The Diversity of Life

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The Diversity of Life

• Classification, Viruses, Prokaryotes, Protists
  and Fungi
• Magnet Parts of Chapters 20-23
• Honors Parts of Chapters 17 -20

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Classification of organisms

• Taxonomy-Discipline of Bio that deals with
  identifying, naming, classifying, organisms
• Aristotle- Grouped organisms as plants or animals
  Grouped animals based on habitat plants based on
  structure (morphology). Believed species were
  fixed
• Linnaeus-Father of taxonomy. Classified species
  based on natural relationships ( behavior,
  structure and habitat)
• Systematics is a broader science that deals with
  taxonomy and evolutionary history
• Binomial nomenclature-2 word Latin name
• Taxons Domain, Kingdom, Phylum, Class, Order,
  Family, Genus, species
• Species-group of organisms that are able to
  produce viable offspring
• Phyla in plants are called divisions
• Dichotomous keys

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How are relationships determined?

• Evolutionary history (phylogeny). Cladistics-
  classifies organisms according to the order they
  diverged from a common ancestor. See cladograms
  (phylogenic trees)- p. 354 (Mag) and p. 497
  (Hon). Sequence orders of organisms based on
  derived characters that evolved with respect to a
  common outgroup
• Development and Behavior
• Biochem (Nucleic acids and amino acids) and
  Genetics
• HW- What is a molecular clock?

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Traditional (old)5 Kingdom System

• Older classification system (before domains)
  Kingdoms Monera, Protista, Fungi. Plantae,
  Animalia
• But now we have added domains.Monerans are now
  divided into 2 domains-Archeae and Bacteria. 3rd
  domain is Eukarya. According to the cladogram on
  p. 354 (Mag) and 497 (Hon)
• , which 2 domains are more closely related?
• Some classification systems are now dividing K.
  Protista into 3 kingdoms

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Evidence for the 3 domain system

• Distinct differences in the rRNA sequence between
  2 groups of prokaryotes
• DNA sequencing data
• Membrane structure
• Cell wall structure bacteria cell wall is made
  of peptidoglycan. Archaea have proteins in their
  walls similar to the ones found in our membranes
• STUDY TABLE 20.3! (Mag)

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Viruses

• Made of protein coat (capsid) and nucleic acid
• 5-300 nm (nm is a billionth of a meter)
• Why arent they considered living?
• No cure. Some can be prevented by vaccination
• Ex- influenza, cold, measles, mumps, HIV,
  hepatitis, chicken pox, herpes

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Reproduction

• Intracellular parasites
• Virus attaches to host cell using their coats
  proteins and the hosts cell membrane receptors.
  Viral genome then enters host cell
• Viruses can be made of DNA or RNA---HIV is a
  retrovirus made of RNA
• Lytic cycle(active-lysis) vs. Lysogenic
  (inactive-virus hidden as prophage). HW-What is a
  prion? Give an example

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Bacteria

• SHAPES- See Book
• Cocci-spheres
• Spirillum (spirochete)-spiral (helical)
• Bacillum-rod-shaped

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Typical bacterial cell

• Know structure p. 63 (Mag) and p 518 (Hon)
• Unicellular
• Prokaryotic
• Large circular chromosome plasmids in nucleiod
  region
• Cell walls (peptidoglycan) Many secrete sticky
  substance that forms capsule outside wall. Both
  surround DNA.
• Usually 1-10 um long
• Cell wall prevents osmotic rupture. Penicillin
  breaks down cell wall and allows rupture

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Bacteria continued

• Some use O2others are anaerobes (may be obligate
  or facultative)
• Some are flagellated
• Fimbriae (once called nonsexual pili)- help
  bacteria to adhere to surfaces.
• Pili (sexual)--used for conjugation
• Reproduce asexually by binary fission
• Endospore- resistant structure with a thick,
  protective coat protecting a bacterium inside.
  Can survive for years before rehydrating.
• MAG Some bacteria have an additional outer
  coat containing lipid. Those that have it are
  not able to absorb a dye called a gram stain
  and are called gram -. Those without it (gram )
  can absorb it and appear purple. Technique is
  often used in (medical) labs to differentiate
  types and narrow down possible diseases .

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Prokaryotes are the foundation of life on earth

• Decompose dead organisms
• Decomposers, saprobes, saprophytes
• Perform nitrogen fixation
• Live in our digestive system and are also used in
  the food industry
• Cheese, yogurt, etc
• Used to decompose waste in sewage
• Disesase causing bacteria Usually produce
  toxins. Ex- bacteria that causes botulism
  (paralyzes nerve cells)

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Some Prokaryotes Cause Disease

• Bacterial Examples cholera, diptheria, leprosy,
  Lyme disease, meningitis, the plague, pneumonia,
  sphylisis, tetanus, tuberculosis, strep throat.
  See book
• Antibiotics are the most effective means of
  fighting bacterial infections
• No known Archaea cause disease

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Major Groups of Archaea

• Extremophiles-3 types
• Methanogens- are poisoned by oxygenuse CO2 as
  the electron acceptor in respiration produces
  methane as a waste product
• Halophiles- lives in very saline places
• Thermophiles (aka hyperthermophiles)

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Archaea

• Used to be grouped with bacteria and called
  monerans
• Now believed eukaryotes split from archaeal
  line of descent
• Archaea and Eukarya share some of the same
  ribosomal proteins and similar tRNA
• Archaea have unusual lipids in membrane that
  allow them to live under extreme conditions
• Cell walls composed of polysacc and some only are
  entirely protein. A few recently discovered
  have no wall (not on test, just FYI)

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The Origin of the Eukaryotic Cell

• Eukaryotic cells arose through a combination of 2
  processes
• -membrane infolding- produced all the
  membrane-bound organelles except the
  mitochondrion and the choloroplasts.
• Endosymbiosis-Mitochondria and chloroplasts
  believed to once be prokaryotic cells that were
  ingested or absorbed by eukaryotic cell.

