SAT II Biology Episode 1 Part 8 pdf

Crossing over exchanges whole parts—however long—of one chromosome with whole CHAPTER 5 138 Peterson’s Success: Biology E/Mn SAT II www.petersons.com... Fundamental to his idea of natura

9 In the illustration below, the strand with an (*) is the

(A) promoter

(B) Okasaki fragment

(C) template

(D) lagging strand

(E) leading strand

10 Darwin’s Natural Selection includes all of the following EXCEPT

(A) Variation can be due to mutations

(B) The difference in survivability between organisms may be due to variation

(C) Not all organisms may survive, due to competition

(D) Organisms produce more offspring than can survive

(E) Some organisms will be more fit to survive than others

EXPLANATION OF ANSWERS FOR MULTIPLE-CHOICE QUESTIONS

1 The correct answer is (B) In RNA, thymine is replaced by

uracil, so the correct choice is (B), where DNA adenine is said to bond to an RNA thymine All the other choices are incorrect, including the DNA guanine to an RNA cytosine The testmaker may depend on the student vaguely remembering that a certain base-pairing between DNA and RNA is not possible and may choose choice (C) as being correct This is not the case

2 The correct answer is (E) Guanine is not replaced in RNA It

is found in both DNA and RNA The trick here, once again, is the vague recollection of something being replaced Of course, thymine in DNA is replaced by uracil in RNA, and uracil is on the list However, the question here asks about the replacement of guanine, which does not occur The bases listed in choices (A) and (C) also are found in RNA

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3 The correct answer is (C) These recent conclusions about

mutations—recall that Darwin did not know of mutations—are all the reverse of those listed in the choices, with the exception of choice (C), the correct answer Rates, in fact, tend to be below

in populations, mutations are generally not lethal, any gene location can be affected, and they are felt to be the source of genetic variation Darwin felt over-production of offspring was the source of potential variation

4 The correct answer is (A) The complimentary strand for the

indicated DNA strand would begin at the 38 end, not at the 58 end In addition, it would also have thymine—T Finally, opposite

A would be T, and vice-versa, and opposite G would be C, also vice-versa

5 The correct answer is (B) Choices (A), (C), and (E) are all

places on the DNA that are constant and form the sides of the DNA “ladder.” The place at which the molecule differs is in the bases that form the rungs of this ladder, providing DNA with a virtually infinite number of variations Ribose, of course, refers to RNA and should not be on the list when discussing DNA

6 The correct answer is (B) tRNA, which contains 3 anti-codon

bases for every amino acid it carries, matches up opposite the mRNA codons that are also three bases long This means that the mRNA in question potentially codes for 429/3 amino acids This gives us a potential of 143 amino acids or choice (A) However, the stop sequence does not code for an amino acid, so this gives

us 142 amino acids coded for Care should be exercised when considering the start sequence While not a part of the resulting protein, that site does code for the amino acid methionine in the translation process

7 The correct answer is (B) The foundation of Griffith’s work

was that the mice that received the killed Smooth-coat strain/ Rough-coat strain mix, in fact, died This suggested that the inheritable trait of producing a lethal substance to mice could be inherited by the R-strain bacteria All the other choices are true and led to the experiment outline briefly in choice (B), but the conclusion of that experiment, once again, was that all the mice died

8 The correct answer is (A) In DNA replication, each new

strand receives half of the original DNA, a process said to be semi-conservative—it conserves only half of the original DNA for each new strand produced Crossing over and non-disjunction are macro-genetic events that occur during meiosis and pass on all of the genetic information for the event Crossing over exchanges whole parts—however long—of one chromosome with whole

