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Biology Chapter 34

by: fwmartin

Biology Chapter 34 BSC 120


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Covers Chapter 34
Honors Gen Biology II
Dr. Martha Powell
Class Notes
Chordates, Vertabrates
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This 8 page Class Notes was uploaded by fwmartin on Wednesday March 16, 2016. The Class Notes belongs to BSC 120 at University of Alabama - Tuscaloosa taught by Dr. Martha Powell in Spring 2016. Since its upload, it has received 17 views. For similar materials see Honors Gen Biology II in Biological Sciences at University of Alabama - Tuscaloosa.

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Date Created: 03/16/16
Chapter 34: Chordates Tunicates (sea squirts) • Resemble other chordates only during brief larval stage • Larvae uses its tail to swim to find suitable substrate on which to settle • Pharyngeal slits used for suspension feeding • Once settled- radical metamorphosis occurs Lancelets • Marine invertebrate • Bladelike shape o couple of cm long • Filter tiny food particles o (Trap food in mucous net over pharyngeal slits) Ancestral chordates may have resembled lancelets. Gene expression in lancelets holds clues to the evolution of the vertebrate form – HOX genes for brains in vertebrates =▯development of lancelet’s nerve cord. The vertebrate brain is an elaboration of an ancestral theme. Hagfishes • Makes slime to protect from predators o Humans interested in it for fabric and medical applications • Has cranium but no vertabre • No teeth or jaw Lampreys • Often considered the oldest living group of vertebrates • Lacks jaws but has a cranium • 35 species, marine and fresh water • Larvae live in fresh water streams o Resemble a lancelet • After several years most adults migrate to the sea or lakes o Fisheries in the Great Lakes have been devastated by the adults • Use rows and rows of raspy teeth to grab on side of fish and then suck the bood out of them. • They are parasites Fishes Fish with fins and jaw • have gills • single-loop blood circulation o heart-gills-tissue-heart • jaws are modification of skeletal arches that supported the gills▯ feeding efficiency….added teeth • have nutritional deficiencies – unable to synthesize the aromatic amino acids and must consume them in their diet. This inability has been inherited by all their vertebrate descendants. There are 2 main groups of fish: Cartilaginous and Bony • both have a lateral line system that detects minor vibrations in the water. Cartilaginous Fishes • Sharks and Rays • Skeleton composed of cartilage • Little changed in 300 million years • Existence is threatened – ▯ shark find soup – fin $500/lb • Have keen sense of smell • Have regions in their skin that can detect electric fields (muscle contractions) • Lateral line system detects water pressure (and minor vibrations) Sharks o Swift swimmers, streamlined body o Propelled forward by trunk and tail fin o If one stops swimming, it sinks o Continual swimming optimizes gas exchange o Despite this, some spend lots of time on the sea floor o Muscles in the jaws and pharynx actively pump water over the gills when motionless o Most sharks are carnivores that swallow their prey whole § Can tear large prey with its teeth § Have several rows of teeth that move o Sharks do not have eardrums o no aquatic vertebrates have ear drums § Their entire body transmits sound to an inner ear Skates and Rays o Very different lifestyle from sharks o Flattened bottom dwellers o Crush molluscs and crustaceans with strong jaws o Pectoral fins greatly enlarged: water wings o Tail- whip like, can contain a venomous barb. Bony Fishes • Operculum – pumps water over gills • Fast and maneuverable swimmers • Lateral line – detect differences in water pressure • Swim bladder (keep them buoyant – conserves energy) o Ray-finned fish o Lobe-finned fishes § Lungfishes § coelacanths Ray-Finned Fishes o Most fish alive today § Ex. bass, trout, perch, tuna, sea horses, eel o Fins are supported by long, flexible rays § Are often modified for specific functions o Major source of protein for humans! Lobe-Finned Fishes o Early species had lungs § Used to breath air and supplement gas exchange in gills § Lungs evolved into swim bladders in many. § Others have both lungs and gills § Skin often covered by flattened bony scales Only two groups survive: o Lungfishes- southern hemisphere, fresh water, Surface to gulp air, also have gills § Some can burrow in the mud when ponds dry up and survive until water returns o Coelacanths two populations exist in the Indian ocean § Thought to have been extinct until recently Tetrapods: (Amphibians, Reptiles, Birds, & Mammals) Many lobe-finned fishes were living in coastal areas 400 million years ago • O 2content in murky waters was poor- o they used their lungs • they used their muscular lobed fins to move on muddy land and “walk” • in the fossil record of certain lineages, lobed fins became more and more limb-like Life on land resulted in other traits: • Fusion of the pelvic girdle (hip) to the backbone o to support the force exerted by the hind legs against the ground. • Head separated from body by a neck o able to swing up and down and side to side • Gill slits are lost in embryonic development to give rise to parts of the ear and lower skull • Airborne sounds are detected by external ears. Some of these traits are dramatically altered to fit particular functions ex: pectoral limbs become wings in birds Amphibia First vertebrates to walk on land. They have legs, lungs, 2-way blood circulation, partial divided heart • Salamanders- retain tails as adults • Frogs- adults have no tail • Caecilians- legless, burrowing • “living a double life”- aquatic and terrestrial adaptations • Tied to the water because of their eggs o Larval stage- aquatic herbivore with gills and tail eat algae o Adult stage- terrestrial hunters § tail, gills disappear § legs, lungs, external ears, and a digestive system suited for a carnivore develop § still