1

Diversity of Life• Origin of Lifebased on radioisotope dating

of oldest life form

(prokaryotes that formed

stromatolites), life most

likely originatedbetween 3.5 to 4 byahypothesized site:hydrothermal vents

hypothesized mechanism:selection for stable protocells

(membranous sacs that

enclosed interacting

organic molecules) which

became reproductive

Phylogeny (evolutionary tree) of life

3 major lineages:Bacteria Archaea Eukarya| |__________||________________|

|Taxonomic classification (based on phylogeny)Domain – largest grouping of relativesKingdom, Phylum, Class, Order, FamilyGenus – smallest grouping of closely relatedspecies, scientific names are made up ofgenus & species names, e.g. Homo sapiens

2

Domain Bacteria• prokaryotic microscopic organisms,

extremely diverse taxonomically &

metabolically,

maybe heterotrophs

or autotrophs

• types based on cell shape: bacilli (straight

rods), spirilla (coiled rods) & cocci (round)

Domain Bacteria• fast reproduction (cell division) by binary fission,

on average, cells divide within an hour so are

able to evolve “adaptations” rapidly

• able to transfer genes (DNA) among existing

individuals by conjugation, by taking up DNA

from environment & via viruses

3

Domain Bacteria• among heterotrophs, have intimate contact with

other organisms (including humans) as

pathogens & food spoilers (decomposers)

• but note that many more are harmless tohumans and may even be beneficial

Domain Archea• prokaryotic organisms but more related to

eukaryotes than to the other prokaryotes

(bacteria),

heterotrophs

• inhabit the most extreme environments on

earth: extreme thermophiles live invery hot places, extreme halophiles livein highly salty places & methanogensare methane-producing organisms

4

Domain EukaryaProtists are eukaryotic organisms that are animal-like (protozoans), plant-like (algae) and fungi-like (slime molds).Protozoans: single-celled organisms, heterotrophs,live in water/bodily fluid, may cause disease

Flagellated protozoansTrichomonas Giardia(sexually transmitted) (intestinal parasite)

Flagellated protozoansEuglena Trypanosoma(with light- (cause sleeping sickness)

detecting eyespots)

5

Ciliated protozoansParamecium(freshwater ciliate)

ApicomplexansPlasmodium Amoebozoans(cause malaria) Amoeba

(pseudopod for motility)

Algae photosynthetic (autotrophs), single-celled,

colonial, multicellular (filamentous, plant-like)

Brown algae Diatoms

Red algae Green algae

6

What are viruses?

Since they are noncellular reproductive entities,

viruses are not considered to be organisms and,

hence, are NOT included in the phylogeny of

life.

They need host cells to survive and reproduce so

they are all infectious agents, the ultimate

opportunistic parasites!

Domain Eukarya Kingdom Fungi• mostly multicellular eukaryotes (such as molds &mushrooms)

• but some are unicellular (yeasts)

• spore-producing heterotrophs, cells with cell wallmade of chitin

7

• obtain nutrients by extracellular digestion(release digestive enzymes outside the body,

absorb digested food from surrounding

medium), hence, allow them to specialize as

saprobes parasites(decomposers)

as mutualistic symbionts

lichens mycorrhizae

8

morphological characteristics• vegetative structures:hyphae & mycelia(mass of hyphae)

• reproductive &dispersal structures:

asexual & sexual

spores producedfrom specialized

hyphal structures

Fungal groups

• Fungi phylogenyZygomycota Ascomycota Basidiomycota

| |___________||________________|

|• Phylum Zygomycota – nonseptate hyphae,sexual spore: zygospore, e.g., Rhizopus (black

bread mold)

9

• Phylum Ascomycota –septate hyphae, form sexual

spores: ascospores, fruiting

body, most diverse, e.g.,

Saccharomyces (Baker’s

yeast), Penicillium

• Phylum Basidiomycota -septate hyphae, form sexual

spores: basidiospores,

fruiting body, e.g., Amanita

(form poisonous mushroom)