Dr. Forbes' Lectures for Biology 252

DIVERSITY:ANIMAL PROTISTS AND ANIMALS

  • Most of the 10-50 million spp. of organisms here

  • All are eukaryotic; recall prokaryote v. eukaryote differences:

    Differentiating characteristics
    ProkaryotesEukaryotes
    No membrane bound nucleusNucleus is memb.-limited
    No mitochondria, plastids, etc.Have them....
    No endoplasmic reticulumHave it....
    Flagella simpleFlagella and cillia of 9+2 type
    Relatively little DNA1000x more
    "Genophore" a DNA ringChromosomes linear, of DNA + protein
    Have plasmids (rings of DNA)No plasmids
    Cell walls of peptidoglycanCell walls, if present, of cellulose
    AmitosisMitosis
    No meiosisMeiosis
    Metabolic diversityStructural diversity
    SmallNot so small to really BIG

    Members of two kingdoms to deal with: PROTISTA (specifically, the "protozoa") and ANIMALIA

    Characteristics of the "protozoa":

    Classification of protozoa in flux; see text, p. 523. E.g., Giardia, long considered in Ph. Zoomastigophora, now in Ph. Archezoa....

    See Table 26. I,. p. 524, for those we'll consider.

    Ph. Rhizopoda: amoebas, etc.:

    Ph. Actinopoda: helizoans, radiolarians

    Ph. Foraminifera: foraminiferans

    Ph. Apicomplexa: sporozoans

    Ph. Zoomastigophora: zooflagellates

    Ph. Ciliophora: ciliates

    KINGDOM ANIMALIA

    General features (compared to protozoa):

    FIG. 29.1: STUDY IT DILIGENTLY & OFTEN!

    Of the ~35 animal phyla currently recognized, we'll consider only 16 (those on fig. 29.1 + one more minor one)...

    SUBKINGDOM PARAZOA, PHYLUM PORIFERA - SPONGES:

  • Classes:
  • CALCAREA
  • HEXACTINELLIDA
  • DEMOSPONGIAE
    • SUBKINGDOM EUMETAZOA: ALL REMAINING PHYLA WE CONSIDER....

    THE "RADIATA": Phylum Cnidaria - Jellyfishes & Relatives

    CLASSES:
  • Hydrozoa - solitary or colonial, varied life histories
  • Scyphozoa - jellyfishes...
  • Anthozoa - corals, sea anemones, etc.; polyps only
  • Note importance of coral reefs , atolls, re biodiversity, etc.

    • The "Radiata":Phylum Ctenophora comb jellies, sea walnuts

    ALL REMAINING PHYLA ARE THE,"BILATERIA"
     bilateral symmetry; triploblastic; organ grade of construction

    Phylum Platyhelminthes - flatworms; ~ 20K spp.

    • salmon-poisoning: carnivore ingests fish harboring metacercariae of Goniobasis silicula, which may harbor the rickettsia Neorickettsia helminthica, which causes salmon-poisoning

      IV: Class Cestoda - tapeworms (29.16)

    • highly specialized obligate parasites, usually in gut
    • unique head (scolex) bears hooks &/or suckers
    • rest of body is a series of proglottids (the strobila) continually generated from posterior end of scolex and of increasing sexual maturity and age posteriorly
    • size varies from nearly microscopic to ~ 20 m in length
    • no gastrovascular cavity;absorb host's digested nutrients
    • life cycles vary; typically, involve an intermediate host that harbors a bladderworm larval stage....

    PHYLUM NEMERTEA - ribbon worms, or proboscis worms (29.17)

    Thus, the nemerteans seem to be intermediate between the acoelomate bilateria and the remaining protostomous phyla.

    PHYLUM ROTIFERA - rotifers (fig. 29.18)

    PHYLUM NEMATODA - roundworms (fig. 29.19)

    The "annelid/arthropod/mollusc superphylum" - the major protostomous, eucoelomate, schizocoelomate phyla: fig 29.4-5

    Phylum Mollusca - mollusks

  • lack metameric segmentation....
  • Classes (only 4 of the 8):
  • Polyplacophora: chitons; all marine, with 8 dorsal plates; common intertidal animals; graze on algae
  • Gastropoda: > 40K spp., incl. snails, slugs; broad ecological distribution; torsion in snails; "lung"....
  • Bivalvia: clams, etc.; shell of 2 halves; filter-feeders; no radula; cephalization obscure; ~ sedentary....
  • Cephalopoda: squids, octopuses, nautilus; largest & most intelligent of invertebrates! Predaceous. Foot -> siphon + tentacles + part of head; shell reduced, internal (except nautilus); squids fast, pelagic; octopus benthic; eyes convergent with vertebrate eyes....

