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Invertebrate Biology

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Invertebrate Biology Invertebrate Biology B215 Dr. Khaled Al-Qaoud 2013-2014 1st Semester Biological Classification Major Taxons • A Supergroup Taxon has been recently added between Domain and Kingdom Taxons. • Several intermediate taxons are also used: E.g. subphylum, superclass. 2 Definitions • A species- a group of individual organisms capable of interbreeding and producing fertile offspring. Another mostly used definition of species is they are “groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups". • Nomenclature (scientific binomial naming)- Each species is given a binomial (two part) scientific name typed in italics because it is treated as “Latin name”- The first part of a binomial name is the generic name (Starts with capital letter), i.e., the genus of the species. The second is the specific epithet (starts with small letter). E.g. Musca domestica (house fly). 3 Domains of Living Organisms A phylogenetic tree based on rRNA data, showing the separation of bacteria, archaea, and eukaryotes P R O K A R Y O T E S E U K A R Y O T E S 4 Major Features of Three Domains Feature Bacteria Archaea Eukarya Unicelular or Unicellular Unicellular Mostly Multicellular Multicellular Membrane lipids Phospholipids Varied Phospholipids, , unbranched branched unbranched lipids Cell Wall Yes, with Yes, without With or without cell peptidoglycan peptidoglycan wall & peptidoglycan Nuclear Envelope No No Yes Membrane-bound No No Yes Cytoplasmic organelles Introns No Yes or No Yes 5 Kingdoms of Life 3. Domain Eukarya • Nuclear envelope, histone proteins covering DNA, membraneous cytoplasmic organelles, • 6 Supergroups that include 3 Kingdoms and many Protistan Phyla -- Protista: Polyphyletic thus NOT a single Kingdom; single-celled (lack tissues or extensive cellular differentiation); 51,000 spp. -Animal-like (Protozoa, 34,000 spp) -Plant-like (Protistan Algae, 16,000 spp) - Fungus- like (Slime Molds, 700 spp) --Kingdom Fungi: single & multicelluar osmotrophic (absorptive) heterotrophic; 99,000 spp. --Kingdom Plantae: autotrophic (photosynthetic), multicelluar, reproduction by spores; 310,000 spp. --Kingdom Animalia: Ingestive heterotrophic; multicelluar ; 1,424,000 spp 7 Most Animals Are Invertebrates • Animal species approximately 1.42 millions of which only 61,700 spp. are vertebrates. THUS INVERTEBRATES ACCOUNT FOR >95%. • Greatest number of extant species belong to Phyla - Arthropoda (1.176 million spp) - Mollusca (85,000 spp) - Protozoan phyla (34,000 spp.). 8 Classification • Based on: – Similarity and – Differences among and within the groups Classification by: 1. Cell number 1. Metazoans: true animals, multicellular develop from blastula 2. Protozoa: Unicellular (single cell) Classification according to body symmetry • Symmetry – Bilateral symmetry: possess right and left sides that are approx mirror images. E.g Grass hopper – Radial Symmetry: such animals can be divided into 2 equal halves by any cut that passes through the center of the organism. E.g Sea urchin – Asymmetric body plan: e.g marine sponge Classification • According to embryonic body layers – Diploblastic animals: possess only 2 germ layers • Ectoderm: outermost layer of cells • Endoderm: the innermost layer of cells – E.g: …………………………… – Triploblastic animals: possess 3rd germ layer arises either from endoderm or ectoderm called • Mesoderm: middle layer, always lies between ectoderm and endoderm. Classification • According to Embryonic formation of coelom – Acoelomates: organisms without a hollow space in their embryonic life. Body wall and gut is solid single layer occupied by mesoderm – Pseudocoelomates: • organisms housing a pseudocoel. • The area between the outer body layer and the gut is fluid filled cavity derived from blastocoel. • Gut is independent from musculature • Space is present where digestive organs can be bulged • Gain more effective locomotory system Classification cont. Classification cont. – Eucoelomates: • Real or true coelom • Internal fluid filled cavity lying between the gut and the outer body wall musculature. • Lined within mesoderm Classification cont. • Development of eucoelomates according to method of coelom development – Protostomes: • coelom formation occurs by gradual enlargement of a split in the mesoderm • The process is called Schizocoely: means split – Deuterostomes: • coelom forms through envagination of the archentron into the blastocoel of embryo • Process called enetrocoely: means envagination Classification cont. • Development of eucoelomates according to origin of mouth – Protostomes: • Means first mouth • The mouth is formed from or near the blastopore – Deuterostomes: • Second mouth • The mouth never develops from blastopore • Blastopore gives rise to anus .
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