Bacteria, Viruses and Protistans



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Bacteria, Viruses and Protistans (chap 18)


  1. Bacteria – Most ancient forms of life (Table 18.1)




    1. Great metabolic diversity (Table 18.2)

      1. Photoautotrophic – synthesize own organic compounds <> using sunlight and carbon dioxide

      2. Photoheterotrophic – use sunlight, but carbon comes from organic compounds

      3. Chemoautotrophic – produce organic compounds using carbon dioxide and energy in inorganic substances

      4. Chemoheterotrophic – cannot produce own organic compounds

        1. Parasitic – draw nutrition from living hosts <>

        2. Saprobic – obtain nutrition from products, wastes, or remains of other organisms




    1. Bacterial sizes and shapes

      1. Usually 1-10 micrometers

      2. Three basic shapes

        1. Coccus – spherical

        2. Bacillus – rod-shaped

        3. Spirillum – spiral-shaped




    1. Structural features

      1. Prokaryotic – no nucleus [or other membrane-bound organelles]

        1. Metabolism occurs in cytoplasm or at plasma membrane

        2. Proteins assembled on floating ribosomes

      2. Nearly all possess cell wall

        1. Gram-positive and gram-negative

      3. Has jellylike capsule for attachment and to deter antibiotic activity

      4. May have filamentous structures attached to cell wall

        1. Flagellum – for movement

        2. Pili – for attachment [incl. conjugation]




    1. Bacterial reproduction

      1. Binary fission – single “chromosome” (Fig. 18.5)

      2. Plasmids carry only a few genes – replicated independently of main “chromosome”




    1. Bacterial classification

      1. Traditionally characterized by staining reactions, cell shape, metabolic patterns, and mode of nutrition

      2. True classification based on evolutionary relationships becoming possible due to biochemistry studies




    1. Major groups of bacteria

      1. Archaebacteria

        1. First living cells – exist in unusual habitats

        2. Methanogens (“methane-makers”)

          1. Inhabitat swamps, mud, sewage, and animal guts

          2. Make ATP anaerobically by converting carbon dioxide and hydrogen to methane

        3. Halophiles (“salt-lovers”)

          1. Tolerate high salt environments [brackish ponds, salt lakes, volcanic vents, etc.]

          2. Most are heterotrophic aerobes

        4. Extreme thermophiles (“heat-lovers”)

          1. Live in hot springs and volcanic vents

          2. Use hydrogen sulfide for ATP formation

      2. Eubacteria

        1. Photoautotrophic eubacteria

          1. Cyanobacteria [blue-green algae] are photosynthetic <>

          2. Green and purple bacteria use hydrogen sulfide and hydrogen gas for photosynthesis

        2. Chemoautotrophic eubacteria

          1. Most important are nitrifying bacteria – nitrogen cycle

          2. Use ammonia in generating ATP

        3. Chemoheterotrophic eubacteria

          1. Some are major decomposers in soil

          1. Actinomycetes produce antibiotics, Lactobacillus used in dairy product conversions, etc.

          2. Some E. coli causes serious diarrhea, Clostridium botulinum – botulism, Borrelia burgdorferi – lyme disease




  1. Viruses




    1. Defining characteristics

      1. Noncellular infectious agent

        1. Consists of nucleic acid core (DNA or RNA) surrounded by protein coat

        2. “Reproduces” by causing host cell to make more viral particles

      2. Vertebrate immune system can detect and fight viruses, but viruses continually mutate




    1. Examples of viruses (Table 18.3)

      1. Bacteriophages – infect bacterial cells

      2. Animal [human] viruses – influenza, chickenpox, colds, HIV (AIDS)

      3. Plant viruses – usually rely on insects to provide penetration of host cells




