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WKU Bio 225 Zoology Unit 2 Notes

Uploaded: 5 years ago
Contributor: Amelia Winrich
Category: Zoology
Type: Lecture Notes
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Filename:   Zoology Notes.docx (36.51 kB)
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Description
Covers reproduction annelids, arthropods, some molluska, and rotifers
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Zoology Notes 9-12-18 Phylum Platyhelminthes Lophotrocozoan Protostomes Adaptions for parasitism: reduced digestive system From 1mm to more than a meter (extremely skinny, even in long individuals) Triploblastic (all 3 skin layers) Acoelomate: body cavity Most are parasitic but some are free living aquatic Bodies dorso-ventrally flattened Incomplete digestive tract Monoecious Adaptations for parasitism: Reduced digestive system Tough outer covering: tegument found when going from one organism to another Monoecious: large gonads (hermaphrodite) Regenerative Powers: Planarians can survive fragmentation Excretory System: removes nitrogenous waste and maintains water balance (osmoregulation) in body Class Turbellaria Usually free-living Dorso-ventrally flattened body Cephalization/ Sensory Receptors: organs that collect information about the environment nodules on side of head “smell” water, eye spots Movement: bilateral symmetry, cilia and muscular undulation Class Cestoda: tapeworm Endoparasites Scolex and proglottids No digestive tracts microtriches on tegument (fingers for more surface area) Taenia solium: pork tapeworm juveniles (cysticerci) can encysts in human muscle and nervous tissue Class Tematoda Parasitic flukes Anterior suckers Digestive tract present Often have vertebrate host/ mollusk intermediate host Schistosoma: blood fluke Phylum Nemertea: ribbon worms About 1000 marine species Most small < 20cm long Similar to Planaria, but dioecious (separate male and female) Proboscis Complete digestive system Simple circulatory system Tissues Cardiac muscle: involuntary, uninucleated, striated muscle found only in the heart of vertebrates Branched Intercalated disks Pacemaker Smooth muscle: also called non-striated or involuntary muscle No striations, uniculeate Encircle blood vessels, the intestine or other ducts Unit 2 09-19-2018 Bivalvia Class Cephalopoda (squid, octopuses, cuttlefishes) All marine predators with highly developed nervous systems Foot is modified for directing water as it is forced out of the mantle cavity and is fringed with tentacles Ancestral cephalopods had straight shell which have been lost (octopi) or coiling (Nautilus). Squid only have a thin remnant of the shell Locomotion: cephalopods move by using the mantle cavity to form a water jet. Octopuses usually walk Squid swim backwards so that they can see predator as they are trying to get away from it Organ systems of cephalopods are well-developed thinking and active predators; more energy and organ needs One set of gills – use mantle to force water flow Closed circulatory system: blood leaving heart goes to body tissues, then to gills, accessory hearts increase blood pressure as blood enters gill Nervous System is very well developed: largest brain of any invertebrate Cephalopod eye is not homologous with vertebrate eye but is remarkably similar neural connection Don’t have blind spot in eyes like humans Octopuses are very smart, can learn quickly through positive and negative reinforcement, observational learning (very important) Camouflage: Octopuses can change their color and shape Communication: octopuses used movements of the arms and color change to communicate Reproduction: dioecious, sperm packaged in a structure called a spermatophore Hectocotylus, a specialized tentacle transfers a spermatophore to the mantle cavity of the female No free-living larvae stage Adaptive radiation Habitat: everywhere Body plan: shell or no shell Nervous system sensory organs Feeding: food sources everywhere for snails Phylogeny: Lophotrochozian Protostomes Phylum Annelida: Lophotrochozoan Protostome Characteristics 15,000 species Trochophore Larvae Body composed repeated segments (metamerism) separated by septa little specialization of segments (ancestral) same in earthworm