Chapter 23 The Vertebrates
23.1 Chordate Heritage 23.2 Vertebrates 23.3 Fishes 23.4 Amphibians 23.5 Vanishing 23.6 Amniotes Intro 23.7 Herptile (Reptiles) 23.8 Aves (Birds) 23.9 Mammals 23.10 Primates 23.11 TBA 23.12 TBA Chapter 23 Outline
Impacts, Issues: Interpreting and Misinterpreting the Past A. The absence of transitional forms was an early obstacle to Darwin’s theory of evolution. 1. The discovery of Archaeopteryx specimens, which display both reptilian and bird features, was significant. 2. Archaeopteryx lived about 150 million years ago. B. Such fossils are witness to the history of life or Are they???
23.1 Chordate Heritage NOT ON EXAM, but please listen • Chordates are deuterostomes • “Second Mouth” • Examples • Chordates • Echinoderms ***Not a chordates***
23.1a For Chordate features • Coelomates (hollow body cavity) • Bilateral • MOST are vertebrates (with a back-bone) • All chordates, at some time in their lives, have four distinctive features:
23.1a For Chordate features 4. All chordates, at some time in their lives, have four distinctive features: • A notochord which is a long rod of stiffened tissue that supports the body. • Later it changes to bony units in vertebrates. • A dorsal, tubular nerve cord • A muscular pharynx with gill slits is positioned at the entrance to the digestive tract • at least in the embryo • A tail, or rudiment thereof, exists near the anus • at least in the embryo
23.1b Invertebrate Chordates • Urochordata (tunicates or Sea squirts ) • Larval stage look like a tadpole • Adult metamorphosis lose tail and notochord • Filter feeder • Cephalochordata (lancelets) • Have all for characteristics, • Filter feeder
23.2a Trends among the Vertebrates • “Non” craniates skull casing • Tunicates and lancelets • Also lack vertebrae • Why can they survive w/o jaws???? HINT • Craniates: skull casing • All chordates (fishmammals)
23.2a Trends among the Chordates This animation (Audio - Important) describes the evolution of chordates.
23.2a Trends among the Chordates This animation (Audio - Important) describes the evolution of chordates.
23.2a+b Trends among the Chordates • Craniates • Notochord replaced by Vertebral column • Modifed near head and Jaws • Notices the loss of armored species • Jaws and Superior Sensory Organs • Tetrapods, Fins, legs • Less dependency on Gills lung development This animation (Audio - Important) describes the evolution of chordates.
23.2b The vertebrates are divided into eight classes • Agnatha - jawless fishes • Placodermi - jawed armored fishes • (extinct) • Chondrichthyes - cartilaginous fishes • Osteichthyes - bony fishes • Amphibia - Amphibians • Reptilia - Reptiles • Aves - Birds • Mammalia - Mammals
23.3a Fish Success • Streamlines bodies • Fish scales protect the body without weighing it down. • 3 Types of fish • Agnathans (Jawless Fish) • Chondrichthyes (cartilaginous) • Osteichthyes (bony fish)
23.3a Agnathan (Jawless Fish ) • Jawless (Agnathan) • lampreys and hagfishes • eel-like body with no paired fins. • A notochord and cartilaginous skeleton are present • Earliest jawless fishes(Agnatha) were the ostracoderms. • They were covered with hardened external plates but did not have a well-developed endoskeleton. The lived on the ocean bottom where they were filter feeders
23.3a Agnathan (Jawless Fish ) • Jawless (Agnathan) • lampreys and hagfishes Ostracoderms
23.3b Jawed Fish Chondrichthyes (cartilaginous fish) • Sharks, Skates and Rays Chimaeras • Cartilaginous endoskeleton, fins and unprotected gill slits • Lacks an operculum Found in Bony Fish • Replaceable teeth • Have a well developed sensory system • NO SWIM BLADDER
23.3c Osteichthyes (bony fishes) 1. Most numerous and diverse of the vertebrates. a. radiated into nearly every aquatic habitat. b. Body plans vary • from torpedo shape to eel to the peculiar sea horse. 2. Operculum, 3. Swim Bladder 4. Extensive gills to maximize the surface area for gas exchange 5. Ectothermic Examples, The ray-finned fishes, lobe-finned fishes, Lungfishes
23.3c Osteichthyes (bony fishes) • Most of the bony fishes have a sac like structure leading from the pharynx. • The connection to the pharynx may be sealed off during development. • This sac, the swim bladder, is a major development to the bony fishes. • It provides the fish with a neutral buoyancy. • Permits the fishes to hover in the water and not have to swim constantly and thus expend energy to avoid sinking. • The reduction in energy expenditure reduces the amount of time required for feeding.
23.3c Osteichthyes (bony fishes) • Respiration in the aquatic environment is difficult for two reasons. • The medium contains far less oxygen per unit volume than air • its viscosity makes it more difficult to move during irrigation of the respiratory surfaces or gills. • Extensive gills to maximize the surface area for gas exchange. • Use counter current system where the blood in the gill capillaries flows in the opposite direction to the water flowing over the gills . • This allows for a higher saturation of the blood with oxygen. • Bony Operculum provides a degree of protection for the delicate gill tissues • By moving the operculum water can be forced over the gills without the fish being compelled to move
23.4 Amphibians Amphibians have a body plan and mode of reproduction somewhere between “fishes” and “reptiles.” Life on land presented new challenges to the emerging amphibians. a. Water availability was not reliable. b. Air temperatures were variable and air itself was not the strong supporting medium that water was, but it was a richer source of oxygen. c. New habitats, including vast arrays of plants, necessitated keener sensory input.
