7/10: Classification, Scientific Inquiry & Chemistry of Life

Question-and-answer flashcards covering cell classification, taxonomy, hypothesis testing, experimental design, the giraffe and ant case studies, and foundational chemistry concepts (atomic structure, isotopes, electronegativity, and bonding).

What distinguishes a prokaryotic cell from a eukaryotic cell?

Prokaryotic cells lack a membrane-bound nucleus, whereas eukaryotic cells have one.

Where is DNA located in a eukaryotic cell?

Inside the membrane-bound nucleus.

In prokaryotes, DNA is concentrated in what region?

The nucleoid region (not membrane-bound).

What is the most reliable modern method for determining relatedness among organisms?

Comparing DNA (nucleotide) sequence similarity.

What is the most inclusive taxonomic rank?

Domain.

Name the three domains of life.

Bacteria, Archaea, and Eukarya.

With which domain do humans share a more recent common ancestor—Bacteria or Archaea?

Archaea.

Write the mnemonic that helps recall the main taxonomic ranks.

King Philip Came Over From Spain (Genus Species).

Which two ranks make up Linnaeus’ binomial naming system?

Genus and species.

How must genus and species names be formatted in scientific writing?

Both words italicized (Genus capitalized, species lowercase).

Why is Latin used for scientific names?

It is a dead language, so words do not change meaning over time, allowing consistency across languages.

Define a scientific hypothesis.

A testable, precise explanation that generates predictions.

Why is the phrase “scientific proof” considered a misnomer?

Science gathers evidence to support or refute hypotheses; proofs exist in mathematics, not empirical science.

What is a null hypothesis?

A statement that there is no effect or relationship; it is what researchers try to reject with evidence.

In the giraffe study, what did the food-competition hypothesis predict about feeding height?

Giraffes should mostly feed at high tree levels.

What alternative hypothesis better explained long giraffe necks?

Sexual selection—males with longer necks win fights and gain more mates.

In an experiment, what is the independent variable?

The factor that is deliberately manipulated by the researcher.

What is the dependent variable?

The response or outcome measured in the experiment.

What purpose does a control group serve in an experiment?

It provides a baseline for comparison, helping attribute effects to the independent variable.

What did the ant ‘pedometer’ hypothesis propose?

Ants gauge distance home by counting steps and using stride length.

How were stride lengths experimentally manipulated in desert ants?

By cutting legs shorter (“stumps”) or gluing bristles on legs (“stilts”).

What happened when ‘stilt’ ants first returned to the nest site?

They overshot the nest (walked too far).

After a second run, how did manipulated ants perform?

They compensated and stopped at the correct nest distance, supporting the pedometer hypothesis.

In atomic structure, what particles reside in the nucleus?

Protons and neutrons.

What charge do electrons carry?

Negative.

Define atomic number.

The number of protons in an atom’s nucleus.

Define mass number.

Total number of protons plus neutrons in the nucleus.

What is an isotope?

Atoms of the same element with different numbers of neutrons (different mass numbers).

Why are radioactive isotopes useful in biology and medicine?

Their predictable decay allows tracing molecules or imaging biological processes.

What is a valence shell?

The outermost electron shell of an atom, involved in bonding.

Which biologically important element is the most electronegative?

Oxygen.

Differentiate non-polar and polar covalent bonds.

Non-polar: electrons shared equally; Polar: electrons shared unequally, producing partial charges.

Why is a water molecule bent?

Oxygen’s high electronegativity pulls shared electrons, creating partial charges and a bent (polar) shape.

What is formed when electrons are transferred, not shared, between atoms?

An ionic bond.

Define cation and anion.

Cation: positively charged ion (lost electrons); Anion: negatively charged ion (gained electrons).

Explain how table salt (NaCl) forms.

Sodium donates an electron becoming Na⁺; chlorine accepts it becoming Cl⁻; opposite charges attract, forming crystalline NaCl.

Why are hydrogen ions written as H⁺ in biology?

They have lost their single electron, leaving a lone proton with a positive charge.

What three bond types form the continuum of electron sharing?

Non-polar covalent, polar covalent, and ionic bonds.

Give an everyday example of a non-polar covalent molecule.

Molecular hydrogen (H₂) or methane (CH₄).