or lobster Advantage: parts of the body can be manipulated individually Anterior end of animal has a prostomium Posterior end of animal has a pygidium New segments are added in front of the pygidium during growth Setae (“hair”): hair-like spikes that can be used to grip sediment (not hair!) Short hard setae: terrestrial worms Longer flexible setae: aquatic worms Complete Digestive tract Musculature with longitudinal and circular muscles Flexible cuticle: secreted by epidermis (not cellular) Respiration: mainly by diffusion across skin Gills and parapodia (increases surface area) as accessory structures Excretion by paired nephridia in each segment Sexual reproduction: monoecious or dioecious Trochophore larvae Asexual reproduction: budding and fragmentation Class Oligochaeta (oligo = few ; chaeta = long hair) 3,000 species, mostly terrestrial and freshwater Australian earthworm can be meters long Respiration: no specialized structures for gas exchange, cutaneous (cuticle) respiration Must keep cuticle moist for oxygen to diffuse into body Drought: if surface dries out, no respiration occurs go deep into soil Flood: can’t get oxygen from water, go to surface to get air Circulatory System: closed in most, respiratory pigments (hemoglobin) dissolved in blood fluid, also contains amoeboid cells Complete Digestive system: mouth pharyx esophagus crop (stores food) gizzard (helps “chew” food; sand helps break down detritus) intestine rectum (absorbs water) anus Typhlosole: invagination of dorsal surface of digestive tract, increases surface area 09-21-18 Excretory System: pair of nephridia per segment Nephridia: generalized term for excretory systems that empty outside the organism Protonephridia: excretory system with tubes ending at flame cells Metanephridia: excretory system with a tube that takes in coelomic fluid and releases waste outside the body through a nephridiophore Nephrostome: where fluid goes in Bladder: where liquid is stored Nephridiopore: where excretion is released Terrestrial: urea Aquatic: ammonia Nervous System: bi-lobed brain, ventral nerve cord, a pair of ganglia branch off in each segment No eyes but simple photoreceptors in epidermis evolved from eyes Reproduction: Monoecious (Hermaphroditic) but cross-fertilize with another worm Sperm are transferred to the mates seminal receptacle. Mucus band secreted by clitellum accepts eggs and sperm, fertilization is external Class Polychaeta: clam worms many arms 10,000 species, marine worms Parapodia: pair extensions on each segment, used in respiration and locomotion Well developed head: eyes, jaws, tentacles Eyes vary from simple photo sensors to image-resolving eyes with a lens for focusing Other sensory organs: Statocyst: orientation; Nuchal organ: chem sensory Some polychaetes are predatory (such as errant polycheate) while others are filter feeders (Christmas tree worm) or deposit (planktonic rain) Many polychaetes burrow in sediments: may use tube to set up water currents Reproduction: no permanent sex organs, gonads develop in the wall of coelom and deposit eggs/sperm into coelom Some produce specialized reproductive segments posteriorly Atoke: anterior section Epitoke: posterior reproductive section In synchrony with other members of the population, the epitokes separate from the atoke and swim to surface where they rupture releasing gametes Advantage: atoke is still safe in burrow while epitoke make perilous journey to surface to mate Class Hirudinida; leeches Mostly fresswater but a few terrestrial and marine Usually < 6 cm but upt to 30cm Body plan: usually 34 segments (may look like more due to superficial annuli) Septa between segments lost Suckker at both ends Dorsoventrallly flattened No setae Digestive tract modified for storage of large volumes of blood from host Leeches release Hirudin into food when feeding anti-coagulant Phylogeny: Annelids are Lophatrochozian Protosomes Ogligochaetes and Hirudinae are sister taxa, rest are basal Reproduction Asexual Reproduction: production of individuals without gametes Advantages Only need one individual No genetic change- good if environment is stable All individuals are producing offspring More efficient at passing on genes Disadvantages No recombination of genes Types: