Practical #3 - Protostomes and Deuterostomes

Question 1

What is the difference between Protstome and Deuterostome, list the examples of each.

Answer 1

• Protostome - The blastopore becomes the mouth first
  
  • Spiral and Determinate Cleavage
  • Annelida, Mollusca, Arthropoda
• Deuterostomes - The blastopore becomes the anus first and then the mouth
  
  • Radial and Indeterminate Cleavage
  • Echinodermata, Chordata

Question 2

Give me the stages of early development in animals

Answer 2

• Zygote –> 2-cell stages –> 4-cell stage –> Morula –> Blastula (hollow ball called blastocoel) –> Gastrula
  
  • blastopore is the opening of the gastrula
  • blstocoel is the hollow center of a blastula

Question 3

Describe radial vs sprial cleavage

Answer 3

• Spiral - the successive planes of cell division in early development are not at right angles
• Raidal - in most deurterostomes
  
  • the planes of division are at right angles
  • The tiers of cells stack up on top of each other in the early embryo

Question 4

Determinate vs Indeterminate Cleavage

Answer 4

• Determinate - the developmental fate of each cell is determiend early on.
  
  • You will not get identical twins of a cell is split in half. You will get tow “halves”
• Indetermiante - Fates of the early cells do not become ‘fixed’ until later in development
  
  • You can get identical twins

Question 5

What is the difference between Enterocoeloms and Schizocoeloms?

Answer 5

• Schizocoelom - solid masses of mesoderm form near the blastopore and these mases split open–forming a fluid filled body cavity
• Enterocoelom - masses of mesodermal cells ‘bud’ off of the wall of the archenteron to form enterocoelom

Question 6

What are the key characteristics of Phylum Annelida?

Answer 6

• Protostomes
• Pronounced Segmentation
  
  • ​Metamerism - identical body compartments along the lengh of the body = metameres
• Complete Digestive System
  
  • ​Typhlosole- ridge-like fold of the intestine into the lumen = increase surface area
• Possess Metanephridia - opens at two ends: one to the outside and one to the coelom
• Closed Circulatory system - with blood vessels and heart
• NO respiration - just diffusion aross body wall
• Cephalization - brain, ventral nerve cord, ganglia
• Circular and longitudinal Muscles
• Cuticle prevents dessication
  
  • ​Coelomic compartments that serve as hydrostatic skeleton
• Posses Trocophore larvae

Question 7

Why is metamerism important evolutionarily?

Answer 7

• Because it allowed specialization of body parts.
• It allowed for separate hydrostatic compartments, which in turn allow for greater behavioral complexity and locomotion

Question 8

How is the metanephridia strcutred and how does it differ from the protonephridia?

Answer 8

• Metanephridia has 2 parts
  
  • Nephrostome - connects the coelom to the metanephridia
  • Nephridiospore - Connects the metanephridia to the outside
• Porotnephridia are close tubes with an opening to the outside
• Metanephridia are larger, more complex structures that often function in both excretion and osmoregulation

Question 9

How does reproduction Differ in Annelids?

Answer 9

• Oligochaetes and leeches are monoeciuos
• Polychaetes are dioecious

Question 10

What are the different classes of Phylum Annelida?

Answer 10

• Class Polychaeta
  
  • ​Mainy hairs per segment
• Class Oligochaeta
  
  • ​two pairs of hairs per segment
• Class Hirudinea
  
  • Oral and caudal suckers

Question 11

What are the Key Characteristics of Phylum Mollusca

Answer 11

• Protsome with sprial cleavage
• Four distinct body parts
  
  • Head, Muscular Foot, Visceral mass, Mantle (which produces the shell if present)
• Skin is usually 1 cell layer thick and ciliated
• Use hydrostatic Skeleton to move appendages
• The foot - uses muscular contractions th move the bottom of the foot
• Extracellular Digestion - Chitinous ribbon of teeth called- radula
• Possess metanephridia
• Open Circulatory System - blood filled cavity called a hemocoel
  
  • ​Cehpalopods have a closed system
• Well developed nerve system with ventral nerve cord, brain and ganglia
• Use gills for gas exchange….some land snails have lungs
• Can be monoecious or dioecious with internal or extenal fetilization
  
  • Also have the trocophore larva
• Basic immune system with integument, amebocytes (phagocytize things)

Question 12

Which class of Mollusca is not bilaterally symmetrical and cephalized?

