Chapter 32: Animal Diversity
Chapter 32: Animal Diversity BYS 120
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This 13 page Class Notes was uploaded by Amelia Notetaker on Tuesday December 1, 2015. The Class Notes belongs to BYS 120 at University of Alabama - Huntsville taught by Dr. Luciano Matzkin in Fall 2015. Since its upload, it has received 15 views. For similar materials see Organismal Biology in Biological Sciences at University of Alabama - Huntsville.
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Date Created: 12/01/15
Chapter 32 Lecture Notes Animals o Multicellular eukaryotes o Heterotrophs o 1.3 million described species General characteristics o Cells lack cell walls o Multicellular bodies are held together by structural proteins (collagen) o Nervous and muscular tissue are a unique characteristic of animals o Tissues: groups of cells that have a common structure, function or both Reproduction o Most animals reproduce sexually o Diploid stage is usually the dominant stage No sporophyte or gametophyte stage o After the haploid sperm fertilizes the haploid egg, a zygote (diploid) is formed Development o Rapid cell division without cell growth that occurs after fertilization is called cleavage Half then half then half o Cleavage leads to formation of a multicellular hollow blastula Cells migrate towards the edge o Many animals at least have 1 larval stage Larval --> diploid o A larva is sexually immature and morphologically distinct from the adults o Larva undergoes metamorphosis, the reorganization of larval tissue into juvenile Caterpillar cocoon o Juvenile resembles an adult but isn't sexually mature Gastrulation o Blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissues Folds and creates wrinkles Produces different organs, tissues, etc hox genes also tell what cells fold in what direction Patterning genes o Only animals (most) have hox genes that regulate the development of body form Animal evolution o Great diversity of extant species 99% of animals are extinct o Common ancestor of living animals may have lived between 675-800 MYA o Ancestor may have resembles modern choanoflagellates o Edicaran Early members of the animal fossil record include the edicaran biota (565-550 MYA) o Cambrian explosion 535-525 MYA, marks earliest fossil appearance of many major groups of living animals Why rapid radiation? Predator/prey interaction Evolution of offensive and defensive structures Evolution of hox genes Changes in atmosphere conditions Increase in O2, allows complex metabolisms that allow production of hard body parts Palozoic o Animal diversity continued to increase through this time period Several mass extinctions o Transition to land by 460 MYA o Vertebrates transition to land 360 MYA Mesozoic o 251-65.5 MYA Coral reefs Dinosaurs dominated terrestrial habitats Mammals evolve Angiosperms and insects diversify Cenozoic o Mass extinction o Mammals filled in all the vacated niches Asteroid impact and extinction o Extinctions likely occurs "immediately" after the impact Body plan o Set of morphological and developmental traits Use to categorize animals Symmetry Tissue development Order of developmental stages (steps) Radial symmetry o With no front or back or left or right "slice" it any way and it's symmetrical o Radial animals are often sessile and planktonic Sessile: doesn't move much Bilateral symmetry o 2 sided: Dorsal and ventral sides Left and right sides Anterior and posterior sides o Develop central nervous system in head, cephalization o Often move actively and have a central nervous system Tissue development o Animal body plans also vary according to the organization of the tissues o Tissues are isolated collections of specialized cells o Not found in sponges o 3 types Ectoderm: germ (outside) layer covering the embryo's surface Mesoderm: middle layer Endoderm: inner most, lines developing digestive tube called archenteron o Diploblastic: animals with only ectoderm and endoderm Comb jellies o Triploblastic: animals with all three layers All bilaterians Vertebrates, arthropods, worms Body cavities o Most triploblastic animals possess a body cavity o A true body cavity is called a coelom, it’s derived from mesoderm, also is lined by mesoderm o Coelom can b used for structural support as well as housing of the protection and isolation of organs and such o Triploblastic animals lacking a body cavity are called acoelomates Flat worms Pseudocoelom is a body cavity derived from mesoderm and endoderm Triploblasts with these are called pseudocoelomates o Coelomates are triploblasts that possess a true coelom Bilateral symmetry is least associated with what? o A sessile condition Triploblastic animals o All have endoderm, mesoderm, and ectoderm Early embryonic development o Most animals can be classified as having either of 2 types of development Protostome Mollusks, annelids Dueterostome Echinoderms, chordates, humans Protostomes o Cleavage Spiral and determinant Rotate as it is dividing Determinant: the ultimate fate of the daughter cells are established very early on If a cell is removed, the structure is removed o Coelom formation Splitting of solid masses of mesoderm forms the coelom Fate of blastopore