Unicellular: Fission (mitosis) Multicellular: mitosis Budding Gemmulation Fragmentation/regeneration Parthenogenesis eggs from diploids Sexual Reproduction: the production of new individuals by the union of gametes, usually from two different parents Advantages Genetic recombination: offspring genetically unique Genetic variation comes from: exchange of genes between homologous chromosomes during crossing over Shuffling of homologous chromosomes in meiosis (independent assortment) Random fusion of gametes Disadvantages Need 2 parents: must expend energy to find, identify (court), and copulate with mate Genetic recombination is counter productive if conditions are stable Only half the individuals are producing offspring Males use resources and contribute little energy to producting new members to the population Less efficient at pass on genes- offspring are only half your genes (clone is 100% 09-24-2018 Types of sexual reproduction Bisexual: union of gamete from male (spermatozoon) and Female (Ovum) Dioecious species: individuals either male or female Hermaphroditism: species are Monoecious each individual produces sperm and egg, individuals called hermaphrodites Sequential hermaphroditism: individual changes sex during life Cells Somatic Cells: cells that make up the body of an individual except gametes Gametes: haploid sex cells (usually called sperm and egg) Primordial germ cells: cells that give rise to gametes through the process of meiosis and cytokinesis Organs Primary sex organs: where gametes are produced- also called gonads (testis and ovary) Accessory sex organs: penis, vagina Syngamy: the union of two gametes to form a zygote Gametogenesis: the process of gamete production Spermatogenesis: the formation of sperm occurs in the testis The testis are composed of coiled tubes called seminiferous tubules Spermatogonia (2n) : mitosis, one produces Primary spermatocye, othe does not go into meiosis, one Primary spermatocyte (2n): starts meiosis Secondary spermatocyte (2n): cells at the end of meiosis I Sperm (n): found in the lumen of the seminiferous tubules Sertoli cells: in seminiferous tubules, nourish sperm cells Characteristics of mature sperm Head: Acrosome (cover nucleus, contains digestive enzymes), Nucleus No cytoplasm Midpiece: mitochondria Tail: Flagellum Nematode: sperm that attaches to substrate and crawls Ova Oogenesis: formation of the ovum occurs in the ovary Oogonia (2n): divides by mitosis and produces primary oocyte Primary Oocyte (2n): undergo meiosis I. Unequal cytokinesis results in 1 secondary oocyte Secondary oocyte (n): undergo meiosis II. Unequal cytokinesis resulting in 1 (n) ovum Polar bodies: other cells produced by meiosis that do not contain organelles, discarded Meiosis I begins in developing embryo, meiosis II is not complete until after sperm enters the egg Fertilization can be internal or external External: sperm and egg are expelled from bodies Internal: sperm transferred from male and female; sperm may be stored in spermatheca (seminal receptacle) for future use common in invertebrates Path of sperm: urogenital system Testes Epididymis Vas deferens Urethra Cloaca (birds, reptiles): vent to transfer sperm Path of ovum: Produced in follicles (tissues surrounding the developing egg) in ovary, the release is called ovulation Egg enters oviduct: a shell may be formed around the egg (zygote) (birds, reptiles) Zygote enters uterus (mammals) Spermatheca: used to store sperm Sperm competition: different deposits of sperm in spermatheca from several different mating; some males will remove sperm from spermatheca or attach until eggs are laid (safe guarding) Oviparous animals release their eggs into the environment before fertilization or zygotes after fertilization Ovoviviparous animals retain the fertilized egg (zygote) internally but do not supply any additional nutrients to the zygote (guppies) Viviparous animals are those that retain the zygote in the mother who provides nourishments to the developing young (mammals and sharks) 09-26-2018 Reproductive hormones Hormones: molecules that are produced in one part of the body and stimulate a response in another part of the body (target or receptor cells) Male: Testosterone: produced the Leydig cells found