Chapter 4 - Diversity of Life PDF

4 – DIVERSITY OF LIFE 4.1 Viruses Virus - Non-living, parasitic, infectious agent that can only replicate in a host cell Viral Structure – RNA or DNA genome encased in a protein capsid -may have a lipid envelope -genome may be circular, linear, single-...

4 – DIVERSITY OF LIFE 4.1 Viruses Virus - Non-living, parasitic, infectious agent that can only replicate in a host cell Viral Structure – RNA or DNA genome encased in a protein capsid -may have a lipid envelope -genome may be circular, linear, single- or double-stranded -no organelles or nucleus -Relatively small genomes (usually) -Much smaller than prokaryotic or eukaryotic cells (usually) -Typically uses host’s machinery for replication and gene expression TYPES OF VIRUSES DNA Viruses Genome may be single- or double-stranded. Use host machinery for replication / gene expression RNA Viruses Genome may be single- or double-stranded. Single stranded RNA may be sense (+) or anti-sense (-). A viral RNA-dependent RNA polymerase is required. Retroviruses Genome is single-stranded RNA (+). A viral reverse transcriptase is required. Bacteriophages (only infect bacteria) Head – the genome is surrounded by a protein capsid. Tail – responsible for binding to the surface of the host cell and penetration. LYTIC CYCLE 1. Attachment Virion binds proteins on host cell’s surface. 2. Penetration Viral genome is injected through the bacterial cell wall. Host cell’s machinery for replication and gene expression are used 3. Biosynthesis to synthesize viral components 4. Assembly Viral components are assembled into mature viral particles. 5. Lysis Host cell lysis and release of mature viral particles. LYSOGENIC CYCLE 1. Attachment Virion binds proteins on host cell’s surface. 2. Penetration Viral genome is injected through the bacterial cell wall. Viral genome is inserted into the host’s genome and viral 3. Integration expression is repressed. The integrated viral genome is referred to as a prophage, and the infected cell as a lysogen. Stress can result in viral expression leading to excision of the viral 4. Induction genome from the host and activation of the lytic cycle. ChadsPrep.com 67 Animal Viruses -Often have a lipid bilayer envelope (w/ proteins & glycoproteins) -Enter the host cell via endocytosis and exit by exocytosis -Have similar cycles to bacteriophage lytic and lysogenic cycles Retroviruse Life Cycle -[+] RNA viruses that convert their genomes into dsDNA (reverse transcriptase) -reverse transcriptase is an RNA-dependent DNA polymerase -dsDNA is integrated into the host’s genome for gene expression/replication Infectious Subviral Particles Prions – Infectious protein particles -a pathogenic, misfolded variant of a certain protein that can act as a scaffold to drive normal host proteins to misfold into the pathogenic form -cause a variety of transmissible spongiform encephalopathies (neurodegenerative disorders) including the following: -Scrapie in sheep -Bovine spongiform encephalopathy in cows (‘mad cow’ disease) -Kuru and Creutzfeld-Jakob disease (CJD) in humans Viriods –Naked circular ssRNA molecules that infect plants -reproduce via a host RNA-dependent RNA polymerase -siRNAs may be produced during replication causing disease ChadsPrep.com 68 4.2 Prokaryotes SPECIES IDENTIFICATION GENUS SPECIES Homo sapiens Tyrannosaurus rex 3 DOMAINS / 6 KINGDOMS Domain Archae Bacteria Eukarya Kingdom Archaebacteria Eubacteria Protista Fungi Plantae Animalia PROKARYOTES EUKARYOTES 1. Unicellular 1. Unicellular & Multicellular 2. Diameter 0.1-5m 2. Diameter ~ 10-100m 3. No nucleus 3. Membrane-bound nucleus 4. No membrane-bound organelles 4. Membrane-bound organelles 5. Single circular chromosome 5. Multiple linear chromosomes 6. Circular plasmid DNA 6. No plasmid DNA 7. Some have histone-like proteins 7. DNA around nucleosomes with histones 8. Cell Division via fission 8. Cell division via mitosis 9. Asexual Reproduction 9. Asexual & sexual reproduction 10. Cell wall (and often a capsule) 10. Plant/fungal cells have a cell wall 11. Flagella made from flagellin 11. Flagella made from microtubules (9+2) 12. Pili 12. No pili ChadsPrep.com 69 Prokaryotes EUBACTERIA ARCHAEBACTERIA 1. Phospholipids with ester linkages 1. Phospholipids with ether linkages 2. Cell walls with peptidoglycan 2. Cell walls with other polysaccharides 3. Some of the replication, transcription, and translation machinery more closely resembles that of eukaryotes. BACTERIAL SHAPES Coccus Bacillus Spirillum (spherical) (rod-shaped) (helical) GRAM POSITIVE GRAM NEGATIVE 1. Cell wall has thicker peptidoglycan layer 1. Cell wall has thin peptidoglycan layer 2. Stain purple (crystal violet) 2. Counterstain pink (safranin) 3. Techoic & lipotechoic acids are also 3. No techoic or lipotechoic acids incorporated into the cell wall 4. No outer membrane 4. Lipopolysaccharide (LPS) outer membrane 5. May have a gelatinous capsule 5. May have a gelatinous capsule Motility Flagellum – some eubacteria and archaebacteria (archaellum) have a flagellum for locomotion -powered by a proton gradient (eubacteria) or ATP hydrolysis (archaebacteria) -made from flagellin in eubacteria and similar protein in archaebacteria Pili – Shorter than flagella, pili may aid in motility, attachment, pathogenicity conjugation Chemotaxis –directed movement toward chemoattractants or away from chemorepellents -sensed by chemoreceptors ChadsPrep.com 70 Prokaryotic Genetics Conjugation – transfer of plasmids from one prokaryotic cell to another Transduction – transfer of genetic material via viral infection Transformation – uptake of genetic material from the environment -Bacteria that can be ‘transformed’ are said to be ‘competent.’ Conjugation in E. coli Cells having an F plasmid (F+) can act as donors to cells that do not have the F plasmid (F-). Mechanism 1. Growth of sex pillus 2. Plasmid Transfer/Replication 3. Destruction of sex pillus -Conjugation involving R plasmids can convey antibiotic resistance. Binary Fission Bacteria reproduce via binary fission. No mitotic spindle apparatus is involved. 1. DNA Replication 2. Growth 3. Segregation of DNA 4. Cell Division (Cytokinesis) PROKARYOTE METABOLISM Autotrophs Both photoautotrophs & chemoautotrophs Heterotrophs Cannot synthesize organic compounds from inorganic precursors but ingest organic compounds by consuming other organisms Aerobes Can survive in an oxygen environment Anaerobes Do not require oxygen to survive Facultative Anaerobe Can carry out metabolic processes with or without oxygen Obligate Anaerobe Can’t survive in the presence of O2 ChadsPrep.com 71 4.3 Protists Endosymbiotic Theory – describes the origins of mitochondria and chloroplasts as distinct prokaryotes that were engulfed by larger prokaryotic cells Supporting Evidence: 1. Endosymbiotic bacteria in protists 2. Mitochondria and chloroplast DNA (circular) 3. Mitochondria and chloroplast ribosomes Most protists are unicellular and include protozoa and single-celled algae. They are best characterized as eukaryotes that are not fungi, plants, or animals. Both asexual (mitosis) and sexual reproduction (meiosis) are known to occur. Asexual budding also occurs in which the daughter cell is considerably smaller than the parent. KINGDOM PROTISTA PROTOZOA PHYLA Examples Characteristics (heterotrophs) Paramecium Unicellular and covered in cilia Ciliophora Blepharisma Amoeba Unicellular & motility via pseudopods Sacrodina radiolarians Many are parasites (cause dysentery) Unicellular, non-motile parasites Apicomplexa Plasmodium Plasmodium causes malaria (formerly Sporozoa) (infects mosquitos and then humans) ALGAE PHYLA Examples Characteristics (autotrophs) Fucus Multicellular, largest protists Phaeophyta (brown algae) Includes brown algae and kelp species Polysiphonia Multicellular; includes red algae Rhodophyta (red algae) Chloroplasts similar to cyanobacteria Very important primary producers Bacillariophyta diatoms Produce lots of O2 in the atmosphere