    • Digression 1: Some minor phyla:
    Three lophophorate phyla:

    The position of the lophophorates now thought to be closer to protostomes (molecular evidence), despite coelom devel't. Lophophore is their feeding structure....

    Digression 2: Kinds of similarity and their significance:

    Understand these concepts and their implications!!!

    Phylum Annelida - segmented worms

  • protostomous, schizocoelous,, etc.; most are vermiform
  • body has both longitudinally and circularly arranged muscles (note implications for movement ... )
  • have homonomous metameric segmentation...
  • 1 pair of metanephridia per body segment, each with a nephrostome (ciliated funnel) draining segment before it
  • have a closed blood vascular system, with multiple "hearts" derived from main dorsal vessel (note direction of flow)
  • ubiquitous in aquatic and moist terrestrial habitats
  • respire through body surface or through "gills"
  • nervous system organized as 1 pr cerebral ganglia, two ventral nerve cords,, and paired segmental ganglia and nerves;
  • distinctive structures include setae and parapodia (in marine annelids; homologous with paired lateral appendages in arthropods?)
  • monoecious or dioecious; trochophore larva (marine spp.) or direct development; some capable of complete regeneration
  • Classes:
  • Oligochaeta: earthworms and relatives (fig. 29.28); familiar occupants of moist soils; many pairs of setae; no parapodia; clitellum is prominent; highly significant 46 macrodecomposers"; hermaphroditic, cross-fertilize
  • Polychaeta: most are marine; pelagic, benthic, sometimes in self-secreted tubes; prominent parapodia, bearing many setae, provide for locomotion, gas exchange; tentacles about mouth,,which in predatory spp. bears chitinous "jaws" and "teeth"; usually dioecious, but lack permanent sex organs; note palolo worm...
  • Hirudinea: leeches (f. 29.29c); no parapodia or setae; first and last segments, respectively, modified as anterior and posterior suckers, the anterior one encircling the mouth; coelom undivided; most are monoecious, cross-fertilize; clitellum present only in breeding season parasites or carnivores, with "jaws"; note Hirudo medicinalis....
    • Phylum Arthropoda - arthropods. - "most successful animals"...
  • protostomous, schizocoelous, etc....
  • basic body plan as in annelids, but significant modification
  • schizocoelom reduced to a hemocoel
  • circulatory system is open...; heart is dorsal
  • have metameric segmentation, but an important trend is -
  • segments often grouped into major body regions (tagmata); e.g., head, thorax, & abdomen, or cephalothorax, abdomen
  • paired, jointed, lateral appendages; primitively l pr/segment but variously reduced, highly specialized (serial homology)
  • chitinous exoskeleton (chitin + protein, sometimes + CaCO3); must be molted (ecdysis) to allow growth
  • highly complex arrangement of muscles (made possible by jointed exoskeleton ... )
  • gas exchange by body surface, "gills", tracheae, or book lungs; includes most spp. of "dry air" dwellers....
  • excretory organs either paired glands (homologous with metanephridia of mollusks) or Malpighian tubules
  • nearly all dioecious, with permanent sex organs; some are seasonally parthenogenetic
  • nervous system annelid-like, but sensory and motor capabilities much more complex (e.g., most insects fly)
  • 4 important evolutionary trends:
  • reduction in total number of segments
  • grouping of segments into tagmata
  • increasing cephalization
  • specialization of appendages for uses other than locomotion

    • Compare a beetle (highly derived) with centipede or Peripatus

    Why are arthropods so successful?

    1. . Exoskeleton: protection (but note liabilities....
    2. . Segmentation + jointed appendages: many adaptations....
    3. . Superior gas exchange (terrestrial spp.): makes high metabolism possible
    4. . Superior sensory systems: visual, acoustic, chemical, mechanical, proprioceptive receptors well-developed
    5. . Complex behaviors, both innate and learned....
    6. . Use of diverse resources through metamorphosis: e.g., individuals of a species at different metamorphis stages use different resources, reducing intraspecific competition.

    As the ultimate example of all these, consider beetles....

    Note Peripatus (Ph. Onychophora; fig 29.3 1): long considered to be descended from an ancient common ancestor for Annelida and Arthropoda; however, molecular evidence doesn't support this view; perhaps annelids and arthropods arose independently from an unsegmented protostome close to mollusks, and segmentation developed independently in the two phyla....