    1. Infectious agents smaller than viruses

      1. Prions – infectious protein particles (“Mad Cow” disease) that destroys nervous system

      2. Viroids – naked pieces of RNA (no protein coat) that cause plant diseases




    1. Viral multiplication cycles (Figs. 18.12 & 18.13)

      1. Steps of viral replication

        1. Virus “recognizes” and attaches to host cell

        2. Nucleic acid core enters host cell

        3. Viral genes direct host cell to replicate new viral components

        4. Host cell ruptures releasing new viral particles

      2. Replication can proceed by two pathways

        1. Lytic pathway [see above] (Fig. 18.12)

        2. Lysogenic pathway – latent period in host (Fig. 18.13)




  1. Protistans – simplest eukaryotic organisms, unicellular and multicellular




    1. Predatory and parasitic molds

      1. Chytrids and water molds

        1. Chytrids – decomposers or parasites in muddy or aquatic habitats

        2. Water molds – attack weakened fish or land plants (e.g., Irish potato famine)

      2. Slime molds (Fig. 18.15)

        1. Heterotrophic, free-living, amoebalike protistans

        2. Feeds by engulfing food particles; reproduces by spores

        3. Two groups – cellular slime molds and plasmodial slime molds




    1. Animal-like protistans – protozoans

      1. Defining characteristics

        1. All are predators or parasites

        2. Mostly asexual reproduction by fission or budding

        3. A few cause diseases in humans <>

      2. Amoeboid protozoans (Fig. 18.17)

        1. Pseudopodia – extensions of cell body

        2. Amoeba proteus – lab animal; Entamoeba – causes dysentery

        3. Foraminiferans – shelled forms; radiolarians – shells of silica; heliozoans – needle-like pseudopods

      3. Ciliated protozoans

        1. Numerous cilia – beat in synchrony

        2. Paramecium – sexual reproduction involves conjugation (Fig. 18.18)

      4. Flagellated protozoans (Fig. 18.19)

        1. One or more whip-like entensions

        2. Tichomonas vaginalis – spread by sexual contact; Giardia lamblia – mild diarrhea to death; Trypanosoma – African sleeping sickness

      5. Sporozoans (Fig. 18.20)

        1. Parasitic – sporozoite stage usually transmitted by insects, and encysted stage

        1. Plasmodium – malaria (transmitted by mosquitoes); toxoplasmosis – can cause birth defects (transmitted from cats to humans through infected feces)




    1. (Mostly) Single-celled photosynthetic protistans

      1. Euglenoids

        1. Mostly photosynthetic autotrophs, some are heterotrophic

        2. Euglena – flexible pellicle, flagellum, eyespot

      2. Chrysophytes

        1. Golden-brown algae

        2. Diatoms – shells of silica

          1. Bottom of marine food chain

          2. Commercially valuable as abrasives and filtering materials

      3. Dinoflagellates

        1. Two flagella located in grooves in cell wall

        2. Some cause “red tides” (producing neutotoxins)




    1. (Mostly) Multicelled photosynthetic protistans

      1. Red algae (Fig. 18.23a)

        1. Pigments trap sunlight in deep marine waters

        2. Complex asexual and sexual life cycles

        3. Some aid in reef building; others yield agar

      2. Brown algae (Fig. 18.23b)

        1. Includes kelps of intertidal zones

        2. Plantlike – with leaflike blades on a stemlike stipe attached to a rootlike holdfast; some have floats

        3. Produce algin – used as a thickening or suspension <> agent

      3. Green algae (Fig. 18.24)

        1. Grow nearly everywhere

        2. Same pigments as land plants; store carbohydrates as starch

        3. Some are symbionts with fungi <> and other organisms, others are colonial (Volvox), many live singly (Chlamydomonas)

Plants and Fungi (chap 19)