23.4 Amphibians BIG 5 STATEMENTS 1. 2. 3. 4. 5.
23.4 Amphibians • Amphibians have a body plan and mode of reproduction somewhere between “fishes” and “reptiles.” 1. “Amphi” meaning dual lived a. First in water, then on land 2. All are dependent on water in juvenal stages, a. They must return to it to lay eggs, which will produce larvae dependent on a watery environment. 3. Most have a Moist mucus covering for respiration a. Depending on their habitat, can respire by use of gills, lungs, skin, and pharyngeal lining. 4. The skin is usually thin and sometimes supplied with glands that produce toxins. 5. Ectothermic
23.4 Amphibians • Three main groups of amphibians. 1. 2. 3.
23.4 Amphibians B. Three main groups of amphibians. 1. (Anura) Frogs and toads are the best known. a. long powerful hindlimbs b. excellent prey-grasping capability of the tongue attached at the front of the mouth. 2. (Caudata) Salamandershave an elongated body with a tail that persists into adulthood. a. Adults may retain larval features including gills and a tail. 3. (Gymnophiona) Caecilians have lost their limbs and vision. a. These unusual creatures live burrowed in the forest floor where they hunt for invertebrate prey. b. They have no limbs but do have small scales embedded in the skin.
23.5 Vanishing Acts of Amphibians • Several frog, toad, and salamander species are currently listed as threatened or endangered. • WHY???
23.5 Vanishing Acts of Amphibians • Several frog, toad, and salamander species are currently listed as threatened or endangered. • Many declines correlate with: • Shrinking and deteriorating habitats • Pollution • Long term changes in climate • Increases in ultraviolet radiation • New diseases may be affecting amphibians sooner than other organisms. WHY???
23.6 The Rise of Amniotes A. The “Reptiles” 1. Four features were critical to amniotes’ escape from water dependency. a. Amniote eggs with covering membranes and a shell, which allow the eggs to be laid in dry habitats. b. Dry or scaly skin that is resistant to drying. c. Their kidneys are good at conserving water. 2. Modification of limb bones, teeth, and jawbones a. Development of the cortex region of the cerebrum permitted greater integration of sensory input and motor response. WHAT????? b. four-chambered heart and more efficient lungs allowed greater activity.
23.7 Existing Reptilian Groups 1. (Chelonia) Turtles possess a distinctive shell • protection while • conserving water and body heat. • Turtle eggs are vulnerable to predators, resulting in declining numbers. 2. (Sauria) Lizards are the most diverse reptiles. • Most lizards are small-bodied insect eaters; their most usual habitats are deserts and tropical forests. • Some such as the monitor lizard can subdue deer. • a long snout; body temperature is regulated behaviorally (ectothermic). • They show complex behavior, as when the parents guard nests and assist hatchlings into the water.
23.7 Existing Reptilian Groups 3. (Serpentes ) Snakes • descended from short-legged, long-bodied lizards. • All are carnivores, many with flexible jaws that permit swallowing quite large, whole prey. • Snakes are limbless but retain vestiges of hind limbs. • Many are venomous and may bite humans, especially when provoked. 4. (Crocodilia) Crocodiles and alligators • all live in or near water 5. (Rhynchocephalia) the tuatara • has a single living member • a lizardlike reptile of New Zealand.
You might have thought tuatara are lizards… but they’re not. (Rhynchocephalia) the tuatara • The arrangement of their teeth is very special. The single row of teeth in the lower jaw fits between two rows of teeth in the upper jaw. This helps tuatara tear apart hard insects such as weta, and chew the heads off small seabirds – yuck! • Tuatara mate differently fromlizards. The male tuatara does not have a penis; he mounts the female and passes sperm straight from his cloaca to hers (the cloaca is the hole that sperm enters the female through). • They have a gland beneath the skin on the head, which contains a simple ‘third eye’. • Lizards have visible ear openings but tuatara do not. • But like lizards, if they lose their tails they are able to regrow them - excellent! • What’s this about a ‘third eye’ ??
23.8 Birds—The Feathered Ones A. Theorized ancestral relationship to reptiles B. Birds have several unique features. • Feathers covering the wings make a good flight surface and conserve metabolic heat in the body. a. ENDOTHERMIC • Heat is generated and regulated from within the body • Heart is four-chambered, and the lungs are highly efficient • Bones are lightweight due to air cavities within them. • Powerful muscles are attached at strategic places on the bones for maximum leverage. a. Keeled sternum C. Migration is a dramatic form of behavior. • Seasonal day length is a triggering factor. • Most of the travel, sometimes very long distances, is from breeding grounds and wintering places.
23.9 Mammals A. Modern mammals are characterized by: • Hair covers at least part of the body (whales are an exception). • Milk-secreting glands nourish the young. • Dentition (incisors, canines, premolars, and molars) specialized to meet dietary habits. • Brain capacity is increased, allowing more capacity for memory, learning, and conscious thought. • Show behavioral flexibility, the ability to expand on the basics with novel forms of behavior.
23.9c What are the Three Types of Mammals: . 1. 2. 3.
23.9c Three Types of Mammals: • Monotremes (Egg-laying) mammals • Ex. platypus and Echidna (spiny anteater) in Australia. • They are practically toothless. • They lay eggs but suckle their young. • Marsupials (Pouched) mammals • Ex. opossum of North America, Kangaroo, Sugar Glider • give birth to tiny, blind, hairless young that find their way to the mother’s pouch where they are suckled and finish their development. • Placental mammals (all the rest) • You mice, dogs, cows, horse • nourish their young within the mother’s uterus by the placenta—a composite of maternal and fetal tissue. .
Stop • it’s Hammer time
links • http://io.uwinnipeg.ca/~simmons/16cm05/1116/chordate.htm • http://trc.ucdavis.edu/biosci10v/bis10v/week5/06week5day1.html • Main index