Diversity II ANIMAL OVERVIEW Animals: multicellular, heterotrophic eukaryotes, obtain nutrients by ingestion, and lack cell wall. Ingestion: eating other organisms or organic material. Collagen: most abundant protein in animals. Anima cell tissues have unique intercellular junctions: 1) Tight/fuse junctions 2) Desmosomes 3) Gap/communication junctions. Animals have both: 1) Conduction/nerve tissue 2) Movement/muscle tissue Most animals reproduce sexually where a flagellated sperm fertilizes a non-motile egg. Zygote then undergoes mitosis/cleavage, which leads to a solid ball of cells called morula blastula (hollow ball) gastrula (ball invaginates). Archenteron: primitive gut in the early developmental stage. If we could trace all animal lineages back to their origin, they would converge to a common ancestor this ancestor was probably a flagellated protist. Phyla sponges (Porifera) represent an early branch have a very simple structure that separates them from other animal phyla and are called parazoa. Parazoa: animals that lack true tissue. Eumetazoa: animals that have true tissue. 2 major branches of symmetry: 1) Radial symmetry: arranged like spokes of a wheel that radiate from the center. Ex: hydra. 2) Bilateral symmetry: has 2 sides, a right and a left and associated with cephalization. Ex: human. Cephalization: concentration of sensory equipment near the head of an animal many animal phyla cephalization occurred when you consider that this is the end that first encounters food, danger, and other stimuli. This concentration of sensory equipment developed into the central nervous system in many bilateral animals. In all animals, except sponges, the embryo becomes layered through the process of gastrulation called germ layers. Germ layers: eventually form the organs and tissue of the body. Ectoderm: outermost layer that gives rise to the skin primarily. Mesoderm: middle layer that forms muscle and the remaining organs. Endoderm: innermost layer that gives rise to the digestive tract and related organs.
Acoelomate: solid bodies. Ex: flatworm. Pseudocoelomate: animals that have a body covering (ectoderm), then the mesoderm (muscles), then a fluid filled body cavity, and then the digestive tract (endoderm). The mesoderm does not completely line the body cavity. Ex: round worm (nematodes) and rotifers. Coelomate: a fluid-filled body cavity completely lined by tissue derived from the mesoderm. This connects the inner and outer layers to form connective tissue that suspend the internal organs. The fluid in the body cavity cushions the suspended organs to help prevent injury. It evolved at least twice in animals in both the protostomes and deuterostomes. Protostomes: literally means first mouth, includes the mollusks, annelids, and arthropods, have spiral cleavage where the cells are diagonal in the developing embryo; and have determinate cleavage very early in development, each cell s developmental fate is already determined. Deuterostomes: literally means second mouth, includes the chordates (humans) and echinoderms (sea stars), have radial cleavage where the cells are on top of each other or parallel, and have indeterminate cleavage each cell in the early cleavage stages is able to develop into a complete embryo. Blastopore develops into the mouth in protostomes. Blastopore develops into the anus in deuterostomes. INVERTEBRATES Phylum Common name Tissue Germ Body Gut Coelom Embryonic Complexity Layers Symmetry Openings Development Porifera Sponges parazoa -- -- 0 * -- -- Cnidaria jelly, corals eumetazoa 2 radial 1 -- -- Platyhelminthes flateworm 3 bilateral 1 a -- Nematoda roundworms 2 p -- Rotifera rotifers p -- Mollusca clams, snails, c protostomes Octupuses Annelida segmented worms Arthropoda insects, spiders Crustaceans Echinodermata Sea stars, sea urchins radial deuterostomes Chordata vertebrates bilateral KEY: *Amoebocytes carry out digestion --character does not apply to this phylum a= acoelomate p=pseudocoelomate c=coelomate
Phylum Digestion Excretion Respiration Nervous Skeleton Locomotion Control Porifera choanoctyes diffusion diffusion none spicules (glass-like none/sessile Amoebocytes made of CaCO 3/SiO 2) Cnidaria gastrovascular nerve net hydrostatic contractile cavity fibers Platyhelminthes diffusion, ganglia, Cilia, muscles, flame cells nerve cord glide or swim Rotifera complete hydrostatic cuticle muscles, tapered foot Nematoda diffusion longitudinal muscles Mollusca kidney gills, diffusion external shell, muscular foot, nephridia hydrostatic jet propulsion Annelida metanephridia diffusion, skin ganglia, ventral hydrostatic, setae (hair) Blood vessels nerve cord compartment Arthropoda malpighian gills, tracheal exoskeleton of jointed legs, tubule system chitin wings Echinodermata diffusion skin gills radial nerve calcium skeleton tube feet, H 2O system vascular system Chordata kidneys, pharyngeal dorsal, hollow notochord muscles, swim (Invertebrate nephrons gill slits nerve cord or sessile Phyla) Porifera (sponges): Literally means pore bearer Most sponges are marine Are filter/ suspension feeder that collect food particles from the water as they pass through flagellated cells called choanocytes then pass to the amoebocyte that are able to move about the sponge and distribute nutrients to the entire organism. They are parazoa. Cnidaria (jellies, hydra, sea anemones, and corals): 2 body forms: 1) Medusa 2) Sessile polyp Have a basic body plan called gastrovascular cavity: a sac with central digestive compartment. There is a single opening for both the mouth/anus. No brain, only a nerve net Have a hydrostatic skeleton: composed of fluid held under pressure in a closed body compartment.
