INVERTEBRATE DIVERSITY SECTION (Biol.201), Spr 2000

Dr. Kathy S. Williams (email kwilliams@sunstroke.sdsu.edu)

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What’s an animal? …… Review animal characteristics
 
 

Evolution of Animals

Five Kingdom System: Recognize 3 kinds of multicellular eukaryotes

* Fig 26.9 Kingdoms

* FIG. 32.2 Evolution of Animals from Protists

* FIG. 32.3 Animal Clade

Since beginning of scientific study of animals, scientists have attempted to sort and group closely related organisms.

Taxonomists have divided the animal kingdom into 2 subkingdoms

Parazoa: only sponges

Eumetazoans: all other animals
Value of Invertebrates

Perceptions of animal diversity are biased toward to terrestrial vertebrates. But ...

Most of world is covered by water & most animals are invertebrates.

Invertebrates support many many functions that keep biotic systems working.
 


Simplicity WORKS! Porifera & Radiata

* FIG. 32.3 Animal Clade

Porifera

* FIG. 33.2 Sponge

Porifera (sponges) are exclusively aquatic aggregations of specialized cells
        that lead a sessile (attached to substrate) lifestyle. (591, 592, 599-601)

Diversity of sponges is great

Simple but specialized cells types

Body of Sponges

Few types of specialized cells • amebocytes

• choanocytes
~ IN LAB see - collar cells

 Body organization (591, 592)
  • lack true tissue-level organization; cells are totipotent

• no regular form of body symmetry

• spicules

• morphology is related to water movement


Reproduction (913)
 

• asexual

• sexual (most are hermaphroditic)
 
 

 Think: How and where do you think O2 and N waste exchange takes place?
        Why is surface area important relative to this problem?
Radiata
 All animals, except sponges, have distinct cell layers & symmetric body plans. (591, 592)

RADIATA are radially symmetrical, diploblastic animals with a gastrovascular cavity. (592, 601-603, 798-800)

* FIG. 32.4 Symmetry

* FIG. 32.5 Body plans of bilateria

* FIG. 33.5 Cnidaria

 They have a little more organization of cells than sponges ­ have cells for simplest of tissues (no organs) Think: What embryological layer gives rise to which cell layer/tissue in adult cnidarians? Cnidaria (anemones, jellyfish, & corals, etc.) are examples of RADIATA (601-603)

                Specialized cells of Cnidaria What are they and what do they do?

• cnydocyte

• nematocyst

* FIG. 33.4 Cnidocytes

~ When you examine these animals in lab look for these special cells. Cnidarian body plan involves several body forms (1040-1041) What are they and how do the differ?  
* FIG. 33.3 Polyp & medusa of Hydrazoa

• polyp

• medusa

• planula larva

hydrostatic skleton & gastrovascular cavity; * FIG. 41.9 gastrovascular cavity of hydra

very simple nerves (in net design); * FIG. 48.13a cnidarian nerve net
 
 

 Diversity among the Cnidaria What’s similar and different about the following Cnidaria? - distinguished by reproductive strategies and body forms

* FIG. 33.6 hydrozoan life cycle

• Hydra (Hydrozoa)

• Jellyfish (Scyphazoa)

• Corals (Anthazoa)
 

 Ecological roles of Cnidaria

Evolutionary success of cnidarians

In class writing (rubric): How is gas exchange and circulation accomplished in Cnidaria?
    see discussion on page 812 of text (and * FIG. 42.1 Internal transport of Cnidaria)

Think: How does reproduction and body form relate to predictability or

quality of environment?

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