Includes photoautotrophs & Heterotrophs Euglenophyta Euglena Includes mixotrophs (both) Motility via flagella Ceratium Photoautotrophs; Motility via two flagella Pyrrophyta (dinoflagellates) Symbiotic with coral & shellfish Responsible ‘red tides’ Unicellular and multicellular Spirogyra Include green algae Volvox Chlorophyta Use chlorophyl a & b Chlamydomonas Cells Walls made of cellulose/pectin (green algae) Store glucose as starch ChadsPrep.com 72 4.4 Fungi Fungi are eukaryotic and may be unicellular (yeasts) or multicellular (mycelia). Mycelia are filamentous and composed of hyphae. They have a common cell wall and may be separated by a septum. The septum may have a pore so that the cytoplasm is continuous between hypha. Hyphae may be monokaryotic, dikaryotic, or multinucleated. Cell walls are made of chitin (polymer of N-acetylglucosamine), and glucose is stored as glycogen. Fungi are heterotrophs. Species of fungi include decomposers (saprotrophs), parasites, and mutualistic symbionts. They may secrete digestive enzymes onto dead or decaying matter and absorb the resulting nutrients, or they may be parasites acquiring nutrients directly from a host. Fungi can reproduce both sexually and asexually including spore formation. Asexual reproduction involves budding (mitosis with asymmetric cell division), fragmentation of hyphae, or spore formation. Mitosis may be confined to the nucleus without breakdown of the nuclear membrane. In some species, cytokinesis doesn’t occur resulting in multinucleation (coenocytic hyphae). The majority of the life cycle is usually haploid. Mitosis of haploid hyphae produce haploid hyphae or spores. But two hyphae may fuse to produce a diploid mycelium, a process termed plasmogamy. This is usually a temporary phase before the fusion of the haploid nuclei to produce a diploid nucleus, a process termed karyogamy. Subsequent meiotic division produces haploid spores. KINGDOM FUNGI Phylum Examples Characteristics Filamentous; monokaryotic/dikaryotic hyphae Basidiomycota mushrooms Sexual reproduction of haploid basidiospores Reproduce asexually & sexually yeasts -Asexual involves budding or conidia formation Ascomycota molds Lichens are an example of mutualism—symbiosis lichens between an ascomycete and cyanobacteria/algae. Obligate symbionts with plant roots (mycorrhizae) Glomeromycota Increase nutrient absorption; receive sugars Asexual reproduction Asexual reproduction is more common Sexual reproduction produces diploid zygospores. Zygomycota bread molds Meiosis doesn’t occur until after germination resulting in a potentially persistent diploid state. ChadsPrep.com 73 4.5a Plants ADAPTATIONS FOR LAND PLANTS Waxy cuticle prevents water loss Stomata (tiny openings) allow for gas exchange (CO2, O2, H2O) Vascular Tissues Xylem – water transport from the roots Phloem –transport of dissolved nutrients and hormones Haplodiplontic Life Cycle – both multicellular haploid and diploid stages Sporophyte – multicellular diploid individual Gametophyte – multicellular haploid individual PLANTS NONVASCULAR VASCULAR (Tracheophytes) Algae Bryophytes Seedless Seed Liverworts Lycophytes Pterophytes Gymnosperms Angiosperms Mosses Ferns Conifers Flowering hornworts Horsetails plants Whisk ferns BRYOPHYTES Nonvascular (transport via simple conducting cells) Rhizoids responsible for absorption/anchoring (no roots) Gametophyte is photosynthetic and is dominant. General Gametangia form at tips of gametophytes. Features Antheridia produce sperm; archegonia produce eggs Flagellated sperm (water-dependent sexual reproduction) Sporophyte typically extends into the air Sporangia form at tips of sporophytes May have flattened gametophytes or resemble mosses liverworts Sporophyte suspended above the ground Unicellular rhizoids Small, leaflike photosynthetic structures with stemlike axis Leaflike structures have no vascular system & lack stomata mosses Sporophyte has stomata Multicellular rhizoids Sporophytes have stomata and are photosynthetic