Consider the following transitions...
Cell Agregates >>> Specialization (tissues)
Sponges >>>>> Cnidaria, Ctenophores
(comlex nervous systems, muscles)
(complex behavior)
| 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 | |||
|
Cambrian | jawless fish-like | |
|
extinct | ||
|
750 | Sharks | |
|
30,000 | 425-45 m.y. | |
|
400 | 365 m.y. | |
|
7000 / 8600 | 300 m.y. / 200 m.y. | Archaeopteryx 150 m.y. |
|
4500 | 220 m.y. | |
|
1 | 100,000 years | ONLY! The first number I can actually imagine. |
|
Invertebrates (non arthropod): |
190,000 |
|
Invertebrates (arthropod) |
2,000,000 (up to 30,000,000) |
|
Vertebrates: |
40,000 |
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
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.