Lecture13

thick-walled spores complex gametangia retention of embryo on parent alternation of multicellular generations gametophyte dominated generation homospory ferns mosses ferns mosses ferns mosses Seed plant synapomorphies (diagnostic homologies that arose in most recent common ancestor to taxon) Heterospory-- sporophyte produces two different kinds of spores Spore retention -- gametophyte then differentiates on sporophyte Seed ? live cycle stage that facilitates dispersal of well-provisioned, well protected, dormant embryonic progeny heterospory & spore retention Cloud of conifer pollen in springtime wind (most conifers are wind-pollinated). Wind transfers pollen from male to female strobili of larch (Larix decidua) ferns mosses Microspore gives rise to pollen ? male gametophytes heterospory & spore retention Life cycle in a representative gymnosperm ? a pine tree ferns mosses ovulate cones surrounding a single pollen-bearing cone heterospory & spore retention ferns mosses ovulate cones surrounding a single pollen-bearing cone Megaspore forms female gametophyte that develops in ovule and is retained through gamete formation, fertilization, and early embryonic development (seed!) extensive parental investment by female in progeny ? nourishment, protection heterospory & spore retention * seed in dormant state on left, beneath soil surface, germinates under favorable environmental conditions mosses ferns Seed Plants heterospory & spore retention * mosses ferns Gymnosperms Seeds are "naked" not enclosed by a ripened ovary (fruit). Angiosperms seeds enclosed by a ripened ovary ? fruit.) Lily of the valley flowers and fruit) Seeds are a major life history innovation that facilitate dispersal of a protected, well provisioned, dormant embryo heterospory & spore retention * mosses ferns Angiosperms seeds enclosed by a ripened ovary ? fruit.) Lily of the valley flowers and fruit) Seeds are a major life history innovation that facilitate dispersal of a protected, well provisioned, dormant embryo Flowers are reproductive organs that increase probability fertilization -- animal mediated fertilization in many angiosperms Fruits are reproductive structures that increase the probability of dispersal ? animal-mediated dispersal in many angiosperms heterospory & spore retention * mosses ferns heterospory & spore retention INTRODUCTION TO ANIMALS * Animals Traits shared by all lineages Eukaryotic, multicellular, heterotrophic ingesters Traits shared by most lineages Developmental program that gives rise to tissues Motility ? locomotion Life cycle characterized by sexual reproduction and a diploid adult phase Introduction to Animals Phylogeny Body plans Feeding Locomotion Life cycles, Life History * Animalia Segmentation Protostoma Bilateria Lophotrochozoa Deuterostoma Ecdysozoa Chordata Echinodermata Arthropoda Nematoda Annelida Mollusca Rotifera Platyhelminthes Acoelomorpha Ctenophora Porifera Cnidaria Choanoflagellates Pseudocoelom Acoelom Protostome development Growth by molting Pseudocoelom Segmen- tation Radial symmetry (in adults) Deuterostome development Segmen- tation Coelom Triploblasty (origin of mesoderm) Bilateral symmetry and cephalization Radial symmetry Diploblasty (ectoderm and endoderm) Epithelial tissue Multicellularity (comb jellies) (sponges) (jellyfish, sea anemeones) (acoels) (rotifers) (flatworms) (segmened worms) (snails, clams, squid) (insects, spiders, crustaceans) (roundworms) (sea stars, sand dollars) (vertebrates, ascidians) Phylogenetic tree based on similarities and differences in the DNA sequences of several genes from various animal phyla. The bars along the branches indicate when certain morphological traits originated Phylogeny of Animal Phyla Based on DNA Sequence Data * Animalia Segmentation Protostoma Bilateria Lophotrochozoa Deuterostoma Ecdysozoa Chordata Echinodermata Arthropoda Nematoda Annelida Mollusca Rotifera Platyhelminthes Acoelomorpha Ctenophora Porifera Cnidaria Choanoflagellates Pseudocoelom Acoelom Protostome development Growth by molting Pseudocoelom Segmen- tation Radial symmetry (in adults) Deuterostome development Segmen- tation Coelom Triploblasty (origin of mesoderm) Bilateral symmetry and cephalization Radial symmetry Diploblasty (ectoderm and endoderm) Epithelial tissue Multicellularity (comb jellies) (sponges) (jellyfish, sea anemeones) (acoels) (rotifers) (flatworms) (segmened worms) (snails, clams, squid) (insects, spiders, crustaceans) (roundworms) (sea stars, sand dollars) (vertebrates, ascidians) Phylogenetic