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Animals Part 1
USC FSH BISC121 Midterm 2 - Animals
| Question | Answer |
|---|---|
| All animal characteristics | A monophyletic kingdom of multicellular eukaryotic heterotrophic organisms that have Hox genes, cells that lack cell walls, and obtain nutrients by ingestion |
| Metazoa | A monophyletic group of multicellular heterotrophic animals with differentiated cells, a digestive cavity, cells with a nucleus and nuclear membrane |
| Who are the closest protist relatives of animals? | Choanoflagellates |
| Most animal characteristics | A monophyletic group of highly mobile organisms that undergo sexual reproduction, have true tissues, are derived from 3 main germ layers: ectoderm, mesoderm, endoderm |
| When did the earliest animals appear? | ca. 600 million years ago |
| Hox genes | A highly conserved 180-nucleotide 'homeobox' that codes for the body axis position in all animals, which corresponds to the position of Hox genes along a chromosome |
| What is the oldest animal synapomorphic trait? | The shared derived trait of Hox genes |
| Meiosis (Step 1) | A small flagellated haploid sperm fertilizes a larger, haploid, non-motile, polarized egg, forming a diploid zygote |
| Mitosis (Step 2) | Mitotic cell divisions lead to the formation of the hollow blastula (blastocyst) |
| Gastrulation (Step 3) | A gastrula is formed with 3 germ layers (ectoderm, endoderm, mesoderm) |
| Differentiation (Step 4) | Tissues differentiate to form the adult animal. Specialized gonads (testes, ovaries) in the body then produce new haploid gametes (sperm, egg) through meiosis |
| General body structure of animals | Three germ layers - ectoderm, mesoderm, endoderm |
| Coelom | A body cavity that many animals have, between the intestinal canal and body wall |
| Ectoderm | The outermost layer of an embryo in early development, develops into the epidermis and nerve tissue. |
| Mesoderm | The middle layer of an embryo in early development, forms a majority of the musculoskeletal and cardiovascular system |
| Endoderm | The innermost layer of an embryo in early development, forms the digestive tract and other related structures |
| Metamorphosis | A growth stage where an animal takes on a different body form as it gradually develops from larva to an adult |
| Larval stage | A growth stage that is radically different from the adult, such as different anatomy, metabolism and diets; many insects and amphibians undergo metamorphosis |
| Radial symmetry | A category of body symmetry for animals that have a top and bottom but lack back and front / right or left sides |
| Bilateral symmetry | A category of body symmetry for animals that have mirror-image right and left sides, and front vs back (anterior, posterior) |
| Animal phyla (sg. phylum) | Consists of seven invertebrate phyla and chordates which include vertebrates, all have radically different body plans |
| Invertebrates | A paraphyletic taxon of organisms that do not have a vertebral column (backbone), includes 97% of all animal species |
| Bauplan | A generalized structural body plan that characterizes a group of organisms and especially a major taxon |
| Porifera (sponges) | A monophyletic phylum of very primitive protist-like suspension feeders that obtain food particles from water, they have no symmetry and no true tissues |
| Suspension feeders | Organisms that capture and ingest food particles that are suspended in water, including porifera |
| Spicules | Structural “skeletal” elements found in most sponges that provide support and deter predators (scientists use for identification). |
| Choanocytes (collar cells) | Flagellated protist-like cells that line the internal chambers of sponges and create a water current through the sponge and resemble choanoflagellate cells |
| Amoebocytes | Amoeba-like cells that slither around using pseudopodia, create spicules and protein fibers in sponges |
| Anatomy of sponges | A highly porous structure, with spicules, amoebocytes, collar cells |
| Porocytes (Pore cells) | Small muscular cells that provide a constant flow of water in sponges |
| Cnidaria | A monophyletic phylum of radially symmetric aquatic carnivores with a simple gastrovascular cavity, and only two germ layers |
| Polyp | A fixed life cycle stage: have a tube with a mouth surrounded by tentacles |
| Medusa | A mobile life cycle stage: a bell capable of muscular contractions, allowing the cnidaria to swim |
