Lecture Notes: Chapters 32-34. Animal Diversity

I. Eukaryotes

1. Nucleus and Organelles
2. Motor Molecules (review p. 119--124)

Microtubules
Centrioles - microtubules

separation of chromosomes during cell division

Flagella - microtubules (9+2) - dynein arms

Basal bodies (similar to centrioles), situated base of flagellum

Animals: Multicellular, Heterotrophic, Elaboration of movement

Consider the following transitions...

	
Cell Agregates >>> Specialization (tissues)
	Sponges    >>>>>  Cnidaria, Ctenophores
                (comlex nervous systems, muscles)
                      (complex behavior)

II. Survey of Animals

The following information was collected from Campbell.


Group (Phyla are bold)	Extant Sp.	Comment 1	Comment 2
Cnidaria radial sym. diploblastic	10,000	SW (FW)	jelly fish, hydra
Ctenophora radial sym. diploblastic	100	SW	comb jellies, cillia for movement
Flat Worms bilateral sym. triploblasic acoelomic	20,000	aquatic, moist	Planeria flukes, tape worms
Nemertea pseudocoelomic protostomes?	900	aquatic, moist
Rotifers coelomic protostomes	1800	FW mostly
Nematodes coelomic protostomes	80,000	aquatic moist	trichinosis C. elegans
Molluscs protostomes	50,000	wet/dry	snails, clams, squid & octopus
Lophophorates Phoronids Bryozoans Brachiopods protostomes	15 5000 330 (30000 extinct)	SW
Annelids protostomes	15,000		worms
Arthropods protostomes	2,000,000+		crabs, spiders, insects 700,000 - 30,000,000 insects ants = 30% Earth Biomass!
Echinoderms deuterostomes	7000	marine	starfish sea urchins sea cucumbers
Chordates:	40,000
1. Urochordates	few		Tunicates
2. Cephalochordata	few		Lancelets
3. Vertebrates
i. Agnatha		Cambrian	jawless fish-like
ii. Placodermi		extinct
iii. Chondrihthyes (sharks)	750		Sharks
iv. Bony Fishes	30,000	425-45 m.y.
v. Amphibians	400	365 m.y.
vi. Reptiles / Birds	7000 / 8600	300 m.y. / 200 m.y.	Archaeopteryx 150 m.y.
vii. Mammals	4500	220 m.y.
....vii. Humans	1	100,000 years	ONLY! The first number I can actually imagine.

9/19/99 I've heard that some astrophysics types think the Sun will blow out in about 5 billion years and incinerate Earth in the process. So, as life, we're about in mid-life, about 50% from the start and 50% from the end. But as Humans (Homo sapiens), we have practically our whole life ahead of us, hopefully. And if we diverged from some ancestral species only 100,000 years ago, what might diverge from us in the next 100,000 years, or less?

NUMBER COMPARISONS - Measure of Success?

 

Invertebrates (non arthropod):	190,000
Invertebrates (arthropod)	2,000,000 (up to 30,000,000)
Vertebrates:	40,000

III. Features Defining Animal Phylogeny

Animal Kingdom - Monophyletic; The Animals.
Animal Phyla - Major divisions.

The following characters have been used to distinguish the Animal Phyla. You should be aware of what these terms refer to and their significance.

1. Radial Symmetry vs. Bilater Symmetry
2. Diploplastic >> Triploblastic (Ectoderm / Mesoderm / Endoderm)
3. Radial vs. Spiral Cleavage of egg (initial cleavages (4 > 8 cell)
4. Protostome vs. Deuterostome (initial embryonic invagination during gastrulation will either become mouth (proto-) or anus (deutero-). Mouth (stome) forms first (proto-) or second (deutero-). Protostomes have become divided into two groups, the ECDYSOZA and the LOPHOTROCHOZOA
5. ECDYSOZA: These animals have an exoskeleton or cuticle, and many regularly shed this cuticle in a hormonally controlled process called "ecdysis".
6. LOPHOTROCHOZA: These animals are recognized as being related based on sequence similarities in their genes, especially sequence similaraties in their 18S ribosomal RNA sequences. The name derives historically from two major animal groups included, the Lophophorata and the Trochozoa.

ANIMALS...
           
    |----------------------- Sponges
 ===|   
(1)>|   |------------------- Cnidaria, Ctenophores 
    |   |<(2)   
    |   | 
    |---|          |-------- Echinoderms
        |   |------|  
    (3)>|   |      |-------- Chordates 
        |   | DEUTEROSTOMA   
        |   |
        |---|   
  BILATERA  |       |------- Rotifers
            |   |---|
            |   |   |   |--- Nematodes
            |   |   |---|
            |   |       |--- Tardigrades, Arthropods 
            |   | ECDYSOZOA
            |   |
            |---| 
     PROTOSTOMA |       |--- Molluscs, Annelids 
                |   |---| 
                |---|   |--- Flatworms 
                    |
                    |------- Brachiopods
                  LOPHOTROCHOZOA


1. Tissue specialization
2. Radial Symmetry, Diploblastic
3. Bilateral Symmetry, Triploblastic

Key Events...

The Origins of Animals probably dates to 1-1.2 billion years ago (DNA sequence analysis).

The fossil record reveals complex animal forms of ALL the major phyla 500-550 million years ago.

The most significant fossil record is the Burgess Shale, a fossil bed that describes the "Cambrian Explosion" that occured about 525 million years ago. These animals had fossilizable skeletons or shells or body parts (i.e. HARD).

PREDATION is thought to have been a MAJOR NATURAL SELECTIVE AGENT in driving evolution of body form and behavior (nervous system complexity) during the Camtrian period to the present.

Interesting Evolutionary Biology Sites: