1 ANIMALS Characteristics


The Kingdom ANIMALS

 Eukaryotic cells  Multicellular  Heterotrophic by ingestion

Classification Tools for Animals

 1. Body Symmetry  2. Level of Body Organization  3. Body Cavities:Presence of a Coelom  4. Embryological Development: Protostome vs Deterostome  5. Segmentation / Cephalization  6. Presence of a Notochord  7. Presence of a Vertebral Column

1. Body Symmetry

 A. Asymmetry  B. Radial Symmetry   C. Bilateral Symmetry D. (Pentaradial symmetry – Echninoderms)

a. Asymmetry –No symmetry at all!

  Example: Porifera Sea Sponges and Corals


Radial Symmetry

 Example: Cnidaria

Cnidaria and Radial Symmetry

 Cnidaria actually go through a developmental stage of bilateral symmetry before they develop their radial symmetry as an adult.

Sea Anemone

Crown Jellyfish

Soft Coral Polyps

Bilateral Symmetry – Candy striped Annelid

Blue Spotted Sting Ray

Marine Flatworm

African Elephants

2. Levels of Organization

 A. Cellular – no true tissues  B. Tissues  C. Organ

a. Cellular Level of Organization

 Porifera are really just an assemblage of different specialized cells. They have no tissues or organs

b. Tissue Level of Organization

 Cnidaria have two tissue layers surrounding it’s sac body plan. They do not have any organs or organ systems

c. Organ Level of Organization

 Platyhelminthes (flatworms) are the first animals on the phylogenetic tree that have simple organs. They have very primitive “brains” in their “heads” called cephalization

Platyhelminthes ( flatworms)- have simple organs and exhibit simple cephalization

Organ System Level of Organization

 As we move up the evolutionary tree, organ systems become increasingly more complicated

Body Cavities

 A. Sac body plan  B. tube-within-a-tube body plan - Acoelomates - Pseudocoelomates - Coelomates

a. Sac Body Plan – only one opening for food to enter and wastes to exit

   Porifera (sponges) Cnidaria (jellyfish) Platyhelminthes (flatworms)

b. Tube-Within-A-Tube Body Plan

  Implies that there is an entrance (mouth) for nutrients and an exit (anus) for wastes Most primitive animal with this plan: Nematodes

Acoelomates, Pseudocoelomates, and Coelomates

Acoelomates: Animals without a Coelom

 There is no internal body cavity aside from the digestive cavity

Pseudocoelomates: Animals with an internal body cavity that is partially lined with mesoderm

Coelomates: Animals with a true Coelom

 A true coelom is an internal body cavity that is completely lined with mesoderm

4. Embryo Development: Protostome vs. Deuterostome

5. Segmentation – Annelids, Arthropods and Chordates

 Repetition of body parts along the length of the body  Leads to specialization of parts because various segments can become differentiated for specific purposes


 - easily seen in the Arthropods

6. Presence of a Notochord

 A notochord is a supporting rod that runs down the dorsal surface, just below the nerve cord. Animals that have a notochord are called chordates.

Vertebrate vs Invertebrate.

vs Internal Fertilization

External Fertilization

a. Invertebrate Chordates: Tunicates

  most animals that have notochords also have vertebrate. However, there are 2 groups that do not.

Those animals that do not have vertebrate are called the INVERTEBRATE CHORDATES

a. Invertebrate Chordates: Lancelets

Vertebrates – Chordates with a backbone