hornworts Typically live in symbiosis with cyanobacteria ChadsPrep.com 74 Vascular Plants (Tracheophytes) Vascular plants (roots, stems, xylem, phloem) Stomata allow for gas exchange (CO2, O2, H2O) Sporophyte is photosynthetic and is dominant. Waxy cuticle (prevents water loss i.e. desiccation) Seedless Plants Sporophyte stage is dominant and photosynthetic. Gametangia form at tips of gametophytes. Antheridia produce sperm; archegonia produce eggs Flagellated sperm (water-dependent sexual reproduction) LYCOPHYTES (club mosses) Herbaceous, having branching stems and simple leaves with small veins Sporophyte is photosynthetic and dominant. Gametophyte may also be photosynthetic. General Gametophyte may live in symbiosis with fungi (mycorrhizae). Features Gametangia form at tips of gametophytes. Antheridia produce sperm; archegonia produce eggs Flagellated sperm (water-dependent sexual reproduction) PTEROPHYTES Sporophyte is photosynthetic and dominant. General Gametangia form at tips of gametophytes. Features Antheridia produce sperm; archegonia produce eggs Flagellated sperm (water-dependent sexual reproduction) Have stems, leaves, roots, & rhizomes (underground stems) Leaves, called fronds, are divided and often ‘feathery’ in appearance. ferns Gametophytes are very small and photosynthetic. Gametophytes lack vascular tissue. Sporangia are in clusters called sori on the underside of fronds. Grow in damp places Have stems, leaves, roots, & rhizomes (underground stems) horsetails Have hollow, ribbed stems joined at nodes Gametophyte is also photosynthetic. Found in tropical/subtropical climates whisk Branching stems but no leaves or roots ferns Gametophyte may live in symbiosis with fungi (mycorrhizae). ChadsPrep.com 75 Seed Plants Seed plants are heterosporous producing both ‘male’ and ‘female’ spores. Microsporangia produce microspores (male spores—become pollen grains). Megasporangia produce megaspores (female spores—become ovules/seeds). A megasporangium (also called the nucellus in seed plants) is surrounded by the integument which will become the seed coat. There is an opening at one end called the micropyle. GYMNOSPERMS Mostly cone-bearing; mostly evergreens Ovules are not completely enclosed at pollination. General Egg is accessed through a pollen tube. Features Sporophyte is dominant Heterosporous Include ~1000 living species Pines, spruces, firs, cedars, etc. (Includes over 600 species) Nonmotile sperm Coniferophyta Needle-like or scalelike leaves (prevent water loss) Seeds often in cones Cycads (palmlike plants) Flagellated sperm Cycadophyta Seeds in cones Includes over 300 species Includes trees, shrubs, and vines (~65 living species) Individual trees are either male or female. Gnetophyta Males produce pollen-bearing cones. Females produce ovule-bearing cones. Nonmotile sperm Ginkgo (deciduous tree—1 species) Fan-shaped leaves Ginkgophyta Flagellated sperm Seeds have a fleshy, odorous outer covering ANGIOSPERMS (Anthophytes) Flower/fruit-producing plants (mostly deciduous) Includes trees, shrubs, vines, grasses, and herbs Ovules are completely enclosed at pollination Seeds enclosed in a fruit General Heterosporous Features Egg is accessed through a pollen tube. Nonmotile sperm Great variety of leaves Includes over 300,000 species ChadsPrep.com 76 4.5b Plant Form and Function ROOT SYSTEM Absorb water and minerals Stores carbohydrates Primary Root – 1st organ to emerge from a germinating seed; lateral roots spring from it Taproot – main vertical root in many tall, massive trees; develops from the primary root SHOOT SYSTEM (Stems and Leaves) Gas exchange Photosynthesis (carbohydrate production) Maximize photosynthesis of the shoot system Stems Presentation of reproductive structures Green stems carry out limited photosynthesis Main photosynthetic organ Gas exchange (stomata) Leaves Dissipate heat Defense against herbivores/pathogens PLANT TISSUES Outer protective covering Defense against damage and pathogens Dermal Epidermis – primary dermal tissue; first line of defense Tissues Periderm – replaces epidermis in older stems/roots in woody plants Cuticle – waxy epidermal coating that helps prevent water loss Xylem – Transport water/minerals from roots to shoots Composed of dead cells hardened with lignin at maturity Tracheids – Long, tapered xylem cells in all vascular plants Water passes from one to another via pits Vessel Elements – Shorter, wider xylem cells that are aligned Vascular end-to-end forming long pipes Tissues Phloem – Transport sugars from leaves to where needed/stored Sieve Cells – Elongated cells that are alive at maturity, though lacking a nucleus and ribosomes Often organized in sieve tube elements/sieve tubes which terminate in porous sieve plates for cell-to-cell transport Non-dermal and non-vascular tissue; the most abundant tissue Parenchyma – have only a thin primary wall; active in metabolism (synthesis and storage) Ground Collenchyma – groups of strands of elongated cells; thicker primary wall; Tissues provide flexible support in regions still lengthening (primary growth) Sclerenchyma – thick secondary wall; provide rigid support in regions no longer lengthening (secondary growth); often dead at maturity ChadsPrep.com 77  PRIMARY AND SECONDARY GROWTH Lengthening of root/shoot tips at apical meristems Primary Meristems are undifferentiated tissues that can divide and Growth become differentiated. Growth in thickness at lateral meristems seen in woody plants Secondary Vascular Cambium – lateral meristem giving rise to Growth secondary xylem/phloem Cork Cambium – lateral meristem giving rise to the periderm ANATOMY OF ROOT GROWTH Root Cap Layer of cells protecting apical meristem Zone of Cell Region where cell division of the apical meristem Division takes place Zone of Region where growth of newly formed cells takes Elongation place Zone of Region where differentiation into dermal, Differentiation vascular, and ground tissues takes place ROOT STRUCURE Lines the outside surface Epidermis Produces root hairs (absorption) Parenchyma cells outside the vascular cylinder for Cortex carbohydrate storage Ring of tightly packed cells separating the cortex Endodermis and vascular cylinder; regulates flow of water & nutrients from the cortex to the stele Contains the pericycle, xylem, and phloem (& pith) Vascular In dicots, xylem occupy an X-shape with phloem Cylinder interspersed. (Stele) In monocots, there are rings of xylem and phloem. Pericycle Outer layer of cells lining the vascular cylinder Parenchyma cells at the center of the vascular Pith cylinder of monocots Stores water and nutrients Waxy lining around endodermal cells Casparian It forces water to pass through endodermal cells for Strip filtering before entering the vascular bundle. ChadsPrep.com 78  STEM STRUCURE Lines the outside surface Epidermis Covered in a waxy cuticle to prevent water loss Cortex Ground cells outside the vascular cylinder in monocots In monocots, there are rings of xylem and phloem that Vascular are connected via the vascular cambium around a pith. Bundles In dicots, they are dispersed throughout ground tissue. In woody plants, the vascular cambium is a ring of cells producing secondary xylem and phloem over time Vascular increasing girth and resulting in the annual rings. Cambium The cork cambium produces the periderm as an outer layer. LEAF STRUCURE Lines the outside surface Epidermis Covered in a waxy cuticle to prevent water loss (transpiration) Stomata Pores in the epidermis for gas exchange (O2/CO2) Guard Cells Regulate opening and closing of stomata Leaf ground tissue that is largely comprised of parenchyma cells Mesophyll specialized for photosynthesis and gas exchange Bundle A protective layer of cells around veins in the leaf regulating Sheath Cells exchange between vascular tissue and the mesophyll Vascular Xylem provide water for photosynthesis. Bundles Phloem transport carbohydrates produced during photosynthesis. ChadsPrep.com 79  TRANSPORT