Platyhelminthes (flatworms-like planarians, tapeworms, and flukes): Are acoelomate Can be free-living scavenger (planarians), internal animal parasites that suck blood/tissues (flukes), or internal parasites in the digestive tract (tapeworm). Flatworms, like planarians, have flame bulbs to maintain osmotic balance. Have a digestive tract with a single opening. Have ganglia or clusters of nerve cells located at the anterior end of flatworms. They are protonephridia. Rotifera (rotifers): Are filter/suspension feeders: use cilia on their head to pull in food. Inhabit fresh water primarily. Have a complete digestive tract separate mouth from anus. Parthenogenesis: some species consist of only female and produce more females from unfertilized eggs Are pseudocoelomates Nematoda (roundworms like nematodes): Nematodes: widely used as a model research organism (c. elegans). Many are found in moist soil/moist plant or animal tissues. One species causes trichinosis that humans acquire from undercooked pork containing juvenile worms. Have a complete digestive tract Are pseudocoelomates Mollusca (snails, slugs, chitons [looks like turtle shell], bivalves [clams], octopuses, and squids): Most mollusks have shell Squids have an internal reduced shell, but octupuses have no shell. All have a simple body plan of 3 parts: 1) Muscular foot movement 2) Visceral mass contain internal organs 3) Mantle fold of tissue over the visceral mass Are coelomate Bivalves: clams, oysters, and mussels. Gastropods: slugs and snails. Cephalopods: squid and octupuses. Octupuses have a highly developed nervous system and a large brain.
Annelida (segmented worms like earthworms and leeches): Literally means little rings Have closed circulatory systems Have metanephridia: excretory tubes with ciliated funnels that excrete wastes from their bodies. Have a brain-like pair of ganglia near their anterior end. Arthropoda (spiders, insects, crustaceans [crabs, lobsters]): Have jointed appendages Have a developed nervous system Have an exoskeletons of chitin Some are born as nymph that change shape slowly as they grow into adults Some are born as larvae (maggots) that undergo metamorphosis Have an open circulatory system and that for excreting wastes Insects use malpighian tubules These out pockets of the digestive system remove metabolic waste from the hemolymph (blood and interstitial fluid). Breathing takes places through spiracle or pores on the body surface.
Echinodermata (sea stars, sea urchins, brittle stars, sea cucumber, sand dollars): Are radial symmetrical as adults Often have 5 spokes Have water vascular system-network of hydraulic canals branching into extensions called tube feet that function in locomotion, feeding, and gas exchange. Chordata (2 invertebrate subphyla and ALL vertebrates): Have 4 main features: 1) Notochord (flexible rod on dorsal side later becomes the backbone in many animals) 2) Dorsal hollow nerve cord (becomes the brain and spinal cord) 3) Gill/pharyngeal slit (some disappear during embryonic development, some keep for gas exchange) 4) Muscular tail (in many the tail is lost during embryonic development) 2 main groups of chordates are the invertebrate chordates like: 1) Lancelets 2) Tunicates/sea squirts Vertebrate chordates like: 1) Fish 2) Amphibians 3) Reptiles 4) Birds 5) Mammals VERTEBRATES 2 invertebrate subphylums: 1) Urochordate (tunicates) 2) Cephalochordate (lancelets) Most tunicates are sessile marine animals that adhere to rocks like sea squirts. Lancelets are blade-like small marine animals that burrow into the sand leaving only their anterior end exposed to catch tiny food particles.
