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Unit 5 Phylum Hemichordata General Characteristics Marine _________________________________ Three body divisions ____________________ circulatory system Complete digestive tract Exhibit two Chordate characteristics Hemichordata Taxonomy Class ______________________________________ Sediment/filter feeders Class _____________________________________ Sessile filter feeders Phylum Chordata General Characteristics Bilateral symmetry Complete digestive tract Ventral, contractile vessel (heart) 5 unique development characters: _________________________________________ Supportive _____________________ running through the length of the animal This structure prevents ______________________ along the longitudinal axis, but allows lateral flexion In vertebrate adults it is usually replaced by ________________________________________ ________________________________________ In some chordates, the opening is never _______________________________ aka _______________________________________ May be used for gas exchange Typically, in terrestrial vertebrates, gill slits are embryonic features and are ________________________ Human structures derived from gill slits include: Tympanic cavity, Eustachian tubes (auditory tubes), Tonsils, Thyroid, Thymus _________________________________________ Nerve cord runs longitudinal with notochord and is usually expanded anteriorly into the brain Central Nervous System (CNS) _________________________________________ Supported by _______________________________________________________________ Humans: it regresses (cell death) in embryo aka ________________________________ _________________________________________ Depending on taxa: Very successful group 45,000 species Three subphyla SubPhylum __________________________________________ Tunicates, sea squirts Some are planktonic, but most are sessile Attach to rocks, pilings, ships, other hard substrates Unattached end contains ______________ siphons for water circulation ________________________________ (incurrent) Incoming H2O and mouth _________________________________ (excurrent) Exiting H2O Large multifunctional pharynx: Body wall ________________________ made of tough connective tissue Secreted by ____________________________ Contain circular and longitudinal muscles below body wall Nervous system in body wall Reproduction Monoecious May have internal or external fertilization Typically cross fertilize Subphylum ______________________________________ Lancelets ≈ 45 species Elongate, laterally flattened and nearly transparent Spend most of their time partially buried in sandy substrates Notochord extends from __________________ to ___________________________ Is contractile and adapted for burrowing Stiffened- _________________________________ Relaxed- _________________________________ Digestion: filter feeders Water enters mouth by ciliary action (wheel organ) Cirri No true heart Dioecious External fertilization Subphylum ____________________________________ Protects ________________________________________________ High degree of ________________________________ Brain, Skull, and Sensory organs Vertebrate Taxonomy ________ Classes of Vertebrates The first five are ____________________ Represent ancestral stock of all other vertebrates Evolved in both freshwater and marine Superclass _____________________________ – Early vertebrates Class ___________________________ Hagfishes Marine sediment dwellers Feed on: Invertebrates Eat sick and dying fish Swim into mouth and eat from the inside out leaving only the bones and skin Class _____________________________ Lampreys Marine and freshwater Temperate regions Mostly predatory or parasitic Have a sucker like mouth surrounded by lips which have sensory and attachment functions Mouths are lined with epidermal teeth and contain a rasping tongue-like structure Possess ________________________________ secretions from salivary glands so they can feed on blood/fluids of other fishes Adult sea lampreys migrate into freshwater to spawn towards the end of their lives This presents a problem with freshwater fisheries in the Great Lakes Only one reproductive event for entire life _____________________________ fishes ‘to run up’ Lamprey & salmon ______________________________ fishes ‘to run down’ american eel Spawn in shallow rocky areas External fertilization Eggs → ammocoete larvae → bury themselves in the substrate for 2-3 years and filter feed → emerge and migrate to ocean → adult → migrate back to freshwater → spawn → die Lampreys of Oklahoma Chestnut lamprey Southern Brook lamprey Superclass __________________________________________ _____________________ fishes (and ____________________________) with paired appendages Benefit of jaws Appendages Increased ____________________ and _______________________ Enhanced escape and predation ____food quality = ___energy =____ complexity Three Classes of Gnathostome fishes Gnathostome fishes We will first look at general characteristic for the classes then we will compare the systems together Class ______________________________________________ ________________________________ fishes Mostly marine Sharks, skates, rays, ratfishes Subclass _______________________________________ Sharks, rays, skates _________________________________________ _______ swim bladder _______ gill