Aquatic Science
Unit 7 Notes
I.
Comparison by Cavity Type
A.
Coelom – liquid filled body cavity
B.
Coelomates – organisms with a body cavity
II.
Classification of Coelomates
A.
Classification by cavity structure
B.
Classification by early development
C.
Classification by cleavage type
III.
Classification by Cavity Structure
A.
Acoelomate
1.
Prefix “A-“ “without”
2.
Organism without a lining in the body cavity
B.
Pseudocoelomate
1.
Prefix “Pseudo-” “false”
Organism having an incompletely lined cavity
C.
Eucoelomate
1.
Prefix “Eu-“ “true”
2.
Organism having a cavity that is completely lined
IV.
Classification by Early Development
A.
Blastula – hollow ball of cells
B.
Blastopore – opening formed by the folding of the blastula
C.
Protostome
1.
Formation of mouth from the blastopore
2.
Anus is the secondary formation
D.
Deuterostome
1.
Formation of the anus from the blastopore

2.
Mouth is the secondary formation
V.
Classification By Cleavage Type
A.
Cleavage – division of early embryonic cells
B.
Embryonic Cleavage
1.
Determinate Cleavage – creates high probability of “unequal” daughter cell survival (one or other survive not both)
2.
Indeterminate Cleavage – division allows for greater probability of “equal” daughter cell survival
3.
Holoblastic Cleavage a.
Definition – complete cleavage in embryos having a small yoke b.
Four Types
1) Bilateral
2) Radial – Deuterostomes
3) Rotational – Mammals
4) Spiral – Protostomes (Annelids & Mollusks)
4.
Meroblastic Cleavage a.
Definition – incomplete cleavage in embryos having a large yoke b.
Two types
1) Discoidal – fish, birds, reptiles
(yolk is generally at one end)
2) Superficial – insects
(yolk is generally in the middle)
C.
Protostomes – spiral cleavage
D.
Deuterostomes – radial cleavage
VI.
Movement and Support
A.
Three Types
1.
Hydrostatic Skeleton (Hydroskeleton)
2.
Exoskeleton
3.
Endoskeleton
B.
Hydroskeleton – lacking hard structures such a bone
(Cnidarians, Flatworms, Roundworms, Earthworms, Mollusks)
C.
Exoskeleton – hard nonliving coating the encloses internal organs and muscles
(Mollusks, Arthropoda)
D.
Endoskeleton – bony internal framework.
(Echinoderms, Chordates)
VII.
Digestion
A.
Three Methods
1.
Intracellular
2.
Incomplete Extracellular
3.
Complete Extracellular

B.
Intracellular – all digestion occurs within individual cells of the animal
C.
Incomplete Extracellular – only one opening for absorption and elimination
D.
Extracellular – two openings: a mouth for absorption and an anus for elimination.
VIII.
Respiration
A.
No respiratory organs
B.
External respiratory organs
C.
Internal respiratory organs
D.
No Respiratory System – diffusion is used to get oxygen through organism’s surface
E.
External Respiratory System – diffusion through skin or special structures such as gills
F.
Internal Respiratory System – uses lungs or tubular system (insects)
IX.
Internal Transport
A.
No Circulatory System – Nematodes and Echinodermata
B.
Open Circulatory System – has no vessels
C.
Closed Circulatory System – has vessels (veins/arteries)
X.
Environmental Response
A.
Nerve Nets
B.
Cephalizaiton – having a head; anterior centralization of sense organs
C.
Central Nervous System
XI.
Reproduction
A.
Asexual – one parent
B.
Sexual – two parents