BIO II - Chapter 26

Homology

Looks the same, functions the same, AND shares common ancestry (ex. limb bones in arthropods like salamanders and humans)

Analogy

Looks the same, functions the same, but DOES NOT share common ancestry

Cladistics

Members of a group/clade share a common evolutionary history

• More closely related to members within the group/clade than outside it

Synapomorphy

Derived features which ALL clade members share

• However, NOT enough to share characteristics

Outgroup

A taxon that represents the ancestral conditions (plesiomorphy)

Do animal cells have cell wall?

No, they use a structural protein called collagen

3 traits of animals

Eukaryotic, heterotrophs, and multicellular

Hox genes

Regulatory genes which control the expression of other genes

• As hox genes increase = Animal complexity increases

• All hox genes have a homeobox

• Hox genes determine the body form of an animal

Homeobox

A sequence of DNA—very similar in unrelated animals

Cleavage

Successive mitotic cell division (eight cell stage)

Gastrulation

Development of emybryonic tissues (germ layers) which leads to formation of body parts

Endoderm

Fills the blastocoel (inside area of blastula) and eventually will form the lining of digestive tract

Parazoans

• Part of phylum porifera

• Sponges

• Asymmetrical

• Lack true tissue

Eumatazoans

• All other animal phyla

  • Have true tissues

Radiata

• Radial symmetry

• Has NO left and right

• Oral (mouth) and aboral (no mouth) sides

• Ex. Phylum Cnidaria and Ctenophora

Bilateria

• Bilateral symmetry

• Dorsal and ventral/anterior and posterior

• Left and right

• Basically, all other animal phyla