    Subphyla (4) and some classes of arthropods:

    *Subphylum Trilobitomorpha - trilobites (fig. 29.32) - common marine animals throughout Paleozoic; vanished during the Permo-Triassic extinction event.

    Subphylum Cheliceriformes - *eurypterids, horseshoe crabs, spiders, pseudoscorpions, scorpions, harvestmen, ticks, etc.

  • body organized into cephalothorax and abdomen
  • six pairs of appendages; first pair are chelicerae; second pair are pedipalps (e.g., pincers of a scorpion); remaining four pairs are walking legs
  • no mandibles, no antennae, simple eyes
  • Classes:
  • Merostomata - *eurypterids, horseshoe crabs
  • Arachnida - Spiders; predaceous, envenomate prey, ingest liquified tissues; gas exchange by book lungs and unique in use of silk to capture food, etc. (29.35)
  • Scorpions; also predaceous, with last segment as sting w/venom gland. (29.34a.)
  • Harvestmen; cephalothorax and abdomen broadly joined. Predominantly scavengers.
  • Ticks & mites: free-living, parasitic, scavenging, or commensalistic depending on species and stage in life cycle. (29.34b & c.)

    • The next two subphyla are similar in having mandibles, 1-2 pr of antennae, and (usually) a pair of compound eyes. They differ as noted below:

    Subphylum Uniramia - millipedes, centipedes, insects.
  • have one pr antennae,
  • appendages are unbranched (uniramous)
  • probably evolved on land; note significance of exoskeleton for support, movement, resistance to evaporation; also superior mechanisms for gas exchange, even in dry air
  • Classes:
  • Diplopoda - millipedes; terrestrial; head of 3 segments; trunk organized into diplosegments, so appear to have 2 pr legs/segment; scavengers; note chemical defenses, aposematism. (Fig. 29.36a.)
  • Chilopoda - centipedes; terrestrial; head of 3 segments, trunk segmentation typical; predaceous; use poison claws on anteriormost trunk segment to paralyze prey
  • Insecta - insects; in - every environment except marine; adult body organized into:
  • head (3 segments),
  • thorax (3 segments, each with 1 pr legs; also, thorax typically bears 2 pr of wings), &
  • abdomen (9-1 1 segments);

    • includes more species than all other taxa combined; see Table 29.1 for some of the major orders, and note variety in body forms, etc.

    Insects also remarkable for variety in life cycles, from direct development (e.g., silverfish, springtails; the primitive condition) to hemimetabolous metamorphosis ("incomplete metamorphosis"; e.g., grasshoppers, true bugs - go through series of nymph stages) to holometabolous metamorphosis (complete metamorphosis - egg, larva with instars, pupa, adult; e.g., beetles, flies, bees, butterflies - nearly 90% of all insects.) Complete metamorphosis allows individuals of a species to saturate the environment in different stages of life cycle while reducing intraspecific competition, especially among the adults.

    • Subphylum Crustacea - crabs, barnacles, shrimp, etc. (see fig. 29.40).

  • two pr antennae
  • appendages are basically branched (biramous)
  • evolution and greatest diversity in aquatic environments
  • several small classes; the two main ones are:
    Maxillopoda - includes ostracods, copepods, and barnacles; ostracods and copepods important in aquatic food chains; barnacles unusual in that the exoskeleton is hardened with calcium carbonate....

    Malacostraca - crabs, lobster, isopods, shrimp; esp. remarkable for diversity regional specialization of appendages; hard to overstate importance.

    The phyla remaining to be discussed are deuterostomous, have radial & indeterminate cleavage, & are enterocoelous. Two minor phyla (Chaetognatha, Hemichordata) & two major ones:

    Phylum Echinodermata - sea stars/urchins/sea cucumbers, etc.

  • described as a "noble group especially designed to puzzle the zoologist' (Hyman). Unique array of characteristics....
  • secondary radial pentamerous symmetry (but basically bilateral)
  • lack cephalization; no head or brain!
  • dermal endoskeleton composed of calcareous plates, typically with spines or bumps, and covered with a thin epidermis
  • water vascular system, derived from coelom; opens to outside through the madreporite, and extends by means of hydraulic canals into the numerous tube feet
  • tube feet: food procurement, locomotion, gas exchange
  • gas exchange also via dermal branchiae
  • pedicillariae sometimes present...
  • body not segmented
  • no specialized excretory organs; circulatory system reduced
  • exceptional ability to autotomize, regenerate lost parts
  • dioecious; develop through free-swimming bilateral larval stages; larva of the dipleurula type, which is bilateral
  • all are marine!
  • Classes:
    Asteroidea - sea stars (29.41, 29.42a, b); "typical" echinoderms; predaceous, using tube feet; stomach everted through mouth to envelope, digest prey...
    Ophiuroidea - brittle stars (29.42c); note distinct central disc, arms don't join each other at disc; move by flailing about with the arms
    Echinoidea - sea urchins (29.42d), sand dollars; lack arms, move by spines . . .; grazers (sea urchin-sea otter story); sea urchins have unique masticatory apparatus, Aristotle's lantern
    Crinoidea     - sea lilies (29.42e); sedentary or attached; a very ancient group....
    Holothuroidea - sea cucumbers (29.42f); no spines; endoskeleton greatly reduced; elongated body; some tube feet specialized as feeding tentacles; unusual regenerative ability....

