v What type of symmetry do echinoderm larvae and adults have? v What are some functions of the water vascular system?

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1 Biosc 41 Announcements 11/3 Review: Echinoderms v Review: Echinoderms & Protochordates v Quiz: Echinoderms & Protochordates v Today s Lecture: Tetrapods- Amphibians & Amniotes v Today s Lab: Fishes (video, specimens & rockfish dissection) v Next quiz: Wed (fishes only) v Do echinoderms have protostome or deuterostome development? (and what does deuterostome mean?) v What type of symmetry do echinoderm larvae and adults have? v What are some functions of the water vascular system? v What are the five extant classes of echinoderms? Distinguishing characteristics of each? Review: Echinoderms Review: Invertebrate Chordates v How do individuals in Class Asteroidea feed? v What is the feeding structure called in Class Echinoidea? v Which of the echinoderm classes possesses a cloaca? v What are the two groups of invertebrate chordates? v Are these protochordates craniates? v What are some features shared by all chordates? v What is the unique defense mechanism of Class Holothuroidea? Quiz 7 1. What type of symmetry do (a) larval and (b) adult Echinoderms have? Review: Osmoregulation in FW Fish Fish is saltier than FW (FW is hypotonic to fish blood) Fish tends to gain H 2 O (needs to get salt and get rid of H 2 O) 2. Identify 3 of the 5 classes of Echinoderms by scientific and common names 3. List three functions of the Echinoderm water vascular system 4. What are the scientific and common names of the two groups of protochordates? 5. List three features shared by all chordates? 1

2 Review: Osmoregulation in SW Fish SW is saltier than fish (SW is hypertonic to fish blood) Fish tends to lose H 2 O (needs to get H 2 O and get rid of salt) Phylum Chordata Part Three Tetrapods: Amphibians & Amniotes Reference: Chapter 34 Tetrapods are gnathostomes that have limbs 1 0 v One of the most significant events in vertebrate history was when the fins of some lobe-fins evolved into the limbs and feet of tetrapods v Derived characters of tetrapods 1. Four limbs, and feet with digits 2. A neck, which allows separate head movement 3. Fusion of the pelvic girdle to the backbone 4. Absence of gills (except some aquatic species) 5. Ears for detecting airborne sounds The first tetrapods appeared 365 MYA The Origin of Tetrapods- Tiktaalik v Tiktaalik is a genus of extinct sarcopterygian from the late Devonian, with many tetrapod features v Represents the evolutionary transition from fish to amphibians v Nicknamed fishapod, show both fish and tetrapod characteristics Fins, gills, lungs, and scales Ribs to breathe air and support body A neck, and fins have bone pattern of tetrapod limb v Tiktaalik could most likely prop itself on its fins, but not walk Figure Fish Characters Scales Fins Gills and lungs Head Eyes on top of skull Flat skull Tetrapod Characters Neck Ribs Fin skeleton Flat skull Eyes on top of skull Neck Shoulder bones Fin Ribs Scales Humerus Ulna Elbow Wrist Radius Fin skeleton 2

3 11/3/14 Class Amphibia Amphibian Biology v Includes ~6,150 species v Ectotherms Orders: Body temp depends on environment, restricts range Urodela includes v Tied to water salamanders (have tails) Thin skin loses water rapidly; restricts terrestrial Anura includes frogs and toads (lack tails) Apoda includes caecilians (legless, resemble worms) forms to moist habitats (a) Order Urodela (salamanders) (b) Order Anura (frogs) Eggs deposited in water or must be kept moist Larvae depend on gills for respiration (c) Order Apoda (caecilians) Order Apoda: Caecilians v ~173 living species v Resemble earthworms or snakes v Mostly live hidden in the ground- least familiar amphibians v Elongate, limbless, burrowing animals v Inhabit tropical forests in (S. America, Africa, India, SE Asia) v Bodies have many vertebrae, long ribs, no limbs v Feed primarily on worms and small underground invertebrates v Fertilization is internal- exception to typical amphibian repro Order Urodela - Salamanders v Breeding Behavior Some aquatic throughout life cycle Most have aquatic larvae and terrestrial adults Internal fertilization in most; female recovers in cloaca a spermatophore deposited on a leaf or stick Aquatic species lay eggs in clusters or stringy masses Completely terrestrial species deposit eggs in small, grapelike clusters under logs or in soft earth Order Urodela - Salamanders v ~553 living species found primarily in northern temperate regions v Most small, under 15 cm long (Japanese giant salamander is 1.5 meters long) v Burrowing species and some aquatic forms may have lost their limbs v Carnivorous as both larvae and adults (feed on worms, small arthropods, and molluscs Order Urodela - Salamanders v Terrestrial species undergo direct development; hatch as miniature adults v Some North American newts have aquatic larvae that metamorphose into terrestrial juveniles that again metamorphose into secondarily aquatic, breeding adults 3

