General Biology: Evolution, Prokaryotes, and Protists

Biological hierarchy

Atoms → molecules → organelles → cells → tissues → organs → organ systems → organisms → populations → communities → ecosystems → biosphere. Each level builds on the organization of the previous level.

Scientific method

A process of observation, asking questions, forming hypotheses, making predictions, testing predictions, collecting data, and drawing conclusions.

Hypothesis

A testable, falsifiable explanation for an observation or question.

Theory

A well-supported explanation that has been repeatedly tested and supported by evidence.

Darwinian evolution

Change in the characteristics of populations over generations, driven by mechanisms such as natural selection.

Natural selection

Individuals with heritable traits that improve survival or reproduction tend to leave more offspring, causing those traits to become more common.

Genetic variation

Differences in genetic traits among individuals in a population; mutation and genetic recombination are major sources.

Homology

Similarity due to common ancestry.

Analogy

Similarity in function or appearance that evolved independently rather than from common ancestry.

Convergent evolution

Unrelated organisms independently evolve similar traits because they experience similar selective pressures.

Divergent evolution

Related populations become increasingly different as they adapt to different environments.

Systematics

The study of biological diversity and evolutionary relationships.

Taxonomy

The science of naming and classifying organisms.

Taxonomic hierarchy

Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species.

Binomial nomenclature

The two-part scientific naming system using Genus + species.

Phylogeny

The evolutionary history and relationships among organisms.

Phylogenetic tree

A diagram representing hypotheses about evolutionary relationships.

Branch point

A point on a phylogenetic tree representing the common ancestor of the lineages branching from it.

Monophyletic group

A group containing a common ancestor and ALL of its descendants.

Paraphyletic group

A group containing a common ancestor but NOT all of its descendants.

Polyphyletic group

A group whose members do not include their most recent common ancestor; members are grouped based on similarities that evolved independently.

Three domains of life

Bacteria, Archaea, and Eukarya.

Bacteria

Prokaryotic organisms with cells that typically have peptidoglycan cell walls.

Archaea

Prokaryotic organisms distinct from bacteria; their cell walls lack peptidoglycan and their membranes have unique chemistry.

Eukarya

Organisms whose cells contain a membrane-bound nucleus and other membrane