Bio II Midterm Essay examples

Submitted By nhinguy727
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Phylogeny and Evolution
Evolution – change in one more heritable characteristics of a population from one generation to the next….random mutation at genetic level
Phylogenetic tree – diagram that shows the hypothesized evolutionary relationships among species.
Monophyletic = clade
Polyphyletic – ancestors missing and species from different lineages grouped
i.e. group and skip
Paraphyletic – taxa constructed with descendants missing
Taxonomy – science of describing, naming, and classifying
Domain, (supergroup), kingdom, phylum, class, order, family, genus, and species.
Create taxonomy based on clades***
Divergent evolution – accumulation of differences between groups which lead to the formation of new species
Homology – similarity among various species because derived from common ancestor
Convergent evolution – two different species have similar characteristics because they occupy similar environment. (homoplasy)
Observation, hypothesis, prediction, experiment, conclusion
Microscopy and Prokaryotes
Two kinds of microscopes: electron or light
Two types of light microscopes
Dissecting (aka stereomicroscope) – lower magnification
More than one illumination source
Compound – small organisms at higher magnification
Two different lens system
Two types of electron microscopes – uses beam of electrons; do not permit viewing of live organisms
Scanning (surface) and transmission (cross-sections)
Total mag. = mag. of objective x ocular lens
Higher the magnification, the more light you will need
Archaea and Bacteria = prokaryotes
Archaea are extremophiles
Cell walls of bacteria = peptidoglycan
Gram negative = think pepti. layer; outer membrane
Gram positive = think peti. layer; no outer membrane
Protists, fungi, and plants = eukaryotes
Gram Stain Procedure: (differential stain – relies on differences in cell wall composition)
Inoculate plate and heat fix (no water)
Add Crystal violet; then rinse with DI water
Add Iodine (help fprce the crystal violet past the thick peptidoglycan layer); then rinse with DI water
Decolorize; then rinse with DI water
Counterstain (Safranin – will turn pink of gram negative); then rinse with DI water
Dry with bibulous paper… visualize with oil immersion
4 forms (directly above), 5 elevations (horizontal/from side), 5 margins (exterior)
Cyanobacteria – major group of bacteria; divides like a prokaryote; exist mostly as colonies and filaments; photosynthetic (contain chlorphyll a – green, phycocyanin - blue, and phycoerythin – red); not classified as eukaryotes because they do not have a nucleus or internal membrane system
Surrounded by a nucilaginous sheath – gelatinous capsules
Vegetative cells – any cell not participating in reproduction (chain beside heterocyst) they are cells that carry our photosynthesis
Heterocysts – ability to fix nitrogen (circular) nitrogen assimilated into organic compounds – not green because do not perform photosynthesis…oxygen kills the nitrogen fixing enzyme akinetes – thick walled dormant cells specialized for survival
Anabena – (chainlike – think of pear necklace) has heterocysts
Oscillatoria – (long, green rodlike noodles) no heterocysts
Merismopedia – (look like square colonies, paired cells)
Gram positive – B. subtilis and S. epidermidis
Gram negative – S. marcescens
Introduction to Eukaryotes: Protists
Protists – all eukaryotes NOT animal, plant, or fungi
Not monophyletic; they are paraphyletic
Total 7 supergroups
Supergroup Excavata  feeding groove
Include euglenoids – freshwater flagellates
Saprophytic – absorb organic nutrients directly from the medium
Phagocytosis – ingest food particles
Flexibility due to pellicle….weird green leaflike structure with flagellum…tadpole looking
Stigma – colored eyespot
Secondary endosymbiosis – when host cell in primary endosymbiosis is itself engulfed by another cell
Supergroup Trypanosoma  parasite occurs in blood (eel)
Erythrocytes – red blood cells
Leukocytes – white blood cells undulating membrane – composed of flagella and body…