CAMPBELL BIOLOGY TENTH EDITION Reece Urry Cain Wasserman Minorsky Jackson 32 An Overview of Animal Diversity Lecture Presentation by Nicole Tunbridge and Kathleen Fitzpatrick
Concept 32.1: Animals are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers Animals are multicellular eukaryotes Nutritional Mode: Animals are heterotrophs that ingest their food and digest within their bodies (unlike fungi) Many have elaborate tissue architecture downside?
Cell Structure and Specialization Their cells lack cell walls Their bodies are held together by structural proteins such as collagen specialization: Tissues are groups of similar cells that act as a functional unit Nervous tissue and muscle tissue are unique, defining characteristics of animals
Reproduction and Development Most animals reproduce sexually, with the diploid stage usually dominating the life cycle After a sperm fertilizes an egg, the zygote undergoes rapid cell division called cleavage Cleavage leads to formation of a multicellular, hollow blastula The blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissues
Figure 32.2-1 Zygote Eight-cell stage Cleavage Most animals reproduce sexually, with the diploid stage usually dominating the life cycle
Figure 32.2-2 Zygote Eight-cell stage Cleavage Cleavage Blastocoel Blastula multicellular, hollow Cross section of blastula
Figure 32.2-3 Zygote Eight-cell stage Cleavage Cleavage Blastocoel Blastula Cross section of blastula Gastrulation Cross section of gastrula Blastopore Blastocoel Endoderm Ectoderm Archenteron different layers of embryonic tissues
Video: Sea Urchin Embryonic Development (Time Lapse)
Most animals have at least one larval stage A larva is sexually immature and morphologically distinct from the adult; it eventually undergoes metamorphosis to become a juvenile A juvenile resembles an adult, but is not yet sexually mature larva
Most animals, and only animals, have Hox genes that regulate the development of body form Although the Hox family of genes has been highly conserved, it can produce a wide diversity of animal morphology
Concept 32.2: The history of animals spans more than half a billion years The common ancestor of all living animals likely lived between 700-770 MYA Ediacaran fossil animals Ediacaran biota ~560 MYA
Steps in the Origin of Multicellular Animals Slime molds Tubulinids Entamoebas Nucleariids Fungi Choanoflagellates Animals Excavata SAR clade Archaeplastida Unikonta
Concept 28.5: Unikonts include protists that are closely related to fungi and animals The supergroup Unikonta includes animals, fungi, and some protists This group includes two clades: the amoebozoans and the opisthokonts (animals, fungi, and related protists)
Figure 28.24 Results Choanoflagellates Common ancestor of all eukaryotes Animals Fungi Amoebozoans Diplomonads Euglenozoans Unikonta Excavata DHFR-TS gene fusion Stramenopiles Alveolates Rhizarians Red algae Green algae Plants SAR clade Archaeplastida
Figure 28.18 Rhizarian amoebas Rhizarians (radiolarians, forams, and cercozoans) differ from amoebas in other clades by having threadlike pseudopodia Pseudopodia 200 μm
Amoebozoans Amoebozoans are amoeba that have lobe- or tube-shaped, rather than threadlike, pseudopodia They include 1) slime molds, 2) tubulinids, and 3) entamoebas
1) Slime Molds Cellular slime molds form multicellular aggregates in which cells are separated by their membranes Cells feed individually but can aggregate to migrate and form a fruiting body Dictyostelium discoideum is an experimental model for studying the evolution of multicellularity
Figure 28.26-2 600 μm Spores (n) Emerging amoeba (n) Solitary amoebas (feeding stage) (n) ASEXUAL REPRODUCTION Aggregated amoebas FERTILIZATION SEXUAL REPRO- DUCTION Zygote (2n) MEIOSIS Amoebas (n) Fruiting bodies (n) Migrating aggregate 200 μm Cellular Slime Molds Haploid (n) Diploid (2n)
2) Tubulinids Tubulinids are a diverse group of amoebozoans with lobeor tube-shaped pseudopodia They are common unicellular protists in soil as well as freshwater and marine environments Most tubulinids are heterotrophic and actively seek and consume bacteria and other protists 3) Entamoebas https://www.youtube.com/watch?v=pvoz4v699gk Entamoebas are parasites of vertebrates and some invertebrates - causes amoebic dysentery
Figure 28.24 Results Choanoflagellates Common ancestor of all eukaryotes Animals Fungi Amoebozoans Diplomonads Euglenozoans Unikonta Excavata DHFR-TS gene fusion Stramenopiles Alveolates Rhizarians Red algae Green algae Plants SAR clade Archaeplastida
Concept 32.2: The history of animals spans more than half a billion years The common ancestor of all living animals likely lived between 700-770 MYA Morphological and molecular evidence points to a group of protists called choanoflagellates as the closest living relatives to animals
Figure 32.3 Morphological evidence Individual choanoflagellate Choanoflagellates OTHER EUKARYOTES Sponges Animals Other animals Collar cell (choanocyte) similar collar cell s seen
Figure 32.4 molecular evidence The origin of multicellularity requires the evolution of new ways for cells to adhere (attach) and signal (communicate) to each other Choanoflagellate Hydra Fruit fly Mouse CCD domain (only found in animals) Cadherin proteins similarities between genes coding for proteins involved in adherence and attachment in choanoflagellates and animals