    • Read text material on "Cambrian explosion" for general information and perspective. Some major body plans appear in rocks -700 myo; all major plans appeared by -545 mya

    Phylum Chordata - lancets, tunicates, vertebrates; highly diverse in adult forms and habits, but united by having at least some time in their lives -

    • a notochord - a stiffening but flexible rod dorsal to the gut and ventral to the nerve cord; fulcrum for the
    • segmentally arranged antagonistic muscles of the trunk and tail, alternating contractions of which provide for movement by lateral undulations, especially of the tail...
    • a dorsal, hollow nerve cord, derived from dorsal ectoderm and which develops into the brain, spinal cord, nerves
    • pharyngeal slits, which originally were an adaptation that made filter-feeding more effective and secondarily became useful as well as structures for effective gas exchange
    • a postanal tail, highly significant in locomotion...
    • metameric segmentation (but merely convergent with that seen in annelids, arthropods); see fig. 30.4 for examples

    There are three subphyla, two of which are entirely marine and never develop a bony vertebral column.

    1. Subphylum Urochordata - tunicates (30.2); most sessile, attached as adults (30.2a, b); have a free-swimming larva (30.2c). Adults are the ultimate filter-feeders.... The larva is considered by some to represent a living version of a creature that may have been ancestral to cephalochordates & vertebrates through paedogenesis (sexual maturity as an immature form; sometimes carelessly called neoteny, which correctly refers to retention of some immature features by an adult. Examples...)

    2. Subphylum Cephalochordata - lancets (30.1, 30.3); burrow near the surface of marine sediments, sands; filterfeeders; typify the primitive chordate plan even as adults; molecular evidence suggests that lancets are the closests relatives of vertebrates. [exclusively marine].

    3. Subphylum Vertebrata - fish, amphibians, reptiles, birds, and mammals; more than 40,000 spp (most of them fish ... ) In addition to the basic chordate features, vertebrates are distinguished by - :
    • presence of a bony endoskeleton, organized into axial (cranium, ribs, vertebral column) and appendicular (limbs, limb girdles) portions; replaces notochord; bone is secondarily lost in living jawless fishes, cartilaginous fishes; improved locomotor ability, greater body size, more effective foraging, etc.
    • well-developed cephalization and highly developed nervous system; complex neuromotor, sensory, learning abilities
    • well-developed endocrine system; esp. important in control of long-term events...
    • well-developed blood vascular, gas exchange, and excretory systems, high level of activity in foraging, etc.

    Classification of vertebrates: done in several ways; text uses a "traditional" approach, recognizing one extinct class (*Placodermi - ancient jaws fishes) and 7 classes with living representatives:

    1. Agnatha;
    2. Chondrichthyes, &
    3. Osteichthyes, collectively called fishes (Pisces);

      and

    4. Amphibia,
    5. Reptilia,
    6. Aves, &
    7. Mammalia, collectively called tetrapods (Tetrapoda).

    Significant adaptive breakthroughs are associated with each of these groups, although not all living species may show them.

    Major breakthroughs (which are cumulative as shown here) and the group in which they first appear include:

  • jaws: first appear in *Placodermi, or perhaps in a group of archaic bony fish, the *Acanthodii. (The relationship between these two groups is controversial.)
  • two pairs of lateral appendages supported by endoskeletal structures: Osteichthyes, specifically a group known as the Sarcopterygii (lobe-finned fishes), ancestral to Amphibia
  • lungs (or their homologues): Osteichthyes (or perhaps in the placoderms.) The swim bladder seen in many more highly derived bony fish is a modification of the ancestral lung.
  • lateral appendages with elbow & wrist, knee & ankle joints: Amphibia. Made possible effective movement on land...
  • amniotic egg: Reptilia. Amnion made it possible to lay eggs out of water, since the amnion enclosed the "ancestral pond" as well as the developing individual.
  • endothermy: probably Reptilia. Ability to regulate body temperature metabolically made it possible to live and remain active in thermally hostile environments....
  • feathers (Aves) and hair (Mammalia): make endothermy somewhat less expensive....
  • vivipary (giving birth to young): has appeared, perhaps independently, in all vertebrate classes except for Agnatha and Aves. Nearly universal in mammals, not uncommon in reptiles, the rule in sharks and their relatives.... Improved matemal care, opportunity to train young, etc.
  • other important adaptations, neither unanimous nor unique, include indirect & direct development, internal fertilization.