| Cnidocytes | A unique venomous stinging cell in cnidarians that capture prey and function in defense |
| Bilateria | A monophyletic superphylum of animals with bilateral symmetry and have three germ layers |
| Protostomes | A monophyletic clade of bilateria that undergo spiral cleavage, whose first opening during gastrulation becomes the mouth, eg. arthropods, molluscs |
| Deuterostomes | A monophyletic clade of bilateria that undergo radial cleavage, whose first opening during gastrulation becomes the anus, eg. chordates (vertebrates), echinoderms (starfish, sea urchins) |
| Platyhelminthes (flatworms) | A monophyletic phylum of bilaterally symmetric primitive animals with three germ layers but not coelom; some are parasitic and can regenerate their entire body from a section |
| Habitat of platyhelminthes | In marine, freshwater, and damp terrestrial habitats |
| What do flatworms eat? | Various organic materials such as algae or bacteria |
| Why can flatworms regenerate sections of their body? | Their entire body contains stem cells inside their tissues |
| Mollusca (molluscs) | A paraphyletic phylum of over 100,000 species of animals with extremely varied anatomy and habitats, but all have a mantle with a mantle cavity, a hard shell, visceral mass, muscular foot, and radula. |
| Visceral mass | A soft body mass contained within the shell that generally holds the bulk of the digestive, reproductive, excretory, and respiratory systems |
| Chitons | A class of marine molluscs, eg. chitons |
| Gastropods | A class of molluscs including snails and slugs |
| Bivalves | A class of marine molluscs including clams, oysters, mussels, scallops |
| Cephalopods | A class of marine molluscs including squids and octopi |
| Annelida (annelids) | A monophyletic phylum of bilaterally symmetric segmented worms that are hermaphrodites, including earthworms, tubeworms, and leeches |
| Hermaphrodites | Organisms that have both male and female sex organs or other sexual characteristics |
| Habitat of Annelids | Found in damp soil, the sea, and most freshwater habitats. |
| Nematoda (roundworms) | A monophyletic phylum of bilaterally symmetric animals with three tissue layers and a pseudocoelom body cavity, with thousands of species |
| Habitat of roundworms | Moist habitats |
| What do roundworms eat? | most eat bacteria, decomposing matter, but many are parasites (e.g. Guinea worm and Trichinella) |
| Arthropoda | A monophyletic phylum of invertebrates, have an open circulatory system, exoskeleton made of chitin, a segmented body, and paired jointed appendages |
| Which is the most abundant animal phylum? | Arthropoda |
| How many described species of arthropods are there? | Over 1 million described species |
| What is the largest subgroup of arthropods? | Insects |
| What is the most closely related sister taxon of arthropods? | Velvet worms |
| Open circulatory system of arthropods | Hemolymph (not blood) pumped from heart through short vessels then to spaces surrounding organs |
| Exoskeleton of arthropods | External skeleton that is periodically molted to permit growth), sometimes reinforced with calcium carbonate (crustaceans) |
| Appendages of arthropods | Most are legs, but some of these have become modified to other functions e.g. mouth parts |
| Other traits of arthropods | Some still have similar and repeated body segments, but many have distinct body segments: head, thorax, abdomen; many have compound eyes |
| Subgroups of arthropods | Crustaceans, Arachnids, Millipedes, Centipedes, Insects |
| Insect morphology | All have six legs. Most have four wings (2 pairs), but there are many variations (some, like the primitive “silver fish” have no wings, diptera have two). |
| Insect development | Some have young that resemble smaller adults (nymphs) and incomplete metamorphosis (e.g. silverfish, termites, bugs); Many have larvae (grubs, caterpillars) that bear no resemblance to the adults, and complete metamorphosis (e.g. butterflies, dipterans) |
| Variation of insects | All land ecological niches, sometimes in fresh water – some only feed as larvae, eg. cockroaches, dragonflies |
| Echinodermata | A monophyletic group of marine invertebrate deuterostomes, radially symmetrical adults, with 5 section body parts, an endoskeleton, and a water vascular system that branches into extensions called tube feet, eg. starfish |
| Chordates | A monophyletic group of deuterostomes, with mostly vertebrates + primitive forms with notochord, including tunicates, lancelets (Amphioxus) |
