Unit 13 - Vertebrates Student Guided Notes

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1 Chordates Unit 13 - Vertebrates Student Guided Notes General Characteristics of Phylum Chordata Although not the largest, Chordates are the most diverse phylum in the animal kingdom. Chordates have at some stage of the life cycle and have made from an outgrowth of the digestive tube. All chordates are deuterosomes and the blastopore during embryonic development forms the anus. They show body segmentation and other characteristics present in the more advanced animals. In order to be classified as a chordate an animal must have the following characteristics. Although it may seem as if many chordates do not possess these characteristics, they do at some point during embryonic development. 1. Notochord. The function of the notochord is to provide support and protection to the nerve chord. In the higher chordates, the vertebrates, the notochord is present in embryonic development and. 2. Dorsal Tubular Nerve Chord The is exactly what its name suggests. The term dorsal means it is on the back side of the animal. The term tubular means it is hollow. It is the nerve chord of the animal. The hollow portion of the nerve chord is filled with fluid that nourishes the nerve cells. I

2 3. Pharyngeal Pouches. In water-breathing animals the pharyngeal pouches become the gills or gill slits. In airbreathing animals the pharyngeal pouches take on a number of functions. None of the pharyngeal pouches are involved in respiration in humans. 4. Post Anal Tail The is simply an extension of the nerve chord and body. There are three sub-phlya that will be discussed in the lessons to follow: Subphylum Urochordata. Subphylum Cephalachordata. Subphylum Vertebrata Endoskeletons All of the chordates have an. The skeleton of chordates varies greatly from the to the and the bony skeletons of humans. This endoskeleton possesses advantages and disadvantages to the previously studied exoskeleton of Arthropods. The endoskeleton doesn't provide the overall protection to the body that the exoskeleton does. Where protection of a certain internal organ is very important it is well protected by the endoskeleton. In humans, the skull, spine, and rib cage would be examples of bones that are providing effective protection for organs like the brain, spinal cord and heart. The endoskeleton has a. Likely, the most important improvement over the exoskeleton is its. The exoskeleton must be periodically shed and regrown. This leaves the animal vulnerable for a short time while it is regrowing its exoskeleton and is also very costly in terms of energy. With the endoskeleton's ability to grow along with the animal, these animals can grow much larger and energy can be expended on the development of other organs.

3 Prochodates General Characteristics of Prochordates are those animals in which during development. The two subphyla of prochordate are the (subphylum Cephalochordata) and the (subphylum Urochordata). (subphlum Cephalochordata). The. A lancelet is very mobile and powers its way through the water with muscles that use the notochord as a point of attachment. The tentacles around the mouth are for searching through mud for microscopic food particles that will filter out of the constant water stream that is moving through the animal.

4 Anatomy of a Lancelet Tunicates. There are an estimated 2000 species of tunicates that are commonly called Tunics meaning tough covering.. Tunicates are hermaphrodites. The adult tunicate (subphylum Urochordata) looks more like an invertebrate than a chordate since the only retained trait from the larval stage are the gill slits. Tunicate larva possesses all of the chordate characteristics. The tadpolelike larvae is bilaterally symmetrical and free swimming which is ideal for the dispersal stage of the tunicate life cycle.. The sessile tunicate will filter feeder by drawing in

5 water thought its incurrent siphon and past the gill slits to filter out oxygen and food. The larvaceans (class Appendicularia) are a group of tunicates that remain in the larval form and do not become the sessile adult.. Vertebrates Diversity of Vertebrates The anatomy and physiology of humans is the focus of Biology 12. For this reason, the study of the vertebrates in Biology 11 will be an introduction to the diversity of the classes within the phylum. The vertebrates are the animals that are more typically used to represent the chordate phylum. With, the vertebrates are the most advanced of all organisms. Vertebrates are distinguished from other chordates by : 1) that surround and protect the dorsal nerve cord. The vertebrae form a vertebral column or spine. 2) A cranium or. 3) An

