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The History Of Life

by: Emmett Heathcote

The History Of Life GLY 1101

Emmett Heathcote
GPA 3.69

Jose Longoria

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Jose Longoria
Class Notes
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This 5 page Class Notes was uploaded by Emmett Heathcote on Monday October 12, 2015. The Class Notes belongs to GLY 1101 at Florida International University taught by Jose Longoria in Fall. Since its upload, it has received 15 views. For similar materials see /class/221777/gly-1101-florida-international-university in Geology at Florida International University.


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Date Created: 10/12/15
THE VERTEBRATES Chordates phylum Chordata are deuterostome coelomates whose nearest relatives in the animal kingdom are the echinoderms the only other deuterostomes However unlike echinoderms chordates are characterized by a notochord jointed appendages and segmentation Four features characterize the chordates and have played an important role in the evolution of the phylum 1 A single hollow nerve cord runs just beneath the dorsal surface of the animal In vertebrates the dorsal nerve cord differentiates into the brain and spinal cord 2 A flexible rod the notochord forms on the dorsal side of the primitive gut in the early embryo and is present at some developmental stage in all chordates The notochord is located just below the nerve cord The notochord may persist throughout the life cycle of some chordates or be displaced during embryonic development as in most vertebrates by the vertebral column that forms around the nerve cord 3 Pharyngeal slits connect the pharynx a muscular tube that links the mouth cavity and the esophagus with the outside In terrestrial vertebrates the slits do not actually connect to the outside and are better termed pharyngeal pouches Pharyngeal pouches are present in the embryos of all vertebrates They become slits open to the outside in animals with gis but disappear in those lacking gis The presence of these structures in all vertebrate embryos provides evidence of their aquatic ancestry 4 Chordates have a postanal tail that extends beyond the anus at least during their embryonic development Nearly all other animals have a terminal anus The Nonvertebrate Chordates Nonvertebrate chordates have a notochord but no backbone The tunicates subphylum Urochordata are a group of about 1250 species of marine animals Most of them are sessile as adults with only the larvae having a notochord and nerve cord As adults they exhibit neither a major body cavity nor visible signs of segmentation Most species occur in shallow waters but some are found at great depths Lancelets are scaleess fishike marine chordates a few centimeters long that occur widely in shallow water throughout the oceans of the world Lanceets subphylum Cephalochordata were given their English name because they resemble a ancet a small two edged surgical knife There are about 23 species of this subphylum Most of them belong to the genus Branchiostoma formerly called Amphioxus a name still used widely In anceets the notochord runs the entire length of the dorsal nerve cord and persists throughout the animal39s ife Characteristics of Vertebrates The evolution of vertebrates involved invasions of sea land and air Vertebrates subphylum Vertebrata are chordates with a spinal column The name vertebrate comes from the individual bony or cartilaginous segments caed vertebrae that make up the spine Vertebrates differ from the tunicates and anceets in two important respects 1 Vertebral column In all vertebrates except the earliest fishes the notochord is replaced during the course of embryonic development by a vertebral column figure 348 The column is a series of bony or cartilaginous vertebrae that enclose and protect the dorsal nerve cord like a sleeve 2 Head Vertebrates have a distinct and well differentiated head the brain is fully encased within a protective box the skull or cranium made of bone or cartilage For this reason the vertebrates are sometimes called the craniate chordates In addition to these two key characteristics vertebrates differ from other chordates in other important respects 1 Neural crest A unique group of embryonic cells called the neural crest contributes to the development of many vertebrate structures These cells develop on the crest of the neural tube as it forms by invagination and pinching together of the neural plate Neural crest cells then migrate to various locations in the developing embryo where they participate in the development of a variety of structures 2 Internal organs Internal organs characteristic of vertebrates include a liver kidneys and endocrine glands The ductless endocrine glands secrete hormones that help regulate many of the body39s functions All vertebrates have a heart and a closed circulatory system In both their circulatory and their excretory functions vertebrates differ markedly from other animals 3 Endoskeleton The endoskeleton of most vertebrates is made of cartilage or bone Cartilage and bone are specialized tissue containing fibers of the protein collagen compacted together Bone also contains crystals of a calcium phosphate salt Bone forms in two stages First collagen is laid down in a matrix of fibers along stress lines to provide flexibility and then calcium minerals infiltrate the fibers providing rigidity The great advantage of bone over chitin as a structural material is that bone is strong without being brittle The vertebrate endoskeleton makes possible the great size and extraordinary powers of movement that characterize this group Overview of the Evolution of Vertebrates The first vertebrates evolved in the oceans about 470 million years ago They were jawless fishes with a single caudal fin Many of them looked like a flat hot dog with a hole at one end and a fin at the other The appearance of a hinged jaw was a major advancement opening up new food options and jawed fishes became the dominant creatures in the sea MAMMALS CLASS MAMMALIA There are about 4500 living species of