Study #1: Test 3: Echinoderms

Question 1

Distinguishing Features of Echinoderms (echinatus, prickly + derma, skin)

Answer 1

1. Secondary radial symmetrical adults; bilateral larvae
2. Endoskeletal calcareous ossicles (plates)
3. Water filled vascular system of canals and tube feet for locomotion, attachment or feeding.
4. Water Vascular system has a ring canal surrounds mouth. Canal opens to outside thru madreporite (pore = opening)
5. Radial canals branch from ring canal.
6. Hemal system runs into each arm near radial canal and circulates fluid containing nutrients, hormones, etc.
7. Echinoderms important for recycling nutrients on seafloor.

Question 2

Features shared with Chordates

Answer 2

Deuterostomes (2nd opening to gut is mouth while anus develops from blastopore
Enterocoelous
Bilateral symmetry of larvae

Question 3

Types of Echinoderms

Answer 3

sea stars (starfish)
brittle stars
sea cucumbers
sea urchins

Question 4

Echinoderm Adult Body Plan?

Answer 4

Radial body plan seen easily in starfish, sand dollar, sea urchin and sea cucumber

Question 5

echinoderm larvae body plan?

Answer 5

Bilateral body plan

Question 6

Significance of bilateral larval form

Answer 6

1. Small size and large amounts of larvae = greater chance of survival
2. Shows relationship in evolution to chordates
3. allows for free motion

Question 7

Significance of Radial adult form

Answer 7

Allows for regeneration of lost appendages
Multiple appendages that work together to gather food
Multiple areas to have suckers that are used for locomotion and feeding

Question 8

Keystone Predator Species

Answer 8

1. disproportionately large effect on its environment relative to its abundance.
2. play critical role in maintaining the structure of an ecosystem, 3. affect many other organisms
3. help to determine the types and numbers of various other species in the community.

Question 9

Sea stars as keystone predators

Answer 9

sea stars prey on sea urchins, mussels, and other shellfish that have no other natural predators.
If the sea star is removed from the ecosystem, the mussel population would explode and drive out most other species, while the urchin population would annihilate coral reefs

Question 10

Otters and kelp forests

Answer 10

Sea otters protect kelp forests from damage by consuming sea urchins. Kelp “roots”, called holdfasts, are merely anchors
Without sea otters, sea urchins increase in abundance. Sea urchins rapidly eat nearshore kelp, severing the structures at the base or kelp root. Where sea otters are present, sea urchins tend to be small and limited to crevices allowing kelp forests to proliferate and serve as important habitat for a number of other species.