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61 Cards in this Set
- Front
- Back
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Which of the following statements is false?
1. Fungi and animals are sister taxa 2. Fungi are more closely related to animals than to plants. 3. The closest living relatives of animals are the choanoflagellate protists 4. Metazoans are a monophyletic group |
1.
Fungi and animals are sister taxa |
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Which of the following features characterizes opisthokonts as a group?
1. Haplontic life cycle 2. Reduction of dikaryon stage 3. Flagellum, when present, single and posterior 4. Multicellularity |
3.
Flagellum, when present, single and posterior |
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Choanoflagellates
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small group of aquatic heterotrophic eukaryotes • ca. 140 species, some unicellular, others colonial • cell similar in structure to sponge choanocytes |
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What is the evidence that choanoflagellates are the sister group of metazoa?
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1.
Collar cells (shared between choanoflagellates and sponges) 2. Structure of mitochondria 3. DNA sequence data 4. Choanoflagellates have homologues of metazoan cell signaling and adhesion genes |
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Characteristics of Metazoa
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Multicellularorganisms, with cell specialization, communication (nutrient exchange) and interdependency• Heterotrophs(require organic compounds as food)• Food ingested, usually followed by extracellular digestion in a gut (intracellular digestion in sponges)• Diplonticlife cycle• Distinctive male gametes: spermatozoa• Distinctive development: zygote →blastula →gastrula(latter not in sponges)• Motility, at least during certain stages of life cycle• Distinctive cell junctions (septatejunctions) unique to metazoans• Collagen(a fibrous protein) in the extracellular matrix
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What are the unique synapormorphies of Metazoa
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Spermatozoa, Blastula, septate junctions, Collagen
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Development, what order?
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Zygote --> Blastula --> Gastrula
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Cleavage
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early stages of cell division after zygote formation, resulting in multiple cells (blastomeres) and establishment of a longitudinal axis (animal-vegetal axis)
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Gastrulation:
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formation of cell layers by invagination (in-pocketing) of blastula to form gastrula
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Diploblasticanimals:
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two cell layers formed, ectodermand endoderm
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Triploblastic
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three cell layers formed, ectoderm, endoderm and mesoderm
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Sponge features
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Asymmetrical gutless animals • Aquiferous system: branched water canals • Differentiated cell types but no true tissues or organs • Cells arranged in gelatinous matrix (mesohyl) with collagen and usually spicules(skeletal elements) • All aquatic, mostly marine • ~8000 species (7000 species of demosponges) • Adults sessile, larvae motile • Mostly filter feeders on microscopic particles (bacteria, organic detritus, etc.), captured on microvilli, digested intracellularly Reproduction- Asexual: through “budding” or fragmentation Sexual: most sponges are hermaphrodites but not self-fertilizing |
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Synapormorphies or Eumetazoa
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gastrulation:formation of gut for extracellular digestion
• diploblasty (later modified to triploblasty) • radial symmetry (later modified to bilateral symmetry) • nervous system • musculature |
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Cnidaria include
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sea anemones, corals, sea jellies, cube jellies, hydrozoans
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Traits of cnidaria
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radial symmetry, around a longitudinal axis
• often with tentacles around the oral end • incomplete gut: single opening (serving as mouth and anus) leads to gastrovascular cavity diploblastic: two cell layers separated by gel-like mesoglea ectoderm epidermis endoderm gastrodermis two body forms: tube-shaped polyp, usually sessile, with oral end up; and bell-shaped medusa, motile, oral end facing down many cnidarians alternatebetween these two body forms during their life cycle cnidocyte: specialized cell with unique stinging or adhesive structure called a cnida (most common type: nematocyst) coiled cnida is discharged suddenly by hydrostatic pressure, penetrating prey and injecting poison |
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Life cycle of Cnidaria
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typically involves alternation between an asexual polyp stageand a sexual medusa stage
Alternation between an asexual polyp and a sexual medusa. • free-swimming medusae release sperm and eggs • zygote develops into a ciliated larva (planula) • larva settles and develops into a polyp • polyp buds asexually, producing a colony of polyps |
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Feeding in Cnidarians
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Cnidarians are all carnivorous .
Small animal prey captured with cnida-laden tentacles and conveyed into the gastrovascular cavity. Extracellulardigestionoccurs here. |
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the largest proportion? Bilateria or Disploblasts
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Bilatera
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Major features of bilateria
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triploblastic construction
• bilateral symmetry • anterior/posterior axis • cephalization |
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Coelom:
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fluid-filled body cavity surrounded by mesoderm
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Developmental tendencies of protostomes
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mesoderm forms near lip of blastopore
• coelom (if present) formed by splitting of mesoderm |
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Developmental tendencies of deuterostomes
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mesoderm and coelom form from outpocketing of gut wall
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Mesoderm
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source of most organs and organ systems
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What species has been around the longest?
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Sponges
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Larva of Mullocks
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Trochophore
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Traits of Mollusca
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complete gut
• reduced coelom • open circulatory system (hemocoel) • characteristic body plan: mantle, visceral mass, and foot • mouth with radula(rasping tongue-like organ) well developed nervous system (especially in cephalopods) • excretory system in form of nephridia |
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Reproduction in Mollusca
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mostly dioecious (separate sexes), some hermaphrodites
• fertilization mostly external in chitons and bivalves, internal in gastropods and cephalopods often: trochophore larva →veliger larva →adult • direct development in some molluscs |
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four major clades of Mollusca
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chitons, gastropods, bivalves, cephalopods
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The cephalopod eye
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single lens eye convergent with that of vertebrates
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Annelids and mulusca both have what?