IN PLANTS Cohesion-Tension Theory – Major mechanism of bulk xylem flow Xylem sap is in a constant state of tension throughout the xylem due to cohesive forces between water molecules and adhesive forces with the xylem walls. Water loss in the leaves (transpiration) pulls the column of xylem sap upward (‘transpiration pull’). Transport of Root Pressure – Water and minerals are pumped into the xylem of root Water cells resulting in the net push of xylem sap upward (minor contribution). Each stomata is surrounded by two guard cells. High turgor pressure in the guard cells opens the stomata. Stomatal regulation can occur in response to a water deficit, high temperatures, light, CO2, and hormones (abscisic acid). Pressure-Flow Hypothesis – The bulk flow of phloem sap is driven by positive pressure. Translocation of sugars from source to sink via phloem. Transport of Sources are where sugar is produced via photosynthesis or starch Sugars breakdown. Sugars are pumped into phloem; water follows. Sinks are where sugar is being used or transported to for storage. Sugars are pumped out of phloem; water follows. PLANT HORMONES Stimulates cell elongation in response to various stimuli Phototropism – Growth of a shoot toward light Auxin Gravitotropism (a.k.a. Geotropism) – growth of a shoot/root in response to gravity Slows leaf abscission Regulate cell division in roots and shoots Cytokinins Promote lateral bud formation Delay senescence Stimulate stem elongation Stimulate pollen development Gibberellins Stimulate flower/fruit growth Stimulate seed development/germination Inhibits growth Stimulates stomatal closure during drought Abscisic Acid Promotes seed dormancy Stimulates leaf senescence Stimulate fruit ripening Response to mechanical stress Ethylene Stimulate senescence Stimulate leaf abscission ChadsPrep.com 80  FLOWER STRUCTURE Female reproductive organ; 3 parts Stigma – Sticky opening for capturing pollen Pistil Style – Long, slender neck joining stigma to ovary Ovary – Contains one or more ovules Male reproductive organ; 2 parts Stamen Anther – Produces pollen Filament – stalk supporting the anther Petals Attract pollinators FERTILIZATION 1. Pollen lands on the stigma. 2. A pollen tube forms to the ovary. 3. Mitosis produces a 2nd sperm cell. 4. Double Fertilization – One sperm fertilizes the ovule producing a seed embryo. The 2nd sperm combines with two polar nuclei to produce a triploid nuclei in a cell that will become the endosperm, a food-storing tissue of the seed. SEED STRUCTURE Epicotyl – Top of the embryo that becomes the shoot tip Embryo Hypocotyl – Embryo just below the cotyledon(s) Radicle - Embryonic root Seed Coat Hard, protective coating Endosperm/ Stores nutrients for the seedling after germination Cotyledon(s) GERMINATION A mature seed enters dormancy. Germination is triggered by environmental cues (water, temperature, light, seed coat damage, etc.). Germination proceeds as follows: 1. Imbibition (absorption of water) Seed coat cracks Activation of biochemical reactions 2. Digestion of endosperm/cotyledon(s) 3. Emergence of the radicle 4. Elongation of the hypocotyl 5. Emergence of the shoot tip from the epicotyl ChadsPrep.com 81 4.6 Animals Animal General Characteristics Heterotrophic Multicellular Lack cell walls Able to move (motility) Reproduce sexually (mostly) Have specialized tissues DISTINGUISHING FEATURES OF ANIMALS Tissue All animals besides sponges have specialized tissues resulting from Specialization permanent differentiation. Sponges do not exhibit body symmetry. Cnidarians exhibit radial symmetry. Most other animals exhibit bilateral symmetry. Symmetry Cephalization typically accompanies bilateral symmetry where nervous tissue is concentrated at the anterior end. Most animals with bilateral symmetry are also triploblastic (3 germ layers—endo-, meso-, ectoderm). A body cavity distinct from the digestive system accommodates internal organs. Body Cavity Acoelomate – no body cavity Pseocoelomate – body