Chapters 34 & 35 Notes
Chapters 34 & 35 Notes Biol 112
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Chapter 34: Protostome Animals Protostomes Are a major source of food for humans Provide ecosystem services such as pollination and soil preparation Include both insects that damage crops and insects that protect crops from pests Provide valuable materials such as silk and pearls Some are common parasites that transmit human disease What is a Protostome? Triploblastic Must have a true coelom Well developed organs Some produce a rigid exoskeleton for support 2 major subgroups within the protostomes: 1. Lophotrochozoa include mollusks, annelid worms, and flatworms 2. Ecdysozoa include arthropods and roundworms The Water to Land Transition To make the transition to land, new adaptations must allow protostomes to 1. exchange gases 2. avoid drying out 3. hold up their bodies under their own weight What is a Lophotrochozoan? Mollusks, annelids, and flatworms The name lophotrochozoan was inspired by the presence of: -a feeding structure called a lophophore, which functions in suspension feeding - a type of larva called a trochophore, which moves via a ring of cilia What is a Mollusk? The mollusk body plan is based on 3 major components: 1. the foot a large muscle located at the base of the animal and usually used for movement 2. the visceral mass contains most of the internal organs and the external gill 3. the mantle an outgrowth of the body wall that covers the visceral mass -forms an enclosure called the mantle cavity -in many species, the mantle secretes one or more calcium carbonate shells The mollusk mouth has a unique feeding structure called the radula -functions like a rasp or file -sharp plates scrape material so that it can be ingested Once the molluscan body plan evolved, mollusks diversified The dramatic radiation of mollusks resulted in several lineages: 1. Bivalves (clams and mussels) has a hinged two-part shell 2. Gastropods (slugs and snails) lower body is a broad foot 3. Chitons (mollusks with plated dorsal shells) 4. Cephalopods (squids and octopuses) predatory, has a closed circulatory system, moves by jet propulsion Lophotrochozoans- Platyhelminthes (flatworms) Flatworms -have a broad, flattened body shape -are unsegmented -lack a coelom, specialized gas exchange structures, and blood vessels for circulating oxygen and nutrients to their cells Biologists hypothesize that the flattened body is an adaptation that provides a large surface area for gas exchange -this requires flatworms to live in an aquatic or moist environment Flatworms lack a lophophore and have a digestive tract with only one opening for ingestion of food and elimination of wastes Most turbellarians are either hunters that prey on protists or small animals, or scavengers that scavenge small animals. They are free living Tapeworms are strictly parasitic and obtain nutrients from the host by diffusion directly across their body wall -they lack a mouth and digestive system Flukes are parasites and feed by gulping host tissues and fluids through a mouth Lophotrochozoans-Annelida (segmented worms) 16,800 described species of annelids have a segmented body plan and a coelom Annelids divided into 3 groups: -polychaeta (polychaetes) -hirudinea (leeches) -oligochaeta (earthworms and other oligochaetes) Numerous, bristle-like extensions called chaetae that extend from appendages called parapodia -polychaetes have more chaetae than oligochaetes a) polychaetes have many bristle-like chaetae b) oligochaetes have few or no chaetae c) some leeches are ectoparasites Polychaetae lineages include suspension, deposit, and mass feeders Oligochaetaes are all deposit feeders that live in soik -they are critical in aerating soil What is an Ecdysozoan? Unlike iophotrochozoans, that grow continuously and incrementally, ecdysozoans grow intermittently by molting -shedding of the soft cuticle or hard exoskeleton Once the animal molts, fluid causes the body to expand, and a new, larger cuticle or exoskeleton forms Ecdysozoans undergo a succession of molts as they grow -sometimes dramatic morphological transformations occur during these molts a) Lophotrochozoans grow incrementally b) Ecdysozoans grow by molting The cuticle and exoskeleton -protect these animals from predators -provide an effective structure for muscle attachment During molting, the animal’s soft body is exposed and vulnerable -For example, remember when Mr. Krabs molted his shell? The most prominent of the seven ecdysozoan phyla are the roundworms (Nematoda) and the arthropods (Arthropoda) What is an Arthropod? Arthropods are defined by 3 characteristics: 1. Segmented bodies -organized into prominent regions called tagmata -head, thorax, and abdomen are common tagmata 2. Chitinous exoskeleton -strengthened by calcium carbonate in crustaceans 2. Jointed appendages -enables them to move their rigid bodies Arthropods have: -a highly reduced coelom -a spacious body cavity called the hemocoel, which circulates hemolymph Jointed appendages are organized in pairs along the segmented body and have an array of functions, including: -gas exchange -sensing the environment -feeding -locomotion Ecdysozoans- Arthropoda 4 main groups of arthropods: -myirapoda (millipedes and centipedes) -insecta (insects) -crustacea (shrimp, lobsters, crabs, barnacles, etc.) -chelicerata (spiders, ticks, horseshoe crabs) Myriapods -16,000 species -have relatively simple bodies with: ~a head region ~a long trunk with a series of segments and each segment has one or two pairs of legs -millipedes are detritivores, meaning they eat organic matter -centipedes are predatory carnivors that use poison to subdue their prey -some millipedes have over 190 trunk sections, each section has 2 pairs of legs -centipedes usually have fewer than 30 segments, each segment has 1 pair of legs Insecta 1 million species thus far -Distinguished by having 3 tagmata: 1) Head - a pair of antennae used for touch and smell -pair of compound eyes -four sets of mouthparts 2) Thorax -3 pairs of walking legs on the lateral surface -1 or 2 pairs of wings attached to the dorsal surface 3) Abdomen Crustacea 47,000 species -lineages include shrimp, lobsters, crabs, barnacles, isopods, and copepods -live primarily in marine and freshwater environments -have a segmented body divided into 2 tagmata: 1) the cephalothorax, which combines the head and thorax 2) the abdomen -many crustaceans have a carapace -a plate-like section of the exoskeleton that covers and protects the cephalothorax -Crustaceans have: ~2 pairs of antennae ~sophisticated, compound eyes usually mounted on stalks ~branched appendages ~4 to 6 pairs of mouthparts (derived from jointed appendages) -Limb structure is highly variable claws, paddle-shaped forms used for swimming, feathery structures used for capturing food suspended in water, slender legs Chelicerata include sea spiders, horseshoe crabs, daddy longlegs, mites, ticks, spiders, and scorpions most prominent chelicerate lineage is Arachnida Body consists of 2 tagmata: -cephalothorax, lacks antennae but usually contains eyes -abdomen with 6 pairs of appendages: 4 pairs of legs, 1 pair of chelicerae, which are found near the mouth and used for feeding, defense, copulation, movement, or sensory reception. & 1 pair of pedipalps, which can be used for diverse functions Chelicerates have a variety of feeding behaviors -spiders, daddy longlegs, and scorpions are predators -mites and ticks are ectoparasites -horseshoe crabs eat animals, algae, and detritus Most spiders secrete digestive enzymes into their prey -digestion thus begins externally, and the spider later drinks the liquid Nematoda Species in the phylum Nematoda are commonly called nematodes or roundworms Nematodes are unsegmented worms that have: -a pseudocoelom -no appendages -a thick, elastic cuticle that must be molted during growth Nematodes lack specialized systems for gas exchange and circulation -gas exchange occurs across the body wall -Nutrients and wastes move by simple diffusion Roundworms eat a wide variety of materials, including bacteria, fungi, plant roots, small protists, or animals, and detritus Nematode body musculature consists solely of longitudinal muscles that shorten or lengthen the body upon contracting or relaxing -they move by using their hydrostatic skeleton Chapter 35: Deuterostome Animals Deuterostomes include largest-bodied and most morphologically complex animals Were initially grouped together because they share important features of embryonic development -the coelom develops from the outpockets of the mesoderm What is an Echinoderm? Echinoderms “spiny-skins” are named for the spines or spikes observed in many species All echinoderms are marine animals 7,000 described species very abundant, especially in deep water environments The Echinoderm Body Plan 3 main traits: 1) radial symmetry in adults 2) endoskeleton of calcium carbonate 3) a water vascular system -a series of branching, fluid-filled tubes and chambers that forms a hydrostatic skeleton -an important part of the water vascular system is tube feet, which are elongated, fluid-filled appendages, each consisting of: a. an ampulla on the inside of the body b. a tube-like podium projecting on the outside How do Echinoderms Feed? Suspension feeders -extend their tube feet out into the water -use them to flick food particles to the cilia -cilia then sweep the food into the mouth Deposit feeders -use tube feet to secrete mucus -sop up food material on the substrate with the mucus -move the food-laden mucus into the mouth with the tube feet What is a Chordate? Chordates have 4 morphological features at some stage in their life cycles: 1. Openings in the throat called pharyngeal gill slits 2. A dorsal hollow nerve chord that runs the length of the body, comprised of projections from neurons 3. A stiff and supportive, but flexible rod called the notochord that runs the length of the body 4. A muscular tail 3 Chordate Subphyla 1. Cephalochordates 2. Urochordates 3. Vertebrates Cephalochordates a.k.a. lancelets Small, mobile suspension feeders that resemble fish Adults burrow in sand in their ocean-bottom habitats Dorsal hollow nerve chord runs parallel to notochord -notochord stiffens the body, muscle contractions on either side result in fishlike movement Adult cephalochordates suspension feed by burrowing in sediment until only their heads are sticking out -they take in water through their mouths