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Animal Evolution Porifera sponges • 5,000 living sponge species • Three Main Groups: – hexactineuida (glass sponges) – demospangia – calcarea (calcareous sponges) • no coelom, organs, or skeleton • no urinary, cardiovascular, respiratory or nervous system • cellular grade of organization Evolutionary Time Frame • Among the oldest known fossils • began in late Precambrian • developed from first multi-cellular organism Tissues • Two layers of cells – layers are separated by gelatinous region called mesohyl • Spongocoel – the central cavity – internal water chambers • water flows in and out of the osculum • coanocytes are flagellated, collar cells – these line the spongocoel – help propel water through cell Reproduction • Reproduce sexually or asexually • Hermaphrodites – this means they are male and female – produce both eggs and sperm • gametes arise from choanocytes or amoebocytes • eggs reside in the mesohyl, while sperm cells are carried out of the sponge by water current • fertilization occurs in the mesohyl • zygotes develop into flagellated, swimming larvae • in asexual reproduction buds are produced – are often packets of several cells inside a protective coating called gemmule Locomotion • No muscles Digestion • No mouths • carnivores • archaiout, cells ingest and digest food • suspension feeders – “filter feeders” – they collect bacteria taken from the water • tiny pores in outer walls – these draw water – called ostia • cells in sponge walls filter water • water is pumped through the body and out larger opening (oscula) • flow of water is unidirectional – driven by beating of flagella which line the surface of chambers and are connected by a series of canals Cnidaria corals, jellyfish, hydra • Four Main Classes – Anthozoa (corals, anemones, sea pens, sea fans, sea anemones) – Cubozoa (box jellies) – Hydrozoa (diverse group of siphonophores, hydroids, five corals, medusae, obella) – Scyphozoa (true jellyfish, jellies, sea wasps, sea nettles) • do not have a cardiovascular system Evolutionary Time Frame Cnidaria first appeared during the Pre-Cambrian era • Corals - first appeared in Vendian – few fossils in Cambrian period, but identifiable corals began evolutionary radiation in Early Ordovician Period – wiped out at end of Permian Period • mass extinction event in which 95% of all marine invertebrate species became extinct – scleractinian corals appeared in the middle of the Triassic (15 million years later) • became dominant hermatypic (reef-building) organisms in shallow tropical marine habitats Tissues • Simplest organisms at tissue level • cells are organized in true tissues • two cell layers - outer ectoderm (epidermis) and inner endoderm (gastrodermis) • Outer Ectoderm – contains cnidocysts (stinging cells) • Inner Endoderm – lines gut (sometimes divided by septa) • Mesoglea (between layers) – layer of jelly-like substance – contains scattered cells and collagen fibers Excretion • Cnidarias have one oral opening • all secretions, including waste materials, exit through this • Undigested remains are sent back through the anus/mouth Reproduction • Alternate between asexual and sexual – sexual reproduction includes free-swimming forms • formation of gametes in medusae and some polyps – asexual budding (polyps) • Gonads are the only organs present in the body cavity of cnidaria Locomotion • Cnidaria move by a decentralized nerve net and simple receptors • movement is coordinated by the nerve net • move freely in water by passive drifting and contractions of its bell-shaped body Digestion • Cnidaria are carnivores • they have tentacles in a ring around their mouth – these capture prey and push food into the gastrovascular cavity • gastrovascular cavity is a sac with a central digestive compartment • cnidaria have one opening which functions as the mouth and anus Respiratory • Done by the diffusion of oxygen through their tissues Nervous • Cnidaria contain muscles and nerves in the simplest form • Cells of the epidermis and gastrodermis have bundles of microfilaments arranged in contractile fibers • there is no brain, and the nerve net is associated with simple sensory receptors that are distributed throughout the body Platyhelminthes flat worms • Means “flat worm” • thin bodies between dorsal and ventral surfaces • Consist of Four Classes: – Turbellaria (free-living flatworms) – Monogenea (monogeneans) – Trematoda (trematodes or flukes) – Cestoidea (tapeworms) • no urinary system Evolutionary Time Frame • Origin of bilaterians, Precambrian period – before Cambrian explosion • early origin of coelom hypothesized by trace fossils left in Precambrian sediments Tissue • Epidermis covers body – made up of layers of