Lecture 20 Invertebrates 1 pdf

Lecture 20 Invertebrates 1 pdf - Invertebrates 1: An...

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1 Dr. Andy Gracey BISC 120 Section 3 Invertebrates 1: An Introduction to Animal Diversity Welcome to Your Kingdom Animal diversity Man Ecology Ecosystem 1.3 million living species of animals have been identified Biosphere What defines animals? Animals are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers 1. Multicellular, heterotrophic eukaryotes 2. Lack the cell walls of plants and fungi 3. 4. Sexual reproduction, diploid adult stage 5. All have Homeotic ( Hox ) genes regulating early development
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2 Nutritional Mode Animals are heterotrophs that ingest their food • Need to consume organic substrates in order to grow • Typically have some sort of orifice through which food enters Cell Structure • Animals are multicellular eukaryotes • Animal cells lack cell walls • Tissues are held together by structural proteins such as collagen (ECM) White adipose tissue Cell specialization Specialized neural cells and muscle cells are unique to animals Cells are organized into nervous tissue and muscle tissue Nervous system allows perception of noxious or favorable environmental conditions, predators, prey Muscle tissue allows the animal to respond to environment or stimuli Most animals reproduce sexually In most species, a small flagellated haploid sperm fertilizes a larger, haploid, non-motile, polarized egg Mitotic cell divisions called cleavage , lead to the formation of the blastula Figure 32.2 Invagination produces the gastrula , endoderm , and ectoderm
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3 Sea Urchin development Fate of germ layers Some tumors arise due to mistakes in germ layer differentiation Teratomas are most common type and frequently derived from ectoderm Ovarian teratoma with teeth! Many Animals have Complex Life Cycles Many animals have distinct larval stages – The larva is sexually immature & morphologically and ecologically distinct from the adult Larvae eventually undergo metamorphosis , transforming into an adult trochophore D-hinge pediveliger
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4 All animals (and only animals) have homeobox- containing family of genes called Homeotic or Hox genes Transcription factors that regulate the genes that control development of body form Because all animals share Hox genes, this gene family may have arisen in the eukaryotic lineage that gave rise to animals Animals have Homeotic genes Nobel prize for medicine 1995 Edward B. Lewis , Christiane Nüsslein-Volhard and Eric Wieschaus for discoveries concerning "the genetic control of early embryonic development". Hox genes discovered by genetic analysis of mutant fruit flies Hox genes control morphology Lewis found a Cluster of homeotic ( Hox ) genes in the chromosome Colinearity in time and space – • The gene order in the cluster mimics the order of expression of genes and their function along the anterior–posterior (A–P) body axis • Exhibit temporal colinearity - anterior genes expressed first during development and posterior later Duplication of
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Lecture 20 Invertebrates 1 pdf - Invertebrates 1: An...

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