Lecture 2-3 - Animal Diversity (Slides 15-50) PDF

Biol 224.3 – Animal Body Systems Evolutionary Aspects of Animal Kingdom Supplementary Textbook Reading: (4th Edition: Chapter 27, page 643-650) 15  General concepts What is an “animal”? Animal div...

Biol 224.3 – Animal Body Systems Evolutionary Aspects of Animal Kingdom Supplementary Textbook Reading: (4th Edition: Chapter 27, page 643-650) 15  General concepts What is an “animal”? Animal diversity Characteristics of animals Evolutionary influence on animal body plan/physiology 16  The colloquial use of the word animal refers to non-human animals The biological definition refers to all members of the kingdom Animalia a.k.a Metazoa From the Latin animalis (“having breath” or “having soul”) 17  Diversity of Animals There are more than 1 million known animal species on earth Diverse species Diverse habitats Diverse characteristics 18  Organization of the Animal Kingdom Animal kingdom is monophyletic – all taxa evolved from a single common ancestor ~35 recognized animal phyla Phyla can be grouped into Clades (monophyletic groups that share a common ancestor) based on shared characteristics 19  What is an Animal? Multicellular eukaryote that lacks cell wall Heterotroph Motile at least at some time in their lives Reproduces asexually or sexually (in most) Most have nerve and muscles 20  Animals: multi-cellular eukaryotes Most likely evolved from a colonial unicellular ancestor during the Precambrian era (700 mya) - Probably a flagellated protist - Cells in these protists gradually became more specialized and layered Hypothesized evolution of a two-layered animal body plan 21  Animals: multi-cellular eukaryotes Similar to a modern colonial flagellated species – the choanoflagellates Supported by morphological and Choanoflagellate cell Sponge cell (choanocyte) molecular evidence Some cells may have taken on specialized functions (a) Colonial choanoflagellate (b) Sponge 22  Animals: multi-cellular eukaryotes Coordinated movement in unicellular choanoflagellates: https://www.labroots.com/trending/microbiology/15933/ancestor- animals-coordinate-movements 23 Animal cells lack cell walls 24  Animal cells lack cell walls Tissue stability in animals is achieved through the extracellular matrix and cell junctions 25 Animals can be characterized by basic features of their “body plan” Animal body plans are influenced by: embryonic development pattern germ cell layers body symmetry body cavity type 26 Most animals undergo some form of sexual reproduction Germ line cells NB: asexual undergo meiosis to reproduction also produce haploid occurs (e.g., gametes budding in hydra, fragmentation in echinoderms, and parthenogenesis in Gametes fuse insects, some during fertilization reptiles) to form a diploid zygote 27 *We will learn more about animal reproduction later in the course  Zygote Cleavage follows fertilization The division of cells in the early embryo – Zygotes undergo rapid cell cycles with no significant growth – Zygote develops into a compact mass of cells termed morula – Morula derives into a hollow sphere of single layer of cells, termed blastula 28 Cleavage patterns are an important trait distinguishing two major animal lineages 29  Cleavage patterns are an important trait distinguishing two major animal lineages Protostomes exhibit spiral cleavage - newly produced cells lie in the space between the cells immediately below them Each cells developmental path is determined as the cell is produced 30 Image source: cronodon.com  Cleavage patterns are an important trait distinguishing two major animal lineages Deuterostomes exhibit radial cleavage - newly produced cells lie directly above and below other cells of the embryo Developmental fates of the first few cells are not determined A cell removed from the morula will go on to form a complete organism (e.g., 31 identical twins) Image source: cronodon.com  Gastrulation follows cleavage Gastrulation begins at the vegetal pole Blastula is unique to animals Blastula invaginates and undergoes further differentiation into 2 or 3 (most animals) germ layers: – Ectoderm – Mesoderm – Endoderm Germ layers differentiate to form tissues and organs 32  Germ layers develop into tissues and organs in the mature animals Diploblastic animals (e.g., jellyfish, corals, anemones) have 2 germ layers: Ectoderm and Endoderm Triploblastic animals (e.g., flatworms, chordates) have 3 germ layers: Ectoderm, Endoderm and Mesoderm Ectoderm – Skin and nervous system Endoderm – Digestive tract Mesoderm – Muscle and skeleton 33 Additional Differences in embryonic developmental pattern between Protostomes and Deuterostomes Protostomes Deuterostomes 34  Additional Differences in embryonic developmental pattern between Protostomes and Deuterostomes In protostomes, mesoderm differentiates near the blastopore and the coelom (body cavity) originates as a split in the mesoderm (i.e., schizocoelom) In deuterostomes, mesoderm originates from outpocketings of the archenteron (primitive gut). The coelom develops from space within the outpocketings (i.e., enterocoelom) 35  Protostomes Deuterostomes Mouth develops from Mouth develops from blastopore secondary opening Spiral cleavage Radial cleavage Determinate cleavage Indeterminate cleavage Mesoderm differentiates Mesoderm originates from near blastopore outpocketings of the archenteron Schizocoelom Enterocoelom 36 Animals can be characterized by basic features of their “body plan” Animal body plans are influenced by: embryonic development pattern (Protostomes vs. Deuterostomes) germ cell layers (Diploblasts vs. Triploblasts) body symmetry body cavity type 37  Organization of the Animal Kingdom Animal kingdom is monophyletic – all taxa evolved from a single common ancestor ~35 recognized animal phyla Phyla can be grouped into Clades (monophyletic groups that share a common ancestor) based on shared characteristics 38  Body Symmetry of Animals Radial symmetry: can be divided equally by any longitudinal plane passing through the central axis Bilateral symmetry: can be divided along a vertical plane at the middle to create two identical halves 39  Animals with radial symmetry Diploblastic (except adult echinoderms) Exhibits no left or right sides – Have a top (dorsal) and a bottom (ventral) side Often circular or tubular in shape with a mouth at one end (e.g., cnidarians and ctenophores) 40  Animals with bilateral symmetry Triploblastic Balanced duplicate distribution of most body parts – Specialized head with feeding and sensory organs (Cephalization) – Digestive chamber with two openings, mouth and an anus 41  Most animals with bilateral symmetry- Segmentation Repeated structures along the anterior-posterior axis Seen in annelids, arthropods, chordates Advantages: movement, specialization 42  In most bilaterally symmetrical animals, a body cavity (coelom) separates the gut from the body wall Most animals are coelomate A fluid-filled cavity between the intestines and the body wall - Formed within the mesoderm of the embryo 43  Differences in body cavity Acoelomate (a = not; koilos = hollow) – No body cavity – Flat worms (Phylum Platyhelminthes) N.B. Diploblasts are all acoelomates Pseudocoelomate (pseudo = false) – Pseudocoelum: Fluid-filled or organ- filled space between endoderm and mesoderm – Roundworms (Phylum Nematoda) 44  Something to Think About What are the advantages of multicellularity over unicellularity? Why bilateral symmetry is more common in animal kingdom? What are the disadvantages of being an acoelomate animal? 45 Why do we study animal diversity and evolution? Animals (and animal body systems) have a common evolutionary history helps us to learn common principles Animals occupy very diverse types of environments helps us understand environmental adaptations The physiological phenotype is a product of the genotype and the environment. 46 Example: Environmental constrains – Respiratory systems 47 What challenges animals must overcome to be able to survive and reproduce? Extract nutrients & O2/energy from the environment Eliminate toxic metabolic wastes from the body Sense the environmental changes and respond favorably Maintain near constant internal body conditions 48 Animals are diverse, yet some common principles apply to all animals (Unifying concepts) Physiological processes must: Obey the laws of physics and chemistry Usually tightly regulated (homeostasis) 49 Physiological processes obey the laws of physics and chemistry Example: Electrical laws describe membrane function of all cells, including excitable cells Neuron Muscles 50