| Vertebrates | A monophyletic group of organisms that possess a cranium (skull) and vertebrae (vertebral column) |
| Tube feet | Extensions of the water vascular system of echinodermata |
| Which is the largest group of deuterostomes? | Chordates |
| Chordata | A monophyletic phylum of deuterostomes that possess a dorsal, hollow nerve cord, a dorsal supportive notochord, pharyngeal slits or pouches, a muscular post-anal tail, myotomes |
| Myotomes | A group of muscles innervated by a single spinal nerve root |
| Lancelet | A monophyletic group of small translucent marine primitive chordate animals that are fishlike in appearance and usually live partially buried on the ocean floor |
| Neural crest | A collection of multipotent stem cells located at the side of the neural tube proximal to the epidermal layer after neurulation; gives rise to numerous tissues such as bones in the skull, sensory neurons, and melanocytes |
| Dorsal hollow nerve cord | Originates embryonically as the infolding of the ectoderm dorsal to the notochord, where neural crest cells are 'pinched off', and eventually develops into the central nervous system |
| Melanocytes | Pigment cells in the skin |
| How did vertebrae form? | Formed around the notochord and spinal cord, with cartilage formed first, then later bone |
| Notochord | A skeletal rod made out of cartilage that supports the body in vertebrates; persists through the vertebral column in many species |
| Intervertebral disc | A cushion of cartilage that serves as the principal joint between two vertebrae in the spinal column; a small piece of the notochord that remains |
| Cranium | Protects the brain and sensory systems of the head in vertebrates |
| Fish ('pisces') | A paraphyletic group of aquatic animals, more recently thought of as Vertebrata minus Tetrapoda |
| What are the most primitive vertebrates? | Hagfish and lamprey, because they have no jaws (cyclostomes) |
| Cyclostomes | A paraphyletic group of vertebrates that lack jaws and paired fins, including modern hagfish and lamprey |
| Cyclostomes traits | A mouth supported by musculature, has “teeth” made from horny material, unpaired fins along the body, has notochord, others supported by cartilage |
| Hagfish | An eel-shaped, slime-producing marine fish, mainly scavengers |
| Lampreys | An aquatic jawless fish with toothed, funnel-like sucking mouth, mainly an ectoparasite - parasites that lives outside of its host |
| Gnathostomes | A monophyletic group of jawed vertebrates, including chondrichthyans and bony fish and tetrapods |
| Chondrichthyans | A monophyletic class of jawed vertebrates with skeletons primarily composed of cartilage and paired fins, including sharks and rays |
| Gnathostome traits | Jaws providing skeletal support of the mouth, paired fins (pectoral, pelvic), lateral line system (sensory system along body); allow them to become more active and to bite off chunks of food |
| How did jaws evolve? | Via modifications of skeletal support (gill arches) of the anterior pharyngeal slits (gills, could be originally for filter feeding and respiration |
| Laterial line system | System of canals in porous skin, cupula with sensory hairs that can sense water displacement in gnathostomes |
| Four major lineages of gnathostomes | Chondrichthyans—sharks and rays, ray-finned fishes—bony fish, e.g. tuna, goldfish, lobe-finned fishes— (bony fish) coelacanths and lungfishes, tetrapods |
| Who are the precursors to tetrapods? | Lobe-finned fishes / bony fish |
| Lobe-finned fish | Fish with muscular pelvic and pectoral fins supported by thicker bones |
| Two lineages of lobe-finned fish | Coelacanths, lungfishes, and technically tetrapods |
| Coelacanths | Lobe-finned fish that live deep in the ocean |
| Lungfishes | Lobe-finned fish that can gulp air into lungs, inhabit stagnant waters in the Southern Hemisphere |
| Why are tetrapods a lineage of lobe-finned fish? | They are specialized lobe finned fish that adapted to life on land |
| Tetrapods | A group of animals with four limbs derived from lobe-fins, consists of amphibians, reptiles and mammals |
| Tetrapod traits | Four limbs, digited feet to transmit muscle force to ground, separated head from body by a neck of 1+ vertebrae, more robust pelvic girdle and pectoral girdle are attached to vertebrae so that force from legs on ground is transferred to rest of body |
