Biology 123 SI- Dr. Raut’s Class
Session 22- 4/20/2015
1. What were the four main stages in the production of early life?
1. The abiotic synthesis of small organic molecules (like amino acids or nitrogenous bases).
2. The formation of macromolecules from smaller molecules.
3. These macromolecules were packaged into droplets of membrane that had an inside chemical
environment that was different than the surroundings called protocells.
4. The origin of self-replicating molecules that eventually made inheritance possible.
2. What are the three eons and the three eras in the geologic record? What happened at the end of
the eras?
Eons: Archaean, Proterozoic, Phanerozoic
Eras (all inside of the Phanerozoic Eon): Paleozoic, Mesozoic, Cenozoic
At the end of the eras there were mass extinctions, except for the Cenozoic era which goes until
present day. Fingers crossed about that one.
3. What happened in each of the following periods?
Cambrian: sudden increase in diversity of many animal phyla (Cambrian explosion)
Denovian: Diversification of bony fishes; first tetrapods and insects appear
Caroniferous: Extensive foress of vascular plants form; first seed plants appear; origin of
reptiles; amphibians dominant
Premian: Radiation of reptiles; origin of most present-day groups of insects; extinction of many
marine and terrestrial organisms at the end of the period (end of the Paleozoic Era)
Triassic: Cone-bearing plants (gymnosperms) dominate landscape; dinosaurs evolve and radiate;
origin of mammals
Jurassic: Gymnosperms continue as dominant plants; dinosaurs abundant and diverse
Cretaceous: Flowering plants (angiosperms) appear and diversify; many groups of organisms,
including most dinosaurs, become extinct at the end of the period (end of the Mesozoic Era)
4. What is adaptive radiation?
Periods of evolutionary change in which groups of organisms forma many new species whose
adaptations allow them to fill different ecological roles, or niches, in their communities.
5. What are heterochrony, paedomorphosis, and homeotic genes?
Heterochrony- a change in the rate or timing of development. Ex: chimp skull vs. human skull
Paedomorphosis- the retention of juvenile characteristics. The sexually mature stage of a species
will retain characteristics that were juvenile structures to the ancestral species.
Homeotic genes- master regulatory genes that control the placement of different body parts. Hox
genes are a class of homeotic genes that are particularly vital to the embryo.
6. What is the order of classification from the most inclusive to least inclusive?
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
7. What are the three different shapes of bacteria?
Rod-shaped, spherical, spiral
8. What is the difference in gram negative and gram positive bacteria?
Gram positive bacteria contain a very thick layer of peptidoglycan in their cell wall.
Gram negative bacteria contain a much smaller layer of peptidoglycan with an extra outer
membrane on the outside of the peptidoglycan.
9. Contrast fimbriae, flagella, and a pili.
Fimbrae-small extensions that help the bacteria stick to its surroundings or other organisms.
Pili-an appendage that pulls two cells together prior to DNA transfer from one cell to another
Flagella- long whip-like appendage that has motility functionality
10. Describe briefly how some prokaryotes can be aerobic or photosynthetic.
Aerobic prokaryotes have respiratory membranes that are formed from the plasma membrane
which can function in aerobic respiration like the cristae of the mitochondria.
Photosynthetic prokaryotes have thylakoid membranes that are formed from the plasma
membrane and function much like the thylakoid membranes in chloroplasts.
11. What are plasmids?
A small ring of independently replicating DNA that is separate from the genome found in the
nucleoid region. They typically only carry a few genes, but they are very important to the
bacteria for antibiotic resistance.
12. What does a bacteria do when it is unfavorable environmental conditions?
The bacteria will form an endospore. The genome will be copied and surrounded with a tough
multilayered structure, forming the endospore. Water is removed and metabolic processes cease.
The original cell lyses, releasing the endospore in the process.