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parts of a homologous chromosome Non-disjunction causes an entire chromosome to be incorrectly separated Translation and transcription pass along the entire code for a protein from RNA

to polypeptide and DNA to RNA, respectively

9 The correct answer is (E) The strand with a (*) is being

replicated from the 58 end onward and will proceed without delay The strand with the 38 end as a start—opposite the 58 end

on its compliment, the sense strand—makes this strand the anti-sense strand and is fashioned piece by piece from Okasaki fragments These fragments are bonded onto the anti-sense strand with DNA ligases The construction of the 38 strand then

proceeds slower than the construction of the 58 end and is said

to lag behind Since the strand with a (*) is the 58 end, it is not

an Okasaki fragment, nor is it a template; the sense strand is the template and a promoter is a molecule that starts the process: it

is not a DNA molecule, but a protein

10 The correct answer is (A) Darwin did not know of mutations,

so choice (A) is the correct answer Fundamental to his idea of natural selection was that, in order, (1) organisms produce more offspring than can survive and, (2) due to competition, not all organisms will survive, which means, (3) some organisms will be more fit to survive than others, and (4) variation may be the reason for the difference in survivability

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adenine

anticodon

base pairing

base substitutions

codons

complementary

cytosine

deletions

deoxyribonucleic acid (DNA)

deoxyribose

DNA polymerase

DNA replication

double helix

Down’s syndrome

duplication

exons

guanine

hydrogen bonds

insertions

introns

inversion

mRNA

mutation nitrogenous base nondisjunction nucelotides peptide bond point mutation promoters proteins protein synthesis ribonucleic acid (RNA) ribose

RNA polymerase RNA primer rRNA template thymine transcription translation translocation tRNA

uracil

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Unit III—Organizations

and Populations

Chapter 6

ORGANISMS AND POPULATIONS

OVERVIEW

This material constitutes about 30 percent of the SAT II Biology exam This part of the study of biology, then, contains the bulk of the material on the scale of entire organisms Previous chapters have dealt basically with how the organisms function mostly at the molecular level We now explore organism-level structure—and, therefore, function—and on a grander scale, the biology of the organism and how organisms as populations interact with one another and with other organisms, as well as with their environment Carolus Linnaeus is credited with organizing living things into

understandable groups based on their structures and giving them a two-part name Today, we use many characteristics, including behavior and, more recently, DNA analysis Since the earliest times, humans have attempted to understand their world, and one of the ways to start the process is to organize it The way humans have done this has changed over time This chapter is about the grouping

of organisms Some of the vocabulary at the end of the chapter will not be detailed here, but we suggest that the student know all of those terms; this holds true for all the chapters in this book

CLASSIFICATION

Taxonomy, or the science of classifying organisms, groups organisms into categories based on various characteristics

SCHEMA

Just as we find in grocery stores, the organisms are placed in specific categories Imagine trying to find an item in the store if all of the delivery vehicles dumped their goods at the front door In a like manner, grouping organisms has many benefits Imagine proposing that a predator of a parasite be introduced into the local environment

in an attempt to control the parasite population, but instead, the organism you believe to be the predator is actually a slight variation

of that predator and has no interest whatsoever in the parasite you are trying to eliminate You may now have two problems to deal with, and at the very least, you haven’t done anything to help control the parasite

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Aristotle’s classification system proposed that if something moves, it

is an animal, and if it doesn’t, it is a plant Of course, sponges were mistakenly taken for plants, and when they threatened the shellfish industry centuries ago, were “killed” by being cut up and tossed back into the sea To the surprise of the shellfish harvesters, the next year, the number of sponges had increased; the shellfishers were actually helping the sponges reproduce (asexually) by their actions

Linnaeus

Linnaeus proposed naming organisms by a two-name system that we

call binomial nomenclature These were very specific names based

on the organism’s characteristics and are the genus and species of today Note that the genus is always capitalized and the species is not, as in Terrestris americanus, and the entire name is underlined or italicized

Modern

The modern system of classification now contains five major groups

called kingdoms Life on the planet could be seen as analogous to a

grocery store The major consumer item areas, such as produce, dairy, and canned goods, would be analogous to the kingdoms of living things As with the grocery store, the sub-categories get more and more specific until it is possible to name an item exclusive of all other items in the store You should know the categories, starting with the largest (the kingdom) and continuing to narrower and narrower groups in the sequence: Kingdom, Phylum, Class, Order, Family, Genus, and Species In plants, the word “phylum” is replaced with the word “division.” Modern day study has become so detailed that we will now find such categories as sub-genus and super-species The student is responsible only for the above schema Most beginning biology students become familiar with the mnemonic—memory

device—in a variety of expressions, one being King Phillip Come Out

F or Goodness Sakes The first letter of each word, in the order given,

is the first letter of each of the major categories in taxonomy

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EXAMPLES OF GENUS AND SPECIES

