Early Branching Animals

When did animals appear?

First appeared 700 mya in the ocean, first large at 600 mya and cambrian explosion at 540 mya.

Sponges

Filter feeding collection of cells built around a water canal system for capturing food. Mostly marine, different cell types but no true organs, have choanocytes

Demosponges

Most diverse of the sponges, 90% of the species

Glass Sponges

Have supporting structures built of silica fibers

Calcareous Sponges

Have calcium carbonate spicules

Ctenophores

Comb jellies, oldest animal with diploblastic embryos, have a nervous system

Cnidarians

aquatic invertibrates, very diverse, include anthozoans (corals), jellyfish, and anemones

Protostomes

Blastopore develops into the mouth, bilateral symmetry, triploblastic embryos

Lophotrochozoans

Part of the protostomes, have either lophophore (ciliated feeding structure) or a trochophore (free swimming larval stage)

Chitons

Part of mollusks, have an 8 plated shell and tightly adhere to rocks

Bivalves

Part of mollusks, soft bodied marine animals that have 2 shells (valves) that open and close like oysters, clams, and muscles.

Gastropods

Part of the mollusks “stomach foots”; used for movement, slugs, snails, and nudibranchs

Cephalopods

Part of mollusks, merged head and foot with a ring of arms/tentacles surrounding it, eyes, squid, octopus, cuttlefish.

Ecdysozoans

Covered by a cuticle they molt, 500 myo, broken into 4 subgroups

Nematodes

Ecdysozoans, Unsegmented body with a thick cuticle, possible the most abundant animal on earth, mostly microscopic, 1st multicellular animal to have its entire genome sequenced

Tardigrades

Ecdysozoans, Water bears, thin cuticle, unsegmented, fleshy legs and claws, can be very abundant, when threatened they cover themselves in a waxy film to survive

Velvet worms

Ecdysozoans, Soft, fleshy, claw-bearing, unsegmented, unjointed legs

Arthropods

Ecdysozoans, segmented bodies, jointed appendages, hard exoskeleton made of chitin

Myriapods

Arthropods; segmented body, many legs, pair of antennae, tracheal breathing, ex millipedes and centipedes

Chelicerates

Arthropods; divided body into cephalothorax and abdomen, have celicerae for feeding and no antennae ex scorpions, spiders, horseshoe crabs

Crustaceans

Arthropods; 3 body regions: head thorax and abdomen, 2 antennae, mandibles, ex shrimp, crabs

Hexapods

Arthropods; 3 pairs of thoracic legs, 3 body regions: head thorax and abdomen, wings come off the back of the thorax ex butterflies, beetles, wasps

Deuterostome

Mouth second, blastopore develops into the anus

Priapulids

Connector between protostomes and deuterostomes

Echinoderms

Deuterostomes, radial symmetry, body plan diversified very early 5 modern groups (sea urchins, star fish, sea cucumbers)

Benthic Grazers

Bottom grazers, both chitin and sand dollars

Benthic Filter Feeders

feeders attached to the bottom, nudibranchs and sea lilly

Pelagic Filter Feeders

mid ocean feeders, anemones, cephalopods and gastropods, sea cucumbers

Chordates

have a notochord, hollow dorsal nerve cord, tail that extends beyond the anus, and pharyngeal slits at some point in life

Notochord

flexible rod that offers structural support for larvae

Lancelets (amphioxus)

Chordate, no pharyngeal slits for respiration

Tunicates

Chordates, most lose the notochord, nerve cord, and tail as adults, sessile filter feeders

Vertebrates

Skull, vertebral column that protects the spinal cord

Hagfish

only vertebrate without an actual vertebrae, has a skull, cyclostome (circular mouth), no jaw, lots of mucus

Lampreys

470 mya, cyclostome, simple vertebrae, cartilage skeleton

Chondrichthyans

Have jaws, teeth, and paired fins, sharks and rays

Bony Vertebrates

Calcified internal skeleton for support and protection, air sac (lungs or swim bladder)

Lobe finned Fishes

Gave rise to the tetrapods; coelocanths

Lungfishes

Internal nares (nasal opening sin the mouth), lungs and gills