  1. Evolutionary trends among plants




    1. Overview of the Plant Kingdom

      1. Mostly multicelled photosynthetic <> autotrophs

      2. Most have vascular tissues for transport of water and nutrients; and roots, stems, and leaves

      3. Nonvascular plants [e.g., bryophytes] lack true roots or leaves




    1. Evolution of roots, stems, and leaves

      1. Roots – absorption of water and minerals

      2. Shoots <> – exploiting sunlight and absorbing carbon dioxide

      3. Lignin – hard substance in cell wall allowing extensive growth <>

      4. Cuticle – covering stems and leaves to minimize water loss; evaporation <> controlled by stomata




    1. From haploid to diploid dominance (Fig. 19.2)

      1. Simple aquatic plants <> dominated by haploid phase

      2. Complex land plants dominated by diploid sporophyte

        1. Parts of sporophyte undergo meiosis to produce haploid spores

        2. Spore develops into gametophyte, which produces gametes <>




    1. Evolution of pollen and seeds

      1. Spores of some algae and simple vascular plants are all alike [homosporous]

      2. In gymnosperms and angiosperms <>, spores are of two types [heterosporous]

        1. Pollen grain = male gametophyte

        2. Female gametophyte remains within plant, producing seeds




  1. Bryophytes – mosses, liverworts, and hornworts [mosses are the most common] (Fig. 19.4)




    1. Lack xylem and phloem <>; rhizoids attach gametophyte to soil




    1. Gametophyte

      1. Developments from spore – haploid, leafy, independent plant

      2. Contains archegonium <> and antheridium <>




    1. Sporophyte

      1. Developments from zygote [fertilized egg] – diploid and dependent on gametophyte

      2. Composed of foot, stalk, and capsule [sporangium] that contains spores




  1. Existing seedless vascular plants – sporophyte is dominant; xylem and phloem are present




    1. Whisk ferns

      1. “Twiggy” looking plant – no roots or leaves [photosynthesis occurs in stem tissue]

      2. Underground rhizome; sporangia on branches




    1. Lycophytes

      1. Once tree-sized, but now small club mosses on forest floor

      2. True roots, stems, and small leaves – cone-like strobili contain sporangia




    1. Horsetails or scouring-rushes

      1. Once treelike, now common “bamboo-like” roadside plants around here

      2. Roots, rhizomes <>, aerial stems <>, but no true leaves [stem is photosynthetic]




    1. Ferns

      1. Roots, rhizomes, and big leaves [fronds – young ones called fiddleheads]

      2. Sporangia are clustered into sori on the underneath of fronds




  1. Gymnosperms – plants with “naked” seeds




    1. Life cycle (Fig. 27.10)

      1. Microspore (in “male” cone) develops into pollen grain – wind pollination

      2. Megaspore develops into ovule [immature seed] – exposed or in “female” cone




    1. Conifers

      1. Cone-bearing trees with needlelike or scalelike leaves [mostly evergreen]

      1. Male pollen cones and female seed cones

      2. Fertilization results in a zygote that develops into an embryo within the seed




    1. Lesser known gymnosperms

      1. Cycads

        1. Small palmlike trees – 100 species of the tropics and subtropics

        2. Large pollen and seeds cones on separate plants

      2. Ginkgos [or Maidenhair tree]

        1. Only one species survived the Mesozoic – living fossil

        2. Leaf fan-shaped, seed exposed

      3. Gnetophytes [e.g., Mormon tea]

        1. Found in tropical and desert areas




  1. Angiosperms – flowering plants (Figs. 19.11 and 19.12)




    1. Produce flowers with special tissues to protect ovules and seeds

      1. Most species coevolved with pollinators

      2. Dominated the land for 100 million years




    1. Monocots and dicots

      1. Monocots – grasses [inclu. cereal grains], lilies, etc. <>

      2. Dicots – trees [except conifers], shrubs, and herbaceous plants <>




    1. Life cycle

      1. The diploid sporophyte has roots and shoots, and retains and nourishes the gametophyte

      2. Flowers attract animal <> pollinators

        1. Sepals and petals

        2. Stamen – anther and filament

        3. Pistil – stigma, style, and ovary [containing ovules]

      3. Embryos nourished by endosperm within seeds, which are packaged inside fruits




  1. Fungi




    1. “Characteristics”

      1. Three major groups [zygomycetes <>, sac fungi, and club fungi] and one “catch-all” category [imperfect fungi]

      2. Nutritional modes

        1. Heterotrophs that utilize organic matter

          1. Saprobes – get nutrients from nonliving matter [valuable decomposers]

          2. Parasites – thrive on tissues in living host

        2. Digest the surrounding food and absorbs nutrients

  1. Life cycle

        1. Reproduce both asexually and sexually, producing spores

        2. Food-absorbing part is a mesh of branching filaments [the mycelium, composed of individual hyphae]




  1. Classification of fungi

      1. Zygomycetes (Fig. 19.15)

        1. Mostly bread molds

        2. Reproduces asexually by small, dustlike spores and sexually by zygospores

  1. Sac fungi (Fig. 19.16)

        1. Edible morels and truffles, plus Penicillium [antibiotics] and Aspergillus [soy sauce]; also single-celled yeasts [bread and alcohol]