tree based on similarities and differences in the DNA sequences of several genes from various animal phyla. The bars along the branches indicate when certain morphological traits originated Key innovations set the stage for adaptive radiation of triploblastic coelomate animals Evolution of tissues and developmental program Evolution of bilaterally symmetric body plan ? directed movement, cephalization Evolution of body cavity between digestive tract and body wall * Animal synapomorphies -rRNA -cell junctions -matrix proteins Radially symmetric Cnidarian Asymmetric sponge (Poriferan) Bilaterally symmetric flatworm (platyhelminthes) * 2 embryonic germ tissue layers 3 embryonic germ tissue layers coelomic body cavity (2 basic, functionally similar, forms have evolved) Coelomate Earthworm The tube-within-a-tube body plan of triploblastic coelomates, in a common Annelid ? the earthworm * * Porifera is a basal lineage of animals lacking true tissues, true symmetry, and other innovations characterizing more recent lineages Cnidarians (and Ctenophores) (secondarily evolved in one lineage of Deuterstomes) Porifera Protostomes and Deuterstomes * * The sponges are sessile organisms with porous bodies and choanocytes: These are flagellated internal water chambers that generate a water current and trap food particles * Evolution of developmental program; embryonic tissue layers that build complex tissues and organs Introduction to Animals Phylogeny Body plans Feeding Locomotion Life cycles ? will get to it over the remaining animal lecture topics Settled sponge larva - sectioned Origin of cell specialization, tissues, developmental program Hypothesis on evolution of animals with specialized cells arranged in two layers Colonial flagellated protist with unspecialized cells Certain cells became specialized for feeding & other functions A developmental reorganization produced a two-layered animal with a sac-within-a-sac body plan * Gastrulation Embryo (blastula) gastrulates giving rise to embryonic tissue layers and the onset of morphogenesis Important events & processeses germ layers body plans inductive interactions * Tissues & Embryonic Tissue Layers* Embryonic Tissue Layers Endoderm Mesoderm Ectoderm Tissue Group of similar cells organized into a functional unit -- often integrated with other tissues to form part of an organ * *22.4 in textbook Mesoderm; triploblast opportunities? Muscle tissue Peritoneum (lining of the coelom) Reproductive organs and ducts Endoskeleton ? bone and cartilage Heart, blood vessels Connective tissues in general Kidney and urogenital ducts Hydra * Cnidarian traits radially symmetric diploblasts a sac-like gastrovascular cavity, contractile fibers that contribute to motility via a hydrostatic skeleton cnidocytes ?specialized stinging feeding-cells Lion's mane jellyfish A sea anemone that swims. When attacked by a predatory sea star Dermasterias, the anemone Stomphia didemon detaches from the bottom and rolls or swims spasmodically to a safer location. * * The hydrostatic skeleton - contractile fibers impinging on incompressible fluid ? is an important form-function complex that has arisen independently in animals many times Epitheliomuscular and nerve cells in Hydra Daphnia Daphnia consumed by Hydra Cross section of Hydra * * Bilateral symmetry, directed movement, and cephalization; key innovations, correlated traits Cnidarians (and Ctenophores) (secondarily evolved in one lineage of Deuterstomes) Porifera Protostomes and Deuterstomes Symmetry, Directed Movement, and Cephalization * * flatworm sea anemone Comparison of nervous systems organization in non-cephalized cnidarians and cephalized platyhelminthes * Evolution of a coelom ? a fluid-filled cavity lying between the digestive tube and the body wall ? is a key innovation that contributed significantly to the adaptive radiation of protostomes and deuterostomes Triploblasts with & without Coeloms Coelom functions -circulation -protected 3D space to suspend organs -body flexibility -hydrostatic skeleton Epithelial tissue Molting * Animations and Videos on hydrostatic skeletons Nematode http://www.eeob.iastate.edu/faculty/DrewesC/htdocs/INT-ANIMA-v inegar.htm Annelids http://www.biology.ualberta.ca/courses.hp/zool250/animations/Earthworm.swf http://www.biology.ualberta.ca/courses.hp/zool250/animations/Polychaete.swf * Hydrostatic skeletons facilitate: -locomotion -burrowing -feeding * Coelom functions -circulation -protected 3D space to suspend organs -body flexibility -hydrostatic skeleton