covers (_________________________) ________________________ scales Why such different body forms? Placoid scales Teeth arranged in rows Skates and rays are specialized for life on the ocean floor Pectoral fins expanded into ‘wings’ Subclass _________________________________ Chimaeras Scavengers, filter feeders, carnivores Have ____________ scales Teeth modified into ____________________ _____________________ present Divergent from Elasmobranchii Notochord persists Group _______________________________________ _____________________ Fishes Used to be Class Osteichthyes but now are broken down into two distinct classes 23,000 + species Have at least some ______________________ in skeleton ________________________________ present _________________________________ Class ____________________________________________ ________________________________ fishes, Lungfishes and Coelacanth Lungfishes Usually associated with freshwater Can survive periods of drought by lung breathing Some have lost ability to gill breath altogether Have muscular lobes associated with their fins ___________________________________ Coelacanth Latimeria Thought to be extinct until 1938 Marine, gill breathing Probably closest living relatives of terrestrial vertebrates Class ____________________________________________ ________________________________ fishes Fins lack muscular ____________________________ Possess _____________________________________ Function in buoyancy by diffusion of gas in and out Sturgeons and paddlefish have secondarily lost their bony _________________________ Subclass _______________________________ Teleost fishes Modern bony fishes, gars, and bowfin Subclass ______________________________ Now let’s look into the systems of the Osteichthyans including aquatic adaptation Aquatic Adaptations Aquatic environments are somewhat constant especially compared to terrestrial however there are still a variety of selective pressure that will lead to diversity _______________________________: Fresh vs. brackish vs. marine _______________________________: Constant by region/depth _______________________________: Deeper= more pressure _______________________________: None after 30m or so 0.53% of the surface light reaches a depth of 100 meters (330 feet) Locomotion Streamline shape and mucous secretions Reduce ______________________ in fluid environment Water offers more resistance than air Buoyancy of water tends to ________________________ the pull of gravity Sarcopterygians and actinopterygian Air bladder Vertical Position in Water Tissues contain _____________ (less dense than water) Bones less ________________ than terrestrial bones Fins to provide _________________ Sharks: Oily liver and tissues and Caudal fin Use fins, body wall, and tail to propel self Nutrition and Digestion Fish have evolved to take advantage of a great diversity of food items hence all the diversity Most fish are predatory upon plankton, invertebrates, and other vertebrates May employ different feeding strategies depending on life stage young vs. adult Filter feeders, Scavengers, Parasitic, Herbivores , Predators Most have a typical vertebrate digestive tract Modifications are taxon dependent Circulation and Gas Exchange Closed circulatory system __________________________________________ Pumping heart To initiate _______________________________________ Gill breathers Systemic circulation ________________________ Two chambered heart Lung breathers Three chambered heart 2 _______________ (functional) & 1 ___________________________ This division helps to keep oxygenated and deoxygenated blood separate ___________________________________________________ _________________________________ Directs blood from right side of heart to pulmonary artery and blood from left side of heart to aortic arches (tissues) Gas Exchange: Must be _______________________ efficient than terrestrial vertebrates Water contains less than _________% of the oxygen available in air How do you combat this problem? __________________________________ and water flow Fluids move across each other in ___________________________ directions ____ rate of diffusion by establishing high concentration gradients Pass more water across gills __________________ and __________________ pumps maintain one way flow of water over the gills Double Pump Others (e.g. elasmobranchs) use ______________________________________________ Hold mouth open while swimming to force water over the gills Remember _______ operculum Gills Gills are supported by _______________________ Gill ____________________ extend from each arch Gill ____________________ are vascularized folds of epithelium on the gill filaments Lungs Pneumatic sacs Gas chambers which evolved as an evagination of the digestive tract Non-teleost fishes swallowed air into sac Gas exchange These primitive lungs later became separated from the digestive tract (in modern teleosts) and functioned as a buoyancy regulator (swim bladder) Nervous and Sensory functions _____________ (central nervous system)and ___________ (peripheral nervous system) sensory receptors Olfaction, Vision, Hearing, Equilibrium, Balance Water movement detectors Lateral line A type of hearing Also detects movement Electroreception Electrogeneration protection, predation, guidance Electric eel ____________________________: used to pump _______ Excretion and