Transcript The Diversity of Life

The Diversity of Life
Classification, Viruses, Prokaryotes,
Protists and Fungi
Magnet: Parts of Chapters 20-23
Honors: Parts of Chapters 17 -20
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
How are relationships determined?
• Evolutionary history (phylogeny). Cladisticsclassifies organisms according to the order they
diverged from a common ancestor. See
cladograms (phylogenic trees)- p. 354. Sequences
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?
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
• , which 2 domains are more closely related?
• Some classification systems are now dividing K.
Protista into 3 kingdoms
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!!!!!!!!
Viruses
• Made of protein coat (capsid) and nucleic
acid
• 5-300 nm (nm is a billionth of a meter)
• Why aren’t they considered “living”?
• No “cure”. Some can be prevented by
vaccination
• Ex- influenza, cold, measles, mumps, HIV,
hepatitis, chicken pox, herpes
Reproduction
• Intracellular parasites
• Virus attaches to host cell using their coat’s
proteins and the host’s 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 (inactivevirus hidden as prophage). HW-What is a prion?
Give an example
Bacteria
SHAPES
• Cocci-spheres
• Spirillum (spirochete)-spiral (helical)
• Bacillum-rod-shaped
Typical bacterial cell
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Know structure p. 63
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
Bacteria continued
• Some use O2—others 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. P. 369
• 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 .
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)
Some Prokaryotes Cause Disease
• Bacterial Examples: cholera, diptheria,
leprosy, Lyme disease, meningitis, the
plague, pneumonia, sphylisis, tetanus,
tuberculosis, strep throat. See p. 375
• Antibiotics are the most effective means of
fighting bacterial infections
• **No known Archaea cause disease
Major Groups of Archaea
• Extremophiles-3 types
• Methanogens- are poisoned by oxygen;use
CO2 as the electron acceptor in respiration;
produces methane as a waste product
• Halophiles- lives in very saline places
• Thermophiles (aka hyperthermophiles)
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)
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.
Kingdom Protista
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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.
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?
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
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.
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)
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
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
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
What is a fungus?
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Heterotrophic
Most are muticellular
Nonphotosynthetic
Digest food outside bodies
(using enzymes) and
absorb it
• some are saprophyteslive off of dead organic
matter)
• Cell walls made of chitin.
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
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.
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-mushroom’s
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
Zygomycota
Ascomycota
Basidiomycota
Deutermycota
Mycorrhizae (“fungus roots”)
• Mutualistic
associations of
plant roots and
fungi
• Almost all
vascular plants
have
mychorrhizae
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