Forms during gastrulation and connects the archenteron to the interior of the gastrula Becomes mouth and anus Deuterstome o Cleavage Radial and indeterminate Indeterminate: each cell retains capacity in early cleavage stages to develop into complete embryo Gives possibility of twins o Coelom formation Mesoderm buds from the wall of archenteron to form coelom Forms anus then mouth Which isn't true about protostomes? o Coelom is formed from folds in archenteron What do coelomate and pseudocoelomate animals have in common? o Presence of a body cavity Phylogenetic relationship of animals o Active research field o Molecular phylogenetics and genomics have helped in rearranging prior phylogenetic relationships Animal phylogeny key points o All share a common ancestor o Sponges are basal branching animals o Eumtazoa: clade of animals with true tissues o Metazoa contains branch of animals without true tissues (sponges) o Bilateria is clade most belong to o Chordates and some other phyla belong to the clade duesterostomia o Ecdysozoans shed their exoskeletons, a process called ecdysis o Some eopotrochozoans have a feeding structure called a lophophore Fan-like, capture food, filter feeders Some do, some don't Others go through a distinct development stage called a trochopore larva Some do some don't Grade vs clade o Grade: group where members share key biological features o Grade isn't necessarily a clade Animal phylogeny o Vertebrates are nested within chordates o Invertebrates make up 95% of phylogeny Porifera o Sponges o Sedentary and live in marine or fresh water o Lack true tissues and organs o Suspension feeders: capture food particles suspended in water o Water is drawn through pores into a cavity (songocoel) and in an opening o Reproduction Hermaphrodites Both male and female Big cloud of a lot of gametes Broadcast sponers Choanocytes o Help sponges feed o Sponges are very similar in structure and function of the choanoflagellates protozoan Cnidarians o True tissues (Eumetazoa) o Oldest group in clade Hydrozoan Marine Alternate between polyps and medusa forms Polyps release sperm and egg, hoping they meet their opposite Dominant stage: diploid Scyplrozoa Jellies are prevalent form Culozoa Box jellies and sea wasps Highly toxic Neurotoxin --> stop breathing Anthozoans Corals and sea anemones Occurs only as polyps o Body plan Sessile and motile Relatively simple diploblastic radial body plan Sac with central digestive compartment is the gastrovascular cavity Mouth and anus Sessile polyps but motile medusa o Feeding Carnivores --> tentacles catch prey Cnidocytes: offense and defense tentacles Nematocytes: eject stinging thread Trigger is activated Jelly fish sting, can be toxic Corals o Symbiosis with algae and secrete hard exoskeleton o Zooranthellae algae sensitive to temperature and pH, coral bleaching Algae leave, but the coral can survive a while but will die eventually Gentrophora o Comb jellies Diploblastic Radial symmetry o Use cilia for locomotion Why do sponges represent a separate linage, distinct from all other animal phyla? o They lack true tissues Cnidaria includes groups with a variety of body forms, but all share which common feature? o All have a gastrovascular cavity and tentacles Cophotrochozoans o Feeding structure lophophore (some) o Others go through trochophore larva o Some don’t have lophophore or trophore larva o Platyhelininthes Flat worms Marine, freshwater, damp land Triploblastic Acoelomates Flattened dorsovenetally and have 1 opening to gastrovascular with 1 opening Gas exchange across surface Protonephridia regulates osmotic balance Rhabditophora Planarians Freshwater Prey on smaller animals Hermaphroditic Sexual or asexual Can be cut in half and regrow Light sensitive eyespots Nervous system more complex and centralized Parasitic Trematodes Parasitize many hosts Complex life cycles --> asexual and sexual stages Part of life in snail hosts Surface proteins that mimic their host's 2 hosts to complete 1 life cycle Tapeworms Vertebrates, parasitic, no digestive system Absorbs nutrients from host's intestines Scolex contains suckers and hooks Fertilized eggs produce sexually and leave in host's feces Rhotifera Tiny, fresh water, ocean, damp sod Smaller than single celled organisms and have specialized organ systems Have alimentary canal with a separate mouth and anus that lies within pilled pseudocoelom Multicellular Reproduce through parthenogenesis Females produce offspring without fertilizing eggs Some species lack males entirely Chain worms: parasites Ectoprocta o Sessile and colonial Lophophore Coelomates o Hard exoskeleton encases colony Builds up reefs Brachiopada o Have shells 2 halves of shells are dorsal and ventral rather than lateral as in clams o Lophophore o Coelomates o Marine and attach to seafloor by stalk Mollusca o Snails and slugs o Most marine and fresh water, few terrestrial o Soft bodied, but most are protected by a shell o Coelomates o Contain Muscular foot Visceral mass Mantle o Many also have water filled mantle cavity and feed using a rasp-like radula Tongue with teeth o Recently gone extinct (some) Land snails o Some are invasive and damage ecosystems Zebra muscles o Reproduction