Biology Lecture: Foundations of Modern Biology, Cell Theory, Information Flow, Evolution, and Scientific Method

These flashcards cover definitions, historical experiments, molecular biology concepts, evolutionary principles, taxonomy, and the scientific method from the provided lecture notes.

What is a scientific theory in biology?

An explanation for a very general class of phenomena or observations that is supported by a wide body of evidence.

How does the scientific meaning of “theory” differ from everyday usage?

In science it is a well-supported explanation; in everyday language it often means speculation or guess.

What three theories form the framework for modern biological science?

Cell theory, the theory of evolution by natural selection, and the chromosome theory of inheritance.

Cell theory addresses the question: ?

"What are organisms made of?"

The theory of evolution by natural selection addresses the question: ?

"Where do organisms come from?"

The chromosome theory of inheritance addresses the question: ?

"How is hereditary information transmitted from one generation to the next?"

Who first observed and named “cells” in 1665?

Robert Hooke using a 30× microscope.

Which scientist observed single-celled “animalcules” with a 300× microscope?

Anton van Leeuwenhoek.

State the two tenets of the original cell theory.

All organisms are made of cells, and all cells come from pre-existing cells.

Define a hypothesis.

A testable statement that explains something observed.

What is an experiment in the scientific method?

A procedure that allows researchers to test the effect of a factor on a particular phenomenon.

What is a prediction in hypothesis testing?

A measurable or observable result that must be correct if a hypothesis is valid.

What competing idea did cell theory challenge?

Spontaneous generation—the belief that living organisms could arise spontaneously under certain conditions.

What was the conclusion of Louis Pasteur’s swan-neck flask experiment?

Cells arise from pre-existing cells; they do not arise spontaneously.

According to current evidence, how did life originally arise on Earth?

Through chemical evolution from non-living molecules.

Who proposed the chromosome theory of inheritance?

Sutton and Boveri.

What molecule was identified in the 1950s as the hereditary material in chromosomes?

Deoxyribonucleic acid (DNA).

Genes are segments of DNA that .

Code for cell products (proteins or functional RNAs).

What four nucleotide bases make up DNA?

Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).

Who proposed the double-helix structure of DNA?

James Watson and Francis Crick.

Which bases pair together in DNA?

A pairs with T, and C pairs with G.

Define the central dogma of molecular biology.

Information flows from DNA to RNA to protein.

What is messenger RNA (mRNA)?

An RNA molecule that is read by ribosomes to synthesize proteins.

Why are proteins important to cells?

They perform most cellular tasks and form structural components.

How can DNA mutations lead to diversity of life?

Sequence changes can alter proteins, producing heritable variations upon which natural selection acts.

List the two fundamental nutritional needs of all organisms.

Energy in the form of ATP and building-block molecules for biosynthesis.

How do plants typically acquire energy?

They use sunlight to produce sugars, then use the sugars to make ATP or store energy.

State Darwin and Wallace’s two key claims about the natural world.

(1) Species are related by common ancestry; (2) Species are modified across generations (descent with modification).

Define evolution in biological terms.

A change in the characteristics of a population over time.

What two conditions are required for natural selection?

Heritable variation among individuals and differential reproductive success linked to that variation.

What is fitness in evolutionary biology?

An individual’s ability to produce surviving, fertile offspring.

Define adaptation.

A heritable trait that increases an individual’s fitness in a particular environment.

Provide an example demonstrating natural selection in Galápagos finches.

During times with abundant small, soft seeds, finches with small, pointed beaks had higher fitness, so that beak type became more common.

What is phylogeny?

The actual genealogical relationships among all organisms.

How do scientists infer phylogenetic relationships today?

By comparing DNA or RNA sequence similarities among species.

Name the three domains of life.

Bacteria, Archaea, and Eukarya.

Differentiate prokaryotes and eukaryotes.

Prokaryotes (Bacteria, Archaea) lack a nucleus; eukaryotes (Eukarya) possess a nucleus and membrane-bound organelles.

What is taxonomy?

The effort to name and classify organisms.

According to Linnaeus, what two parts comprise a scientific name?

Genus (capitalized) and species (not capitalized), both italicized.

Describe the food-competition hypothesis for long giraffe necks.

Long necks evolved so giraffes could reach food high in trees inaccessible to other mammals.

What alternative hypothesis better explains giraffe neck length?

The sexual-competition hypothesis: longer-necked males win more fights and sire more offspring.

In an experiment, what is a null hypothesis?

A statement describing what should be observed if the tested hypothesis is wrong.

What did Wittlinger’s desert ant experiment test?

The pedometer hypothesis that ants use stride number and length to gauge distance back to the nest.

What were the results of the ant stride-manipulation experiment?

Stump-leg ants stopped short, normal ants reached the nest, and stilt-leg ants overshot, supporting the pedometer hypothesis.

List two important characteristics of good experimental design.

Use of a control group and keeping experimental conditions constant.

Why is sample size important in experiments?

Larger sample sizes reduce the influence of random variation and increase confidence in results.