cavity formed between the mesoderm/endoderm Coelomate – body cavity formed within the mesoderm PROTOSTOMES DEUTEROSTOMES Blastopore → mouth (usually) Blastopore → anus Development Spiral cleavage Radial cleavage Determinate Indeterminate (Blastomeres are NOT totipotent.) (Blastomeres are totipotent.) The presence of linearly arrayed compartments, may provide (1) Segmentation redundancy and (2) more efficient locomotion. ChadsPrep.com 82  PARAZOA Sponges (mostly marine, some freshwater) Lack specialized tissues/organs Asymmetrical Porifera Filter feeders via flagellated cells called choanocytes which absorb food and pass it to amoebocytes for digestion Asexual and sexual reproduction RADIATA Comb jellies, sea walnuts Gelatinous, transparent, and often bioluminescent Ctenophora Specialized tissues but no organs Radial symmetry Diploblastic Jellyfish, hydra, coral, sea anemone Specialized tissues but no organs Cnidaria Radial symmetry Diploblastic Many have stinging tentacles (nematocysts) ChadsPrep.com 83  PROTOSTOMES ACOELOMATES Flatworms (tapeworms, planarians, flukes) Marine, freshwater, and terrestrial habitats Bilateral symmetry / cephalization / unsegmented Platyhelminthes Digestive cavity has a single opening (except tapeworms which have no digestive tract) Many species are parasites. PSEUDOCOELOMATES Roundworms (pinworms, hookworms, ascaris) Over 60,000 species Marine, freshwater, and terrestrial habitats Nematoda Bilateral symmetry / cephalization / unsegmented Tubular digestive tract with mouth and anus Many species are parasites. Rotifers Marine and freshwater habitats Rotifera Bilateral symmetry / cephalization / segmented externally Complete digestive tract (mouth, stomach, intestine, anus) Cilia for locomotion COELOMATES Segmented worms (earthworms, leeches, polychaetes) Marine, freshwater, and terrestrial habitats Annelida Bilateral symmetry / cephalization / segmented Complete digestive tract (mouth, gizzard, intestine, anus) Mollusks (snails, clams, oysters, slugs, octopuses, squid) Marine, freshwater, and terrestrial habitats Mollusca Bilateral symmetry / cephalization / unsegmented Many species have a secreted shell. Arthropods (insects, spiders, scorpions, crabs) Over 1 million species Arthropoda Marine, freshwater, and terrestrial habitats Bilateral symmetry / cephalization / segmented Exoskeleton made of chitin ChadsPrep.com 84  DEUTEROSTOMES Starfish, sea urchin, sand dollar, sea cucumber Only marine habitats Radial symmetry / no cephalization / unsegmented Echinodermata Bilateral symmetry in larvae Sexual reproduction (mostly) Coelomates Endoskeleton made of calcium carbonate Marine, freshwater, and terrestrial habitats Coelomates Common Characteristics 1. Hollow Nerve Cord – becomes spinal cord/brain Chordata 2. Notochord – flexible rod below the nerve cord 3. Pharyngeal Slits – become gills in aquatic chordates -just pharyngeal pouches in terrestrial chordates 4. Postanal Tail – extends past the anus in development Urochordata (tunicates) are marine animals having chordate larval forms but not adult forms. Adults are Nonvertebrate typically immobile. Chordates Cephalochordata (lancelets) have notochords spanning the entire dorsal nerve chord throughout life. Fishes, amphibians, reptiles, birds, and mammals Distinct Characteristics of Vertebrates 1. Vertebral Column – replaces the notochord early 2. Head – brain and sensory organs Vertebrate 3. Neural Crest – pinch off from neural tube to form PNS Chordates and other tissues 4. Internal Organs – circulatory, excretory, and endocrine 5. Endoskeleton – made from cartilage or bone Notochord is replaced by the vertebral column early. VERTEBRATE CHARACTERISTICS Fishes Amphibians Reptiles Birds Mammals Jaws Legs Amniotic egg Feathers Hair Paired Lungs Dry, waterproof Flight skeleton Mammary glands appendages Cutaneous skin Endothermic Internal gills respiration Thoracic breathing Placenta Closed circulatory Pulmonary veins system Partially divided heart ChadsPrep.com 85