and trap food particles by using mucus on their pharyngeal gill slits Urochordates a.k.a. tunicates or sea squirts Both larvae and adults have pharyngeal gill slits that function in feeding and gas exchange Traits that define urochordates include: -an external coat of polysaccharide called a tunic - a u-shaped gut -2 body openings called siphons Adult tunicates use their pharyngeal gill slits to suspension feed -a mucus sheet traps particles Larvae are a dispersal stage and don’t feed Adult sea squirts are sessile and adult salps drift in currents Vertebrates Include hagfish, lampreys, sharks, rays, bony fish, amphibians, mammals, reptiles, and birds The dorsal hollow nerve chord is elaborated into the spinal chord The pharyngeal pouches present in embryos develop into gills in aquatic species, but not terrestrial species Vertebrates share 2 main traits: 1. vertebrae, which form along the dorsal side of most species -protects the spinal cord 2. cranium-bony, cartilaginous case that encloses the brain several evolutionary innovations contributed to the success of these lineages, including: 1. The Vertebrae Jaw Leading hypothesis for origin of the jaw proposes that: -natural selection acted on developmental regulatory genes that determine gill arch morphology -gill arches are curved regions of tissue between the gills 2. The Tetrapod Limb The lungfish is the closest living relative to the tetrapods -lungfish live in shallow, oxygen-poor water -supplement oxygen obtained through the gills with lungs that breathe air Some species have fleshy fins supported by bones and are capable of walking short distances 3. The Amniotic Egg Amphibians must lay their eggs, which only have a single membrane, in water -reptiles, birds, and egg-laying mammals are able to lay amniotic eggs outside of water Amniotic eggs have an external membrane and 3 internal membranes -the additional membranes provide mechanical support and increase surface area for gas exchange The outermost membrane encloses a supply of water in a protein- rich solution called albumen -cushions the developing embryo and provides nutrients The 3 inner membranes surround: -the embryo itself -the yolk provided by the mother -the waste from the embryo Amniotic eggs are surrounded by a shell -in lizards and snakes, it is leathery -in turtles and crocodiles, it is stiffened by some calcium carbonate deposits -in birds, it is stiffened by extensive calcium carbonate deposits 4. The Placenta -rich in blood vessels -facilitates flow of oxygen and nutrients from mother to embryo -facilitates removal of nitrogenous wastes and carbon dioxide Advantages of retaining the embryo within the body: -offspring develop at a more constant, favorable temperature -offspring are protected -offspring are portable 5. Parental Care - any action by a parent that helps its offspring survive -extensive parental care requires a fitness trade-off -they can produce fewer offspring, but the offspring they do produce are more likely to survive - lactation 6. Wings and Flight A series of adaptations made powered, flapping flight increasingly efficient -bird sternum has a projection called the keel which provides a large surface area to which muscles attach Birds are light for their size because they have a drastically reduced number of bones and their larger bones are thin-walled and hollow Birds are endothermic- they maintain a high body temperature by producing heat in their tissues Hagfish and Lampreys Only living jawless vertebrates 120 living species species in both groups have long, slender bodies and are all aquatic Hagfish are scavengers and predators -they deposit feed on dead wish and whales Lampreys are ectoparasites -they attach to hosts by suction and rasp a hole in their victim’s side by using spines in their mouth and tongue -once the hole is formed, they suck blood and other body fluids Chondrichthyes Distinguished by their cartilaginous skeleton -they also have jaws and paired fins Sharks, rays, skates Most species are predators, although a few are suspension feeders -skates and rays feed on benthic animals like snails and clams The largest shark, the whale shark, is a suspension feeder that filters plankton from water as it passes over its gills Ray-finned fishes Fins supported by long, bony rods arranged in a ray pattern A bony skeleton A stiff, but flexible body covering of interlocking scales Unlike chondricthyes, ray-finned fish don’t have to swim to avoid sinking -instead, a gas-filled swim bladder provides buoyancy Major predators Coelacanths and Lungfish 2 independent lineages, but are often grouped together as lobe- finned fish lobe-finned fish are common and diverse in the fossil record, but only 8 species are alive today They represent an important link between the ray-finned fish and the tetrapods -the bony elements of their fleshy, lobe-shaped fins extend down the fin and branch -this structure is similar to the bony elements in tetrapod limbs Coelacanths live 150-700 m below the ocean surface Lungfish live in shallow, freshwater rivers and ponds -when oxygen levels in their habitats drop, lungfish can breathe air and survive Coelacanths prey on fish, lungfish are omnivorous Both groups swim by undulating their