chapter 17

Question 1

what are the three main characteristics we have traditionally used to determine animal phylogeny

Answer 1

• -»eukaryotic; multicellular; heterotrophic;
• -»self-propelled; diploid
• -»develop from embryos

Question 2

what are the more modern techniques we are now also using to determine animal phylogeny

Answer 2

**–»symmetry— arrangement of body parts;
Radial—parts arranged around a central axis [top & bottom but no front, back, left or right sides]
Bilateral—parts are arranged on either side of central axis[dorsal, ventral, anterior & posterior]

• *—»number of germ layers –»early embryo undergoes gastrulation
  - -Diploblastic— 2 germ layers; ectoderm & endoderm
  - -Triploblastic–3 germ layers; ectoderm, mesoderm & endoderm

**–»type of body cavity or coelom –»[in triploblastic animals]
Acoelomate – no body cavity between the digestive tract and outer wall [flatworms]

   Pseudocoelomate--- fluid-filled body cavity separates the digestive tract and outer body wall [roundworms]

   Coelmate--- fluid-filled body cavity completely lined with mesoderm separates the digestive tract and outer body wall [segmented worms]; helps cushion body organs; serves as a hydrostatic skeleton in soft bodied animals

Question 3

what are the four unique chordate characteristics

Answer 3

**–»notochord–»a longitudinal, flexible rod located between the intestinal tract and nerve cord—develops into the backbone in vertebrates
dorsal, hollow nerve cord develops into brain and spinal cord

**–»pharyngeal slits[gill slits]–» openings on sides of the pharynx – develop into gills in aquatic forms and other structures in terrestrial forms

**–»postanal tail –»contains skeletal elements and muscles

Question 4

what are the major characteristics of the classes of vertebrates (7)

Answer 4

***agnatha–» jawless, cartilaginous skeleton, lack paired appendages, notochord persists [lampreys, hagfishes]

**chondrichthyes–»cartilaginous skeleton, jaws, paired appendages, gills for respiration, internal fertilization, may lay eggs or bear live young [sharks, skates, rays]

**osteichthyes–»bony skeleton, fins, gills for respiration, most have external fertilization [tuna, perch, trout]

**amphibia–»appendages adapted for moving on land[tetrapod] aquatic larval stage metamorphosing into terrestrial aquatic stage, respiration through lungs and/or skin, may lay eggs or bear live young [frogs, toads, newts, salamander]

**reptilia–»terrestrial tetrapods with dry scaly skin, respiration by lungs, lay amniotic shelled eggs or bear live young [snakes, lizards, turtles, crocodiles, birds]

**aves–»tetrapods with feathers, forelimbs modified as wings, respiration by lungs, endothermic, internal fertilization, shelled amniotic eggs [owls, robins, sparrow, eagles, bluebirds, chickens]

**mammalia–»tetrapods with young nourished from mammary glands of females, hair, diaphragm that ventilates lungs, endothermic, most bear live young [monotremes(such as platypuses) marsupials(such as kangaroos) placentals(such as rodents, cats, primates)]