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General Biology 2 Modules 5-8 ODULE 5.1: THE EVOLUTION & DIVERSITY OF M ost reproduce sexually...
General Biology 2 Modules 5-8 ODULE 5.1: THE EVOLUTION & DIVERSITY OF M ost reproduce sexually, with the diploid stage M ANIMALS usually dominating the life cycle. nimals: Multicellular, heterotrophic eukaryotes A leavage: It is the cell division that the zygote C with tissues that develop from embryonic layers. undergoes after a sperm fertilizes an egg. ost animals are mobile and use traits such as M leavage leads to theformationofamulticellular, C strength, speed, toxins, or camouflage to detect, hollowblastula. capture, and eat other organisms. Ex: Chameleon capturesinsectpreywithits T he blastula undergoes gastrulation, forming a long sticky, quick-moving tongue. gastrula with different layers of embryonic tissues. utritional Mode: Heterotrophs that ingest their N EPRODUCTION AND DEVELOPMENT OF ANIMALS R food. Most animals haveat least one larval stage. L arva: It is sexually immature and morphologically ELL STRUCTURE AND SPECIALIZATION OF ANIMALS C distinct from the adult; it eventually undergoes Overallanimalshavethefollowingcharacteristicsin metamorphosis (frogs and caterpillars) to become terms of their cell structure: a juvenile. Multicellular eukaryotes There are NO cell walls J uvenile:Itresemblesanadultbutisnotyetsexually Bodies are held together by structural mature. proteins such as collagen oxGenes:Aclassofhomeoticgenesthatprovide H ervous Tissue & Muscle Tissue: These are the N positional information during animal embryonic unique, defining characteristics of animals. development. Most animals,andonlyanimals,havethese T issues: Groups of similar cells that act as a genes that regulate the development of functional unit body form. REPRODUCTION AND DEVELOPMENT OF ANIMALS lthough the Hox family of genes has been highly A conserved, it can produce a wide diversity of animal morphology. 1 aralogues: When two species share similar P ey events in life’s history include the o K rigins of ancestral genes. Two segments of DNA that unicellular and multicellular organisms and the have shared ancestry. colonization of land istory of Animals spans more than half a billion H eologic Record: It is divided into Hadean, G years Archaean, Proterozoic, and Phanerozoic eons. ore than 1.3 million animal species have been M named to date; far more are estimated to exist. T he common ancestor of all living animals likely lived between 700 and 770 million years ago. The Fossil Record documents the history of life F ossilRecord:Itrevealschangesinthehistoryoflife onEarth.Itshowschangesinthekindsoforganisms on Earth over time. edimentary Rock: These are deposited into S layerscalledstrataandaretherichestsourceof fossils. adiometricDating:Thisishowtheabsoluteagesof R fossils can be determined T he Phanerozoic eon includes the last half billion Aradioactive“parent”isotopedecaystoa years. It is divided into 3 eras: “daughter” isotope at a constant rate. Paleozoic Mesozoic Cenozoic HOTOSYNTHESIS AND THE OXYGEN REVOLUTION P O2 produced by oxygenic photosynthesis reacted with dissolved iron and precipitated out to form banded iron formations. y about 2.7 million years ago, O2 b B egan accumulating in the atmosphere and rusting iron-rich terrestrial rocks. T his oxygen revolution from 2.7 to 2.3 billion years ago caused the extinction of many prokaryotic groups (they found it to be toxic). S ome groups survived and adapted using cellular respirationto harvest energy. 2 THE FIRST EUKARYOTES T heoriginofmulticellularityrequirestheevolutionof T heoldestfossilsofeukaryoticcellsdatebackto1.8 new ways for cells to adhere (attach) and signal billion years. (communicate)to each other. ukaryoteshaveanuclearenvelope,mitochondria, E olecular Analysis: Revealed similarities between M endoplasmic reticulum, and a cytoskeleton. genes coding for proteins involved in adherence and attachment in choanoflagellates and animals. T he Endosymbiotic (Endosymbiont) Theory: The CCDDomain:Theproteinpresentinanimals prokaryotic ancestors of mitochondriaandplastids and is also involved with choanoflagellates. probably gained entry to the host cell as undigested prey or internal parasites. NEOPROTEROZOIC ERA ( 1 Billion - 542 Million Years Ago) In the process of becoming moreinterdependent, Multicellular eukaryotes were formed during this the host and endosymbionts would have become era. a single organism. diacaranBiota:Anassemblageoflargerandmore E diverse soft-bodied organisms that livedabout560 million years ago (Mollusks, Sponges). arly animal embryos and evidence of predation E have also been found in Neoproterozoic