Separate sexes with gonads located on the visceral mass Many snails are hermaphrodites Life cycle of many include a ciliated larval stage (trophophore) o Polyplacophore (chiton) Oval-shaped and marine Encased in amour of 8 dorsal plates Foot used as a suction cup and use radula to scrape up and eat algae o Gastropoda Marine, fresh water, terrestrial Majority of mollusks Snails and slugs Most common characteristic: torsion Causes anus and mantle to end up above its head Single spiraled shell o Bivalia Marine Clams, oysters, mussels, and scallops Shell divided into 2 halves drawn together by adductor muscles Some have eyes and sensory tentacles alone the edge of the mantle o Cephalopoda Carnivores with beak-like jaws surrounded by tentacles Partly modified foot Closed circulatory system, well developed sense organs and complex brain Octopi Squid Nautiluses Annelida o Bodies composed of a series of rings o Coelomates o Polyhcaetes Paddle-like parapodia Marine o Oligochaetes Named for relatively sparse chaete, bristles made of chitin Earthworms Leeches are some that are either predators or blood sucking parasites The group lophotrochozoa includes 18 phyla and have huge diversity of body forms. On what basis are all these animals thought to be in the same clade? o DNA sequencing You find an animal with a shell and ciliated tentacles, what is it? o Brachiopod Ecdysozoa o Covered in tough coat called cuticle o Cuticle is shed or molted through ecdysis o Nematoda Round worms found in most aquatic habitats and soil Can be parasitic They have Alimentary canal Pseudocoelom No circulatory system No segmented body o Usually sexual reproduction but same can sexually reproduce Internal fertilization o Caenorhabditis elegans is a model organism in research o Some are parasites to plants and animals o Thrichinella spiralis can be acquired by humans in undercooked pork o Arthropoda 2 out of every 3 known species of animals are arthropods Extremely diverse Body plan consists of Segmented body Hard exoskeleton Jointed appendages Body plan dates to Cambrian explosion Early ones show little variation from segment to segment Evolution characterized by a decrease in number of segments by an increase in appendage specialization May have been caused by hox gene sequence or regulation Walking, feeding, sensory reception, reproduction, and defense Completely covered by cuticle, are exoskeleton made of layers of protein and chitin When it rows it needs to molt its exoskeleton Have eyes, olfactory receptors, and antennae that function in touch and smell Open circulatory system in which hemolymph is circulated into the spaces surrounding the tissues and organs Chelicerata Claw-like feeding appendages (chelicerae) Most marine forms are extinct but some survived, like horse-shoe crabs Most modern ones are arachnids Spiders, ticks Body plan is Abdomen Cephalothorax with 6 pairs of appendages Cheliceral: poison needle Pedipalps: smell 4 pairs of walking legs Many spiders produce silk ligail protein from specialized abdomenal glands Myriapoda Millipedes and centipedes Jaw-like mandibles, and terrestrial Millipedes eat decaying leaves and plant matter, have many legs and 2 pairs per segment Centipedes are carnivorous with 1 pair of legs per segment Hexapods Insects and relatives is most specious Live in every terrestrial habitat and fresh water Internal anatomy includes several complex organs Key innovations allowed insects to radiate Evolution of flight Adaptation of gymnosperms and angiosperms Many undergo metamorphosis Incomplete metamorphosis: the young nymphs resemble adults but are smaller and go through a series of molts until they reach full size Not sexually mature Complete metamorphosis: have larval stages before pupating, looks different from the adult Most have separate sexes and fertilize internally Individuals find each other through smells, bright colors, and sounds Come insect are pollinators, harmful, or pests Coleptera Beetles 2 pairs of wings, one thick and strong Complete metamorphosis Diptera Flies and mosquitoes 1 pair of wings and halteres (balances the bug and is reduced) Complete metamorphosis Hymenoptera Bees, ants, and wasps Social 2 pairs of wings Complete metamorphosis Lepidoptera Moths and butterflies 2 pairs of wings Covered in scales Colorful or camouflage Complete metamorphosis Hemiptera Assassin bugs and kissing bugs 2 pairs of wings, one leathery Incomplete metamorphosis Orthoptera Grasshoppers and crickets 2 pairs of wings, one leathery and large hind legs Incomplete metamorphosis Crustacea Banded appendages that are extensively specialized Marine Separate sexes Small ones exchange gases through cuticles Larger ones have gills Isopods Terrestrial, freshwater, marine Decapods Lobsters, crabs, crayfish, shrimp Copepods Small but very important ecologically Barnacles Mostly sessile Have cuticle that is hardened into a shell Evolutionary origin of arthropods' body plan is associated to which of these changes? o Specialization of diverse body segments All of the following contribute to the large adaptive diversity of insects except o Multiple origins of wings in different insect groups
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