Unit III Biology Study Guide – Step-by-Step Guidance

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Q1. A nucleic acid is constructed from what monomer?

Background

Topic: Macromolecules – Nucleic Acids

This question tests your understanding of the basic building blocks (monomers) that make up nucleic acids, which are essential biomolecules in all living organisms.

Key Terms:

Monomer: A small molecule that can join with others to form a polymer.
Nucleic Acid: A polymer such as DNA or RNA, made up of repeating units.

Step-by-Step Guidance

Recall that nucleic acids are large polymers found in cells, such as DNA and RNA.
Think about what smaller units (monomers) are linked together to form these polymers.
Consider the structure of DNA and RNA: what repeating unit is present in both?

Try solving on your own before revealing the answer!

Final Answer: Nucleotide

The monomer that makes up nucleic acids is the nucleotide. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base.

Q2. The 3 parts to every nucleotide include:

Background

Topic: Structure of Nucleotides

This question checks your knowledge of the components that make up a nucleotide, the building block of nucleic acids.

Key Terms:

Nucleotide: The monomer of nucleic acids.
Phosphate group, sugar, nitrogenous base: The three main components.

Step-by-Step Guidance

Recall the general structure of a nucleotide as seen in DNA or RNA diagrams.
Identify the three distinct chemical groups attached to each nucleotide.
Think about how these parts connect to form the backbone and the variable part of the molecule.

Try solving on your own before revealing the answer!

Final Answer: Phosphate group, five-carbon sugar, nitrogenous base

Every nucleotide contains a phosphate group, a five-carbon sugar (deoxyribose in DNA or ribose in RNA), and a nitrogenous base.

Q3. In DNA, there are 4 different nucleotides. The portion of a nucleotide which differs among the 4 types is what?

Background

Topic: DNA Structure

This question focuses on the structural differences between the four types of DNA nucleotides.

Key Terms:

Nitrogenous base: The part of the nucleotide that varies among the four types in DNA.
Deoxyribose sugar, phosphate group: These are constant in all DNA nucleotides.

Step-by-Step Guidance

List the four nucleotides found in DNA: adenine, thymine, cytosine, guanine.
Compare their structures to see which part is different among them.
Recall which parts of the nucleotide are the same in all four types.

Try solving on your own before revealing the answer!

Final Answer: Nitrogenous base

The nitrogenous base is the portion that differs among the four DNA nucleotides (A, T, C, G).

Q4. Explain why nucleotide bases are said to be ‘complementary’.

Background

Topic: DNA Base Pairing

This question tests your understanding of the base-pairing rules in DNA and why certain bases pair together.

Key Terms:

Complementary bases: Bases that pair specifically due to hydrogen bonding.
Base-pairing rules: Adenine pairs with thymine, cytosine pairs with guanine in DNA.

Step-by-Step Guidance

Recall the base-pairing rules for DNA: which bases pair together?
Think about the chemical interactions (hydrogen bonds) that allow these pairs to form.
Consider why these specific pairings are important for DNA structure and replication.

Try solving on your own before revealing the answer!

Final Answer: Because each base pairs with a specific partner (A with T, C with G) due to hydrogen bonding

Nucleotide bases are complementary because their structures allow only specific pairs to form stable hydrogen bonds, ensuring accurate DNA replication.

Q5. DNA is a code to generate what other type of molecule? What is a codon?

Background

Topic: Central Dogma of Molecular Biology

This question tests your understanding of how genetic information is used to produce proteins and the role of codons in this process.

Key Terms:

Protein: The type of molecule coded for by DNA.
Codon: A sequence of three nucleotides that codes for a specific amino acid.

Step-by-Step Guidance

Recall the flow of genetic information: DNA → RNA → Protein.
Think about what molecule is synthesized using the instructions in DNA.
Define what a codon is and its role in translation.

Try solving on your own before revealing the answer!

Final Answer: Protein; a codon is a sequence of three nucleotides that codes for an amino acid

DNA contains the instructions for making proteins. A codon is a triplet of nucleotides in mRNA that specifies a particular amino acid during translation.

Q6. Describe what a gene is, in relation to the human (or any species’) genome.

