Unit 5: Exploring Diversity

Microorganisms

Kingdoms of Life

Reminders: Living organisms are divided into domains/kingdoms according to

their characteristics…….such as:

cell type (prokaryotic or eukaryotic)

cell construction (Ex: presence and kind of cell wall)

body type (Ex: unicellular or multicellular)

nutrition (autotrophic or heterotrophic)

Table 26.2 (page 514) lists the categories and their characteristics.

Microorganisms

Microorganisms have a tremendous impact on:(a) ecology of Earth (as decomposers and recyclers)(b) health of other organisms (some can be pathogens)(c) occupational areas

Ex: yeast in brewing and bakingbacterial plasmids in biotechnology

Included in the study of this unit:virusesbacteriaprotistsfungi

Viruses Viruses are not cellular, do not carry on all life processes, and therefore

are not considered to be living organisms.

Significance: may be virulent (disease-causing)

See Table 27-1, p. 527

may be used in genetic engineering

virus - a strand of nucleic acid (DNA or RNA) encased in a protein coat (capsid) that can infect cells and replicate within them

** Many viruses also have an envelope (helps them enter a cell)

Early work: Edward Jenner (smallpox), Louis Pasteur (rabies),

Dimitri Iwanowski and Martinus Beijerinck (tobacco mosaic)

Wendell Stanley (purified TMV in 1935)

Appearance: usually rodlike (helical) or spherical (polyhedral)

Size: 20 nm - 250 nm (nm = 1 X 10-9 m)

Classified as: DNA viruses, RNA viruses, or retroviruses

Attack on a cell:

(1) Entry into a cell can vary:bacteriophages inject their DNA like a hypodermic needleplant viruses enter through rips in the plant’s cell wallsanimal viruses enter by endocytosis

(2) Viral genetic material then(a) takes control of the invaded cell (lytic cycle) or (b) inserts itself into the cell’s chromosome (lysogenic cycle).

Mammals can fight viruses with immune chemicals called antibodies, but viruses are not treatable with medicines called antibiotics.

Prokaryotes Prokaryotes are cellular and therefore are living organisms. Significance: oldest, simplest, and most abundant form of life

important for ecology (photosynthesis, recycling, symbiotic relationships, nitrogen fixing, and bioremediation)can cause disease by either: (a) destroying cells or (b) producing toxins

May be treated with antibiotics (Ex: penicillin) Classification into two groups: Archaea and Bacteria (or

Eubacteria) Basic cell shapes: bacillus (rod-shaped)

coccus (spherical)spirillum (spiral or helical)

*** Gram stain can be used to help identify bacteria and then also help with the choice of antibiotics.

Size: about 1 micron (micron = 0.000001 m)

Three basic shapes:

Gram staining:

Structure of bacteria: See Fig. 28.3 (p. 542)

basic structures: cell wallplasma membranecytoplasm containing ribosomesDNA chromosome (circular) in a

nucleoid some also have: gelatinous capsule

flagella for movementpili for attaching to surfacesplasmids - extra pieces of DNA

Reproduction - by binary fission (asexual)… but can exchange DNA Ex: conjugation

Some bacteria form resistant endospores for survival.Ex: Clostridium botulinum (cause of botulism) and tetanus

Nutrition (how they obtain food) is varied but most are heterotrophs. Respiration: some are anaerobic, some aerobic, and some both Examples: E. coli, M. tuberculosis, and other pathogens (p. 555)*** Current concern: increase in antibiotic-resistant bacteria

Protists

*** Kingdom Protista is a very diverse collection of organisms. General characteristics:

• eukaryotic• mostly unicellular; some multicellular• autotrophic, heterotrophic, or both• reproduce asexually; some also sexually (especially during

environmental stress)• lack specialized structures• tend to live in moist environments• can be: free-living or

parasitic (such as Plasmodium, which causes malaria)• many have ways to monitor and respond to the environment

(ex: eyespots)

Examples of protists Ameba

Examples of protists Euglena

Examples of protists Paramecium

Examples of protists Algae

Fungi General characteristics:

• eukaryotic• mostly multicellular; some unicellular• cell walls made of chitin• usually filamentous bodies (filaments call hyphae)• external heterotrophs; principal decomposers• exhibit nuclear mitosis• reproduce sexually or asexually

Examples:• Amanita muscaria - mushroom (p. 604)• Penicillium and Aspergillus (p. 613)• Rhizopus stolonifer (black bread mold) (p. 609)• yeasts ex: Saccharomyces cerevisiae (p. 611)

Candida - cause of thrush• pathogens that cause athlete’s foot and ringworm

Fungi examples:

Structure and functions of fungi: Structure:

hyphae - the filaments of a fungusmycelium - tangled mass of hyphae *** large surface area, therefore good

absorption of food

septa - dividing walls in a hypha Nutrition: All fungi digest food outside their bodies

(external digestion).

*** Important decomposers*** Can compete for our food

Reproduction in fungi: Reproduction: release of spores (either sexual or asexual)

sporangia zygospore

Classification is partially based on the method of sexual reproduction.

Rhizopus life cycle:

Impact of fungi in ecosystems:

Fungi form symbiotic relationships with other organisms:

mycorrhizae = fungus + plant roots lichen = fungus + photosynthetic partner

(ex: green alga)

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