Chapter 14: Echinoderms and Hemichordates Flashcards
Libbie Hyman described echinoderms as “a noble group especially designed to puzzle the zoologist.” Why is this an accurate description?
They have many different characteristics, forms, and behaviors that vary between species. Unique combination of characteristics
Who are the closest extant relatives of echinoderms?
Hemichordates and Chordates
List and describe the classes that comprise phylum Echinodermata.
Class Asteroidea- 1500 extant species, Sea stars
Class Ophiuroidea- bittle stars and basket stars
Class Echinoidea- Sea urchins, sand dollars, and heart urchins; 2 shapes (irregular and regular); wide distribution; test
Class Holothuroidea- sea cucumbers; 1150 extant species
Class Crinoidea- sea lilies and feather stars; attached to substrate for most of life; 625 extant species.
Describe the functions of pedicellariae
Used for protection; contain venomous glands.
Explain catch collagen. Why is it advantageous to sea stars?
Connective tissue that can quickly change from a liquid to solid; allow echinoderms to hold posture without muscles.
How does gas exchange and excretion occur in sea stars?
The coelom allows for an exchange of gases and excretion of wastes via diffusion. Wastes exit through tube feet.
Describe feeding in sea stars.
Mouth contains a 2-part stomach in the central disc. The cardiac stomach can be everted through the mouth during feeding.
Describe reproduction in sea stars.
External fertilization
Regeneration- can regenerate even when all arms are lost; only requires central disc
Describe regeneration and autotomy in sea stars.
Regeneration- able to replicate new sea stars as long as central disc is present.
Autonomy- detachment of a body part voluntarily if injured; takes month to regenerate
Describe the ways that brittle stars differ from sea stars.
Arms are slender, no peridellariae, ambulacral grooves are closed and covered in ossicles, tube doesn’t have suckers, arms are jointed,no anus, leathery skin
Do brittle stars share any similarities with sea stars? If so, what are those similarities?
Yes, they both contain a nervous system and Water Vascular system.
What sets a basket star apart from a brittle star?
Contain branching tendrils and much larger
How many sets of branching legs do basket stars typically have?
5 sets or more
Can basket stars regenerate their limbs like sea stars do?
Yes
Describe the distribution of basket stars.
Found in all of the world’s oceans, and live at depths of a few feet to over 4000 feet.
Basket stars eat a variety of foods. What are they?
Plankton, jellyfish, Fish Larvae, and Crustaceans
Describe the way that basket stars catch prey.
Their branches contain hooks that snag food from the water. The branching tendrils then travel to their jaws where food is deposited.
Basket stars are nocturnal. What is the advantage to hunting at night?
Predators are less likely to spot them at night
Does the life cycle of all basket stars include a larval stage?
No, some do not have a larval stage and appear as adults
Describe asexual reproduction in basket stars.
Splitting, a piece of one individual can become separated and form into a clone