mammals class Mammalia the smallest number of species in any of the five classes of vertebrates Most large land dwelling vertebrates are mammals figure 3438 and they tend to dominate terrestrial communities as did the dinosaurs they replaced Major Orders of Mammals Order Typical Examples M Key Characteristics Approximate Number of Living Species Rodentia Beavers mice porcupines rats Small plant eaters Chisel like incisor teeth 1814 Chiroptera Bats Flying mammals Primarily fruit or insect eaters elongated fingers thin wing membrane nocturnal navigate by sonar 986 lnsectivora Moles shrews Small burrowing mammals Insect eaters the most primitive placental mammals spend most of their time underground 390 Marsupialia Kangaroos koalas Pouched mammals Young develop in abdominal pouch 280 Carnivora Bears cats raccoons weasels dogs Carnivorous predators Teeth adapted for shearing flesh no native families in Australia 240 Primates Apes humans lemurs monkeys Tree dwellers Large brain size binocular vision opposable thumb group that evolved from a line that branched off early from other mammals 233 Artiodactyla Cattle deer giraffes pigs Hoofed mammals With two or four toes mostly herbivores 211 Cetacea Dolphins porpoises whales Fully marine mammals Streamlined bodies front limbs modified into flippers no hind limbs blowholes on top of head no hair except on muzzle 79 Lagomorpha Rabbits hares pika Rodent like jumpers Four upper incisors rather than the two seen in rodents hind legs often longer than forelegs an adaptation forjumping 69 Pinnipedia Sea lions seals walruses Marine carnivores Feed mainly on fish limbs modified for swimming 34 Edentata Anteaters armadillos sloths Toothless insect eaters Many are toothless but some have degenerate peg like teeth 30 Perissodactyla Horses rhinoceroses zebras Hoofed mammals with one or three toes Herbivorous teeth adapted for chewing 17 Proboscidea Elephants Long trunked herbivores Two upper incisors elongated as tusks largest living land animal 2 Key Mammalian Characteristics Mammals are distinguished from all other classes of vertebrates by two fundamental characteristics hair and mammary glands and are marked by several other notable features Hair All mammals have hair Even apparently naked whales and dolphins grow sensitive bristles on their snouts The evolution of fur and the ability to regulate body temperature enabled mammals to invade colder climates that ectothermic reptiles could not inhabit and the insulation fur provided may have ensured the survival of mammals when the dinosaurs perished Mammary glands All female mammals possess mammary glands that secrete milk Newborn mammals born without teeth suckle this milk Even baby wha es are nursed by their mother39s milk Milk is a fluid rich in fat sugar and protein A liter of human milk contains 11 grams of protein 49 grams of fat 70 grams of carbohydrate chiefly the sugar lactose and 2 grams of minerals critical to early growth such as calcium About 95 of the volume is water critical to avoid dehydration Milk is a very high calorie food human milk has 750 kcal per liter important because of the high energy needs ofa rapidly growing Endothermy As stated previously mammals are endothermic a crucial adaptation to that has allowed them e active at any time of the day or nig tan to colonize n Placenta In most ma mal species emales carry their young in a uterus during development nourishing them through a placenta and give birth to live young The placenta is a specialized organ within the uterus of the pregnant mother that brings the bloodstream of the fetus into close contact with the bloodstream of the mother Teeth Reptiles have homodont dentition meaning that their teeth are all the same However mammals have heterodont dentition with different types of teeth that are highly specialized to match particular eating habits figure 3440 It is usually possible to determine a mammal39s diet simply by examining its teeth Compare the skull of a dog a carnivore and a deer an herbivore The dog39s long canine teeth are well suited for biting and holding prey and some of its premolar and molar teeth are triangular and sharp for ripping off chunks of flesh In contrast canine teeth are absent in deer instead the deer clips off mouthfuls of plants with flat chisellike incisors on its lowerjaw e eer39s molars are large an covered with ridges to ef fectively grind and break up tough plant tissues Rodents such as beavers r awers a have long incisors for c ewing t rough branches or stems T ese incisors are evergrowing that is the ends wear down but new incisor growth maintains the length LD Mammals have different types of specialized teeth While reptiles have all the same kind of teeth mammals have different types of teeth specialized for different feeding ll lClSOfS Canine Carnivores such as dogs have canine teeth that are able to rip food some of the premolars and molars in dogs are also ripping teeth Herbivores such as deer have incisors to chisel off vegetation and molars designed to grind up the plant material In the beaver the chiseling incisors dominate In the elephant the incisors have become specialized weapons and molars grind up vegetation Humans are omnivores we have ripping chiseling and grinding teeth Digestion of plants Most mammals are herbivores eating mostly or only plants Cellulose the major component of plant cell walls forms the bulk of a plant39s body and is a major source of food for mammalian herbivores Hooves and horns Keratin the protein of hair is also the structural building material in claws fingernails and hooves Hooves are specialized keratin pads on the toes of horses cows sheep antelopes and other running mammals The horns of cattle sheep and antelope are composed of a core of bone surrounded by a sheath of keratin The bony core is attached to the skull and the horn is not shed Flight Bats are the only mammals capable of powered flight figure 3441 Like the wings of birds bat wings are modified forelimbs The bat wing is a leathery membrane of skin and muscle stretched over the bones of four fingers


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