cells • the middle embryonic layer is the mesoderm – here occurs the development of complex organs and organ systems to true muscle tissue • inner layer of cells forms intestine Reproduction • Most Reproduce asexually – while some do reproduce sexually • the parent constricts in the middle – each half regenerates its missing end • cross-fertilization between individuals Locomotion • Glide along a film of mucus, secreted by themselves • the cilia on the ventral epidermis able them to move Digestion • Have a gastrovascular cavity with one opening • they lack a digestive tract • absorb nutrients across the body surface • branched gut to transport food Cardiovascular • Lack organs for circulation • fluid filled spaces aid in transport Respiratory • Lack organs for gas exchange • internal tissues are near the surface of the skin – this is because of their flattened bodies – gas and nutrients exchange with environment Nervous • Pair of cerebral ganglia • longitudinal nerve cords connect to transverse nerves Nematoda roundworms • Nematoda consist of no distinct classes • Nema - “thread” • 90,000 known species • do not have a respiratory system Evolutionary Time Frame • Found as early as the Carboniferous period • fossils of nematodes were found in amber, these dated back to the Cenozoic era • relatives of nematoda date back to Cambrian – nematodes remain in the same form since then • because nematodes are microscopic, fossils are difficult to find – they lack hard body parts Tissue Layers • Contain internal body cavity – pseudoderm • lack cilia and well-defined head • the epidermis (skin) is composed of a mass of cellular material and nuclei, these are not separated by membranes • a thick outer cuticle which is tough and flexible is secreted – this cuticle is shed, usually about four times before it becomes an adult – tough exoskeleton Excretion • Some nematodes have specialized cells that excrete nitrogenous waste • canals are present in others to excrete wastes Reproduction • Reproduce sexually with internal fertilization – males use copulatory spines to open female reproductive tract and inject sperm • sperm lack flagellae and move by pseudopodia • females are larger than males and deposit about 100,000 eggs a day Locomotion • Muscles are longitudinal and contract producing a thrashing motion – only bend from side to side – muscle cells branch toward nerve • the internal pressure is high, this causes the body to flex, rather than flatten • nematoda have no cilia or flagellae Digestion • Have mouth opening into pharynx (throat) – food is pulled in and crushed – pharynx leads to a long simple gut cavity lacking muscles – it is then led to the anus at the tip of the body • nutrients and wastes are distributed in body cavity – this is regulated by an excretory canal along each side of the body Cardiovascular • No cardiovascular system • nutrients are transported through the body by fluid in the pseudocoelom Nervous • Ring of nervous tissue around the pharynx • gives rise to two nerves: dorsal and ventral – nerve cords – run the length of the body – muscle cells branch toward nerve Mollusca snails, slugs, oysters, clams, octopuses, squids • Over 150,000 known species • molluscous are soft bodied – protected by a hard shell made of calcium carbonate • Classes: – Plolyplacophora (chitons) – Gastropoda (snails and slugs) – Bivalvia (clams, oysters, bivalves) – Cephalopida (squids, octopuses, hautiluses) Evolutionary Time Frame • Lived in freshwater streams as early as 400 million years ago • developed the ability to be able to live in most aquatic environments – 300 million years ago Tissue • Three main parts: – Muscular foot (for movement) – visceral mass (containing the internal organs) – mantle (fold of tissue, drapes over visceral mass, secretes shell) • houses gills, anus, excretory pores • some produce a water filled chamber – called a mantle cavity Excretion • Excretory organs called nephridia – remove metabolic wastes from hemolymph Reproduction • Separate sexes with gonads in the visceral mass • life-cycle includes ciliated larva (trochophore) Locomotion • Muscular foot • no bones • Outer shell made of calcium carbonate supports and protects • some also have inner shells for support – called cuttlebones in cuttlefish – pen in squids Digestion • Feed by a strap like rasping organ called the radula to scrap food – ribbon like, hooked teeth • have jaw, pharynx, esophagus, stomach, intestine and anus Cardiovascular • Open circulatory system • no true heart • blood is pumped along by vessels and join with open sinuses – bathes internal organs Respiratory • Gills housed in mantle cavity – function in gas exchange • terrestrial snails lack gills – instead, lining of mantle cavity