key terms

• evolution is the change on a timescale of generations
• Morphology - some anatomical structures have lost their original function; some are reduced in size (vestigial structures)
• Homology - similarity due to descent from a common ancestor
• transitional form (fossils): A fossil that shows ancestral and derived traits in a combination not seen in living species
• biogeography - the study of the distribution of organisms and their evolutionary relationships
• Embryology - early development features shared by very different organisms
• Taxonomy is the science of naming and classifying organisms
• Binomen means the two-part name used for species
• operational definition


  A species is a group whose members can produce fertile offspring in nature (biological species concept)
• non-operational definition


  a species is an evolutionary independent population or group of populations (evolutionary species concept)
• A clade is a branch on a phylogeny tree that contains all the descendants of a common ancestor
• synapomorphy is a shared derived trait that evolved in an ancestor of a clade that is unique to the clade
• A monophyletic is a group that includes a common ancestor and ALL of its descendants; also called a clade
• A paraphyletic is a group that includes a common ancestor and SOME of its descendants
• Polyphyletic is a group that does not include the most recent common ancestor
• choanoflagellate are sister group (close relatives) of animals
• metazoan is another word for the animal clade of multicellular organisms
• diploblast: endoderm and ectoderm
• triploblast: endoderm (gut), ectoderm (outside), and mesoderm (middle)
• A coelom is a fluid-filled, mesoderm-lined body cavity
• pseudocoelomates a fluid-filled body cavity that is not completely lined with mesoderm
• determinate: cell fates fixed early
• indeterminate: cell fates fixed later
• protostomy: mouth arises from the blastopore (mouth of embryo or larva)
• deuterostome: mouth does not arise from blastopore (maybe arise from anus)
• pinacocytes: flattened "epidermal" cells (gives color)
• Choanocytes: collared cells
• Porocytes: tubular cells containing ostias (makes pores)
• myocytes: cells that contract to shrink oscula (muscle that adjust water flow)
• freshwater sponges can produce gemmules: tough packets of archaeocytes
• sperm usually arise from choanocytes
• Cnidaria: phylum consisting of jellies, corals, anemones, etc.