depend on moist skin for gas exchange § Squeeze throat to pump air into their lungs • Not all species live in two different habitats during their life cycle. • Salamander and caecilian larvae look like adults and both stages are carnivores. • External fertilization o Male deposits sperm over eggs as they are laid o Eggs are laid in water or in moist soil § Eggs lack a shell and dehydrate easily § Mortality is high, some species lay huge numbers of eggs • Over the past 25 years, populations around the world have rapidly declined • Habitat degradation, spread of fungal pathogens, acid rain • Amphibian populations are often studied as an indicator of the health of a particular ecosystem. Amniotes: The Clade of Tetrapods with eggs adapted for land Major derived trait : the amniotic egg • Includes two clades: 8. Reptiles (including birds) and 9. Mammals • Eggs have extraembryonic membranes: specialized membranes that protect embryo • not part of the embryo body • Function in gas exchange, waste storage and transfer of stored nutrients • One layer, the amnion surrounds the embryo in a contained pocket of fluid • Shock absorber • Unlike amphibian eggs, amniotic eggs of most reptiles and some mammals have a shell • Bird eggs have calcium carbonate: inflexible • Most other reptile eggs are flexible • Most mammals have no shell and the embryo avoids drying out by remaining inside the mother. Amniote traits • Less permeable skin • Muscular rib cage that ventilates lungs • Generally display a more elevated stance Reptiles • Have scales with the protein, keratin – Unlike amphibians – Waterproof barrier – Prevents breathing through skin, rely on lungs • Most lay shelled eggs on land (amniotes) (first group on land without water for reproduction) – Fertilization internal – some are viviparous- placenta gives nutrients to growing embryo • Adaptation to land • = watertight (amniotic eggs) • = dry skin • = thoracic breathing • Body temperature – Many do not use their metabolism to regulate body temperature. – Use behavior – Ectothermic- they absorb external heat as the main source of body temperature – Since they do not rely on heat from the metabolism of food, they can survive on less than 10% of the food energy required by a mammal of the same size – Although birds are in the reptile clade, they are endothermic Turtles All have a boxlike shell: excellent defense upper and lower shields, fused to vertebrae Adapted to deserts, rivers, ponds, the ocean Leatherbacks: the largest living sea turtles eat jelly fish endingered due to fishing nets and development of beaches where they lay their eggs Snakes • Some have vestigial hip and limb bones – Evidence of ancestry • Carnivorous – Acute chemical sensors • Ex. Olfactory organs on roof of mouth – flick tongue to fan odors to these organs • Ex. Pit vipers have heat detecting organs that enable detection of warm bodied prey at night – Poisonous snakes inject toxin through hollow teeth • Most snakes can swallow prey larger than their diameter – loosely held jaws and elastic skin Crocodiles and Alligators • Both in the group Crocodilians • Living varieties confined to warm climates Earliest members: small, terrestrial, long thin legs Birds Most are traits to enable or facilitate flight • Wings: edited forelimbs – Bones often filled with air- honeycombed – Contractions in the pectoral (breast ) muscles cause wing to flap – Various adaptations • Ex. Soaring in hawks, continual rapid flapping in hummingbirds • Feathers: made of keratin (like reptile scales) – Contour feathers: stiff, aerodynamic – Downy feathers: for insulation Other adaptations for flight: • Weight lessening traits – No bladders, females have one ovary, toothless, light skull • Efficient respiratory and circulatory system – Supports high metabolism • Acute vision • Complex mating rituals • Elaborate plumage adapted through sexual selection • Parental care for eggs and young A few species are flightless • Ratites: ostrich, emu etc – lack strong pectoral muscles • Penguins: use strong pectoral muscles for swimming • Some ducks, rails and pigeons are flightless Disapperance of Birds • Bird-watchers can easily determine species based on flight style, colors, behavior, etc. – Birds as a group are the most well studied animals. From the International Council for Bird Preservation (ICBP): • About 9000 species of birds exist today. • Since 1600, 108 species in N. America and Europe are known to have become extinct. • Today, 1,666 species (almost 20%) are either endangered or at risk of extinction • How many species will be around in 50 yrs? Mammals • The other lineage of amniotes besides reptiles • 1. Amniotes that have: 1. hair and 2. produce milk • First mammals were probably small, nocturnal insect-eaters • Became more diverse after the downfall of dinosaurs. Characteristics • Mammary glands: produce milk for offspring • Hair • A layer of fat underneath the skin- insulation • Endothermic (like birds), high metabolism • Efficient respiratory and circulatory systems • Diaphragm to help ventilate lungs • Larger brain • Long duration of parental care • Differentiation of teeth- adapted for chewing a variety of food • Most are terrestrial (marine secondary adaptation) • 3 major groups of mammals – a. Monotremes – hatched from eggs – b. Marsupials – embryonic at birth – C. Eutherians – young fully developed at birth – Underwent adaptive radiation after the end of the dinosaurs monotremes • 1 species of platypus and 2 species of echidna – Australia and New Guinea • Lay eggs • Produce milk from glands, lack nipples – Young lick up milk from mother’s fur Marsupials • Opossums, kangaroos, koalas • Once found world wide, now only in N. and S. America and Australia • Embryo develops in the uterus and has a placenta • Born very early in their development • Embryo completes development while attached to the mother’s nipples Eutherians • Have a complex placenta • Longer time in the uterus • Originated in the late cretaceous period


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