        2. Larger ones produce structures with sacs that contain ascospores; yeasts mostly reproduce asexually, by budding

a. Club fungi (Fig. 19.14)

        1. Mushrooms, puffballs, shelf fungi, rusts, and smuts

        2. Produce basidiospores on club-shaped cells; mushroom has stalk and cap [with gills]

  1. Imperfect fungi

        1. All fungi lacking a sexual stage – gets moved out when sexual spore are discovered




    1. Symbiotic associations between fungi and plants

      1. Lichens

        1. Mutualistic associations between fungi and cyanobacteria or green algae

          1. Algae is protected from drying out

          2. Fungi feeds on sugars produced by the algae

        2. Can live in inhospitable places such as bare rock and tree trunks, but are sensitive to air pollution

        3. Three body forms – crustose, foliose, and fruticose

      2. Mycorrhizae

        1. Symbiotic relationship in which fungi hyphae surround roots of woody plants

        2. Increases the absorption power of the roots [water and minerals]

Animals: The Invertebrates (chap 20)


  1. General characteristics of animals




    1. Multicellular, heterotrophic, aerobic, reproduce sexually, motile at some point in life cycle




    1. Life cycles include period of embryonic development; germ tissue layers (ectoderm, mesoderm, endoderm) give rise to adult organs




    1. Diversity in body plans

      1. Vertebrates – have a backbone; invertebrates – lack a backbone

      2. Body symmetry

        1. Radial – round

        2. Bilateral – left and right sides

          1. Show anterior (head), posterior (tail), dorsal (back), and ventral (belly) orientations

      3. Cephalization – have a definite head, usually with feeding and sensory features

      4. Type of gut

        1. Saclike – with one opening

        2. Complete – with two openings (mouth and anus)

      5. Body cavities

        1. Coelom – space between gut and body wall; lined with peritoneum

        2. False coelom – such as in roundworms; not lined with peritoneum

        3. No coelom – packed solidly with tissue

      6. Segmentation – composed of repeating body units (may be grouped and modified for specialized tasks)




    1. Possible origin of animals

      1. Compartmentalization of a ciliate (like Paramecium)

      2. Arose from colonial organisms like Volvox




  1. Sponges – 8,000 species




    1. Asymmetric body with no true tissues or organs

      1. Flattened cells cover the exterior

      2. Collar cells line interior chambers – move water and trap suspended food particles

      3. Jelly-like matrix (with wandering amoeboid-like cells) between the two




    1. Reproduce asexually (by fragmentation) and sexually (zygote produces swimming ciliated larva)




  1. Cnidarians – tissues emerge (11,000 species)




    1. Tentacled, radial animals

      1. Inclu. jellyfishes, sea anemones, hydrozoans

      2. Name comes from ability to sting by discharging nematocysts




    1. Body plans

      1. Medusa – jellyfish body plan; polyp – tubelike and usually attached (may be solitary or part of a colony)

      2. Digestive cavity is saclike (only a mouth)

      3. Outer epidermis, inner gastrodermis, and jellylike mesoglea between

      4. Nerve net that coordinates sensory and motor activities




    1. Reproduce asexually, and sexually (with swimming ciliated larva)




  1. Flatworms, roundworms, rotifers – simple organ systems




    1. Flatworms – 15,000 species (Table 28.2)

      1. Body plan

        1. Saclike gut (but none in tapeworms)

        2. Bilateral symmetry, and cephalization

        3. No coelom

        4. Hermaphroditic – both sexes in one body

      2. Planarians

        1. Free-living, freshwater aquatic

        2. Possess a pharynx tube that extends to feed

        1. Flame cells – regulate body fluid volume

        2. Asexual reproduction by fission of body

      1. Flukes

        1. Internal parasites of liver, lung, or blood

        2. Complex life cycle – requires primary host for sexual reproduction, and intermediate host (usually a snail)

      2. Tapeworms (Fig. 20.14)

        1. Internal parasites of vertebrate intestines

        2. Body – scolex (head) and proglottids (segments)




    1. Roundworms – 20,000 species

      1. Most small and free-living, but some parasitic (ex., hookworms in human organs)

      2. Bilateral symmetry, complete digestive tract in a pseudocoelom, cuticle covers and protects body




    1. Rotifers – 1,800 species

      1. Microscopic, multicelled aquatic animals

      2. Complex, with a complete set of organs

E. Mollusks – 110,000 species


1. Body usually incl. head, foot, shell, mantle, gills, and radula
2. Gastropods – snails and slugs

a. "Belly footed" animals – most organs in spiraled shell

b. Torsion – 180 turn that places some organs toward the head
3. Bivalves – clams, scallops, oysters, mussels, etc.