Paleozoic Era (542 251 Million Years Ago) The Cambrian explosion (535 to 525 million years ago) marks the earliest fossil appearance of many major groups of living animals
Paleozoic Era (542 251 Million Years Ago) Most of the fossils from the Cambrian explosion are of bilaterians, organisms that have the following traits: Bilaterally symmetric form Complete digestive tract One-way digestive system
Figure 32.7 A Cambrian seascape Hallucigenia fossil (530 mya) 1 cm
There are several hypotheses regarding the cause of the Cambrian explosion and decline of Ediacaran biota New predator-prey relationships A rise in atmospheric oxygen The evolution of the Hox gene complex
Concept 32.3: Animals can be characterized by body plans body plan - a set of morphological and developmental traits 1) Symmetry (e.g.radial symmetry-with no front and back, or left and right) Radial animals are often sessile or planktonic (drifting or weakly swimming)
Two-sided symmetry is called bilateral symmetry Bilaterally symmetrical animals have A dorsal (top) side and a ventral (bottom) side A right and left side Anterior (front) and posterior (back) ends Many also have sensory equipment, such as a brain, concentrated in their anterior end Bilateral animals often move actively and have a central nervous system Bilaterians- flatworms, arthropods, vertebrates, and others
Figure 32.3 Choanoflagellates OTHER EUKARYOTES Sponges Sponges lack true tissues Animals Other animals
2) organization of the animal s tissues Tissues are collections of specialized cells isolated from other tissues by membranous layers During development, three germ layers give rise to the tissues and organs of the animal embryo Diploblastic animals have Ectoderm is the germ layer covering the embryo s surface Endoderm is the innermost germ layer and lines the developing digestive tube, called the archenteron Triploblastic animals intervening mesoderm layer
Figure 32.9 Body cavity- coelom derived from mesoderm body cavity derived from the mesoderm and endoderm (a) Coelomate (b) Psuedocoelomate Coelom Body covering (from ectoderm) Body covering (from ectoderm) Digestive tract (from endoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) Pseudocoelom Digestive tract (from endoderm) Muscle layer (from mesoderm) (c) Acoelomate Body covering (from ectoderm) Wall of digestive cavity (from endoderm) Tissuefilled region (from mesoderm) Key Ectoderm Mesoderm Endoderm Body cavities of triploblastic animals
Terms such as coelomates and pseudocoelomates refer to organisms that have a similar body plan and belong to the same grade A grade is a group whose members share key biological features A grade is not necessarily a clade, an ancestor and all of its descendants
3) Protostome and Deuterostome Development based on early development
Figure 32.10a Cleavage of early embryo In protostome development, cleavage is spiral and determinate In deuterostome development, cleavage is radial and indeterminate With indeterminate cleavage, each cell in the early stages of cleavage retains the capacity to develop into a complete embryo Indeterminate cleavage makes possible identical twins, and embryonic stem cells (a) Cleavage Protostome development (examples: molluscs, annelids) Eight-cell stage Deuterostome development (examples: echinoderms, chordates) Eight-cell stage Spiral and determinate Radial and indeterminate
Figure 32.10b (b) Coelom formation Key Ectoderm Mesoderm Endoderm Protostome development (examples: molluscs, annelids) Archenteron Coelom Deuterostome development (examples: echinoderms, chordates) Coelom Mesoderm Blastopore Blastopore Mesoderm Solid masses of mesoderm split and form coelom. Folds of archenteron form coelom.
Figure 32.10c (c) Fate of the blastopore Protostome development (examples: molluscs, annelids) Anus Deuterostome development (examples: echinoderms, chordates) Mouth Digestive tube Key Ectoderm Mesoderm Endoderm Mouth Mouth develops from blastopore. Anus Anus develops from blastopore.
Concept 32.4: Views of animal phylogeny continue to be shaped by new molecular and morphological data By 500 million years ago, most animal phyla with members alive today were established Phylogenies now combine morphological, molecular, and fossil data Zoologists recognize about 36 animal phyla
Five important points about the relationships among living animals are reflected in their phylogeny 1. All animals share a common ancestor 2. Sponges are basal animals 3. Eumetazoa ( true animals ) is a clade of animals with true tissues 4. Most animal phyla belong to the clade Bilateria 5. There are three major clades of bilaterian animals, all of which are invertebrates, animals that lack a backbone, except Chordata, which are classified as vertebrates because they have a backbone
Figure 32.11 Porifera ANCESTRAL PROTIST Metazoa 770 million years ago Eumetazoa 680 million years ago Bilateria 670 million years ago Bilateral symmetry Three germ layers Deuterostomia Lophotrochozoa Ecdysozoa Ctenophora Cnidaria Acoela Hemichordata Echinodermata Chordata Platyhelminthes Rotifera Ectoprocta Brachiopoda Mollusca Annelida Nematoda Arthropoda
Figure 32.11b The bilaterians are divided into three clades: Lophotrochozoa have a feeding structure called a lophophore Ecdysozoa is a clade of invertebrates that shed their exoskeletons through a process called ecdysis