Canis familiarus

domesticated dog

Felis feline

domesticated cats

Homo sapiens

modern humans

MODERN

TAXONOMY

Today, scientists generally agree on five major categories of living things, or kingdoms, although there are several classification systems Students may want to become familiar with how these categories came to be agreed upon You should recall that some of these organisms were mentioned in other chapters and at other levels The good news is that the SAT II Biology exam does not test for informa-tion as detailed as how the phylogenic categories arose A brief word about viruses seems appropriate at the beginning of a discussion on the taxonomy of living things Viruses, while not considered a living thing, can, nonetheless, take over the cell chemistry of a living thing

to reproduce We will now outline the schema of living things

PROKARYOTE (MONERAN)

Prokaryotes are single-celled, microscopic prokaryotic (see Chapter 2) cells with no distinct nucleus or other membrane-enclosed organelles

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Bacteria have cell walls composed of peptidoglycan, an amino acid–sugar complex, and circular DNA Composition of the cell wall provides us with the Gram staining means of identifying certain types

of bacteria Reproduction of bacteria was outlined in an earlier chapter Some bacteria possess flagella While many bacteria are decomposers, some fix nitrogen and other elements in a form usable

by organisms, and some are pathogenic

A Shapes

Bacteria can be found in three shapes: coccus (round-shaped), bacillus (rod-shaped)—the one the SAT II Biology exam commonly refers to when asking a question about bacteria—and spirillus (spiral-shaped)

B Types

Aerobic (oxygen-needing) bacteria are the largest group of bacteria Anaerobic (not needing oxygen) bacteria are found in two groups: those that need an oxygen-free environment (obligate) and those that

do not need a lack of oxygen, but a small amount of oxygen will not kill them (facultative)

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C Significance

Bacteria are the most populous organisms on earth—they can be useful for things like making pickles from cucumbers, or they can be lethal, as in the case of pneumococcus and several STDs

Cyanobacteria

Producer prokaryotes, their numbers can “explode” under the right conditions and are the cause of water pollution associated with algal blooms They are photosynthesizers that sometimes fix nitrogen They, in symbiotic association with fungi, form lichens

PROTISTA

Protista (also called protoctist) are single-celled eukaryotes This kingdom is a composite for organisms that do not fit in other kingdoms

Protozoan

Protozoan are classified by their mode of locomotion Amoeba and paramecium are two of the Protists about which test questions are asked The amoeba is a heterotrophic, shapeless organism that moves

by pseudopods and engulfs its food by the endocytotic method known as phagocytosis The paramecium, also a heterotroph, moves about using tiny hair-like projections known as cilia Cilia also help the paramecium in engulfing food

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Eukaryotic algae

The plant-like protists, they include green algae, brown algae, golden algae, diatoms, dinoflagellates, red algae, and the euglena The euglena, heterotrophic in the absence of light, possess chlorophyll and from one to three flagella Green algae, in association with fungi, also form lichens

Slime molds

Fungi-like protists that resemble fungi because at one point in their life cycle they come together as a unit—looking like a multicelled organism—and form spores

FUNGI

Formerly classed as plants, fungi do not possess chlorophyll—making them heterotrophs The fungi are structurally different from plants, so they have been placed in their own kingdom For example, they have

no cell membrane Some fungi are unicellular, while others are multicellular Fungi are predominantly haploid, becoming diploid for the purpose of reproduction through the production of spores

Types

Fungi are classed into three groups based on how they obtain nutrients

A Saprophytic

Live off dead organisms

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B Parasites

Live off live organisms

C Symbiotic

Work in concert with other organisms

Members

The following are the major groups of fungi covered on the SAT II Biology Exam

A Molds (the zygospore fungi)

Molds invade hosts through root-like hyphae, which they also use for reproduction Bread molds are an example of this group

B Yeast (the sac fungi that form ascospores)

Along with mildews, they are primarily unicellular but form fruiting bodies containing ascospores for reproduction This group also includes the much sought after truffle

C Mushroom (the club fungi that form basidiospores)

Multicellular fungi include the well-known mushroom

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