rocks. Ex:The550-million-year-oldfossilofCloudina was attacked by a predator that bore a hole through its shell. ALEOZOIC ERA P (542 - 251 Million Years Ago) T HE ORIGIN OF MULTICELLULAR ANIMALS ambrian Explosion: This marks the earliest fossil C A second wave of diversification occurred when appearanceofmanymajorgroupsoflivinganimals multicellularity evolved, giving risetoalgae,plants, (535 - 525 million years ago). Thesegroupsinclude fungi, and animals. arthropods (insects), echinoderms, and chordates. hoanoflagellates: These are a group of protists C ilaterians: These were mostofthefossilsfound B that have morphological and molecularevidence intheCambrianexplosionandtheseorganisms as theclosest relatives to animals. have the following traits: Bilaterally symmetric form Complete digestive tract One-way digestive system T he Cambrian Explosion also refers to the sudden appearance of fossils resembling modern animal phylain the Cambrian period. A few animal phyla appear even earlier: sponges, cnidarians, and mollusks. 3 ypotheses regarding theCambrianExplosionand H T he ancestors of plesiosaurs were reptiles that the decline of the Ediacaran Biota are the returned to the water. following: New predator-prey relationships inosaurswerethedominantterrestrialvertebrates. D A rise in atmospheric oxygen levels Thefirst mammalsemerged. The evolution of theHoxgene complex ENOZOIC ERA C (65.5 Million Years Ago to the Present) The beginning of the Cenozoic Era followed the mass extinctions of both terrestrial and marine animals. These extinctions included the large, non flying dinosaurs and the marine reptiles. ammals increased in sizeandexploitedvacated M ecological niches. Lastly, the global climate cooled. BIG FIVE MASS EXTINCTION EVENTS In each of the five mass extinction events, 50% or more of marine species became extinct. The Colonization of Land nimal diversity continued to increasethroughthe A Paleozoic but was punctuated by mass extinctions. F ungi, plants, and animals began to colonizeland about 500 million years ago. F actors that might have contributed to Mass rthropodsandtetrapodsarethemostwidespread A Extinctions and diverse land animals. #1:Intense volcanism in what is now Siberia. T etrapodsevolved from lobe-finned fishes around Global warming and ocean acidification 365 million years ago. result from large amounts of CO2 emission from the volcanoes. MESOZOIC ERA 2: Anoxic conditions resulting from nutrient # ( 251 - 65.5 Million Years Ago) enrichmentof ecosystems. Coral reefs emerged, becoming important marine ecological niches for other organisms. 3: The presence of iridium in sedimentary rocks # suggeststhatameteoriteimpacted65millionyears ago. 4 C louds caused by the impact would have ilateral Symmetry: Two-sided symmetry is called B blocked sunlight and disturbed the global bilateral symmetry. Bilateral animals often move climate. actively and have a central nervous system. Is a Sixth Mass Extinction Under Way? T ISSUES Animal body plans also vary according to the S cientistsestimatethatthecurrentrateofextinction organization of the animal’s tissues. is 100 to 1,000 times the typical background rate. T issues: These are collections of specialized cells xtinction rates tend to increase when global E isolated from other tissues by membranous layers. temperatures increase. uring development, three germlayersgiveriseto D ata suggest that a sixth, human-caused mass D the tissues and organs of the animal embryo. extinctionislikelytooccurunlessdramaticactionis taken. ctoderm: The germ layer covering the E embryo’s surface. MODULE 5.2: THE ANIMAL FORM ndoderm: The innermost germ layer and lines E Animals can be characterized by “Body Plans” the developing digestive tube, called the archenteron. ody Plan: A set B of morphological and developmental traits. Sponges and a few other groups lack true tissues. S ome body plans have been conserved, while iploblastic Animals: These animals have an D others have changed multiple times over the ectoderm and endoderm (cnidarians and a few course of evolution. (See Hox Genes) other groups. T riploblasticAnimals:Asidefromtheendodermand YMMETRY S ectoderm, these animals have an intervening Animals can be categorized according to the mesoderm layer (bilaterians). symmetry of their bodies, or lack of it. These include flatworms, arthropods, vertebrates [chordates], and others. adial Symmetry: Some animals have radial R symmetry, with no front and back, nor left and right. BODY CAVITIES Bilaterally symmetrical animals have: Coelomates:Animals that possess a true coelom. A dorsal (top) side and a ventral (bottom) True body cavity is called a coelom and is side derived from the mesoderm. A right and left side Anterior(front) andposterior(back) end seudocoelomates: Triploblastic animals that P Many have sensory equipment, such as a possess a pseudocoelom. brain, concentrated in their anterior end Pseudocoelom:Abodycavityderivedfrom the mesoderm and endoderm. adial Animals are often sessile or planktonic R (drifting or weakly swimming). coelomates:Triploblasticanimalsthatlackabody A cavity. 