Chapter 17 - Hemichordata and Invertebrate Chordates - Test 3

characteristics Hemichordata

1. dorsal nerve cord

2. pharyngeal slits (water comes in and out)

3. 3 body regions (proboscis, collar, and trunk)

4. open-circulatory system

5. complete digestive system

functions of the proboscis Hemichordata

sediment excavation; digging;capure food

two ways that enteropnuests feed Hemichordata

1. burrowing - sediment feeding

2. non-burrowing - proboscis to capture food

mechanism of gas exchange and waste removal

diffusion across body wall

reproduction Hemichordata

dioecious and external fertilization

characteristics Chordates

1. notochord (rod - becomes vertebral column)

2. dorsal nerve cord (brain +spinal cord)

3. pharyngeal puches and slits

4. endostyle or thyroid (1. mucus for filter (larval) 2. hormones for growth (adult))

5. post anal tail (posterior to anus)

why are called tunicates Chordates

they have a tunic that protects them

life history Chordates

retention of larval characteristics unisexually mature adults

unique about the feeding method of the tunicate class Larvacea (Chordates)

build temporary - bubble houses for filter feed (discard)

Why do most zoologists believe that lancelets are the closest living relatives of vertebrates ( Chordates)

1. segmented myomeres

2. dorsal and ventral aortas

3. aortic arches

4. podocytes

how are lancelets different than the most recent common ancestors of vertebrates (Chordates)

1. no tripartite braine

2. no chambered heart

3. no special sense organs

4. no muscular gut and pharynx

respiration Chordates

diffusion across skin surface

reproduction Chordates

dioecious and external fertilization

feeding Chordates

water enters mouth → pharyngeal slits → food trapped by mucus → cilia transfers food to esophagus

pedomorphosis (chordates)

adults retain juvenile or larval traits that were previously only seen in the young

reproduction (chordata) (tunicates and regular)

1. asexual

2. sexual