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Spiral cleavage and trochophore larva
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Which group has setae
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Annelida
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Polychaete have
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parapodia
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Physical characteristics of Annelida
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Bilaterally symmetrical coelomate protostomes with following features…
• segmented (metameric) body • each segment with paired bundles of chitinous setae • each segment with parapodia (polychaetes only) • body wall with inner longitudinal and outer circular muscles • presegmental head and postsegmentalterminal part (pygidium ) closed circulatory system; cutaneous respiration Complete gut well developed excretorysystemand central nervous system |
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Polychaeta
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marine worms
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clitellum
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thickened band in middle of body that secretes a cocoon for protection of young
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Athropoda
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segmented body, with structures repeated in each segment
• paired jointed appendages • strong tendency towards tagmosis: regional specialization of body (tagmata, e.g., head, thorax, abdomen exoskeleton(composed of chitin and cuticle proteins) organized into articulating plates growth by periodic molting of exoskeleton (ecdysis) paired compound eyes composed of many photoreceptive units (ommatidia) complete gut with regional specialization well developed nervous system with dorsal brain and ventral nerve cord complex but variable excretory and respiratory systems |
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Arthropoda Reproduction
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nearly all arthropods are dioecious
• fertilization usually internal • development often involves larval stage (but some taxa have direct development) • complex metamorphosis in some insects and crustaceans |
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Similarities observed between myriapods and hexapods probably represent
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convergent adaptations to life on land.
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Chelicerata
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horseshoe “crabs”, scorpions, mites, ticks, spiders and kin (90,000 species)
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traits of chelicerata
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two body tagmata: cephalothorax and abdomen
• characteristic appendages: chelicerae (pincers), pedipalps, usually 4 pairs legs • mostly predators and parasites • spiders use silk (produced by glands in abdomen) to snare prey |
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Myriapoda
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Centipedes and millipedes
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Myriapoda traits
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two body tagmata: head and trunk
• numerous segments, each with one (centipede) or two (millipede) pairs of legs • centipedes: carnivorous, with poison fangs • millipedes: scavengers (some secrete cyanide in defense |
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Crustaceans
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crabs, shrimp, lobsters, barnacles, isopods, copepods, etc. (50,000 species)
• three body tagmata: head, thorax and abdomen • appendages (some two-branched) specialized for sensing, locomotion, respiration, etc. • dorsal carapace • diverse feeding habits (predators, filter feeders, scavengers…) |
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Hemimetabolous (incomplete) metamorphosis
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metamorphosisThree stages: egg →nymph →adult
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Hexapoda –insects and allies
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three tagmata: head, thorax and abdomen
• one pair of antennae (two pairs in other crustaceans) • three pairs of legs (located on the thorax) • respiration by tracheae (system of air tubes extending into body) • originally: mouthparts with mandibles (later modified) What about wings? Wings evolved (once) withinthe insects |
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Holometabolous (complete) metamorphosis
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metamorphosisFour life stages: egg →larva →pupa →adultMajor reorganization at pupal stage
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coevolution with flowering plants had an effect on diversification
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withininsect orders, not on the origin of major clades
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Eusocial insects live in colonies with division of labor: some individuals reproduce (queen, male), but most individuals belong to a
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non-reproductive worker caste.
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Major eusocial insects
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(1) termites, (2) ants, (3) some bees and (4) some wasps.
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Army ants: rapacious predators!
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mass foraging, nomadic ants with specialized queens
colonies can contain up to 20 million workers prey upon invertebrates and occasionally small vertebrates “keystone species”: because of (1) intensity of predation and (2) a diverse fauna of dependent organisms (e.g., antbirds) |
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Deuterostome traits
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radial cleavage
• blastopore →anus • enterocoely |
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Echinodermata
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sea lilies, sea stars, brittle stars, sea urchins, sea cucumbers
• bottom-dwelling marine organisms; predators, grazers, particle feeders • 7,000 extant species; 13,000 fossil species calcareous endoskeleton, composed of plates or ossicles, often with spines and pincer-like structures (pedicellariae) complex water vascular system, derived from the coelom complete gut with regional specialization diffuse nervous system (nerve net, nerve rings), no brain respiration and excretion by diffusion across epidermis |
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calcareous endoskeleton,
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Because it is derived from mesoderm, and covered in epidermis
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Echinodermata reproduction
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EchinodermataSexual reproduction: mostly dioecious, with external fertilizationRegeneration of body parts is common →means of asexual reproduction
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What are chordates?
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Sea squirts, lancelets, jawless fishes, jawed fishes, and tetrapods (amphibians, reptiles, mammals)
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What are chordates? Deuterostomes with…
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1.
Notochord 2. Dorsal hollow nerve cord 3. Postanal tail 4. Pharyngeal slits |
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Other important innovations arose withinchordates including…
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Internal skeleton with vertebrae
2. Jaws 3. Two pairs of walking limbs |
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Notochord
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dorsal supporting rod, semi-rigid yet flexible
• develops in embryo (replaced by vertebrae in most vertebrates) |
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Dorsal hollow nerve cord
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develops from infolding of ectoderm above the notochord |
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sea squirts (ascidians
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sea squirts are bag-like, with enlarged perforated pharynx for filter-feeding
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Amniotes
Key innovations to exploit terrestrial environment: |
impermeable skin
• efficient kidneys • amniote egg |
