Opisthokonta Traits - Lecture notes Unit Three PDF

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Caroline McMillan Oct. 29, 31, Nov. 2 Opisthokonta Traits ● Opisthokonta Traits ○ Posterior flagellum (cell movement) ○ Chiton (cell protection) ○ Extracellular digestion (cell energy) ● Gastrulation and Derm layers ○ Ectoderm ■ Epidermal and nervous ○ Endoderm ■ Digestive and respiratory ● Protostome = “mouth developed first” ● Deuterostome = “mouth developed second” ○ Mesoderm ■ Muscle, bone, and circulatory ● Support Structures ○ Endoskeleton (under epidermis) ■ Allows more movement, more growth but energy expensive and not very protective ○ Exoskeleton (outside epidermis) ■ Protection but heavy, limit movement ○ Hydroskeleton ■ Flexibility, aquatic environment, can squeeze through anything but not structurally beneficial to large growth and cannot live on land ● Symmetry ○ Radial Symmetry ■ Sessile or floating animals ■ Sensory inputs from all directions ■ A line can be drawn anywhere on the body and symmetry be found ● Ex. Starfish ○ Bilateral Symmetry ■ Advantageous for animal moving through the environment; most sensory input from one direction ■ Associated with cephalization ● A grouping of nervous tissue on one end of the body, concentration of neurons and sensory structures in the head region ● “the concentration of sense organs, nervous control, etc., at the anterior end of the body, forming a head and brain, both during evolution and in the course of an embryo's development.” ● A line cannot be drawn anywhere on the body and symmetry be 1

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found ○ Ex. Humans Segmentation and Limbs ○ Segments = repeated limbs ○ Allows for movement and modification of segments ○ These segments/limbs are evolved multiple times Circulation ○ Diffusion ■ No specialized structures to distribute nutrients and waste ○ Open circulation ■ Fluids pumped around a cavity ○ Closed circulation ■ Fluids pumped through vessels P. Porifera (sponges) ○ Tissue differentiation: limited ○ Asymmetry ○ Sponges have an outer layer of cells, but have an endoskeleton ○ Spicules = internal structural support (defensive and structural) ○ Choanocytes are found on the inside of the sponge ○ Sponges eat by diffusion ○ Choanocytes and Choanoflagellates ■ These are the most ancestral of all animals P. Cnidaria (jellyfish and coral) ○ Germ layers: two (division of labor) with “jelly” in between ○ Incomplete digestive tract ○ Corals, Hydra, Jellyfish Two basic body forms ○ Polyp - sessile ○ Medusa - free living Coral Reefs: coral and sponges ○ Biodiversity and nutrient source ■ Sponges are perhaps one of the most important factors of building a coral reef ○ Ocean acidification and warming (coral “bleaching”) ■ When coral “spit out” their algae, they get white and this is coral bleaching ○ Chemicals/plastics P. Platyhelminthes (flatworms) ○ Cephalization ○ Incomplete digestion (most), no circulatory system ○ Diffusion of gases, nutrients, waste 2

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○ Many parasites, some terrestrial ○ Advantages of being flat ■ easy to hide from predators ■ easy to diffuse nutrients ■ more surface area for excretion ■ absorb nutrients if living in host's digestive system P. Rotifera (rotifers) ○ “Wheel animals” ○ Complete digestive system ○ Ecology ■ Diverse ■ Found in all habitats ■ Important primary consumers ■ Bioindicators ● Organisms that reflect qualities of the environment ○ General pollution levels, salinity, presence of metals, low/high oxygen, etc. ● The use of bioindicator species is a type of indirect measurement of water quality/environment quality P. Mollusca ○ High diversity ○ Mantle and foot ○ Three Classes: ■ Snails (gastropods) ■ Bivalves ● ex. Clams ■ Octopuses (cephalopods) ○ Mollusks have an exoskeleton, slugs and octopuses have a hydroskeleton, and many other cephalopods have an endoskeleton P. Annelida (segmented worms) ○ Segmented (for burrowing) ○ Closed circulation P. Nematoda (roundworms) ○ Thick cuticle (made of chitin) ○ Parasites, soil ○ Hydroskeleton ○ C. elegans - genetics, development, neuroscience P. Arthropoda ○ Four Classes: ■ Insects (75% of all animals) ■ Spiders 3

■ Milli-/Centipedes ■ Crustaceans ● The oldest arthropod class ○ Exoskeleton (of chitin) ○ Open circulation (there is a heart) ○ Lots of segmentation ■ Body segmentation ■ Jointed appendages ■ Variable mouthparts ○ Complex sensory structures ○ Terrestrial arthropods ■ Tracheal tubes for respiration ○ Aquatic arthropods ■ Gills for respiration ● Echinoderms ○ Closest relatives to vertebrates ○ No cephalization (radial symmetry) as adults ■ As larvae, they are bilateral ■ Derived trait ○ No segmentation ○ Water vascular system** ■ Unique circulation - defining trait ○ Eg. starfish, sea urchins, sand dollars ● Chordata ○ Sea squirts and salps ○ Lancelets ○ Vertebrates (groups based on characteristics) ■ Fish ● 5 major groups ● 2 are jawless (wormlike) ● Cartilaginous fish ● Ray-finned (Marlin and Dory) ● Lobe Finned fish/lungfish (Humans) ■ Amphibians ● Evolved around 400 mya ● Cutaneous respiration ● Sirens, toad and frogs, salamanders ■ Reptiles ● Mammals ○ About 200 mya ○ Monotremes 4

■ Egg laying (e.g. platypus) ○ Marsupials ■ Sort internal development, born immature ● E.g. kangaroo, opossum ○ Placentals ■ Long internal development ● Birds ■ Sauropsida ● Evolved about 300 mya ● Lizards and snakes, turtles ● Alligators and birds (about 150 mya) ● AMNIOTIC EGGS ○ Reptiles, birds, mammals ■ Four membranes: ● Chorion (gas exchange) ● Amnion (protective fluid-filled) ● Yolk sac (food) ● Allantois (excreted wastes) ● Non-permeable skin ○ Able to leave water because moisture is retained better, no competition

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