| Amphibians | A class of tetrapods that retain a larval stage in water, including salamanders, frogs, and caecilians |
| Amphibious traits | Use their moist skins to supplement their lungs for gas exchange, eggs and larvae in water or very moist habitats, undergo metamorphosis, mostly predators that eat insects and other small animals |
| Hellbender | An aquatic salamander found in the USA |
| What were the earliest amniotes? | Carboniferous in the Palezoic era, ca. 300 mya |
| Amniotes | A group of animals with relatively large eggs laid on land and no larval stage in water, including reptiles and some mammals, eg. Hylonomus |
| What is in an amniote egg? | Extraembryonic membranes: amnion (amniotic fluid), yolk sac (nutrient), chorion (gas exchange), allantois (disposal of waste products) |
| Amniotic traits | Have eggs with extraembryonic membranes such as an amnion (extraembryonic membrane) or the embryo inside the mother is surrounded by the amnion (in viviparous amniotes; e.g. most mammals) |
| Thermal conditions | Many amniotes are ectothermic (primitive condition) but birds and mammals are endothermic |
| Reptiles | A polyphyletic group of amniotic tetrapods with a terrestrially adapted egg, including turtles, crocodilians, snakes, birds |
| Reptile traits | Have a shelled amniotic egg (4 internal membranes), mostly waterproof scaly skin - no respiration through skin, most need to spend time in the sun to increase activity level |
| Birds (Aves) | A polyphyletic group of endothermic feathered reptiles with adaptations for flight. |
| Bird traits | Feathers insulate and help flight; high metabolism and insulation to help survive in cold, relatively large brains -> for flight but also other complex behaviors, corvids (crows) are considered more “smart”, modern birds do not have teeth -> beak instead |
| Bird flight adaptations - Feathers | Feathers are aerodynamically shaped – small hooks and barbules help to keep shape |
| Bird flight adaptations - Wings | Forelimbs developed into wings – connected to powerful pectoral muscles (pectoralis) connected to the keel of the sternum, bones are hollow and light (bill is also light), |
| Bird flight adaptations - Bones | Hollow and light bones, light bill |
| Bird flight adaptations - Lungs | Air sacs connected to lungs - highly efficient respiration, supports high metabolism and energy demands of endothermy and flight |
| What is the largest bird group? | Perching birds, including finches, sparrows, crows |
| Mammals | A monophyletic group of endothermic amniotes that have hair and produce milk. |
| Mammalian traits | Mammary glands produce milk, hair help retain metabolic heat, endothermic, differentiated teeth for efficient eating, large brains, skull with zygomatic arch (fused mandible in humans), a pair of bones in the lower jaw, most, not all, bear live young |
| Monotremes | A group of mammals where their young hatch from eggs, lay eggs and produce milk, but have no nipples; small group including duck-billed platypus and echidnas with highly specialized ecological niches; only found in Australia and New Guinea |
| Marsupials | A group of mammals with live births after short gestations and small placenta; great degree of convergent evolution with eutherian mammals |
| Eutherians | A group of mammals with a long pregnancy and complex placenta |
| Marsupial examples | Kangaroos, Tasmanian devils, koalas, wombats, opossums, marsupial moles, etc. |
| Marsupial traits | Embryo nurtured by a small placenta, born early in embryonic development; climb into mother's pouch to receive milk, pouch with developed mammary glands and nipples; found mostly in Australia (+America - opossum) |
| Eutherian traits | Most numerous mammalian group, large complex placenta, longer gestation period, well-developed mammary glands, no pouch; found all over the world, but mostly only bats in Australia (apart from dingoes and humans) |
| Eutherian examples | Includes e.g. shrews, whales, rodents, bats, carnivores (Carnivora), ungulates, and primates (including humans) |
| Ceteceans | A group of large mammals, including the largest living animal in the world -- the blue whale |
| Primates | Group of mammals including plesiomorphic lemurs, tarsiers, monkeys, apes including humans (Hominoidea). |
| Primate adaptations | Forward facing eyes with color vision (often eat fruit), grasping hands, a flexible opposable thumb |
| Arboreal | Living in trees |
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