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Kingdom Protista

• Domain Eukarya
• Very diverse group of organisms
• Most are unicellular
• The most elaborate cells of all the kingdoms
• Most are aerobic use mitochondria for
  respiration
• Some are autotrophs, some are heterotrophs
• 3 types ingestive, absorptive, photosynthetic.

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Kingdom Protista

• Motility flagella, cilia, pseudopodia
• Some reproduce sexually, some reproduce asexually
• - the haploid stage is the main vegetative stage
  of most protists only the zygote is diploid.
  Zygotes undergo meiosis and become haploid (see
  life cycle in book)
• Can form cysts that survive harsh conditions
• Most are aquatic (plankton). What adaptation
  prevents them from lysing in water?

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Protozoa animal-like protists

• Heterotrophic and ingestive Grouped by their
  means of locomotion (only know these)
• 1-ciliophorans (P. Ciliophora) move with
  _______
• examples include Paramecium Stentor
  Blepharisma
• paramecium have a macronucleus (for everyday
  metabolism) and micronucleus (reproduction)
• 2 -zooflagellates (P. Zoomastigophora) move
  with ________
• examples include Giardia, Trypanasoma
• 3 -sarcondines (some texts P. Sarcodina
  others P. Rhizopoda) move with _______
• examples include amoeba
• 4 -sporozoans (P. Apicomplexa/ P. Sporozoa)
  don't move parasitic Plasmodium

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Algae the plant-like protists

• Autotrophic
• Classified by the pigments they contain
• All of the algae contain chlorophyll
  (photosynthetic), but some contain different
  types of chlorophyll and accessory pigments,
  causing them to appear other colors than green.

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The Plant-Like Protists

• P. Chlorophyta green algae
  -Chlamydomonas, Volvox, some seaweeds, sea
  lettuce
• P. Chrysophyta golden-brown algae -Ex Diatoms!
  Contain silica (some books are classifying this
  differently now, but I am still going with this)
• P. Euglenophyta Ex Euglena (are
  photosynthetic, but can ingest if too deep in
  water to get light)
• P. Dinoflagellata/ P. Pyrrophyta -
  -dinoflagellates
  cause red tide (toxic to fish)

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More Plant-Like Protists

• P. Phaeophyta the brown algae
  -include the largest seaweeds, the kelps
  (multicellular)
• P. Rhodophyta the red algae
  -include the red seaweeds, some encrusted
  and common in coral reefs

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The Fungus Like Protists

• Unicellular, heterotrophic, absorbative (usually
  feed on decaying matter)
• Cell walls mainly made of cellulose (like
  plants). No chitin, which is found in true
  fungal walls
• Most known as slime molds or water molds
• When food is not plentiful, they produce spore
  producing structures (sporangia) and the wind
  disperses the spores
• Ex- slime molds

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Lichens

• Look similar to some species of moss, but are
  not!
• Lichens are symbiotic associations between a
  fungus (often an ascomycete) and green algae or
  cyanobacteria
• The fungus usually give lichens shelter
  (optimal environment) which gives rise to their
  shape
• Alga provides the fungus with food
• Fungus provides a suitable physical environment
  for growth

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What is a fungus?

• Heterotrophic
• Most are muticellular
• Nonphotosynthetic
• Digest food outside bodies (using enzymes) and
  absorb it
• some are saprophytes-live off of dead organic
  matter)
• Cell walls made of chitin.

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Structure and Function of Multicellular Fungi

• Composed of tiny filaments called hyphae
• Hyphae are long strings of cells. Mass called
  mycelium. Some species can grow a km of
  hyphae/day!
• Can reproduce asexually by releasing haploid
  spores
• Unicellular fungi-yeast
• Multicellular ex mushrooms, molds

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Life cycle

• See supplement for life cycle of mushroom
• Stages of a mushroom (Basidiomycetes)
• Dikaryotic (contains 2 haploid nuclei/cell)
• Diploid- Haploid nuclei fuse in fruiting body of
  mushroom forming diploid zygote
• Haploid-Zygote undergoes meiosis and forms
  haploid spores. Spores then germinate and fuse.

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Classification

• Phyla
• Zygomycota- Common mold(ex-Rhizopus). Reproduce
  by conjugation
• Ascomycota- Sac fungi Contain ascus which are
  sac like structures that contain spores.
  Ex-Yeast, mildew
• Basidiomycota-Have fruiting bodies (ex-mushrooms
  cap). Contain basidium which are spore bearing
  repro. structures on the gills of the mushroom
  caps
• Deuteromycota Imperfect fungi. Sexual repro.
  has not been observed. Ex Penicillium,
  ringworm, athletes foot

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Zygomycota
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Ascomycota
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Basidiomycota
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Deutermycota
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Mycorrhizae (fungus roots)

• Mutualistic associations of plant roots and fungi
• Almost all vascular plants have mychorrhizae

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Ecological Impacts of Fungi

• Decomposers! Important nutrient recyclers
• Some are pathogens, such as ringworm and athletes
  foot.Plant pathogens--Dutch elm disease, Chestnut
  blight
• some produce deadly toxins-ex-some species of
  mushrooms
• we use them for their antibiotics-penicillium.
  Produce enzymes that rupture bacterial cell walls