    • See Figure 30.6 for relationships and adaptive breakthroughs among the vertebrates. Consult this figure often!

    Some notes on the classes of vertebrates:

    Class Agnatha - *ostracoderms, lampreys, hagfishes. Jawless; lampreys & hagfishes have soft cartilaginous skeletons, lack lateral appendages; median fins present. *Ostracoderms, the first vertebrates, had bony skeletons; appeared ~ 510 mya, probably in marine water. Lampreys parasitic, anadromous; hagfishes saprozoic, marine. Many pr gill pouches. Oviparous.

    *Class Placodermi - archaic jawed (gnathostomous) fishes with at least some bone in their skeletons. One pair pectoral, I pr pelvic appendages + median fins. Mostly marine. Important during Devonian; rapidly replaced by chondrichthyans at end of Devonian. Relationship to bony & cartilaginous fishes unclear.

    Class Chondrichthyes - cartilaginous fishes [sharks, skates, rays (the elasmobranchs) and ratfishes]. Gnathostomous, with 1 pr each of pectoral & pelvic appendages, + median fins. Skeleton never bony. Teeth not fused to jaws, replaced serially. No lungs or swim bladder. Usually 5 pr gill slits. Fertilization usually internal; ovoviviparous. Isoosmotic with sea water by retention of urea, trimethylamine oxide. Mostly marine.

    Class Osteichthyes - bony fishes (all have at least some bone in their skeleton.) Gnathostomous, typically with 2 pr lateral fins + median fins (many exceptions). Groups: *Acanthodii (ancestral to other bony fishes?); Sarcopterygii [lungfishes & lobe-finned fishes (ancestral to amphibians)]; & Actinopterygii (ray-finned fishes; most living bony fishes). Gills beneath an operculum. Lungs (primitive) or swim bladder (derived) usually present. Most oviparous. Represented any place that will support a fish!

    Class Amphibia - frogs, salamanders, apodans; ~4600 extant spp. Gnathostomous; usually 2 pr limbs, each with 2 flexures (elbow/wrist, knee/ankle - the tetrapod limb); adults lack median fins on body. Ectothermic. Epidermis highly permeable to water. Usually with I pr lungs (lacking in plethodontid salamanders); retention of gills considered a persistent larval characteristic. Most are oviparous; usually a larval stage. Note paedogenesis. N-waste ammonia in larvae, urea in adults.

    Class Reptilia - crocs., turtles, snakes, lizards (& more.... -6000 living spp. Gnathostomous; usually 2 pr limbs (except snakes) of tetrapod design. Living forms ectothermic. Thick, comified epidermis resists movement of water. All respire with lungs, never gills or external surface. Amniote egg! Most oviparous; many in cool environments ovoviviparous or truly viviparous. Incl. ancestors of birds, mammals. N-waste uric acid

    Class Aves - birds. At least 10,,OOO spp (20K?) Gnathostomous; 2 pr limbs, pectoral pr usually modified as wings. Endothermic; feathers present, -> insulation & more. Epidermis comifted, - resistant to water loss. Respire by lungs; air sacs important in ventilation. Amniote egg. All oviparous (body temp. too high?). Living forms toothless. N-waste is uric acid.

    Class Mammalia - mammals; - 5000 spp. Gnathostomous; 2 pr limbs (except whales, sirenians). Endothermic; hair present, usually abundant. Epidermis thick, comified. Respire by lungs; muscular diaphragm aids ventilation. Amniote. All but duckbill & echidnas are viviparous; either yolk-sac placenta (marsupials) or chorio-allantoic placenta. Young fed milk. N-waste is urea.

    Links: Campbell's On-line
    (http://heg-school.awl.com/bc/bio/index.html)

    This site provides quizes, biology related sites, etc.

    Other links later. Hopefully answer keys to prior finals by Forbes. Dr. Calvin: Dr. Calvin's web site
    (http://www-adm.pdx.edu/user/bio/calvin/course/win98/bi252/bi252.htm)

    (Higher directories and ASCII versions: http://www.navi.net/~rsc/biol252/)