Metazoan Origins - General Anatomy (Chapter 10)

Question 1

Metazoan

Answer 1

first complex, multicellular organism

Question 2

Types of evidence of PreCambrian Metazoan

Answer 2

• body fossils - rare, Edicarian Biota
• trace fossils - rare, no older than 635 Ma
• embryo fossils - rare, microscopic
• molecular clock - general agreement with fossil record–divergence of many Metazoan groups began in Edicarian of PreCambrian
• biomarker - hydrocarbon, amino acids, & various carbon isotopes

most fossils are rare due to earliest metazoans having soft parts & geological processes which distort or destroy them

Question 3

Parazoan Body Plan

Answer 3

• a group of cells usually organized into 2 layers of collar cells (cells with flagellum)
• separated by jelly-like material
• no celom or tissue
• blastula (“small spout”) larva = hollow ball
• limited to Porifera

Question 4

Diploblastic Body Plan

Answer 4

• having 2 layers, outer ectoderm & inner endoderm
• separated by a cellulor, gelatinous mesoglea
• cnidoblasts (stinging cells)
• “planula larva”
• corals, jellyfish, & hydra (limited to cnidarians)

Question 5

Triploblastic Body Plan

Answer 5

• having 3 tissue layers: ectoderm, mesoderm, & endoderm
• complex organs & tissues
• various types of larval stage
• bilateral symmetry with digestive tract
• all animals except Porifera & Cnidarians

Question 6

invertebrate endoskeleton

Answer 6

mineralized structure that remain inside animal (e.g. belemintes’ pen)

Question 7

invertebrate exoskeleton

Answer 7

mineralized structure that is outside the animal (e.g. mollusks’ shells)

Question 8

accretion

Answer 8

skeletal growth by addition of new material (ex: mollusks)

Question 9

ecdysis

Answer 9

growth of body (& skeleton) by means of molting (ex: arthropods)

Question 10

protosomes

Answer 10

animals whose mouths develop directly from blastophore through cell growth & migration

Question 11

deuterostomes

Answer 11

animal whose mouth develop from secondary opening, while true blastophore develops into anus

Question 12

planktotrophic larval stage

Answer 12

larvals are free-living & feeding on plankton

Question 13

lecithotrophic larval stage

Answer 13

larvals are benthic & feeding on yolk sacs

Question 14

Edicara biota

Answer 14

• upper most Pre-Cambrian rock, reaching acme during Late Proterozoic
• contain soft-bodied metazoans of uncertain phylogeny
• may represent earliest ecosystem dominated by large, multicellular organisms
• define uppermost Proterozoic period

Question 15

Small shelly Fauna/Tommotian fauna

Answer 15

• first metazoans with hard parts with shells or sclerites composed of phosphatic mineral
• microscopic
• includes many form taxa
• may explain explosion of large shelled organisms in Cambrian