a. Two shells for protection – formed by mantle

b. No head; foot usually specialized for burrowing

c. Water and suspended food particles are drawn in by action of cilia on the gills


4. Cephalopods – squids, cuttlefishes, octopuses, nautiluses

a. Largest of the invertebrates

b. Body modified for active predatory life-style – tentacles, beaklike jaws, and jet propulsion

c. Closed circulatory system, nervous system well developed, eyes form images, learning and memory possible


F. Annelids – segmented worms (15,000 species)
1. Annelid groups

a. Earthworms – valuable tillers of soil

b. Leeches – aquatic "blood suckers"

c. Polychaetes – marine worms (with tentacles and "gills")


2. Annelid adaptations [of the earthworm]

a. Extensive segmentation with internal partitions; fluid filled to provide a hydrostatic skeleton

b. Paired nephridia in every segment for body fluid and liquid waste control

c. Digestive system is complete; circulation is closed


G. Arthropods – 1,000,000+ species
1. Adaptations

a. Hardened exoskeleton of protein and chitin (plus calcium in some)

1) Flexible and lightweight; good barrier to water loss

2) But, must be shed periodically

b. Fewer body segments – grouped to form head, thorax, and abdomen

c. Jointed appendages for feeding, sensing, and locomotion

d. "Breathe" using tubes (trachaeas) connected to holes (spiracles) in the abdomen segments

e. Multi-faceted compound eyes allow for wide angle of vision and motion perception, but not focusing

f. Metamorphosis – larval stages concentrate on feeding and growth; adults specialize in dispersal and reproduction

1) Complete metamorphosis – egg, larva, pupa, adult

2) Incomplete metamorphosis – egg, "nymph," adult

3) Gradual metamorphosis – egg –> adult




    1. Spiders and relatives – 25,000 species

      1. Chelicerates – spiders, scorpions, ticks, mites, horseshoe crabs, sea spiders (Fig. 20.22)

        1. Spiders – eight-legged predators that trap insects in webs

        2. Mites – some free-living, others are pests of plants and animals

        3. Ticks – blood-suckers and disease carriers

      2. Body plan – chelicerae (piercing), pedipalps (grasping), open circulatory system, book lungs




    1. Crustaceans – 35,000 species

      1. Shrimps [and krills], lobsters, crayfishes, crabs, barnacles, copepods, pillbugs

      2. Important components of food webs and some serve as human food

      3. Body plan

        1. Cephalothorax and abdomen; gills in aquatic ones; ventral nerve cord (Fig. 20.24)

        2. Appendages – two pairs of antennae, a pair of mandibles and maxillae, and five pairs of legs




    1. Millipedes and centipedes – long, segmented body with many legs

      1. Millipedes

        1. Cylindrical body with two pairs of legs on each body segment

        2. Slow-moving vegetarians

      2. Centipedes

        1. Flattened body with one pair of legs on each body segment

        2. Fast-moving carnivore of small invertebrates




    1. Insects – 900,000+ species

      1. Body plan

        1. Three regions – head (sensory and feeding), thorax (locomotion – six legs, two pairs of wings), and abdomen

        2. Malpighian tubules process metabolic waste and aid in water retention

      2. Most successful of all groups




    1. Echinoderms – spiny skinned animals (6,000 species) (Fig. 20.30)

      1. Sea stars (starfish), brittle stars, sea urchins, sand dollars, sea cucumbers, sea lilies, feather stars

      2. Larvae are bilateral; adults are radially symmetrical

        1. Five-rayed body plan; spines and skin gills

        2. Tube feet (locomotion and capture of prey) connected to water vascular system

        3. Sea stars feed on bivalve mollusks – can evert stomach for exterior digestion

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