Background

Topic: Genes and Genomes

This question asks you to define a gene and explain its place within the entire genetic material (genome) of an organism.

Key Terms:

Gene: A segment of DNA that codes for a functional product, usually a protein.
Genome: The complete set of genetic material in an organism.

Step-by-Step Guidance

Recall the definition of a gene and what it encodes.
Think about how many genes are present in the human genome and their arrangement.
Consider the relationship between individual genes and the entire genome.

Try solving on your own before revealing the answer!

Final Answer: A gene is a segment of DNA that codes for a specific protein or functional RNA; the genome is the complete set of all genes and non-coding DNA in an organism.

Genes are the functional units within the genome, each responsible for a particular trait or function.

Q7. Explain the main differences between transcription and translation: what is each one, where do they occur in the cell and what is the end result of each?

Background

Topic: Gene Expression

This question tests your understanding of the two main steps in gene expression: transcription and translation.

Key Terms:

Transcription: The process of copying DNA into RNA.
Translation: The process of synthesizing a protein from an mRNA template.

Step-by-Step Guidance

Define transcription and state where it occurs in the cell.
Define translation and state where it occurs in the cell.
Describe the end product of each process.
Compare the two processes in terms of their roles in gene expression.

Try solving on your own before revealing the answer!

Final Answer: Transcription is the synthesis of RNA from DNA (in the nucleus); translation is the synthesis of protein from mRNA (in the cytoplasm/ribosome).

Transcription produces mRNA, while translation produces a polypeptide (protein).

Q8. How is RNA different from DNA? List 2 types of RNA.

Background

Topic: Nucleic Acid Structure and Function

This question asks you to compare the structures and functions of RNA and DNA, and to identify types of RNA.

Key Terms:

DNA: Double-stranded, contains deoxyribose, uses thymine.
RNA: Single-stranded, contains ribose, uses uracil.
Types of RNA: mRNA, tRNA, rRNA, etc.

Step-by-Step Guidance

List the structural differences between DNA and RNA (sugar, bases, strands).
Recall the main types of RNA involved in gene expression.
Think about the functions of these RNA types.

Try solving on your own before revealing the answer!

Final Answer: RNA is single-stranded, contains ribose, and uses uracil; examples include mRNA and tRNA.

RNA differs from DNA in structure and function. Two types are messenger RNA (mRNA) and transfer RNA (tRNA).

Q9. List the contributions to the development of the theory of evolution by all the historical figures that were discussed in class.

Background

Topic: History of Evolutionary Theory

This question asks you to recall the scientists and thinkers who contributed to evolutionary theory and what each contributed.

Key Terms:

Evolution: The process by which species change over time.
Historical figures: Examples include Darwin, Lamarck, Wallace, Lyell, Malthus, etc.

Step-by-Step Guidance

List the main figures discussed in your class notes or textbook.
For each figure, recall their main idea or contribution to evolutionary thought.
Organize your answer by figure, summarizing each contribution in a sentence or two.

Try solving on your own before revealing the answer!

Final Answer: Key contributors include Darwin (natural selection), Wallace (independent theory of natural selection), Lamarck (inheritance of acquired traits), Lyell (uniformitarianism), Malthus (population growth and competition).

Each figure provided important ideas that shaped the modern theory of evolution.

Q10. Describe Darwin’s hypothesis for evolution.

Background

Topic: Darwinian Evolution

This question tests your understanding of Darwin's main ideas about how evolution occurs.

Key Terms:

Natural selection: The mechanism proposed by Darwin for evolution.
Variation, competition, adaptation: Key components of Darwin's hypothesis.

Step-by-Step Guidance

Summarize the main points of Darwin's hypothesis (variation, overproduction, competition, survival of the fittest).
Explain how natural selection leads to adaptation over generations.
Connect these ideas to the concept of descent with modification.

Try solving on your own before revealing the answer!

Final Answer: Darwin hypothesized that evolution occurs through natural selection, where individuals with advantageous traits survive and reproduce more successfully, leading to adaptation over time.

His theory emphasized variation, competition, and the gradual change of species.

Q11. Describe the concept of natural selection and apply to various examples.