Osmoregulation _____________________________________ Serve to maintain ionic balance in tissues (Balance between ions and water) Kidneys are located along the midline and somewhat caudally in the visceral cavity Kidneys are composed of ____________________________ (Functional unit of the kidney) Function: Filter blood borne nitrogenous wastes, ions, water, and organic compounds from glomerulus Glomerulus: Osmoregulation Freshwater Saltwater Freshwater Osmoregulatory Adaptations Water tends to move into the organism (Expel excess water) Water is gained across the gills, through the mouth, and across intestinal surfaces Ions tend to move out of the tissues (Actively retain ions) Ions are lost at the gills and through excretion and defecation How do they control osmoregulation? Marine Osmoregulatory Adaptations Water tends to move out of organism by osmosis Ions tend to move into tissues How do they control osmoregulation? Elasmobranchs Convert nitrogenous wastes to urea Held in tissues to make shark tissues isosmotic with sea water Rectal gland that actively removes excess NaCl from tissues Anadromous/Catadromous fishes? Reproduction and Development Most external fertilizers Produce thousands of eggs to ensure the survival of just a few Because many eggs are: Not fertilized, Preyed upon, Enter unfavorable habitats (dessicate, too saline, too dilute), and Destroyed by mechanical factors (waves) 3 possible developmental/birthing paths _____________________________ Egg birth Eggs externally spawned (fishes) and are fertilized and develop outside of the female _____________________________ Egg → internal fertilization → female holds until they hatch and yolk nourish fetus → live birth Many sharks _____________________________ Live birth Young develop in and are nourished by the mother some sharks, guppies, mosquito fish Some fish brood (sea horses), protect (sticklebacks) young, Most don’t Some utilize internal fertilization, Most don’t What is the relationship between the number of young produced and the degree of parental care? What is the advantage of brooding, protecting, and internal fertilization? What is the disadvantage? Class Amphibia General Characteristics Frogs, toads, salamanders, caecilians Partially terrestrial These are the first ____________________ (4 feet) we study Originated in late Devonian How did this group diverge from fishes? As vertebrates (fishes) began to diversify and proliferate in aquatic environments 300-360 mya Almost every available niche was filled However On land there Organisms that possessed (by mutation or chance) adaptations that permitted them to invade the terrestrial environment enjoyed increased fitness Who do you think were the first to invade terrestrial environments? Two distinct lines of amphibians evolved from these fishes ___________________________ Dry resistant egg These amniote amphibians are all ___________________ perpetuated in the reptile, bird, and mammal lines Early Carboniferous ___________________________ Occur almost worldwide Modern amphibians arose about 200 mya Three distinct orders Order _____________________________ Salamanders ≈ 360 species Small unspecialized legs ½ of all species occur in North America Some are endemic to Oklahoma Habitat Typically, associated with moist forest floors and leaf litter Most have aquatic larvae Require a constant external environment No major fluctuations Micro environment (climate) is stable Some may be _______________________________ ________________________ Most terrestrial of salamanders Eggs laid on land, hatch as miniature adults ________________________ Order _______________________________ Caecilians ≈ 60 species Confined to tropical regions Wormlike burrowers Feed on worms and other invertebrates of the soil Order ______________________________ Frogs and toads ≈ 3500 species Mostly moist environments Some live on islands and in deserts Long muscular hind limbs with webbed feet Toads Frogs Evolutionary Pressures Evolutionary pressures for amphibians include those of both terrestrial and aquatic environments Gas exchange, Osmoregulation, and Buoyancy/gravity External Addaptations Integumentary adaptations: Amphibian skin is not typical of terrestrial or aquatic vertebrates Lacks scales, feathers, hair Highly glandular (secretory) which prevents dessication, used as protection (toxic secretions), and reproductive adhesion Possess chromatophores Specialized dermal and epidermal cells responsible for skin color and color change Types of coloration ___________________________- camouflage, markings and coloration for blending into the background ___________________________ which is warning coloration (Dart frogs) ___________________________ - The adoption of one species of the color, habits, sounds, and/or structures of another species ____________________________ One species is harmful the mimic is not (e.g. Viceroy and Monarch butterflies) ____________________________ All mimics are harmful (e.g. bees) Support and Locomotion Skeleton must be adapted to support the body against the pull of gravity Also, must be strong enough to support the muscles that propel the animal At the same time, it must be relatively buoyant for the aquatic lifestyle Appendages have evolved support and locomotion function Appendages are tied to the vertebral column Not so in fishes (Floating bones) In