functions as a lung – exchanges respiratory gases with air Nervous • Clams and chitons have no nervous system • squid and octopus have most sophisticated nervous system of all vertebrates – they have large brains and eyes – giant axon transmits messages Annelids earthworms, leeches, marine worms • 15,000 species • Three classes: – Oligochaeta (earthworms) – Polychaeta (polychaetes) – Hirudinea (leeches) • Annelids means “little rings” • segmented worms Evolutionary Time Frame • Originated in Precambrian Tissue • Coelom partitioned by septa – penetrated by digestive tract, longitudinal blood vessels and nerve cords Excretion • Metanephridia – excretory tubes in each segment – ciliated funnels – remove waste from blood and coelomic fluid – lead to exterior pores, discharges waste • nephridia excrete waste – these are coiled tubes with expanded funnel shape (nephostrome, attached to septum) – leads to outside on posterior end Reproduction • • • • • Cross-fertilization Sperm is stored clitellum secretes a mucous cocoon cocoon picks up eggs and stored sperm some reproduce asexually by fragmentation Locomotion • Two types of muscles: circulatory and longitude • when muscles tighten, others lengthen Digestion • Contains specialized regions – pharynx – esophagus – crop – gizzard – intestine • • • • Cardiovascular Closed cardiovascular system has a network of vessels blood and oxygen carrying hemoglobin dorsal and ventral blood vessels – main blood vessels • blood transported by contractions of the walls of the vessels – called peristalsis • pairs of vessels connect dorsal and ventral vessels Respiratory • The respiratory organ is the skin • epidermis layer is very thin and moist – this allows for gas exchange Nervous • Cerebral ganglia is located above and in front of the pharynx • ring of nerves around pharynx connects to sub-pharyngeal ganglion • nerve cords run posterioly Arthropods crustaceans, spiders, insects • Consist of over one million species • arthropod means “jointed feet” • make up over 3/4 of all known living and fossil organisms • conquered the land, sea and air • Classes: Triolbita, Chelicerata, Uniramia, Diplopoda (millipedes), Chilapoda (centipedes), Insecta (insects) • do not have a urinary system Evolutionary Time Frame • Soft-bodied relatives began during the Vendian • rapid evolution in Cambrian Period • Trilobites (the dominant marine group) began in the Paleozoic • arachnids moved onto land during Devonian – 385 million years ago • oldest insect fossil from the Devonian Period – 400 million years ago Tissue • The cuticle covers the entire body • exoskeleton – made of tough compounds, chitin and protein – outer shell – structure against which muscles pull – reduces water loss (impermeable to water) – protection – chitin laid in plates with joints – exoskeleton is molted (shed) occasionally • leaves temporarily vulnerable • legs have two branches (biramous appendages) – outer branch are flattened gills – inner branch is used for walking, grasping, chewing, or reproduction Reproduction • Paired reproductive organs (ovaries and testes) • dioecious • internal fertilization • most lay eggs and development proceeds with some form of metamorphosis Locomotion • Movement of appendages is controlled primarily by a complex muscular system – muscular system divided into smooth and striated components Digestion • Mandible or jaws chew food Cardiovascular • Open circulatory system • fluid called hemolymph is propelled by the heart through short arteries and into spaces called sinuses surrounding tissues and organs – blood flows and bathes tissues and organs – dorsal tubular heart is perforated by pores – generally lack blood vessels • resembles open circulatory system of mollusks, but arose independently Respiration • • • • • Organs specialized for gas exchange – allow diffusion of respiratory gases in spite of exoskeleton aquatic species – gills with thin feathery extensions – place extensive surface area in contact with surrounding water terrestrial – have internal surfaces – insects • tracheal systems • branched air ducts, lead into interior from pores in cuticles gas exchange occurs inside book lungs – these are stacked plates in internal chambers its extensive surface area is a structural adaptation – enhances exchange of oxygen and carbon dioxide between hemolymph and air Nervous • Well developed sensory organs, include: – eyes – olfactory receptors for smell – antennae for touch and smell – sensory organs concentrated at anterior end • Three Regions: – deutocerebrum – protocerebrum - receives nerves of eyes and other organs – tritocerebrum • association with neuropils (antennae) • nerves innervate mouth parts and anterior digestive canals • contains annelid-like brain (cerebral ganglion) – nerve ring surrounding pharynx connects the brain with the pair of ventral nerve cords • these cords contain numerous ganglia Echinodermata starfish, sand dollars, brittle stars, sea cucumbers, sea urchins • Pentameral (fivefold symmetry) – rays or arms in fives or multiples of fives • echin “spiny” derma “skin” • suckered tube feet which move and grip • Classes: – Concentricycloidea (sea daisies) – Asteroida (starfish, sea stars) – Crinoidea (sea lillies, feather stars) – Ophiuroidea (brittle or snake stars) – Echinoidea (sea urchins, sand dollars) – Holothuroidea (sea cucumbers) • about 7,000 known species • no urinary system • poorly developed nervous system Evolutionary Time Frame • Fossils are not pentameral • oldest known Venedian fossil is Arkarua – soft bodied with unmineralized plates • modern echinodermata (with mineralized skeleton) entered the fossil record in early Cambrian • Asterozoans date back to Ordivician • crineids and blastoids are the later Paleozoic – became extinct at the end of the Permian Period Tissue • Spacious coeloom – open, fluid-filled body cavity • large gonads • complete gut • interlocking calcium carbonate plates and spines – enclosed by epidermis (endoskeleton) Reproduction • External fertilization – egg and sperm are freely discharged into water • provide no parental care • go through planktonic larval stages before settling down • separate males and females Locomotion • Tube feet – extend, grip, contract and release • do this over and over again • hydrualic water vascular system – network of fluid filled canals – function in locomotion, feeding and gas exchange Digestion • Some turn stomach inside out through the mouth • sea urchins scrape algae from rocks with five large teeth • secrete juices that digest soft body of mollusks in its own shell Cardiovascular • Does not have a cardiovascular system • functions of the cardiovascular system are taken over by the water vascular system Respiration • No respiratory system • once again, functions of the respiratory system are done by the water vascular system Chordata vertebrates • Includes humans and vertebrates • all have the same features at some point in life – these features include: • pharyngeal slits - digestive tube from mouth to anus – pharynx posterior to mouth, slits • dorsal, hollow nerve cord - develops into central nervous system: brain and spinal cord • notochord - longitudinal, flexible rod between digestive tube and nerve cord • muscular post-anal tail - skeletal elements and muscles – propulsive force in aquatic species • Echinoderms are the closest living relative of humans Chordata • Vertebrates have the ability to regenerate ATP by cellular respiration – this is the consumption of oxygen • adaptations of vertebrate respiratory and circulatory systems support mitochondrion muscle cells and active tissues • all have a closed circulatory system with ventral, chambered heart – pumps blood through arteries to microscopic vessels called capillaries • capillaries branch throughout every tissue in the body • blood is oxygenated as it passes through capillaries in gills or lungs Chondricthyes sharks, rays • Have cartilaginous skeletons Evolutionary Time Frame • Appeared 450 million years ago • cartilaginous skeleton is a derived characteristic – ancestors had bony skeletons, cartilaginous skeleton characteristic evolved secondarily Tissue • Made up of cartilage – this has a lower density compared to bones – more flexible Excretion • Two kidneys – hundreds of units of renal corpuscle, deals with excess water • in renal corpuscles water and dissolved substances are squeezed into the end of the tubule • cells in this tubule allow certain substances to pass out and back into capillaries • tubules join at the end of the urinary duct – carries urine to urinary sinuses • urine exits body Reproduction • Sexually dimorphic – separate females and males • fertilization inside female body • three ways of reproducing: – oviparity (female lays eggs) – oviviparity (eggs hatch in oviduct of female, develops in uterus) – viviparity (embryo nourished in placenta) Digestion • Jaw and muscles push food down esophagus • enters stomach – gastric juices produced by microscopic glands • then enters intestine – digestive juices produced by liver and pancreas – absorb nutrients – intestines twist around themselves to increase surface area • rectal gland filters waste and empties into the rectum • cloaca opens to the outside Locomotion • Powerful swimming muscles in caudal (tail) fin – propel them forward • dorsal fins stabilize • pectoral and pelvic fins provide lift in water • gains buoyancy by storing large amounts of oil in its liver – still sinks if it stops swimming Cardiovascular • Two chambered heart with one atrium and one vesicle – not strong enough to get blood to the gills – must swim constantly to produce heart contractions Respiratory • Gills pull oxygen from the water • Ramjet ventilation must occur – constant flow of water through the gills • Blood is pumped through brachial arteries to blood vessels in gills • oxygenated blood circulates back through the system Nervous • Central nervous system with a brain and spinal cord • brain is simple with three parts – forebrain (obtains information from sight and smell detectors) – midbrain (coordinates sensory information) – hindbrain (coordinates basic life functions and movement) Osteoicthyes ray-finned, lobe-finned, lungfish • Bony fishes • ossified endoskeleton with hard matrix of calcium phosphate • skin is covered by flattened, bony scales • appeared in the Devonian and Carboniferous Periods Evolutionary Time Frame • All bony fishes combined into single vertebrate class, osteoichthyes – based on cladistics, now recognized in three extant classes: ray-finned fishes, lobe-finned fishes and lungfishes Tissues • Have ossified endoskeleton with hard matrix of calcium phosphate • skin is covered by flat, bony scales Excretion • Two small kidneys work to excrete wastes Reproduction • Oviparous • external fertilization • female sheds large numbers of small eggs Locomotion • Glands in skin secrete mucus giving sliminess, reduces drag during swimming • flexible fins steer and propel Digestion • Digestive tract includes: liver, stomach, intestine, anus Cardiovascular • Swim bladder – air sac – helps control buoyancy – transfer of gases between swim bladder and blood – varies inflation of bladder and adjusts density of fish • Three chambered heart – consists of two atria, one ventricle – little mixing of oxygenated and deoxygenated blood – allows animal to control blood flow • is able to shunt deoxygenated and oxygenated blood to body or lungs Respiratory • Draw in water over gills located in chambers covered by protective flaps – overculum • water is drawn in through pharynx and out between gills by movement of operculum and contraction of muscles surrounding gill chambers • many different forms of lung ventilation – squamates - axial musculature – crocodilians - muscular diaphragm Nervous • Two pairs of cranial nerves • advanced nervous system • compared to amphibians Amphibia salamanders, frogs, caecilians • Orders: Urodela (salamanders) – Anura (frogs) – Apoda (Caecilians) • Amphibian means “two lives” – close ties with water, most abundant in damp habitats (swamps and rainforests) – rely heavily on moist skin Evolutionary Time Frame • Earliest amphibia found in early Devonian period – 363 millions years ago • modern amphibia didn’t appear until Mesozoic era – 248 million years ago Tissue • Coelom – houses all internal organs Excretion • Ureters carry liquid waste to bladder • leaves through cloaca and cloacoe vent – same way as solid waste Reproduction • External fertilization • male grasps female and spills sperm over eggs of female as she sheds them • lay eggs in a moist environment • some reproduce on land where eggs are deposited • some give live birth • most fertilized eggs are deposited in water – eggs hatch into larvae Locomotion • Salamanders move by side-to-side bending • frogs have powerful hind legs Digestion • Mouth • esophagus (tube to stomach) • stomach (food is mixed and partly digested) • small intestine (most digestion takes place, absorbs nutrients) – digestive juices come from liver and pancreas • Frogs – long sticky tongue, nabs insects • attached to front of mouth Cardiovascular • Three chambered heart – two atria, one ventricle • double circulation – blood is pumped twice – provides blood flow to brain, muscles and other organs Respiratory • Rely on moist skin – network of blood vessels run through skin – this carries out gas exchange with environment • some lack lungs and breathe through the skin and oral cavity Reptilia snakes, lizards, crocodiles, turtles, birds • Have scales containing the protein keratin – this water proofs the skin – prevents dehydration in dry air • 6,500 species of extinct reptiles • Four Groups: – Testudines (turtles – Sphenodontia (tuatara) – Squamata ( lizards and snakes) – Crocodilia (alligators and crocodiles) Evolutionary Time Line • • • • • • • • Reptilia were more numerous and diverse during the Mesozoic era go as far back as the late Carboniferous Period – 350 million years ago the oldest fossils were found in Kansas in the late Carboniferous period – 300 million years ago ancestors are the Devonian amphibians first major reptilian radiation occurred during the dawn of Permian – last Paleozoic era – gave rise to three main branches: Synapsida, Aapsida, Diapsida second great radiation by late Triassic – 200 millions years ago – dinosaurs (land) and pterosaurs (flying reptiles) dinosaurs extinct at the end of Cretaceous – last period of Mesozoic turtles appeared during the Mesozoic era and haven’t changed since Excretion • Two small kidneys • main nitrogenous waste product is uric acid Reproduction • Lay shelled amniotic eggs on land • fertilization is internal as eggs pass through the reproductive tract of the female Locomotion • Agile and fastmoving • very diverse – swim, slither, crawl, run, fly Digestion • Dinosaurs: – Ornithischians are herbivores – saurichians are herbivorous and carnivorous • birds – food isn’t chewed in mouth, ground in gizzard (digestive organ near stomach) – crocodiles and dinosaurs also have gizzards Cardiovascular • Closed circulatory system • three chambered heart – two atria, one ventricle – little mixing of oxygenated blood and deoxygenated blood in heart – blood flow can be altered to shunt deoxygenated blood to the body or oxygenated blood to the lungs • Birds – four chambered heart • keeps tissues supplied with oxygen and nutrients Respiratory • Cannot obtain oxygen through their skin which is keratinized and dry • Obtain oxygen using lungs • many turtles obtain gas exchange through the moist surface of their cloaca Nervous • Advanced nervous system compared to amphibians • consists of 12 cranial nerves Mammalia • Characteristics of mammalia – Possession of mammary glands – produce milk – hair – endothermic – efficient respiratory and circulatory systems – live birth • Three Major Groups: – Monotremes (egg-laying mammals) – Marsupials (mammals with pouches) – Eutherian (placental) Evolutionary Time Frame • Evolved from reptilian stock during Mesozoic era, even before birds did – 180 million years ago • became dominant form of life 65 million years ago • oldest mammalian fossils date back to 200 million years ago (Triassic Period) • fossils from Permian and Triassic connect mammals with reptilian ancestors • Mesozoic mammals were small and probably ate insects • Great adaptive radiation occurred during the Cenozoic era, dawned in the wake of Cretaceous extinction Tissue • Four types of tissue – epithelial • covers external surfaces, internal cavities and organs – connective • binds and supports body parts, protects, fills spaces, transports materials and stores fat • two kinds - loose and dense – nerve • responds to stimuli and transports impulses from one part of the body to another – muscle • contracts in response to stimulation Excretion • Kidney – main excretory organ • blood enters kidneys through nephrons • capillaries and tubules filter blood • first water, ions and small organic molecules are removed • next, water and selected minerals are reabsorbed, returned to bloodstream • urine is the final product – carried out through the ureter – stored in bladder – exits through urethral opening • Internal fertilization • separate sexes • male – two testes lie in skin covered sac (scrotum) – sperm is produced in testes and deposited in female genital tract • female – two ovaries, produce ova – embryos develop inside uterus of female reproductive tract – placenta (the lining of the mother’s uterus and extraembryonic membranes) • nutrients diffuse into embryo’s blood • Monotremes - platypuses and echidnas – only living mammals that lay eggs • Marsupials are born early in development – they complete embryonic development while nursing inside mother’s pouch Reproduction • Bones – axial and appendicular skeleton • muscles include: – diaphragm, separates thoracic cavity from abdominal – musculation of jaw region and limbs help with getting food and movement – muscles associated with outer hairy skin allow automatic responses and facial expression Locomotion Digestion • Differentiation of teeth for different foods • stomachs vary in complexity • herbivores have more complex stomachs and produce certain bacteria for breaking up cellulose • carnivores have relatively simple stomachs Cardiovascular • Active metabolism • four chambered heart • complex way to distribute oxygen, digested food, hormones and other chemicals • carries away waste products • oxygenated blood carried away from heart to body • deoxygenated blood pumped back to lung Respiratory • Diaphragm ventilates lungs • external openings in head region • passes through pharynx, trachea, bronchi and into lungs • lungs are the main organ of gas exchange – carbon dioxide and oxygen exchanged • deoxygenated blood pumped to lung • tiny air sacs – location of gas exchange Nervous • Larger brains • contains two primary parts – central nervous system – peripheral nervous system • mammals have a larger cerebrum – many are capable learners