4 Order Urodela - Salamanders v Respiration- wide array of respiratory mechanisms! Vascular nets in skin exchange both O 2 and CO 2 At various stages, may have external gills, lungs, both, or neither Salamanders with aquatic stage hatch with gills which are lost at metamorphosis Some lineages retain gills and a fin-like tail In species with lungs, lungs are present from birth and become functional following metamorphosis v ~5,300 species v Dates from Triassic period, 250 million years ago v Must live near water source Reproduction mode requires water Skin is water-permeable v Ectothermy prevents anurans from inhabiting polar and subarctic habitats v All have a tailed larval stage and tailless, jumping adults (except for 1 species) v Life Cycle Most larger frogs are solitary until breeding season During breeding season, males are especially noisy Hold forelimbs near body when swimming with hindlimbs Surface to breathe with only head exposed During winter in temperate climates, Hibernate in soft mud in bottom of pools Frost-tolerant frogs prepare for freezing by accumulating glucose and glycerol in body fluids During hibernation, the little energy used is provided by stored glycogen and fat v Frogs can be easy prey for carnivores Defend themselves by aggression, concealment, and poison glands v Climatic change is a threat Reduced water depth at oviposition sites increases ultraviolet exposure of embryos More susceptible to fungus v Invasive amphibian species such as Bufo marinus can outcompete and/or prey on other frogs v Skeletal and Muscular Systems Well-developed endoskeleton of bone and cartilage provides for body support and muscular movements Landing posed new mechanical stress problems Musculoskeletal changes allowed jumping, swimming Vertebral column lost much flexibility to transmit force from limbs to body Extremely shortened body; only nine trunk vertebrae Caecilians have not moved toward tetrapod locomotion and have as many as 285 vertebrae

5 v Respiration and Vocalization Amphibians use 3 respiratory surfaces for gas exchange in air: 1. Skin provides cutaneous breathing 2. Mouth provides buccal breathing 3. Lungs are usually present in adults Frogs and toads depend on lung breathing more than salamanders Skin is critical during winter hibernation Carbon dioxide is mostly lost across skin while oxygen is absorbed across the lungs v Lungs supplied by pulmonary arteries, return blood to left atrium Frog lungs are ovoid, elastic sacs; inner surfaces divide into a network of smaller chambers Absorptive surface is 20 cm 2 /cc of air compared to 300 cm 2 for humans v Positive Pressure Breathing Air moved into lungs by force Rhythmic throat movements gulp air and force it backward Rib cage does not expand to draw air into the lung v Vocal cords are located in the larynx; much more developed in males v Air is passed back and forth over vocal cords between the lungs to a large pair of vocal sacs v Most species have unique sound patterns v Circulation Circulation is closed with a single pressure pump moving blood through the peripheral network Main difference in circuitry is the shift from gill to lung breathing Elimination of gills reduced one obstacle to blood flow Evolution of pulmonary artery provided circuit to lungs BUT, separation of oxygenated blood from deoxygenated blood circuit is only partial

6 11/3/14 v Feeding and Digestion v Nervous System and Special Senses Most adults are carnivorous (feed on insects, spiders, Brain is gradually assuming more information Frogs are sensitive to low-frequency sound energy worms, slugs, etc) Free end of tongue is glandular (sticky secretion adheres to prey) Any teeth that are present function to hold prey (do not chew) Short digestive tract Tadpoles are usually herbivorous (longer digestive) processing, independent of spinal cord under 4000 Hz (cycles per second) Except for blind caecilians, vision is dominant sense in many amphibians v Reproduction and Development v Typical Metamorphosis Ectothermic; breed, feed, and grow during warm seasons In spring, males call to attract females Hindlegs appear first Forelegs temporarily hidden in folds When eggs are mature, females enter water and males of operculum clasp them in amplexus After fertilization, jelly layers of egg absorb water Eggs usually laid in large masses, and development begins immediately (tadpole may hatch in 6 9 days) Tadpole head has horny jaws for feeding and a ventral adhesive disc for clinging to objects Tail is resorbed Intestine becomes shorter Mouth transforms to the adult condition Lungs develop and gills are resorbed v Exception: Eleutherodactylus mate on land and eggs hatch directly into froglets Amniotes have a terrestrially adapted egg v Amniotes are a group of tetrapods whose living members are reptiles, including birds and mammals