addition to protecting the spinal cord, the vertebral column acts to distribute the weight of the trunk between two anterior and two posterior appendages ___________________________ (Helps support the pectoral girdle) ___________________________ (Supports the pelvic girdle) Amphibians have a lighter, relatively smaller and more flattened skull than fishes They also have a neck which permits lateral/vertical movement of the head Tetrapod movement relies more on appendages than on the body wall Frogs have more muscular appendages than fishes Nutrition and Digestion Adults are carnivorous (remember evolutionary pressures) Depending on taxon studied, diet varies from a narrow choice of food items (salamanders) to a diverse array of opportunistic feeding (frogs) Bullfrogs eat each other Primarily determined by prey size and availability Typically employ a waiting tactic Sit at a potential feeding spot and wait for prey to come (Waters edge, openings in litter, etc.) May simply capture prey in jaws or use tongue (e.g. Plethodont salamanders & Anurans) Tongue lies in front of mouth and is literally flipped out to capture prey which makes them visual predators Larvae are herbivorous Circulation Separation in heart similar to, but ___________________________________________________ 2 Atrium and 1 ventricle Atrium is partially divided in Urodeles (Caudata) and totally divided in Anurans _____________________ and __________________________ circulation Spiral valve is present in aorta This helps direct blood into the pulmonary and systemic circuits This decrease in efficiency from lungfishes is greatly compensated for by amphibian gas exchange systems Fish: Amphibian/primitive reptile: Gas Exchange ______________________ respiration- The exchange of O2 and CO2 must occur across a moist surface Exposure of respiratory surfaces to air causes water loss 30-90% of gas exchange is cutaneous (salamanders) When completely submerged in water, gas exchange is entirely across the skin Cutaneous respiration is particularly adaptive in amphibians that overwinter in mud _________________________ respiration – respiration via the mouth/pharynx surfaces therefore it is well vascularized Most amphibians have lungs (not plethodonts they have simple sacs) What about the lungs? Actuated by a buccal pump (A negative pressure pump) Muscles of the mouth and pharynx create a positive pressure gradient, forcing air into the lungs What about the paedomorphs? Why have lungs? Temperature Regulations Ectotherms – Take on water temperatures when in water due to heat absorbing properties of water On land, they regulate body temperature to some extent Mainly _____________________________ Nocturnal Burrow in leaf litter to remain cool (microhabitat regulation) Some evaporative heat loss Bask to warm Conduction from warm surfaces Can take on a heat surplus to increase rate of metabolism to increase temperature by basking after meals Amphibians are capable of withstanding a wide range of temperatures (Range from -2˚→ 41˚ C) Avoidance (______________________ in the summer and ____________________________ in the winter) Nervous system Three brain regions ____________________________ - Olfactory, color change, visceral regulation ____________________________ - Sensory assimilation and initiation of motor responses ____________________________ - Motor coordination, heart rate, mechanisms of respiration Widely distributed sensory receptors (skin) Respond to heat and pain Lateral line system similar to fishes which responds to low frequency vibrations, especially in water Peripheral chemoreceptors located in nose, mouth, tongue, skin and function in olfaction Vision Primarily sight feeders May or may not have binocular vision (Do not see detail well they just see and respond to movement against a stationary background) Auditory system Receives substrate and airborne vibrations Anurans Tympanic membrane with middle and inner ear that can block out high or low frequency sounds High frequency sounds are transmitted through the tympanic membrane to the inner ear (Mating) Low frequency sounds are transmitted through the front appendages and pectoral girdle to the inner ear Low frequency are usually substrate borne (Warning) Excretion and Osmoregulation Kidneys and urinary bladder Outgrowth of cloaca Excrete ammonia or urea Freshwater → ammonia Marine/terrestrial → urea (Can be stored) Some can produce both depending on habitat Amphibian kidneys: Produce large quantities of hypotonic urine Skin and urinary bladder walls transport ions back into blood In water, they have the same osmoregulatory problems as fishes On land, they must conserve water Mostly behavioral by avoid dessicating situations Water is lost across skin, but is quickly reabsorbed when animal enters water or flattens on moist surfaces Animals may form cocoon Old layer of skin that prevents dessication Reproduction Dioecious Usually tied to moist environments Eggs lack resistant coverings Salamanders and Caecilians - Mostly internal fertilization (Spermatophores) Anurans - External fertilization Timing of reproduction Largely under hormonal control External environmental cues Salamanders Rely on visual and olfactory cues in courtship and mating Anurans Rely on auditory vocalizations Calls are species specific Once mate is attracted - tactile cues are important Amplexus