5 3: Eumetazoa (“true animals”) is a clade of # animals with true tissues. #4:Most animal phyla belong to clade Bilateria. ROTOSTOME AND DEUTEROSTOME DEVELOPMENT P 5: There are three major clades of bilaterian # They differ basedontheearlydevelopmentofthe animals, all of which are invertebrates, except animal. Chordata, which are classified as vertebrates. Indeterminate Cleavage: Each cell in the early stagesofcleavageretainsthecapacitytodevelop into a complete embryo. Makes possible identical twins, and embryonic stem cells. The bilaterians are divided into three clades. oelom Formation: If only mesoderm is involved, C then it’s protosome. If both mesoderm and the euterostomia: Includes hemichordates (acorn D archenteron, then it’s deuterostome. worms), echinoderms (sea stars and relatives, and chordates. Also includes vertebrates and F ate of the Blastophore: The Blastophore forms invertebrates. during the gastrulation and connects the archenteron to the exterior of the gastrula. cdysozoa:Acladeofinvertebratesthatshedtheir E exoskeletonsthrough a process calledecdysis. THE DIVERSIFICATION OF ANIMALS Z oologists recognize about three dozen animal L ophotrochozoa:Haveafeedingstructurecalleda phyla. Phylogenies now combine morphological, lophophore. Others go through a distinct molecular, and fossil data. developmental stage called thetrochophore larva. F iveimportantpointsabouttherelationshipsamong living animals are reflected in their phylogeny #1:All animals share a common ancestor. #2:Sponges are basal animals. (Parazoa) 6 Invertebrates are animals that lack a backbone. DEUTEROSTOMIA EXAMPLES Phylum Description T hey account for more than 95% of knownanimal species. They arealsomorphologicallydiverseand chinodermata E oelomates C with bilaterally occupy almost every habitat on Earth. (sea stars, sea symmetrical larvae and five-part urchins) body organizations as adults Unique water vascular system Has an endoskeleton. hordata C oelomates with notochord; dorsal, C (lancelets, hollow nerve cord tunicates, vertebrates) Has pharyngeal slits; post-anal tail LOPHOTROCHOZOA EXAMPLES Phylum Description hordates (phylum Chordata) have a notochord C latyhelminthes D P orsoventrally flattened and a dorsal, hollow nerve cord. (flatworms) acoelomates T hese are bilaterian animals that belong to the astrovascularcavityornodigestive G clade Deuterostomia. Chordates also comprise all tract. vertebrates and two groups of invertebrates, the urochordatesandcephalochordates. otifera R seudocoelomates with alimentary P (rotifers) canal(digestivetubewithmouthan anus) CHORDATES ll chordates share a set of derived characters. A J aws (trophi) and a head with Somespecieshavesomeofthesetraitsonlyduring ciliated crown embryonic development. L ophophorates; C oelomates with lophophores There arefour key characters of chordates. Ectoprocta, (feeding structures bearing ciliated Brachiopoda tentacles) otochord: Itisalongitudinal,flexiblerodbetween N ollusca M oelomates with 3 main bodyparts C the digestive tube and nerve cord. It provides (clams, snails, (muscular foot, visceral mass, skeletal supportthroughoutmostofthelengthofa squids) mantle) and coelom reduced chordate. ost have a hard shell made of M orsal, Hollow Nerve Cord: The nerve cord of a D calcium carbonate chordate embryo develops from a plate of nnelida A oelomates with segmented body C ectoderm that rolls into a tube dorsal to the (segmented wall and internal organs (except notochord. worms) digestive tract) T he nerve cord develops into the central nervous system: the brain and the spinal cord. haryngeal Slits or Clefts:Thesearegroovesinthe P pharynx that are called pharyngeal clefts. These 7 evelop into slits that open to the outside of the d body. They have the following functions: Suspension-feeding structures in many invertebrate chordates Gas exchange in vertebrates (except vertebrates with limbs, the tetrapods) Develop into parts of the ear, head, and neck in tetrapods. uscular, Post-Anal Tail: Chordates have a tail M posterior to the anus. In many species, the tail is greatly reduced during embryonic development (ex: urochordates - during larval stage). T he tail contains skeletal elements and muscles. It also provides propelling force in many aquatic species. 8
