2025 Honors Biology Exam Study Guide

Scientific Method

A systematic process for investigating phenomena, which includes steps such as observation, question, hypothesis, experiment, data collection, analysis, conclusion, and repeat.

Observation

Noticing and describing a phenomenon.

Question

Asking a question about the observation.

Hypothesis

Proposing a testable explanation.

Experiment

Testing the hypothesis with a controlled experiment.

Data Collection

Gathering and recording results.

Analysis

Interpreting the data.

Conclusion

Drawing conclusions and sharing results.

Repeat

Repeating the experiment for verification.

Control Group

The set of plants that receive no fertilizer or a standard fertilizer, serving as a baseline for comparison.

Hypothesis

A specific, testable prediction (e.g., 'If plants get more sunlight, they will grow taller.').

G1 Phase

Cell grows and carries out normal functions.

S Phase

DNA is replicated.

G2 Phase

Cell prepares for mitosis, making proteins and organelles.

Mitosis

Division of the cell nucleus and chromosomes.

Cytokinesis

Division of the cytoplasm, forming two cells.

Phases of Mitosis

prophase, metaphase, anaphase, telophase

Meiosis Importance

It reduces chromosome number by half, producing gametes (sperm/egg), allowing genetic diversity and maintaining species chromosome number.

Mitosis vs. Meiosis

Mitosis: 1 division, 2 identical cells, diploid cells. Meiosis: 2 divisions, 4 genetically different cells, haploid cells.

Genetic Variation in Meiosis

Contributes through crossing over and independent assortment of chromosomes.

Differences between Mitosis and Meiosis

Mitosis forms 2 identical cells; meiosis forms 4 different cells. Mitosis has 1 division; meiosis has 2.

Similarities between Mitosis and Meiosis

Both involve DNA replication and cell division.

Sexual reproduction

Involves two parents and genetic mixing.

Asexual reproduction

Involves one parent and produces genetically identical offspring.

DNA

A double helix with sugar-phosphate backbones and nitrogenous base pairs (A-T, C-G).

DNA replication

DNA unwinds, each strand serves as a template, and new complementary nucleotides are added, resulting in two identical DNA molecules.

Protein synthesis

Transcription: DNA is copied into mRNA in the nucleus. Translation: mRNA is read by ribosomes in the cytoplasm to assemble amino acids into a protein.

Transcription

DNA is used as a template to make mRNA, which carries the genetic code out of the nucleus.

Translation

mRNA is decoded by ribosomes, tRNA brings amino acids, and a protein chain is formed.

Mutation

A change in the DNA sequence.

Substitution mutation

One base is replaced by another.

Insertion mutation

Extra base(s) are added.

Deletion mutation

Base(s) are removed.

Gene coding for a protein

The sequence of DNA bases (codons) determines the order of amino acids in a protein.

Importance of amino acid sequence

The sequence determines the protein's shape and function; a change can alter or destroy its activity.

Law of Dominance

Some alleles are dominant, others recessive.

Law of Segregation

Alleles separate during gamete formation.

Law of Independent Assortment

Genes for different traits can segregate independently.

Punnett square probability

Probability of short (tt): 1/4 or 25%.

Incomplete dominance

Heterozygote is a blend (e.g., red + white = pink flowers).

Co-dominance

Both alleles show (e.g., AB blood type).

Sex-linked trait

A trait controlled by a gene on a sex chromosome (e.g., colorblindness on the X chromosome).

Chromosomal mutation

Change in structure or number of chromosomes (e.g., deletion, duplication).

Non-disjunction

Failure of chromosomes to separate during meiosis, leading to extra or missing chromosomes (e.g., Down syndrome).

Environmental influence on gene expression

Environmental factors (like temperature, nutrition) can turn genes on or off or affect how they are expressed.

Inbreeding

Breeding similar individuals to preserve traits.

Hybridization

Breeding different individuals to combine traits.

Genetically modified organism

Its DNA has been altered using genetic engineering to express new traits.

Benefit of genetic engineering

Can produce crops with better yield or disease resistance.

Drawback of genetic engineering

Potential unknown effects on health/environment.

Bacterial transformation

To introduce new genes into bacteria, enabling them to produce useful substances (like insulin).

Darwin's theory of natural selection

Organisms with traits best suited to their environment survive and reproduce, passing those traits to offspring.

Comparative anatomy

Evidence for evolution based on homologous structures.

Molecular biology

Evidence for evolution based on DNA similarities.

Homologous structures

Same structure, different function (e.g., human arm and bat wing).

Analogous structures

Different structure, same function (e.g., bird wing and insect wing).

Gene pool

All the genes in a population.

Relative frequency

How common an allele is in the gene pool.

Zones of inhibition

The larger the zone, the more effective the antibiotic is at inhibiting bacterial growth.

Levels of organization in the biosphere

Organism → Population → Community → Ecosystem → Biome → Biosphere.

Biotic factors

Examples include plants and animals.

Abiotic factors

Examples include water and sunlight.

Producer

Makes own food (plants).

Consumer

Eats other organisms.

Herbivore

Eats plants.

Carnivore

Eats animals.

Omnivore

Eats both plants and animals.

Niche

Role or job of an organism in its environment.

Habitat

Where an organism lives.

Invasive species impact

They can outcompete native species, disrupt food webs, and reduce biodiversity.

Symbiotic relationships

The relationship between two species that live in close association with each other

Population growth trends

Look for exponential or logistic growth, carrying capacity, and possible limiting factors.

Theory

A well-supported, broad explanation of natural events (e.g., the Theory of Evolution).

Prophase

Chromosomes condense, nuclear envelope breaks down.

Metaphase

Chromosomes align at the cell equator.

Anaphase

Sister chromatids separate to opposite poles.

Telophase

Nuclear envelopes reform around chromosomes.

mutualism

Both benefit (bee and flower),

Commensalism

One benefits, other unaffected (barnacle on whale),

parasitism

One benefits, other harmed (tick on dog).