Presentation on theme: "Chapter 17 - The Evolution of Animals"— Presentation transcript:
1Chapter 17 - The Evolution of Animals What Is an Animal?Are eukaryotic, multicellular, heterotrophic organisms that obtain nutrients by ingestionDigest their food within their bodies..
2Animal PhylogenyTo reconstruct the evolutionary history of animal phyla, researchers must depend on clues from comparative anatomy and embryologyFour key evolutionary branch points have been hypothesizedPresence or absence of true tissuesRadial or bilateral symmetryPresence or absence of a body cavity (coelom)Mechanism of coelom formation..
44 3 2 1 Coelom from digestive tube Pseudocoelom True coelom MulticellularityTrue tissuesRadial symmetryBilateral symmetryNo body cavityBody cavitiesPseudocoelomTrue coelomCoelom from cell massesCoelom from digestive tube1234SpongesCnidariansFlatwormsRoundwormsMollusksAnnelidsArthropodsEchinodermsChordates
5Includes sessile animals once believed to be plants Phylum PoriferaIncludes sessile animals once believed to be plantsLack true tissuesResembles a sac perforated with holes (pores)Draws water into a central cavity, where food is collected..PoresWater flowSkeleton fiberCentral cavityChoanocyteAmoebocyteChoanocyte in contact with an amoebocyteFlagella
6Phylum CnidariaCharacterized by organisms with radial symmetry and tentacles with stinging cells (cnidocytes)Sac body plan with a gastrovascular cavityDo not have true organsLife cycle includes two body forms:Sessile polypFloating medusa..Mouth/anusTentacleGastrovascular cavityMedusaPolyp
7Cnidarians are carnivores that use tentacles armed with cnidocytes, or “stinging cells,” to capture prey..TentacleCoiled threadCapsule“Trigger”Discharge of threadCnidocytePrey
8Phylum Platyhelminthes Is represented by the simplest bilateral animalsHave true organs but no body cavity – acoelomateDigestive tract is two directional – only one opening = incomplete digestive tractIncludes free-living forms such as planarianIncludes many parasitic forms such as tapeworms and flukes..
11Phylum Nematodaexhibit an important evolutionary adaptation; a digestive tube with two openings, a mouth and an anusA complete digestive tract can process food and absorb nutrients efficientlyOnly phylum with a pseudocoelom..
12Phylum MolluscaIs represented by soft-bodied animals, but most are protected by a hard shellAll have a similar body plan:Muscular foot; maybe modified into tentacles – for locomotion and defense and food gatheringMantle – secretes shell and aids in respirationVisceral mass containing internal organsFirst group with a true coelom – eucoelomates..
15Phylum AnnelidaIncludes worms with body segmentation – division of the body along into length into a series of repeated segments; look like rings..
16This is the largest group of animals Phylum ArthropodaAll have exoskeleton of chitinAppendages are jointedAppendages are highly specialized for the environmentUndergo metamorphosis – change in body form during developmentThis is the largest group of animalsIncludes insects – most abundant animals..
18Phylum Echinodermata Is named for the spiny surfaces of the organisms Have endoskeletonHave water-vascular system – hydraulic pumps that circulate water for gas-exchange, waste disposal, circulation of nutrients, and locomotion with tube feetAll aquatic..
19Phylum Chordata – all possess these characters at some point during development Have notochord = supporting rod of tissue; becomes vertebrae in one subphylumHave dorsal, hollow nerve cordHave post-anal tailHave pharyngeal pouches..Muscle segmentsPost-anal tailNotochordAnusDorsal, hollow nerve cordPharyngeal slitsBrainMouth
20Lungs or lung derivatives ErasCenozoicMesozoicPaleozoicPrecambrianTertiaryCretaceousJurassicTriassicPermianCarboniferousDevonianSilurianOrdovicianCambrianTunicatesLanceletsAgnatha (jawless vertebrates, such as lampreys)Chondrichthyes (sharks and rays)Osteichthyes (bony fishes)Amphibia (frogs and salamanders)Reptilia (reptiles)Aves (birds)Mammalia (mammals)Ancestral chordateVertebraeJawsLungs or lung derivativesLegsAmniotic eggHairFeathersChordatesVertebratesTetrapodsAmniotesPeriodsChordate Evolution
21The subphyla include the invertebrate chordates – lancelets (cephalochordata) and tunicates (urochordata), which also share four key chordate characteristics..
22This phylum includes the subphylum Vertebrata The notochord develops into the vertebral column..
23The first three major classes of the phylum are fishes Agnatha – jawless fishes, eg. lampreysChondrichthyes – cartilage fishesOsteichthyes – bony fishes..
24Cartilaginous fishes have a flexible skeleton made of cartilage; the only bone is found in the jaw Includes sharks, rays, and skates..
25Bony Fish Have a skeleton reinforced by hard calcium salts Have a lateral line system, a keen sense of smell, and excellent eyesightMost bony fishes are ray-finned fishesA second evolutionary branch includes lungfishes and lobe-finned fishes..
26Terrestrial vertebrates are collectively called tetrapods, which means “four legs” Class AmphibiaExhibit a mixture of aquatic and terrestrial adaptationsUsually need water to reproduce..
27Class Reptilia - can live totally on land Have scales to prevent dehydrationHave claws for digging and protectionHave lungs for breathingFirst group to develop the amniotic egg..
28Class Aves Evolved the ability to fly and only animals with feathers Bird anatomy and physiology are modified for flightBones are honeycombed, which makes them lighterSome specific organs are absent, which reduces weightA warm, constant body temperature is maintained through endothermy..
30There are three major groups of mammals Class MammaliaIncludes mostly terrestrial organismsHave hairHave mammary glands that produce milk and nourish the youngThere are three major groups of mammalsMonotremes – lay eggsMarsupials – do not have a placentaEutherians (placental mammals) – have placenta to nourish young inside mother’s body..