Background

Topic: Mechanisms of Evolution

This question asks you to explain natural selection and show how it works in real-world scenarios.

Key Terms:

Natural selection: Differential survival and reproduction of individuals due to differences in phenotype.
Adaptation: Traits that increase fitness in a given environment.

Step-by-Step Guidance

Define natural selection in your own words.
Describe the conditions necessary for natural selection to occur (variation, heritability, differential survival/reproduction).
Think of an example (e.g., peppered moths, antibiotic resistance) and explain how natural selection operates in that case.

Try solving on your own before revealing the answer!

Final Answer: Natural selection is the process where individuals with beneficial traits are more likely to survive and reproduce; over time, these traits become more common in the population. Example: Peppered moth coloration changing due to industrial pollution.

Natural selection explains how populations adapt to their environments.

Q12. Explain how beneficial alleles enter a population: mutation, genetic drift, migration.

Background

Topic: Sources of Genetic Variation

This question tests your understanding of the mechanisms that introduce new genetic variants into populations.

Key Terms:

Allele: A variant form of a gene.
Mutation: Random changes in DNA that can create new alleles.
Genetic drift: Random changes in allele frequencies, especially in small populations.
Migration (gene flow): Movement of alleles between populations.

Step-by-Step Guidance

Define each mechanism: mutation, genetic drift, migration.
Explain how each can introduce or change the frequency of beneficial alleles in a population.
Give an example for each mechanism if possible.

Try solving on your own before revealing the answer!

Final Answer: Beneficial alleles can arise through mutation (new genetic changes), genetic drift (random changes in small populations), or migration (gene flow from other populations).

These mechanisms increase genetic diversity and can introduce advantageous traits.

Q13. Compare & contrast natural selection and artificial selection.

Background

Topic: Evolutionary Mechanisms

This question asks you to distinguish between natural and artificial selection, including similarities and differences.

Key Terms:

Natural selection: Driven by environmental pressures.
Artificial selection: Driven by human choice (selective breeding).

Step-by-Step Guidance

Define natural selection and artificial selection.
List similarities (both result in changes in traits over generations).
List differences (who/what determines which traits are favored).
Provide an example of each type of selection.

Try solving on your own before revealing the answer!

Final Answer: Natural selection is driven by environmental pressures, while artificial selection is guided by humans. Both change traits in populations, but the selective force differs (nature vs. humans).

Examples: Natural selection – camouflage in animals; artificial selection – dog breeding.

Q14. Describe the evidence that supports the theory of evolution.

Background

Topic: Evidence for Evolution

This question asks you to summarize the main types of evidence that support evolutionary theory.

Key Terms:

Fossil record, comparative anatomy, molecular biology, biogeography, embryology: Main lines of evidence.

Step-by-Step Guidance

List the different types of evidence for evolution.
Briefly describe how each type supports the theory.
Give an example for at least one type of evidence.

Try solving on your own before revealing the answer!

Final Answer: Evidence includes the fossil record, comparative anatomy, molecular similarities, biogeography, and embryological development. Each shows patterns consistent with common ancestry and change over time.

For example, homologous structures in different species suggest descent from a common ancestor.

Q15. Discuss how sexual selection contributes to fitness and apply to examples.

Background

Topic: Sexual Selection

This question tests your understanding of how sexual selection operates and its impact on reproductive success (fitness).

Key Terms:

Sexual selection: Selection for traits that increase mating success.
Fitness: The ability to survive and reproduce.

Step-by-Step Guidance

Define sexual selection and how it differs from natural selection.
Explain how traits favored by sexual selection can increase an individual's fitness.
Provide examples (e.g., peacock tails, antler size in deer).

Try solving on your own before revealing the answer!

Final Answer: Sexual selection favors traits that improve mating success, increasing fitness. Examples include bright plumage in birds or elaborate courtship behaviors.

These traits may not always aid survival but enhance reproductive success.

Q16. Correctly define a biological species.

Background

Topic: Species Concepts

This question asks you to state the biological species concept as used in biology.

Key Terms:

Biological species concept: Definition based on reproductive isolation.

Step-by-Step Guidance

Recall the definition of a species according to the biological species concept.
Think about the importance of interbreeding and reproductive isolation.
Consider limitations of this concept (e.g., asexual organisms, fossils).