6 Features of Vertebrates A living endoskeleton with vertebral column that can grow.. Paired appendages. Efficient respiration and excretion.. Adapted to active lifestyles. Fishes Vertebrates first appear in the fossil record. Today there are an estimated 45,000 species of vertebrates. More than 24,000 of these are fish species.. Class Class Class General Characteristics of Fishes Fish have a stream-lined shape for to reduce drag with paired fins that allow movement left or right. Secretion of a mucus layer helps to reduce friction. Fish have an air bladder which stores carbon dioxide to control their buoyancy in the water. Gills allow for gas exchange between the blood stream and water. Fish also have a lateral line or row of sensory structures along the side of the body that can detect vibrations in the water. Jawless Fishes It is predicted that the

7 since they are the most similar to the prochordates and are the oldest known vertebrate fossils. Jawless fishes have. They rely on external fertilization for reproduction. Examples of these fishes include the. Both of these fishes rely on symbiotic relationships. are deep sea bottom dwellers named for their slimy coat. They take part in a commensalistic relationship as.. The circular rasping teeth of the lamprey attach to a fish. Rasping at the flesh of the host fish the lamprey will feed off of the blood. Lampreys are an exotic species introduced into the Great Lakes through the discharge of ballast tanks from ships. They devastated native fish populations in the 1970's and 1980's. Cartilaginous Fishes The next group of fishes are the. This class includes sharks, skates and rays.. The cartilaginous fishes are all marine and all are carnivorous except the whale shark. They have jaws, paired appendages, visceral arches, three semi-circular canals, paired nasal cavities, and placoid scales that feel like sandpaper, and a well developed sense of smell. As their name suggests they have an endoskeleton made entirely of cartilage. Other features include no swim bladder or lung, a heterocercal or asymmetrical tail, and respiration by means of five to seven pairs of

8 gills with gill slits. These fish have separate sexes and utilize several reproductive strategies. Some species are oviparous (eggs hatch outside the body), others are ovovivparous (eggs hatch inside the body), and others are viviparous (young are cared for completely internally). have very well developed senses that are used to locate prey. In fact, they actually have seven senses. The two extra senses are the ability to detect slight electric currents in water which could be caused by the muscle contractions of another animal and the ability to detect changes in pressure in water currents with their lateral line. Sharks have 6-20 rows of teeth that are continually being replaced and may use over 20,000 teeth in a lifetime. The paired pectoral fins in sharks are located just behind the head and jut out from the body like wings on a plane to provide lift when swimming. have flattened bodies, paired wing like pectoral fins, and some species have a whip like tail. Rays have diamond shaped bodies while skates have triangular shaped bodies. Both are bottom dwellers and their flat shape and color camouflage them with the ocean floor. Bony Fishes have a. Bony fish are characterized by three key features; bone, lungs or swim bladder, and scales. The tail is usually homocercal or symmetrical on the top and bottom. They have skin with mucous glands and embedded dermal scales. The operculum, a bony plate that protects the gills, is found in bony fishes.

9 These are the fishes that we generally think of when we think of fish. From the fish that we eat to the ones we keep as pets in a fish tank. One of the most unique organs in the bony fishes is the swim bladder. This is a relatively large air sac within the fish that increases in size when the fish wants to go up and decreases in size when the fish wants to go down. Most of the bony fishes are ray-finned fish. However, a very important group of fish in terms of evolution are the lobe-finned fishes.. These fishes not only had fleshy appendages instead of flat fins, but they also had a lung that could be used for respiration. Lobe-finned fish were long thought to be extinct, but in 1938 a lobe-finned fish called a coelacanth was caught off the coast of Madagascar. These are the only known living lobe-finned fish. Bony fish all have a very similar internal anatomy. The circulatory system consists of a with separate arterial and venous systems and four aortic arches. The nervous system consists of a well developed brain with well developed olfactory and optic lobes. Most species are oviparous and fertilization is external. Life in the Water Scales found in fishes prevent diffusion through body tissues so gills are needed for gas exchange. In marine fish water is continually leaving the body by osmosis and ions are continually entering. To keep from dehydrating they must drink large amounts of water and produce a small amount of concentrated urine. Their gills are also adapted to lose salt. In freshwater fish water is continually entering the body of the fish by osmosis so they do not drink water and produce large amounts of dilute urine. Amphibians Amphibians are the most primitive of the animals to possess true limbs and are tetrapods with four legs. Other features are