between the seminiferous tubules of the testes Female: hormones from the brain and ovaries function to control the release of gametes and the state of the uterus Estrus cycle: reproductive cycle of most mammals Female only receptive to copulation during estrus Endometrium (nutrient rich layer) is absorbed if no pregnancy Menstrual Cycle: reproductive cycle found in monkeys, apes, and humans. Females are receptive throughout cycle (Menstration) Pituitary gland of brain produces: Follicle-stimulating hormone (FSH) Luteinizing Hormone (LH): released and egg goes to uterus Estrogen; produced by follicle (around growing egg) Progesterone : produced by the corpus luteum. Increases during ovulation Human Chorionic Gonadotropin (hCG): hormone produced by developing embryo Development Fertilization (syngamy): the union of sperm and egg Restores diploid state in zygote Stimulate mitotic division Layers of the outer covering of mature egg (sea urchin) Jelly layer Vitelline envelope Plasma membrane When the sperm contact the vitelline envelope, species specific proteins bind to receptors The sperm penetrates the vitelline membrane and the sperm membrane fuses with the plasma membrane Prevention of Polyspermy: the fertilization of an egg by more than one sperm Fast block: the time frame of seconds; a change in the electrical potential of the plasma membrane prevents any other sperm from fusing with it Cortical reaction (slow block): time frame of 1 minute; vesicles (cortical granules) fuse with the egg membrane. Water diffuses in fertilization membrane, Pronuclei of egg and sperm fuse to form zygotic nucleus. Stages of development Fertilized egg (zygote) Cleavage stage: zygote divides repeatedly by mitosis no increase in size Blastula: hollow chamber develops in the center of the morula (blastocoel) Gastrulation: invagination of cells forms the primitive gut (archenteron) Neurogenesis: (only in Chordata) nerve cord develops Organogenesis: formation of the organs of the body; takes months to develop How zygote develops will be greatly affected by the amount of yolk in the ovum Isolecithal egg: little yolk, yolk evenly distributed (echinodermis, mammals) Mesolecithal egg: moderate amount of yolk, unevenly distributed (amphibians) Vegetal pole: hemisphere of the egg with the most yolk Animal pole: hemisphere with the least yolk Telolecithal egg: large amount of yolk, unevenly distributed (fist, reptiles, birds); cytoplasm found in blastodisc Patterns of cleavage: The differences in the amount and distribution of yolk will affect how cleavage proceeds Holoblastic cleavage: cytokinesis divides the cell in two Found in isolecithal and mesolecithal eggs In mesolecithal eggs, the vegetal pole divides slower resulting in fewer cells than in the animal pole. The blastocoel is in the animal pole Merolastic Cleavage: cytokinesis Symmetry of Cleavage Radial cleavage: as cells divide , the cells appear stacked parallel to a central axis Found in amphibians and echinoderms: characteristic of deuterostomes Spiral Cleavage: as cells divide, the stacked layers lie in the furrows from the layer below Found in annelids, Mollusca, and Arthropoda- characteristics of protostomes During gastrulation the three germ layers are generated Ectoderm, Mesoderm, endoderm There are two basic patterns by which the mesoderm layer originates Enterocoelous: mesoderm forms as pouches off the archenteron seen in Deuterostomes Schizocoelous: Mesoderm cells develop around the base of the archenteron seen in Protostomes Development in telolecithal eggs Meroblastic cleavage: cleavage only occurs in the active cytoplasm results in layers of cells Primitive streak: groove down central axis of blastodisc During gastrulation, cells start to differentiate (the process by which a cell becomes specialized) Neurogenesis (Chordata): development of the nerve cord from ectoderm tissue Neural plate forms neural fold that form a tube hallow nerve cord Neural crest cells split off tube, develop into: cranial nerves, pigment cells, bones of the skull, parts of endocrine glands Organogenesis: development of the organs of the body. Embryo (2 weeks to 2 months), organ systems are developing Cell Fates: as cells divide and the number of cells in the body increase, the