Biol exam 4

• Animals


  Organisms that ingest things through their mouths
• Animals


  • Multicellular
  • Have tissues that develop from embryonic layers
• Choanoflagellates


  • Eukaryotes that move around via flagella
  • Multiple cell types, possesses collar cells
• Choanocytes


  AKA collar cells, very similar to individual choanoflagellates, thought to be most closely related to them
• Cell structures and specialization in animals


  • Cells are supported by structural proteins such as collagen, rather than cell walls
  • Nervous tissue and muscle tissue are unique, defining characteristics of animals
• Cleavage


  Rapid cell division undergone by a diploid animal zygote leads to the formation of a blastula
• Blastula


  An animal embryo at the early stage of development when it is a hollow ball of cells
• Blastocoel


  Hollow space inside a blastula
• Gastrulation


  An infolding process of the blastula, forms a gastrula with different layers of embryonic tissues
• Gastrula


  An embryo at the stage following the blastula, when it is a hollow cup-shaped structure having three layers of cells. Blastocoel is still present ectoderm, endoderm, blastopore, and archenteron present
• Ectoderm


  • The outer layer of the gastrula
  • Turns into outer covering (ex, skin, exoskeleton, etc)
• Endoderm


  • Innermost layer of the gastrula
  • Lines the developing digestive tube, called the archenteron (the hollow part)
• Mesoderm


  • Middle layer of the gastrula
  • Forms more complicated organs, muscle tissue, and body cavity in some species. Stuff in the middle only present in triploblastic animals
• Blastopore


  The first opening in the embryo – the point of invagination during gastrulation
• Archenteron


  • 2nd, innermost hollow opening in the gastrula
  • Forms inside of the digestive tract
• Body plan


  • A set of morphological and developmental traits zoologists use to classify animals
  • Includes Symmetry, Tissue Organization, Body Cavity Organization, Protostome vs. Deuterostome
• Radial symmetry


  • Type of symmetry found in a flower pot
  • Radially symmetrical animals have a top and a bottom, but no front and back, or left and right
  • Found in anchored or planktonic animals; no real directed movement
• Bilateral symmetry


  • A dorsal (top) side and a ventral (bottom) side
  • A right and left side
  • Anterior (front) and posterior (back) ends
  • Found in organisms with directed movement
  • Because humans are bipedal, what used to be their dorsal side is now their posterior side, etc
• Diploblastic animals


  • Have only ectoderm and endoderm
  • These include cnidarians
• Triploblastic animals


  • Also have an intermediate tissue layer called mesoderm
  • All bilaterally symmetrical animals are triploblastic
• Body cavity


  A hollow cavity inside the adult organism found in most triploblastic animals
• Coelom


  A true body cavity, derived from the mesoderm
• Coelomates


  • Animals that possess a true coelom
  • Major examples of coelomates include molluscs, arthropods, echinoderms, and chordates
• Pseudocoelom


  A body cavity derived from the mesoderm and endoderm
• Pseudocoelomates


  Triploblastic animals that possess a pseudocoelom
• Acoelomates


  • Triploblastic animals that lack a body cavity
  • ex) platyhelminthes
• Protostome development


  • Cleavage: spiral and determinate (have a predetermined type)
  • Coelom formation: still have a body cavity derived from the mesoderm, but formed when the solid mesoderm splits away
  • Fate of blastopore: mouth develops from blastopore
• Deuterostome development


  • Cleavage: radial and indeterminate (cells can turn into several different types of cells)
  • Coelom formation: Folds of the archenteron form coelom
  • Fate of blastopore: anus develops from blastopore
• 5 important points of animal phylogeny


  • All animals share a common ancestor
  • Sponges (phylum Porifera) are the sister group to all other animals
  • Eumetazoa ("true animals") is a clade of animals with tissues
  • Most animal phyla belong to the clade Bilateria
  • There are three major clades of bilaterian animals (Deuterostomia, Lophotrochozoa, and Ecdysozoa), all of which are invertebrates, animals that lack a backbone, except Chordata, which includes vertebrates, animals with a backbone
• Segmented worms


  • Annelida
  • Earthworms, leeches, clam worms, etc
• Roundworms


  • Nematoda
  • Heartworms, vinegar eels, etc
• Deuterostomia


  • Includes hemichordates (acorn worms), echinoderms (sea stars and relatives), and chordates
  • This clade includes both vertebrates and invertebrates
• Ecdysozoa


  • Secrete external skeletons
  • As they grow, they shed their exoskeletons through a process called ecdysis
  • The most species-rich animal group
  • Exoskeleton called the cuticle
• Lophotrochozoa


  Another clade of bilaterian invertebrates
• Invertebrates


  Animals that lack a backbone
• Sponges (porifera)


  • Basal animals that lack tissues
  • Sedentary and live in marine or fresh waters (sessile animals)
  • No digestive tract
  • No cephalization (no head)
  • No body cavity
  • Asymmetrical
  • Soft sponges are composed of spongin (typical soft yellow sponge)
  • Filter feeders
  • Most are hermaphrodites
  • Important for water filtration, human welfare (sponges for cleaning, economic and tourism), antibacterial secretions possible for antibiotics
• Sponge epidermis


  Superficial covering littered with pores
• Spongocoel


  Big hollow space in the middle of the sponge
• Osculum


  Opening at top of sponge
• Spicules


  • Structural support system of the sponge. Made of different things
  • Spongin for soft sponges
  • Calcium or silica components for harder sponges