Animal Evolution

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Animal Evolution
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Poriferasponges

• 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

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Evolutionary Time Frame

• Among the oldest known fossils
• began in late Precambrian
• developed from first multi-cellular organism

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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

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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

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Locomotion

• No muscles

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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

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Cnidariacorals, 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

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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

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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

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Excretion

• Cnidarias have one oral opening
• all secretions, including waste materials, exit
  through this
• Undigested remains are sent back through the
  anus/mouth

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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

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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

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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

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Respiratory

• Done by the diffusion of oxygen through their
  tissues

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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

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Platyhelminthesflat 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

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Evolutionary Time Frame

• Origin of bilaterians, Precambrian period
• before Cambrian explosion
• early origin of coelom hypothesized by trace
  fossils left in Precambrian sediments

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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

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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

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Locomotion

• Glide along a film of mucus, secreted by
  themselves
• the cilia on the ventral epidermis able them to
  move

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Digestion

• Have a gastrovascular cavity with one opening
• they lack a digestive tract
• absorb nutrients across the body surface
• branched gut to transport food

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Cardiovascular

• Lack organs for circulation
• fluid filled spaces aid in transport

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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

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Nervous

• Pair of cerebral ganglia
• longitudinal nerve cords connect to transverse
  nerves

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Nematodaroundworms

• Nematoda consist of no distinct classes
• Nema - thread
• 90,000 known species
• do not have a respiratory system

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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

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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

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Excretion

• Some nematodes have specialized cells that
  excrete nitrogenous waste
• canals are present in others to excrete wastes

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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

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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

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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

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Cardiovascular

• No cardiovascular system
• nutrients are transported through the body by
  fluid in the pseudocoelom

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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

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Molluscasnails, 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)

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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

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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

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Excretion

• Excretory organs called nephridia
• remove metabolic wastes from hemolymph

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Reproduction

• Separate sexes with gonads in the visceral mass
• life-cycle includes ciliated larva (trochophore)

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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

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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

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Cardiovascular

• Open circulatory system
• no true heart
• blood is pumped along by vessels and join with
  open sinuses
• bathes internal organs

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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

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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

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Annelidsearthworms, leeches, marine worms

• 15,000 species
• Three classes
• Oligochaeta (earthworms)
• Polychaeta (polychaetes)
• Hirudinea (leeches)
• Annelids means little rings
• segmented worms

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Evolutionary Time Frame

• Originated in Precambrian

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Tissue

• Coelom partitioned by septa
• penetrated by digestive tract, longitudinal blood
  vessels and nerve cords

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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

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Reproduction

• Cross-fertilization
• Sperm is stored
• clitellum secretes a mucous cocoon
• cocoon picks up eggs and stored sperm
• some reproduce asexually by fragmentation

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Locomotion

• Two types of muscles circulatory and longitude
• when muscles tighten, others lengthen

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Digestion

• Contains specialized regions
• pharynx
• esophagus
• crop
• gizzard
• intestine

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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

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Respiratory

• The respiratory organ is the skin
• epidermis layer is very thin and moist
• this allows for gas exchange

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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

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Arthropodscrustaceans, 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

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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

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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

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Reproduction

• Paired reproductive organs (ovaries and testes)
• dioecious
• internal fertilization
• most lay eggs and development proceeds with some
  form of metamorphosis

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Locomotion

• Movement of appendages is controlled primarily by
  a complex muscular system
• muscular system divided into smooth and striated
  components

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Digestion

• Mandible or jaws chew food

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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

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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

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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

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Echinodermatastarfish, 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

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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

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Tissue

• Spacious coeloom
• open, fluid-filled body cavity
• large gonads
• complete gut
• interlocking calcium carbonate plates and spines
• enclosed by epidermis (endoskeleton)

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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

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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

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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

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Cardiovascular

• Does not have a cardiovascular system
• functions of the cardiovascular system are taken
  over by the water vascular system

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Respiration

• No respiratory system
• once again, functions of the respiratory system
  are done by the water vascular system

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Chordatavertebrates

• 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

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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

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Chondricthyessharks, rays

• Have cartilaginous skeletons

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Evolutionary Time Frame

• Appeared 450 million years ago
• cartilaginous skeleton is a derived
  characteristic
• ancestors had bony skeletons, cartilaginous
  skeleton characteristic evolved secondarily

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Tissue

• Made up of cartilage
• this has a lower density compared to bones
• more flexible

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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

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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)

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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

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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

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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

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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

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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)

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Osteoicthyesray-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

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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

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Tissues

• Have ossified endoskeleton with hard matrix of
  calcium phosphate
• skin is covered by flat, bony scales

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Excretion

• Two small kidneys work to excrete wastes

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Reproduction

• Oviparous
• external fertilization
• female sheds large numbers of small eggs

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Locomotion

• Glands in skin secrete mucus giving sliminess,
  reduces drag during swimming
• flexible fins steer and propel

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Digestion

• Digestive tract includes liver, stomach,
  intestine, anus

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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

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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

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Nervous

• Two pairs of cranial nerves
• advanced nervous system
• compared to amphibians

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Amphibiasalamanders, 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

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Evolutionary Time Frame

• Earliest amphibia found in early Devonian period
• 363 millions years ago
• modern amphibia didnt appear until Mesozoic era
• 248 million years ago

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Tissue

• Coelom
• houses all internal organs

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Excretion

• Ureters carry liquid waste to bladder
• leaves through cloaca and cloacoe vent
• same way as solid waste

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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

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Locomotion

• Salamanders move by side-to-side bending
• frogs have powerful hind legs

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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

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Cardiovascular

• Three chambered heart
• two atria, one ventricle
• double circulation
• blood is pumped twice
• provides blood flow to brain, muscles and other
  organs

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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

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Reptiliasnakes, 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)

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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
  havent changed since

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Excretion

• Two small kidneys
• main nitrogenous waste product is uric acid

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Reproduction

• Lay shelled amniotic eggs on land
• fertilization is internal as eggs pass through
  the reproductive tract of the female

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Locomotion

• Agile and fast-moving
• very diverse
• swim, slither, crawl, run, fly

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Digestion

• Dinosaurs
• Ornithischians are herbivores
• saurichians are herbivorous and carnivorous
• birds
• food isnt chewed in mouth, ground in gizzard
  (digestive organ near stomach)
• crocodiles and dinosaurs also have gizzards

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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

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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

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Nervous

• Advanced nervous system compared to amphibians
• consists of 12 cranial nerves

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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)

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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

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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

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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

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Reproduction

• 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 mothers uterus and
  extraembryonic membranes)
• nutrients diffuse into embryos blood
• Monotremes - platypuses and echidnas
• only living mammals that lay eggs
• Marsupials are born early in development
• they complete embryonic development while nursing
  inside mothers pouch

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Locomotion

• 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

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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

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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

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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

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Nervous

• Larger brains
• contains two primary parts
• central nervous system
• peripheral nervous system
• mammals have a larger cerebrum
• many are capable learners