cells are induced to use different genes. During this process, called differentiation, the cells turn into one of the mature cell types Determined: the point at which a cell has differentiated so it cannot be induced to become a different type of cell Totipotent Cell: can develop into an embryo and eventually individual Deuterostomes: regulative (can form more embryos) Protostomes: mosaic (will die) Skin Integument: protective outer covering of the body Invertebrates: epidermis, sometimes covered by a non-cellular cuticle Vertebrate integument 2 basic layers Epidermis: layer of cells of ectodermal origin Dermis: layer of cells of mesodermal origin Epidermis gives rise to hair, feathers, scales, and claws Stratified squamous epithelium The proximal layers undergo mitosis Keratin and lipids produce tough waterproof barrier 4 Stratum Corneum: layer of cells that have undergone keratinization, resistant to water Skeletal Systems Hydrostatic Support Exoskeleton Endoskeleton (chordates and echinoderms) from mesoderm origins Notochord: large cells within a fibrous sheath covered by an elastic sheath Cartilage: (Chondrocytes imbedded in a protein gel with strands of collagen (another protein) Bone: Osteocytes imbedded in a matrix of collagen and calcium phosphate salts Endochondral bone: develops from cartilage Intramembranous bone: sheets of cells that lay down CaP (skull cap, pelvis, shoulder blade) Spongy bone: inside of bone, cavities to store other materials (bone marrow) Compact bone: outer part of bone, solid bone material 9-28-2018 Phylum Rotifera: Roto-wheel, fera – bearing Characteristcs Mostly freshwater Few marine species Lophotrochozoan protostomes Trochophore larvae Have Pseudocoelom Corona: ciliated structure on anterior end used for generating water currents (feeding and locomotion) Lorica: protective plates or rings, from fibrous layer in epidermis Nervous system: bi-lobed brain (cephalization) Reproduction: both asexual and sexual Parthenogenesis: most of the year reproduction is asexual population is composed of females that produce diploid amictic eggs. When conditions worsen, females produce haploid mictic eggs If not fertilized, eggs develop into haploid males If males fertilize the eggs then develop into diploid zygote called a dormant egg Phylum Nematoda: nematos = thread Characteristics 25,000 species described Have pseudocoelom Density of billions per acre Ecdysozoan protostomes (molting) Many are parasitic: infect most plants and animals Ascaris lumbricodies: large roundworm of humans (infect up to 25% of human population in some US SE areas) Often pass through stomach during life cycle Cuticle: non-cellular, secreted by hypodermis (epidermis) Longitudinal muscles are used to make the body wiggle for locomotion Different from earthworm (no circular muscle) High coelomic pressure: higher pressure inside of body than outside Sexual dimorphism: Copulatory spicules Sperm have no flagellum ameboid movement Females can release 200,000 eggs/day Some nematode examples Hookworm: enter through skin and migrate to intestine where they feed on hosts blood Can crawl 5ft from feces Outhouses- 10ft holes to stop infections Trichinella spiralis: cause trichinellosis (very rare in US); enters through undercooked pork, young enter bloodstream and encyst in various tissues (especially muscle) Pinworm: most common nematode parasite (16% adults/30% children). Females migrate at night to lay eggs around anus Filarial worms: infect lymphatic system associated with growth of connective tissue and swelling of extremities. Elephantiasis, river blindness, dog heartworm (45%; spread from mosquitoes) Additional Phyla that have a pseudocoelom 10-1-2018 Phylum Arthropoda: “jointed foot” Characteristics About 1.1 million species described Body composed repeated segments (metamerism) but septa have been lost In contrast to annelids, much specialization of segments is seen Tagmosis: the fusion of segments to form a larger specialized body sections Head: appendages used a sensory and feeding structure Thorax: Contains many organs and legs used for locomotion Abdomen: man contain organs (esp. reproduction) or be used in locomotion Body Structures Arthropods exhibit much more specialization of appendages