Answer 12

Bivalves

Question 13

What are the 4 classes of Phylum Mollusca

Answer 13

• Class Bivalvia
  
  • ​Two shells (clams, scallops, mussels
  • Dreissena
• Class Gastropoda
  
  • ​Named for ventral location of foot (snails and slugs)
  • Physella
• Class Polyplacophora
  
  • ​8 calcareous plates (The chitons)
• Class Cephalopoda
  
  • ​most have well developed brain (octopi and squid)

Question 14

What are the key characteristics of Phylum Arthropoda?

Answer 14

• Protostomes
• Coelom is a body cavity called hemocoel
• Segmented body plan - segments fused into tagmata
  
  • ​head, thorax, abdomen
• Jointed appendages called podomeres
• Exoskeleton composed of chitin
  
  • ​Can molt and undergo ecdysis allowing growth
• Extracellular digestion
• Green Glands or Malpighian Tubules- for osmoregulation and exxretion
• Open Circulatory System - uses fluid called hemolymph instead of blood
• Respiration 3 forms
  
  • Gills, tracheae, Book lungs
• Anterior brain, paired ventral nerve cord
• Normally dioecious with internal fertilization. Metamorphosis is common
• Non specific immune system with amebocytes

Question 15

What is the difference between green glands and Malpighian Tubules?

Answer 15

• Green Glands
  
  • ​type of nephridium that exretes large amounts of ammonia and water
• Malpighian Tubules
  
  • ​blind tubes that dump nitrogenous waste and water into the gut
  • The gut then reabsorbs water and the uric acid is eliminted with with other stuff
  • Since less water is need, uric acid is insoluble in water, it allows for arthropods to colonize land!

Question 16

Is the circulatory invovled in Oxygen transport in Arthropods?

Answer 16

No, just the respiratory system

Question 17

What are the subphylum for Phylum Arthropoda and what are their associated classes?

Answer 17

• Subphylum Chelicerata
  
  • ​Class Arachnida (Spiders)
• Subphylum Crustacea
  
  • ​Class Malacostraca (crabs)
• Subphylum Uniramia
  
  • ​Class Insecta

Question 18

What are the key charactertistics of Phylum Echinodermata?

Answer 18

• Deuterostome, Enterocoelous coelom
• Integumentary - Dermal Endoskeleton
  
  • ​made of calcareous ossicles
• Sessile animals with pedicellariae - prevent smaller organisms from resting on their body
• Bilaterally Symmetrical as larvae but radially symmetrical as adults
• Body plan is an oral-aboral axis
• Coelom forms a series of water filled canals and cavaties called water vascular system
• Extracellular digestion with a complete tract
• NO exretory, respiratory or circulatory systems
  
  • ​everything just diffuses directly across body
• Nerve net
• Dioecious, with external fertilization
• Possess wondering phaogcytes

Question 19

What are the classes of Phylum Echinodermata?

Answer 19

• Class Asteroidea - Sea stars
• Class Echinoidea - Sea Urchins
• Class Holothuroidea - sea cucumbers
• Class Ophiuroidea - Brittle stars

Question 20

What is the water vascular system in Echinoderms?

Answer 20

• THe coelom forms a series of water filled canals and cavaties collectively called the water vascular system
• A unique homolgy to all echinoderms
• Acts as a hydrostatic skeleton
• Helps move many tube feet use in prety capture and locomation
• Each tube foot end has a sucker on it
  
  • Except brittle stars