2. Who is in the Kingdom Animalia?
Let’s create an Animal list…

3. Characteristics Multicellular heterotroph Lack cell walls
Most have nerves, muscles, capacity to move at some point in the life cycle
Ability to reproduce sexually
Specialized sensory structures and nervous system
Cells exist in extensive extracellular matrix
Unique cell junctions

4. Traditional classifications
Most biologists agree kingdom is monophyletic
Animal genomes are very similar
Most likely ancestor a colonial flagellated protist similar to choanoflagellates
About 35 recognized animal phyla

5. Who are the animal phyla?

7. Traditional classification based on body plans
4 main morphological and developmental features used
Tissue types
Symmetry type
Body cavity
Embryonic development

8. Tissues
Metazoa divided into Parazoa (no specialized tissues or organs) and Eumetazoa (more than one type of tissue and organs)

10. Symmetry
Eumetazoa are radially symmetrical (Radiata) or bilaterally symmetrical (Bilateria)
Bilateral animals have cephalization and dorsal and ventral surfaces
Radial animals have oral and aboral sides

11. J.B.S. Haldane
The Creator would appear as endowed with a passion for stars, on the one hand, and for beetles on the other, for the simple reason that there are nearly 300,000 species of beetle known, and perhaps more, as compared with somewhat less than 9,000 species of birds and a little over 10,000 species of mammals. Beetles are actually more numerous than the species of any other insect order. That kind of thing is characteristic of nature.

13. Number of cell layers Radial animals have 2 embryonic cell layers
Diploblastic
Bilateral animals have 3 germ layers
Triploblastic
Cell layers develop during gastrulation
Inner layer – endoderm
Outer layer – ectoderm
Mesoderm - 3rd layer in bilateral animals
Forms muscles and most other organs

15. Body cavity
True coelom – body cavity is completely lined with mesoderm (coelomates)
Pseudocoelom – coelom is not completely lined by tissue derived from mesoderm (pseudocoelomates)
Acoelomates – lack a body cavity entirely
Fluid-filled body cavity can protect internal organs or be used as hydrostatic skeleton

17. Embryonic development
Which is which (usually)?!?
Spiral cleavage
Schizocoelous coelom development
Blastopore becomes anus
Cleavage is indeterminate- pluripotent stem cells
Radial cleavage
Enterocoleus coleom development
Blastopore becomes mouth
Cleavage determinate

18. Other methods of classification
Possession of exoskeleton
Development of notochord
Presence or absence of metamerism (segmentation)
Traced to changes in Hox genes

20. Molecular views of animal diversity
Molecular techniques used to classify animals by comparing similarities in the DNA and the ribosomal RNA of animals, especially sequences of nucleotides in the gene that encodes RNA of the small ribosomal subunit (SSU rRNA)
Advantage generally more objective and subject to more rigorous testing

23. Similarities between traditional and molecular phylogeny
The clade called Metazoa is monophyletic, meaning all animals came from a single common ancestor.
At the earliest stages of evolution, molecular phylogeny supports the traditional view of the split between Parazoa and Eumetazoa.
There is also agreement about an early split between Radiata and Bilateria, with most animal phyla belonging to the Bilateria.
Molecular phylogeny also agrees that the echinoderms and chordates belong to a clade called the Deuterostomia.

24. 2 key differences between traditional and molecular phylogeny
Division of protostomes into 2 clades
Traditionally split into Deuterostomia and Protostomia based on embryonic development
Deuterostomes still separate but protostomes divided into Lophotrochozoa and Ecdysozoa
Presence or absence of a body cavity
Traditionally split into coelomates, pseudocoelomates and acoelomates
Molecular evidence indicates presence or absence not a useful characteristic