10 . Frogs, toads, newts and salamanders all undergo metamorphosis from a. Amphibians must lay their eggs in a place where they will hatch in water. Respiration occurs in the. Adaptation to Land Two Hypothesis: 1) Aquatic vertebrates first moved onto land as shallow pools of water began drying up. This theory is no longer accepted. 2) More likely that ancestors of amphibians left the water to escape predation, competition and gain access to the abundance of resources on land. Characteristics of Early Amphibians Amphibians. Four strong limbs developed from fins. The adaptations for living on land included sense organs for detecting scents and sound million years ago early amphibians split into two main evolutionary lines that led to modern amphibians and reptiles. Diversification of Amphibians Today there are an estimated 4,500 species of amphibians in three Orders. Modern amphibians share the five key characteristics of metamorphosis,.

11 The Order Anura includes frogs and toads. They are found worldwide except in polar climates. Frogs and toads live in a variety of habitats. The term toad is commonly used for any anuran that has rough bumpy skin. The term frog is commonly used when anurans have smooth moist skin. Frogs and toads spend part of their life in water (if not all). They are characterized by a body adapted for jumping and are carnivores (some have a sticky tongue). Many return to the water to reproduce where their eggs hatch into larvae called tadpoles. The Order Urodela includes salamanders that are characterized by elongated bodies, long tails, and moist skin. Most salamanders have four limbs and are aquatic and terrestrial. They are carnivores who are mainly active at night. Most of them live in North America and Central America. The Family Plethodontidae or with more then 300 species is the largest group of salamanders.. Fertilization is internal and they lay eggs in water (larval stage) or in moist land environments (no larval stage). The Order Apoda includes caecilian or legless amphibians as the name suggests. They resemble small snakes and are often blind. Caecilians are rarely scene and little is known about their ecology and behavior. Most of them burrow in soil and some are aquatic. All species have teeth and eat worms and other invertebrates that they detect using chemosensory

12 tentacles on the side of their head. They can be found in Asia, Africa and South America. Reproduction in Amphibians The reproductive system of the male frog includes two bean shaped testes located near the kidneys. During the breeding season sperm develop in the testes and pass through the tubes to the kidneys and urinary ducts. During mating sperm leaves the body through the opening. The reproductive system of the female frog includes a pair of large, lobed ovaries containing thousands of tiny immature eggs that lie near the kidneys. During the breeding season the eggs enlarge, mature and burst through the thin ovarian walls into the body cavity. Cilia move the egg forward into a funnel like opening of the oviducts. As eggs pass through the oviduct they are coated with jelly like material. The eggs exit through the cloaca to the external environment where fertilization occurs. Courtship and Fertilization In early spring frogs emerge from hibernation and migrate to ponds and slow moving streams. Males call to attract females and warn off other males. Each species has its own mating call. When a mating pair find each other, the male frog climbs onto the females back in an embrace called amplexus that may last for days. The female leases legs into the water and the male discharges sperm over them called direct external fertilization. Metamorphosis Increasing levels of a hormone called thyroxine which circulates throughout the bloodstream stimulates metamorphosis. Within a few days of fertilization tadpoles emerge. They live off the yolk stored in their body. Tadpoles grows larger and develop three pairs of gills. Eventually the

