Section 30.1 (Exam 2) Flashcards
Protostomes Account for More Than Half of All Described Species (28 cards)
What are some characteristics of protostomes?
Triploblastic
Bilateral symmetry
Embryonic blastopore becomes the mouth
Spiral cleavage
Ventral nerve cord
Anterior brain that surrounds entrance to digestive track
What are two major derived traits of protostomes?
Anterior brain that surrounds the entrance to the digestive tract
Ventral nervous system with paired or fused longitudinal nerve cords
Based on DNA sequencing, what are the two major clades protostomes have been divided into?
Lophotrochozoans and Ecdysozoans
Where do lophotrochozoans derive their name from?
Having a trochophore larva and a lophophore.
Name the 4 groups that have a lophophore.
Bryozoans, entoprocts, brachiopods, and phoronids.
What is a lophophore?
Circular or U-shaped ring of hollow, ciliated tentacles around mouth; functions in food collection
Nearly all animals with a lophophore are ________ as adults.
sessile
What cleavage do some lophotrochozoans have?
spiral
What are some examples of lophotrochozoans with spiral cleavage?
flatworms, ribbon worms, annelids, mollusks
What are ecdysozoans?
They have an external cuticle secreted by the epidermis. This cuticle restricts growth.
If external cuticles restrict growth, then how do ecdyzoans increase in size?
To grow, the cuticle must be shed, or molted, and replaced with a larger one (ecdysis)
What is the process of shedding an ecdysozoans external cuticle called?
ecdysis
What is the purpose of the ecdysozoan cuticle?
Protection and support
What is the cuticle in arthropods?
An exoskeleton thickened by proteins and chitins
What is chitin?
a waterproof polysaccharide
What does the exoskeleton do in arthropods?
restrict movements and gas exchange
Because the arthropod exoskeletons restrict movement and gas exchange, new mechanisms needed to evolve to complete these functions. What are these mechanisms?
Arthropods have appendages manipulated by muscles for locomotion. Their appendages are also used for gas exchange.
What are the uses of arthropod appendages?
Gas exchange, copulation, and sensory perception
What were some benefits of the hard exoskeleton of arthropods?
It prevented drying up, which allowed arthropods to walk on dry land.
How many species of arrow worms are there?
180 species
Why were the evolutionary relationships of arrow worms debated?
The blastopore gave rise to the anal opening, which is a characteristic of deuterostomes, but they also have a ventral nerve cord and spiral cleavage, which is a characteristic of protostomes.
Were arrow worms ultimately decided to be protostomes or deuterostomes, and what was it based on?
Gene sequencing identified arrow worms as protostomes.
Arrow worms are transparent. What are the 3 main parts of an arrow worm’s body?
Head, trunk, and tail
What are some characteristics of arrow worms?
3-part body, marine, coelomates
Small and hermaphroditic
No circulatory system or larval stage
Major predators of planktonic organisms
