CHAPTERS 18 AND 19

Classification and the Tree of Life

SYSTEMATICS The scientific way of organizing and

naming living things Dichotomous keys are used for

identification purposesBased on physical traits

CLADOGRAMSCladograms are diagrams the depict the pattern of shared characters, either derived characters or primitive charactersPrimative: characteristic shared by all organisms in the cladogram (Vert. ColumnDerived: trait that arose in the most recent common ancestorBased on DNA, skeletal, and comparisons

CLADOGRAMS Clade: Consists of a single

common ancestor and all the groups that descended from that ancestor Organism A,B,C are all

related because they are in the same Clade

Organisms B and C are more closely related than B and A because organisms B and C share a common trait

Node: Point where two groups branch off from each other

CLADOGRAM

1. Which traits does a lizard and a salamander share?2. Which two organisms are most closely related?3. What trait does a human have that gorilla does not?

PHYLOGENY & SYSTEMATICSCarolus Linnaeus first to assign each species a two-part latinized name called binomial nomenclature (Genus species)Ex: Homo sapians

PHYLOGENY & SYSTEMATICS

Phylogenetic trees show the relationship between classification and phylogenyYear 2525 Activity

OLD WAY 5 Kingdoms – Bacteria grouped into one kingdom called Monera

NEW WAY 6 Kingdoms1. Eubacteria*2. Achaebacteria*3. Plantae4. Animalia5. Fungi6. Protista

3 Domains: Bacteria, Achaea, and Eukarya (Plantae, Animalia, Fungi, and Protista)

BACTERIA VS. ARCHAEA The first two of the 3 domain system Kingdom Bacteria (Eubacteria) Kingdom Archaeabacteria Both are unicellular and

prokaryotic

BACTERIA Bacteria are classified by

shape: Spheres are cocci –us Rods are bacilli –us Curves or spirals are spirilli

-um

EUBACTERIA• Free living or parasitic• Unicellular• As a group they exhibit

much more nutrition diversity than eukaryotes, ex: cyanobacteria

ARCHAEABACTERIA• They are the oldest life-

forms & remain the most numerous & widespread organisms

• Unicellular or multicellular

• Archaea are extremeophiles• Halophiles – salt loving• Thermophiles – hot vents• Methanogens – gassy

areas

REPRODUCTION Reproduce via binary fission or conjugation Binary Fission = form of asexual reproduction Conjugation = Transfer of genetic material by

cell to cell contact

BACTERIA

BACTERIA External Structures: Capsule - the cell wall is

covered in a sticky capsule, this slime layer helps to evade the immune system & adhere to surfaces

BACTERIA External Structures: Pili - used to stick to

their substrate, hair-like projections, & can be used for the exchange of genetic material (sex pili)

BACTERIA• External Structures:• Flagella - enable bacteria

to move, embedded in the cell membrane & cell wall

• Other forms of motility include chemotaxis, phototaxis & magnetotaxis

BACTERIA• Internal Structures:• Endospores - some

prokaryotes can withstand harsh conditions by remaining dormant, until conditions become favorable; just encloses the DNA

BACTERIA Some bacteria cause

disease, called pathogenic bacteria

They can release exotoxins or endotoxins

BACTERIA Bacteria can be used

as biological weapons Ex: anthrax

BACTERIA

• Prokaryotes help recycle chemicals, dead and decaying materials and they can help clean the environment

• Examples of bioremediation: sewage treatment facilities, oil spills & toxic mine wastes

VIRUSES Non-living particles composed of two main

parts: Nucleic Acids (DNA or RNA) Protein Coat (capsid) No membranes, cytoplasm, ribosomes or

other organelles They cannot move or grow, and can only

reproduce inside a host cell (No Kingdom affiliation)

Extremely small and only visible with advanced electron microscopes

VIRUSES Human Examples: Chickenpox Smallpox Rabies AIDS Cancers Hepatitis Influenza A, B & C

BACTERIOPHAGES Bacteriophage Virus that infects bacterial

cells Structure: Head (Capsid),

DNA, Tail & Tail Fibers

LIFE CYCLE OF A VIRUSLYTIC CYCLE LYSOGENIC CYCLE

DNA or RNA injected into host

Replication, transcription, and translation occurs

Cell bursts and new bacteriophages emerge

**Kills host cell**

DNA or RNA injected into host

Prophage is made = cell DNA + bacterial DNA

Virus can be released or remain within host cell

**Coexists within host cell**