Try solving on your own before revealing the answer!

Final Answer: A biological species is a group of organisms that can interbreed and produce fertile offspring, and are reproductively isolated from other such groups.

This concept emphasizes reproductive barriers between species.

Q17. Distinguish between the various prezygotic and postzygotic reproductive isolation barriers and apply to examples.

Background

Topic: Reproductive Isolation

This question tests your understanding of mechanisms that prevent gene flow between species.

Key Terms:

Prezygotic barriers: Prevent mating or fertilization (e.g., temporal, behavioral, mechanical, habitat, gametic).
Postzygotic barriers: Occur after fertilization (e.g., hybrid inviability, hybrid sterility).

Step-by-Step Guidance

List the main types of prezygotic barriers and give an example of each.
List the main types of postzygotic barriers and give an example of each.
Explain how these barriers maintain species boundaries.

Try solving on your own before revealing the answer!

Final Answer: Prezygotic barriers include temporal, behavioral, mechanical, habitat, and gametic isolation; postzygotic barriers include hybrid inviability and sterility. Examples: Mating seasons (temporal), mule sterility (postzygotic).

These barriers prevent gene flow and maintain species integrity.

Q18. Describe speciation by allopatric and sympatric mechanisms.

Background

Topic: Speciation

This question asks you to explain how new species arise through geographic (allopatric) and non-geographic (sympatric) means.

Key Terms:

Allopatric speciation: Speciation due to geographic separation.
Sympatric speciation: Speciation without geographic separation, often due to genetic or ecological factors.

Step-by-Step Guidance

Define allopatric speciation and describe how geographic barriers lead to new species.
Define sympatric speciation and describe mechanisms (e.g., polyploidy, ecological niche differentiation).
Provide an example of each type of speciation.

Try solving on your own before revealing the answer!

Final Answer: Allopatric speciation occurs when populations are geographically separated; sympatric speciation occurs without physical separation, often via genetic changes or ecological factors.

Examples: Darwin's finches (allopatric), polyploid plants (sympatric).

Q19. Explain and be able to contrast convergent and divergent evolution.

Background

Topic: Patterns of Evolution

This question tests your understanding of how species evolve similar or different traits.

Key Terms:

Convergent evolution: Unrelated species evolve similar traits due to similar environments.
Divergent evolution: Related species evolve different traits due to different environments or selective pressures.

Step-by-Step Guidance

Define convergent evolution and give an example (e.g., wings in bats and birds).
Define divergent evolution and give an example (e.g., Darwin's finches).
Contrast the two processes in terms of ancestry and trait development.

Try solving on your own before revealing the answer!

Final Answer: Convergent evolution produces similar traits in unrelated species; divergent evolution produces different traits in related species. Example: Dolphin and shark fins (convergent), finch beaks (divergent).

Convergent evolution is due to similar environments, divergent due to different selective pressures.

Q20. Explain the difference between gradualism and punctuated equilibrium.

Background

Topic: Rates of Evolution

This question asks you to compare two models of evolutionary change over time.

Key Terms:

Gradualism: Evolution occurs slowly and steadily over time.
Punctuated equilibrium: Evolution occurs in rapid bursts separated by periods of little change.

Step-by-Step Guidance

Define gradualism and describe its pattern of evolutionary change.
Define punctuated equilibrium and describe its pattern.
Compare and contrast the two models.

Try solving on your own before revealing the answer!

Final Answer: Gradualism suggests slow, continuous change; punctuated equilibrium suggests long periods of stability interrupted by rapid change.

Both models explain patterns seen in the fossil record.

Q21. List the components of the classification system in order.

Background

Topic: Biological Classification (Taxonomy)

This question tests your knowledge of the hierarchical system used to classify living organisms.

Key Terms:

Taxonomic ranks: The ordered levels of classification.

Step-by-Step Guidance

Recall the main taxonomic ranks from broadest to most specific.
List them in order, starting with domain or kingdom (depending on your course).
Remember the mnemonic devices that can help you recall the order.

Try solving on your own before revealing the answer!

Final Answer: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

This is the standard hierarchy used in biological classification.