13 mouth opens and allows it to feed. A process of change called metamorphosis results in the legs growing and the tail and gills disappearing. The mouth broadens and develops teeth and jaws. The lungs then become functional. Parental Care Parental care is common among amphibians. Eggs and larvae are vulnerable to predators so parental care increases the likelihood that offspring will survive. Most often the male remains with eggs to guard them. Darwin s males take young into their mouth. Female gastric-brooding frogs swallow their eggs. Both appear to have become extinct!! Reptiles Reptiles are by the Permian period. Reptiles have a that is keratinized and. They are usually tetrapods and have. Reptiles have evolved to be completely terrestrial in many cases and are no longer dependent upon water for the laying of eggs. This is because of the *** ****. This egg is developed from. Reptiles, fish and amphibians are cold blooded or. This does not mean that their blood is cold. The body temperature of an ectotherm is. Therefore, ectothermic animals regulate their body temperature by regulating their

14 surroundings. They will lie in the sun if it is cold out, and shade themselves if they are hot. Ectotherms must still regulate their body temperature in order for normal internal body functions to take place. The image to the right shows the American Alligator, Garter snake close up, Gopherus polyphemus, and the Collared Lizard. Birds Birds are. Often referred to as, birds and other endothermic animals regulate their body temperature internally. By maintaining a constant internal body temperature bodily functions occur at optimum levels of efficiency. This self regulation is known as. This is important for animals such as birds that require a great deal of energy for flight. Birds also have other adaptations for flight such as. Since we can see a bird s beak, we can easily hypothesize what it might eat. We can watch birds catch, handle, and swallow different foods to test our hypotheses based on the shape of the bill. The sharp thin bill of herons and egrets spear fish. The hooked bills of hawks and owls grab and rip apart prey and the short conical bills of sparrows crack seeds. Flight is very efficient but requires a lot of energy. Flying birds have 5-20 times their resting metabolic rate while running mammals only have 2-4 times their resting metabolic rate. To produce the level of energy required for flight, birds have incredibly efficient and

15 . These systems allow both fast flight and long distance migration. In addition, that greatly aid in flight.. Air passes through bird lungs into posterior by a different route. As a result, there are two passes of air in each respiratory cycle and because of countercurrent flow the oxygen extraction is very high. Birds have a. This efficiency of respiration and circulation enables birds to fly over the Himalayans at the altitude of Mount Everest. Mammals Mammals are thought to have evolved during the Mesozoic Era from therapsids. The mammalian skull accommodates a larger brain relative to its body size and differentiated teeth. Mammals are characterized by having Mammals have a high level of infant care, because the young are fed by means of the mammary glands. The adults must expend a lot of energy in the young, but it increases the chances of having successful offspring. This high-energy load on the mother means fewer offspring are produced. Mammals share other characteristics with birds. For example, efficient circulatory and respiratory systems, a

16 and being are characteristic shared by both. Mammals are divided into three groups; monotremes, marsupials, and placental mammals. Monotremes The. They are different from the other mammals in that they and have a cloaca. Interestingly, the platypus lacks a true stomach and digests its food in a enlarged area of the esophagus. Marsupials Marsupials (like the wombat above) are found mainly in Australia, but some marsupials are found in South and Central America as well. The only marsupial living in North America is the opossum. These opossums, although not native to the area, are found as far north as Hornby Island, British Columbia. In Australia, marsupials have filled many of the niches held by placental mammals in the rest of the world. Marsupials spend comparatively less time with pregnancy and they are born very immature. Once born they enter a pouch on the mother. Fed by the mammary glands the newborn will remain in the pouch until mature. The vast majority of marsupial fossils have been found in Australia including those of a huge ten foot tall kangaroo ancestor. Placental Mammals Due to the presence of the, a longer pregnancy is possible. The increased gestation time allows more energy to be used for the development of the nervous system. As a result of this development, placental mammals have the largest brain to body weight ratio. Even after the lengthy pregnancy

17 brain development continues under parental care. The larger brain has resulted in social development and communication in many mammals. Placental mammals are very widely distributed around the world and have members in almost every niche. Bats have taken to the air, whales to the water, and many examples exist on land. Placental mammals can be. Major Orders of Placental Mammals Perissodactyla - Horses. Artiodactyla - Deer. Carnivora - Cats. Primates - Monkeys. Cetacea - Whales. Chiroptera - Bats. Rodentia - Mice. Proboscidea - Elephants. Lagomorpha - Rabbits.