bodies -some lungfish can use their fins to walk along pond bottoms Amphibia 6,800 extant species live in ponds, lakes, moist terrestrial environments feed on land, but lay their eggs in water in many species, gas exchange occurs exclusively or in part through their moist, mucus-covered skin adult amphibians are carnivores -most frogs and toads are sit-and-wait predators, using their extensible tongues to catch prey -salamanders also have an extensible tongue most amphibians have four well-developed limbs -frogs and toads kick their hind legs to swim or jump -salamanders walk on land and undulate their bodies to swim caecilians: aquatic and land snake-like species -terrestrial species prey on soil-dwelling animals, such as earthworms -aquatic species eat small fish Reptilia Reptiles have several adaptations for terrestrial life: 1. Their skin is made watertight by a layer of keratinous scales 2. They breathe air through well-developed lungs 3. They lay amniotic eggs enclosed in shells Except for birds, almost all reptiles living today are ectothermic -individuals don’t use internally generated heat to regulate their body temperatur e Reptiles include dinosaurs, lizards, snakes, crocodiles, alligators, turtles, and birds Today, reptiles are represented by four major lineages: 1. Lepidosauria- lizards and snakes Small lizards tend to be predators, but large ones are often herbivorous 2. Testudinia- turtles and tortoises Turtles’ skulls are highly modified versions of other reptiles They lack teeth, the jawbone and lower skull from a bony beak 3. Crocodilia- crocodiles and alligators Eyes are located on top of the head and nostrils are on top of their long snouts These are adaptations that allow them to sit semi- submerged for extended periods All crocodilians are predators -prey include amphibians, turtles, fish, birds, and mammals 4. Aves- birds Fossil record provides conclusive evidence that birds descended from feathered dinosaurs Feathers provide insulation, are used for display, and furnish the lift, power, and steering needed for flight Adaptations for flight include: -feathers -large chest muscles -lightweight bodies -bones filled with air sacs Birds are endotherms -they have a high metabolic rate and maintain a constant body temperature Feeding strategies vary greatly, including -plant-eaters that feed on nectar or seeds -omnivores -predators that feed on insects, mammals, fish, other birds, lizards, and invertebrates Size and shape of beak correlate closely with diet Flightlessness has evolved repeatedly in some groups -the size and shape of birds’ wings correlate with the type of flying they do Many seabirds are efficient swimmers Some ground-dwelling birds can run long distances at high speed Mammalia 3 distinguishing characteristics: 1. hair or fur-used for insulation 2. endothermy- mammals regulate their body temperature with internally generated heat 3. mammary glands- for lactation -evolution of mammary glands gave mammals the ability to provide their young with extensive parental care 3 major mammalian lineages: 1. monotremata –platypuses, echidnas (hedgehogs) -lay eggs 2. Marsupiala - have a poorly developed placenta, but well-developed pouch for rearing offspring 3. Eutheria- placental mammals -well-developed placenta and extended pregnancy Monotremata most ancient group of mammals living today 5 living species, the platypus and 4 species of echidna, are only found in Australia they lay eggs and have low metabolic rates leathery beak or bill -platypuses feed on small animals in streams -echidnas feed on ants, termites, and earthworms on land platypuses lay their eggs in a burrow echidnas keep their eggs in a pouch on their belly Young monotremes hatch quickly -the mother must keep them warm and dry for another four months -like all mammals, monotremes produce milk and nurse their young Eutheria 5,100 species most species-rich and morphologically diverse group of mammals rodents, bats, carnivores, and primates internal fertilization and viviparous their young are much better developed at birth than marsupials, due in part to an extensive placenta -some young are able to walk or run minutes after birth The Primates the primate lineage consists of 2 main groups: 1. prosimians “before-monkeys” 2. anthropoids “human-like” What Makes a Primate a Primate? -hands and feet that can grasp -flattened nails instead of claws -relatively large brains -color vision -complex social behavior -extensive parental care of offspring -forward-facing eyes Great apes a.k.a. hominids are large-bodied with long arms, short legs, and no tail Hominids walk on their fists Humans are the only living great ape that is bipedal Fossil Humans DNA sequence data shows that humans are most closely related to chimpanzees and bonobos, followed by gorillas Homo sapiens have: -flatter faces -smaller teeth -larger braincases Out-of-Africa Hypothesis Leading hypothesis for the evolution of Homo sapiens Fossil finds and genetic studies indicate that H. sapiens originated in Africa H. sapiens evolved its distinctive traits in Africa and then dispersed throughout the world Molecular and phylogenetic analyses -support the hypothesis that human migration out of Africa in more than one wave