Biological Diversity

Taxonomy In chapter 26 you learned the most commonly used taxonomic scheme is as follows: Domain Kingdom Phylum (Division) Class Order Family Genus Species

From 5 Kingdoms to 3 Domains This new scheme represents a change from the previous 5 or 6 kingdom scheme. The old 5 kingdom scheme grouped all prokaryotes together: i.e. eubacteria and archaebacteria were grouped into the Kingdom Monera. The six kingdom scheme recognized that archaebacteria were significantly different from eubacteria and should be placed into their own kingdom.

However, neither of these schemes showed a phylogenic relationship…i.e. how did the kingdoms evolve from an ancient ancestor. The concept of 3 Domains was then developed and a phylogenic tree of life was created. This tree begins with a common ancestor.

The Common Ancestor The common ancestor was most likely a small, unicellular prokaryote. It would have had Nucleic Acid (DNA or RNA) as genetic material to code for proteins It would have had ribosomes to produce proteins It would have been surrounded by a phospholipid bilayer It would have used glycolysis as a means of extracting energy from glucose

The three domains now show that eubacteria represent one of the branches descending from the common ancestor. The second branch divides into the archaebacteria and eukaryotes This illustrates that archaebacteria are believed to be more closely related to eukaryotes than to the other prokaryotes.

Goal of Taxonomy A major goal of taxonomy is to organize taxa on the basis of phylogeny (evolutionary relationships) Systematics = study of the evolutionary relationships among organisms

Review of the Fundamental Cell Types Eukaryotic Cells Long, linear DNA molecule packaged into chromosomes by wrapping around histone proteins DNA is enclosed in the nucleus Specialized membrane-bound organelles isolate metabolic activities Flagella and cilia, when present, are made of the protein tubulin arranged in a 9 + 2 array.

Prokaryotic Cells Short, circular DNA creating a single chromosome Many contain plasmids in addition to the major chromosome No nucleus No organelles (some have various membranes that serve similar functions) Flagella, when present, consist of the globular protein flagellin

Domain Archaea Archaea (Archaebacteria) are prokaryotes that differ from other prokaryotes and from eukaryotes in the following manner: Cell walls only contain various polysaccharides, not peptidoglycans (as in bacteria), cellulose (as in plants) or chitin (as in fungi) The phospholipids of the plasma membranes differ in their chemical structure from the phospholipids of prokaryotes and eukaryotes

Archaea are similar to eukaryotes DNA of both are associated with histones (Bacteria DNA is not) Ribosome activity of both is not inhibited by antibiotics (streptomycin and chloramphenicol) Bacteria is inhibited.

Domain Bacteria Bacteria (Eubacteria): differ from archaea and eukaryotes by the following Cell walls are made of peptidoglycan (a polymer of a monosaccharide with amino acids) DNA is not associated with histone proteins Ribosome activity inhibited by streptomycin and chloramphenicol

Domain Eukarya Four Kingdoms: Protista, Fungi, Plantae, Animalia

Kingdom Protista Protists can be animal- like, plant-like or fungus- like Protists can be unicellular or multicellular Determining evolutionary relationships in this kingdom is very difficult Groupings are more morphologically based.

Plant-like (algaelike) Photosynthetic protists Euglenoids: one to three flagella, locate light for photosynthesis with an eyespot, can become heterotrophic in the absence of light. Dinoflagellates: two flagella, spin through water, many produce a nerve toxin that is poisonous to fish, shell fish and humans: cause red tides

Diatoms: have shells made of silica that fit together like box lid: many shapes Phaeophyta (brown algae) multicellular— kelp

Rhodophyta (red algae): multicellular with red accessory pigments (phycobilins) Chlorophyta (green algae): unicellular, colonial, or multicellular: probably the ancestor to plants.

Animal-like Protists (protozoa) Heterotrophic protists Rhizopoda (amoebas): move with pseudopod Foraminifera (forams): made of calcium carbonate: amoeboid protists

Apicomplexans (animal parasites): do not move on their own: must live within a host (malaria parasite) Ciliates (paramecium): move using cilia: most complex: contain two nuclei

Fungus-like Protists Either form filaments or spore-bearing bodies similar to the fungi. Cellular Slime Molds: go through different life stages: spores germinate into an amoeba stage which feeds on bacteria: fungus stage in which cells unite to form fruiting bodies that produces spores

Plamodial Slime Molds: single spreading mass called a plasmodium feeds on decaying vegetation grows from diploid cells that arise from the joining of haploid spores.

Oomycota: water molds and downy mildews: form hyphae (much like fungi): cell walls are cellulose not chitin: parasitic or saprophytic Watermold on a fish Downy mildew on a leaf

Kingdom Fungi Fungi are either parasites or saprophytes Absorb nutrients by the breakdown of products by digestive enzymes. Their bodies consist of long filaments known as hyphae (mass of hyphae = mycelium) Reproduce asexually by fragmentation, budding or producing asexual spores. Six groups are identified:

Zygomycota: form haploid zygospores that grow into new hyphae: ex: bread mold Glomeromycota: exist in a mutualistic relationship with plant roots ( mycorrhizae): plant provides carbs for the fungus; fungus increases the ability of the plant roots to absorb nutrients.

Ascomycota: produce haploid ascospores inside a structure called an ascus: Ex: Yeast, truffles Basidiomycota: produce haploid spores in a basidia Ex: Mushrooms

Deuteromycota: imperfect fungi: no sexual cycle has been determined Deuteromycota: imperfect fungi: no sexual cycle has been determined. Ex: Penicillium Lichens: mutualistic relationship between algae and fungi. Algae provides sugar (photosynthesis); fungi provides water and improves growing conditions.

Kingdom Plantae Multicellular, photosynthetic, eukaryotic organisms with cell walls made of cellulose. Dominant generation is usually diploid Six major divisions: Bryophyta (mosses, liverworts, hornworts) Lycophyta (club moss) Sphenophyta (horsetails) Pterophyta (ferns) Coniferophyta (gymnosperms) Anthophyta (angiosperms)

Kingdom Animalia Multicellular, heterotrophic, eukaryotic organisms Dominant generation is diploid Usually motile Embryonic development involves the formation of tissue layers Very diverse

Major groups of animals: Porifera (sponges) Cnidaria (jellyfish) Platyhelminthes (flatworms) Nematoda (roundworms) Annelida (segmented worms) Mollusca (mollusks: snails, clams, octopus ) Arthropoda (arthropods: crustaceans, insects) Echinodermata (starfish) Chordata (vertebrates)