Functions: sensory, feeding, locomotion, reproduction Presence of antenna and mandible are important taxonomic characters The cuticle of Arthropods is greatly modified from that annelids: more durable, specialized for molting Molting: process of shedding old cuticle and secreting a new one Cuticle contains two laters Epicuticle: outermost layer; first thing that is made for molting Procuticle: innermost; contains chitin (nitrogenous polysaccharide); proteins and calcium salt: increase rigidity, made of two layers Exocuticle: secreted prior to molting temporary protection Endocuticle: secreted after molting, forms tough durable shell The cuticle of Arthropods is greatly modified from that of annelids more durable specialized for molting Organ Systems Arthropods have various adaptations for gas exchange- tracheal system – branching system of tube that deliver atmospheric gases directly to cells Malpighian Tubules: An arthropod adaptation of terrestrial life excretory vessels that releases into the digestive tract Use uric acid for waste Metaporphosis is an adaptation seen in insect Arthropods that decreases competition between larvae and adults- the body form changes between larvae and adult Holometabolous metamorphosis Metamorphosis is rapid Egg Larva (specialized for feeding) Pupa (larva undergoes drastic metamorphosis into adult) Adult (specialized for dispersal and reproduction) Menimetabolous Metamorphosis Metamorphosis is more gradual Egg Nymph Adult Wings: outgrowth of cuticle, not a modified leg No wings Rigid wings Hidden wings Non- hidden (one set of wings disappears and used for balance) Subphylum Trilobita; all extinct Very successful from pre-Cambrian to carboniferous (about 200my) Body with head thorax and abdomen Two grooves running longitudinally Subphylum Chelicerata: horseshoe crab, spiders First pair of appendages modified into Chelicerae which are used to grasp food or inject poison Four or five pairs of walking legs No mandibles or antennae Class Merostomata- horseshoe crabs Living fossils: have changed little through time Synchronize mating by moon/tides Cephalothorax: head and thorax fused 2 simple, 2 compound eyes Telson: most posterior segment tail spine, anus 10/3 Class Arachnida: spiders, ticks, scorpions 80,000 species 4 Pair walking legs, 1 pair pedipalps, 1 pair Chelicara (fangs) Four pairs of eyes Spinning gland produces webbing: used in capture of prey, creating shelter, protecting eggs Subphylum Myriapoda: “many footed”, centipedes, millipedes One pair of antennae Appendages uniramous: one leg (not pincers) contrast with crustaceans Mandibles Terrestrial adaptations: trachea and malpighian tubules Class Chilopoda: centipedes Dorsoventrally flattened with many segments Tubular, usually with segments Two pair of legs per segments Subphylum Crustacea: “shell” 70,000 species described Most are marine but are important and abundant in freshwater; there are a few terrestrial species Most mobile, some sessile (barnacles) 2 pair of antenne Pair of mandibles: bi-ramous legs modified for masticating food Exoskeleton of crustaceans is very strong, fortified with calcium. Areas around joints are not calcified so flexibility is not lost Characteristics: Excretory system: antennal glands function mostly in osmoregulation (maintaining water balance): ammonia diffuses across thin parts of cuticle Reproduction: Sexual: usually cross fertilize Asexual: may be parthenogenic Development is usually indirect with a larval form called a nauplius Class Malacostraca: largest and most diverse taxa of Crustacea (20K species) Includes crabs, crayfish, shrimps- mostly marine but some freshwater and terrestrial Subphylum Hexapoda- “6 foot” Over 1 million species described (250-380 k beetles) One pair of antennae Appendages uniramous (contrast with crustacean biramous legs) Terrestrial adaptations: trachea and malpigian tubules Mouth with mandibles Three tagmata: head, thorax, abdomen Typically 2 pairs of wings Phylogeny Arthropods were once thought to have evolved from Annelids, current phylogenies place them with ecdysozans Arthropodization (Tagmosis) may have happened a few times in evolutionary history Arthropoda may be polyphyletic

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