Vertebrates are associated with larger size and an active lifestyle. Superclass Agnatha: Oldest vertebrate fossils Fish-like animals in an armor of bony plates Includes the jawless vertebrates. Ex: lamprey and hagfish. Their mouths are circular or slit-like Their bodies are eel-shaped. Lampreys use their rasping tongue to break through the skin of prey and live off the blood of its host. Hagfish are scavengers. Superclass Gnathostomata: Replaced the jawless fishes Literally means jaw mouth Class Chondrichthyes: Includes sharks and rays Are also called cartilaginous fishes due to their endoskeletons of cartilage. Sharks have acute senses to go along with their active, carnivorous lifestyle, have sharp vision and a great sense of smell as well as can detect electrical fields generated by the contraction of their prey s muscles. Running along the sides of sharks is the lateral line: organs sensitive to changes in pressure. Sharks use lateral line to detect even minor vibration. Shark skin is covered with tiny tooth-like projections called dentacles. Their liver stores a lot of oil to help sharks float. Class Osteichthyes: Largest of all the vertebrate classes Includes bony fishes Covered in scales, bony fishes secrete mucus to reduce drag in swimming, have a lateral line to detect vibrations and a swim bladder filled with air to help control buoyancy. Most bony fishes are oviparous: reproduce by external fertilization Example of bony fishes: lobe finned fishes and lung fishes. The lobe finned fishes have muscular fins to aid in walking and occasionally waddle on land. Lungfishes are able to breathe air and can survive when ponds shrink; they burrow in the mud and go into a state of torpor.
Class Amphibia: Literally means 2 lives (reference to metamorphosis) Oldest tetrapods: 2 pairs of limbs to support them on land Early amphibians probably resembled the lobe finned fishes. Includes frogs, toads, salamanders, and newts. Most amphibians have close ties to water and carry out gas exchange on their moist skin. Amphibian eggs lack a shell and dehydrate quickly in dry air. Class Reptilia: Starting to have amniotic sac: membranes function in gas exchange, waste storage, and transport of stored nutrients to the embryo. Include lizards, snakes, turtles, crocodiles, and alligators. They have water proof skin to prevent dehydration and get oxygen through lungs, not through moist skin. They are ectoderm/cold-blooded Class Aves: Amniotic eggs and scale on the legs are 2 reptilian features seen in birds. Almost all parts of birds are modified for flight. Ex: honeycombed bones are strong, but light. They are endoderm that uses their own metabolic heat to keep warm. Feathers are made of keratin and function for insulation as well as flight in many birds. Ratites: flightless birds, they lack large chest muscles for flight. Class Mammalia: Have hair/fur made of keratin Are endoderm produce milk most are born being nourished by a placenta have larger brain capable of learning have differentiated teeth for chewing many kinds of foods some lay eggs like platypuses called monotreme Marsupials: young are born very early in its development and completes development by nursing in a pouch. Ex: opossums, kangaroos, and koalas. Eutherian: complete embryonic development within the uterus joined to the mother by the placenta. Ex: humans. Misconceptions about human evolution: 1) Humans didn t evolve from chimpanzees. Humans and chimps just evolved from a common ancestor. 2) Humans did not evolve as a ladder of steps leading to present day Homo sapiens. This is often illustrated as the parade of hominids (human like) progressively becomes more modern. But human evolution wasn t so orderly. There have been many splinter groups that have traveled down dead end branches. And at times in hominid history, several different human species coexisted. 3) Upright posture and an enlarged brain evolved in unison. A popular image is of early cave dwellers as half-stooped over and half-witted. Different features evolved at different rates with erect posture or bipedalism leading the way. Based on the fossil record and DNA comparisons, most agree that humans and apes diverged from a common ancestor 6-8 million years ago in Africa. The first skull found was Australopithecus africanus the first hominid to be bipedal. But the brain was only about 1/3 size of modern human brains. In 1974, researchers found another Australopithecus afarensis fossil that was 40% complete and named it Lucy. It was only about one meter tall with the head size of a softball. Lucy s bones differed enough to be considered another species.
Humans walked upright way before the enlargement of the brain; the making of sophisticated tools came much later. Enlargement of the human brain came with Homo habilis ( handy man ). This hominid coexisted alongside Australopithecus. Homo erectus (upright man) was the first hominid to migrate out of Africa into Europe and Asia. This species is much taller than H. habilis with a larger brain. H. erectus built fire, clothed themselves, and designed more refined tools than that of their predecessors. Descendents of H. erectus were the Neanderthal who lived in Europe, the Middle East and Asia. Compared to us, they have had heavier brow ridge and less pronounced chins, with bigger brains than ours. Neanderthals were skilled toolmaker that participated in burial and rituals that required abstract thought. The debate currently is whether Neanderthals had the anatomical equipment for speech. Multiregional model: Some believe the Neanderthals gave rise to H. sapiens and that modern humans evolved at the same time in different parts of the world. Some believe that Neanderthals and modern humans coexisted and did not interbreed. If this is true, then Neanderthals could not have been the ancestors of modern humans. So perhaps instead Neanderthals were evolutionary dead ends. Out-of-Africa /monogenesis model: H. erectus left Africa and replaced Neanderthals; it is the idea that modern humanity did not emerge in many parts of the world, but only in Africa. This model has been heavily supported with mitochondrial DNA evidence that traces the source of all mitochondrial DNA back to Africa.