7 Characteristics of Amniotes à Terrestrial Life 1. Thicker, more waterproof skin Amniote skin tends to be more keratinized Structures composed of keratin include scales, hair, feathers, and claws that project from the skin Keratin protects skin from physical trauma, and lipids prevent water loss 2. Lungs are the primary organ for gas exchange Keratin and lipids limit exchange of gases across skin 3. Amniotes lack gilled larvae no need for aquatic habitats 4. Internal fertilization Penis is the most common copulatory organ, and appears to be an amniote innovation Characteristics of Amniotes à Terrestrial Life 5. Rib ventilation of the lungs negative ventilation Amniotes draw air into lungs by expanding the thoracic cavity 6. High-Pressure Cardiovascular system Limits mixing of oxygen-rich and oxygen-poor blood Mammals, birds, and crocodilians have two completely separated ventricles 4 chambered heart 7. Water-conserving nitrogen excretion Birds and non-avian reptiles excrete nitrogenous wastes as uric acid- relatively non-toxic, and can be concentrated to reduce water loss 8. Expanded brain and sensory organs Major Derived Character the Amniotic Egg v External shell with internal membranes that protect the embryo The extraembryonic membranes are the amnion, chorion, yolk sac, and allantois v Permitted development of a larger, faster-growing embryo v Replacement of the amphibian jelly layer with a shell Better support and movement of oxygen Provides calcium for growing skeletal structures Figure Embryo Amniotic cavity with amniotic fluid Amnion Extraembryonic membranes Allantois Chorion Yolk sac Yolk (nutrients) Shell Albumen 40 Early Amniotes v Living amphibians and amniotes split from a common ancestor ~350 million years ago v Early amniotes were more tolerant of dry conditions v The earliest amniotes were small predators with sharp teeth and long jaws Reptiles - Sauropsids v The reptile clade includes the tuataras, lizards, snakes, turtles, crocodilians, birds, and extinct dinosaurs v Most reptiles are ectothermic, absorbing external heat as the main source of body heat v Birds are endothermic, capable of keeping the body warm through metabolism v Reptiles have scales that create a waterproof barrier v Most reptiles lay shelled eggs on land 7

8 11/3/14 Circulation in Reptiles (Except Birds) v Turtles, snakes, and lizards have a threechambered heart (two atria, one ventricle) v In alligators, caimans, and other crocodilians a septum divides the ventricle v Reptiles have both a pulmonary circuit (lungs) and a systemic circuit (body) Lepidosaurs - Tuataras v One surviving lineage of lepidosaurs is represented by two species of lizard-like reptiles called tuataras v Endemic to New Zealand Testudines: Turtles v All turtles have a boxlike shell made of upper and lower shields fused to vertebrae, clavicles, and ribs v Some turtles have adapted to deserts and others live entirely in ponds and rivers v Marine turtles return to land to lay their eggs Reptile Origins v Diapsids were early terrestrial amniotes, and consisted of two main lineages: the lepidosaurs and the archosaurs Lepidosaurs- tuataras, lizards, snakes Archosaurs- crocodilians, pterosaurs, dinosaurs (and birds!) v Turtles (Testudines) classification unclear Some place them within the archosaur lineage, some within the lepidosaurs, and some outside the diapsids altogether Lepidosaurs: Squamates lizards and snakes v Lizards are the most numerous and diverse reptiles, apart from birds Archosaurs: Crocodilians v Crocodilians (alligators and crocidiles) coexisted with dinosaurs, avoided extinction at the end of Cretaceous v Largest extant reptiles 8

9 Archosaurs: Birds (Clade Neornithes) Figure v Birds are archosaurs, but almost every feature of their reptilian anatomy has evolved in adaptation to flight v Derived characters of birds: Wings with keratin feathers Hollow bones Loss of teeth Lack of a urinary bladder Females have only one ovary, small gonads Hard-shelled eggs v Flight requires a great expenditure of energy, acute vision, and fine muscle control (a) Wing Vane Shaft Forearm Wrist Finger 1 (b) Bone structure Palm Finger 2 Finger 3 Shaft Barb Barbule Hook (c) Feather structure Double Circulation in Mammals and Birds Birds lungs facilitate rapid gas exchange v Mammals and birds have a four-chambered heart with two atria and two ventricles v Left side of the heart pumps and receives only oxygenrich blood; right side receives and pumps only oxygen-poor blood v Mammals and birds are endotherms and require more O 2 than ectotherms v Birds have 8-9 air sacs that function as bellows to keep air flowing through lungs v Air passes through lungs in one direction only v Every exhalation completely renews the air in the lungs The Origin of Birds v Birds probably descended from small theropods, a group of carnivorous dinosaurs v Early feathers might have evolved for insulation, camouflage, or courtship display v Early feathers might have helped dinosaurs Gain lift when they jumped Gain traction running up hills Glide from trees v By 150 MYA, feathered theropods had evolved into birds v Archaeopteryx remains the oldest bird known Airfoil wing with contour feathers Toothed beak Wing claw Long tail with many vertebrae Mammals last of the synapsids v Class Mammalia Amniotes that have hair and produce milk Represented by >5,300 species v Mammals evolved from synapsids ca 200 MYA Two bones that formerly made up the jaw joint were incorporated into the mammalian middle ear 9

