ECOL 182R 1st Edition Lecture 11 Outline of Last Lecture I Symbiosis II Recent research A DNA sequencing III Bacteria on animals IV Bacteria in animals V Bacteria in guts A Development B Preventing disease Outline of Current Lecture I What are they II Body plans III Tissues A Diploblasts Triploblasts IV How they move V Basal Lineages A Porifera Cnidaria Ctenophora Acoelomorpha Current Lecture They are a species rich and morphologically diverse lineage of multicellular organisms Recognized by their basic body plan which differs in number of tissues in embryos symmetry the presence or absence of a body cavity and the way in which early events in embryonic development proceed Recent phylogenetic analyses show there were three fundamental splits as animals diversified What are they Monophyletic group that s recognized by three traits Multicellular Heterotrophs ingest their food Move under their own power at some point in their life cycle Methods of sexual reproduction vary widely and many species can reproduce asexually Many undergo metamorphosis More characteristics No cell walls but do have an extensive extracellular matrix Animals are the only lineage with muscle nerve tissue None undergo alternation of generations Adults of most species are diploid only gametes are haploid 34 major phyla 1 100 000 species of arthropods O Body plans Most morphological diversity is based on mouth and limb differences for eating and moving However the basic architecture has been highly conserved throughout evolution Four features of animals body plans Number of embryonic tissue layer Type of body symmetry and degree of cephalization formation of head Presence absence of a fluid filled body cavity How the earliest events of embryonic development proceed Different ways to feed Shark jaws teeth to capture prey Feather worm tentacles filter debris Caterpillars have mandibles to harvest leaves Evolution of animal tissues All have tissues tightly integrated structural and functional units of cells All have epithelium a layer of tightly joined cells that covers the body Diploblasts are animals whose embryos have two types of tissues germ layer the ectoderm outside skin and the endoderm inside skin Triploblasts have three those two AND a mesoderm a middle skin Symmetry Cephalization Most sponges are asymmetrical Animals with radial symmetry cut anywhere and left right will be identical Bilateral symmetry single plane of symmetry and face their environment in one lizards Allows cephalization head development Evolution of a body cavity May or may not have an enclosed fluid filled cavity called a coelom see lum Triploblasts that doesn t have one are called acoelomates those with one are coelomates The coelom forms from within the mesoderm and thus is lined on both sides with cells from the mesoderm It creates a container for circulation of oxygen nutrients and also acts as an efficient hydrostatic skeleton that allows soft bodied animals to move even without fins limbs Patterns of development Except for adult echinoderms all coelomates including juvenile echinoderms are bilaterally symmetric and have three embryonic tissue layers This group called the bilatera can be divided into protostomes and deuterostomes Protostomes and deuterostomes Three events in embryonic development cleavage gastrulation and coelom formation Cleavage is a rapid series of mitotic divisions that occurs in the absence of growth Gastrulation is a series of cell movements where embryonic tissues form and coelom forms Protostomes have spiral cleavage and vagination turns a pore into a mouth Deuterostomes have radial cleavage and vagination turns pore into an anus Molecular phylogenies After the split between protos and deuteros the protos split to form two major subgroups the Ecdysozoa and the Lophotrochozoa Segmentation evolved independently in annelids arthropods vertebrates and maybe molluscs Vertebrates are animals with skulls and usually backbones are monophyletic Invertebrates is everything else and are paraphyletic Those aren t natural groupings but a grouping of convenience Feeding Suspension or filter feeders capture food by filtering out particles suspended in air or water Deposit feeders eat their way through a substrate Fluid feeders suck mop up liquids like nectar plant sap blood or fruit juice Mass feeders take chunks of food into their mouths What they eat Only plants or algae herbivores Other animals carnivores Only dead matter detritivores Plants and animals omnivores Herbivores and carnivores can be subclassified Predators kill other organisms using mouthparts and hunting strategies Parasites take nutrients from living animals Endoparasites live inside their hosts Ectoparasites live outside How they move Many are sit and wait predators and some are sessile permanently attached to a surface The vast majority though move under their own power Allows them to more easily Find food Find mates Escape predators The major innovation of limbs made highly controlled rapid movement possible Reproduction and birth Eggs or embryos may be retained in the female s body during development viviparous basically live birth Or eggs laid independently of female oviparous like chickens Some are ovoviviparous Female retains eggs inside her body during early development but the growing embryos are nourished by yolk inside the eff and not by the nutrients from the mother Life cycles Metamorphosis change from juvenile to adult body type Holometabolous metamorphosis juvenile individual is called larva and looks really different than the adult caterpillar and butterfly for example When it grows enough it encases itself and becomes a pupa In this stage it turns into an adult This is known as complete metamorphosis Hemimetabolous metamorphosis juvenile is called a nymph and looks like a mini adult Complete metamorphosis is common in insects and marine animals Something about polyp and a medusa BASAL ANIMAL GROUPS The basal lineages of animals Porifera sponges Cnidaria jellyfish others Ctenophora comb jellyfish Acoelomorpha Porifera 7000 species Benthic bottom of aquatic environments Body is built around a system of tubes and pores that create channels for water currents Suspension feeders Cnidaria majority of the 11 000 are marine Radially symmetric diploblasts with a cell called a cnidocyte to capture prey More have a life cycle that includes both polyp and medusa forms Can reproduce asexually by budding fission or fragmentation or may reproduce