feature distinguishes lobe-finned fishes from ray-finned fishes?Answer: Their fleshy fins are supported by internal bones.

Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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