10 Derived Characters of Mammals v Mammals have Mammary glands, which produce milk Hair A high metabolic rate, due to endothermy A larger brain than other vertebrates of similar size Differentiated teeth Modern Mammal Groups v Differentiated primarily on the basis of how they gestate their young Monotremes, marsupials, and eutherians Monotremes v Monotremes are a small group of egg-laying mammals consisting of echidnas and the platypus Marsupials v Marsupials include opossums, kangaroos, and koalas v Embryo develops within a placenta in the mother s uterus v A marsupial is born very early in its development v It completes its embryonic development while nursing in a maternal pouch called a marsupium Marsupial mammals Plantigale Marsupial mole Sugar glider Wombat Tasmanian devil Eutherian mammals Deer mouse Flying squirrel Mole Woodchuck Wolverine Kangaroo Patagonian cavy Eutherians (Placental Mammals) v Compared with marsupials, eutherians have a more complex placenta v Young eutherians complete their embryonic development within a uterus, joined to the mother by the placenta Figure 34.41a ANCESTRAL MAMMAL Monotremes Marsupials Eutherians (5 species) (324 species) (5,010 species) Monotremata Marsupialia Proboscidea Sirenia Tubulidentata Hyracoidea Afrosoricida Macroscelidea Xenarthra Rodentia Lagomorpha Primates Dermoptera Scandentia Carnivora Cetartiodactyla Perissodactyla Chiroptera Eulipotyphia Pholidota 10

11 Figure 34.41ba Orders and Examples Monotremata Platypuses, echidnas Marsupialia Kangaroos, opossums, koalas Proboscidea Elephants Sirenia Manatees, dugongs Tubulidentata Aardvarks Hyracoidea Hyraxes Echidna Koala African elephant Manatee Aardvark Rock hyrax Main Characteristics Lay eggs; no nipples; young suck milk from fur of mother Completes embryonic development in pouch on mother s body Long, muscular trunk; thick, loose skin; upper incisors elongated as tusks Aquatic; finlike forelimbs and no hind limbs; herbivorous Teeth consisting of many thin tubes cemented together; eats ants and termites Short legs; stumpy tail; herbivorous; complex, multichambered stomach Figure 34.41bb Orders and Examples Xenarthra Sloths, anteaters, armadillos Lagomorpha Rabbits, hares, picas Rodentia Squirrels, beavers, rats, porcupines, mice Primates Lemurs, monkeys, chimpanzees, gorillas, humans Tamandua Jackrabbit Red squirrel Golden lion tamarin Main Characteristics Reduced teeth or no teeth; herbivorous (sloths) or carnivorous (anteaters, armadillos) Chisel-like incisors; hind legs longer than forelegs and adapted for running and jumping; herbivorous Chisel-like, continuously growing incisors worn down by gnawing; herbivorous Opposable thumbs; forward-facing eyes; well-developed cerebral cortex; omnivorous Figure 34.41bc Orders and Examples Carnivora Dogs, wolves, bears, cats, weasels, otters, seals, walruses Coyote Cetartiodactyla Artiodactyls Sheep, pigs, cattle, deer, giraffes Cetaceans Whales, dolphins, porpoises Main Characteristics Sharp, pointed canine teeth and molars for shearing; carnivorous Hooves with an even number of toes on each foot; herbivorous Bighorn sheep Aquatic; streamlined body; paddle-like forelimbs and no hind limbs; thick Pacific white- layer of insulating blubber; sided porpoise carnivorous Perissodactyla Hooves with an odd Horses, number of toes on zebras, each foot; herbivorous tapirs, rhinoceroses Indian rhinoceros Chiroptera Bats Eulipotyphla Core insectivores : some moles, some shrews Frog-eating bat Star-nosed mole Adapted for flight; broad skinfold that extends from elongated fingers to body and legs; carnivorous or herbivorous Eat mainly insects and other small invertebrates 11