Biodiversity and Classification Flashcards

Organisms can be classified based on similarities and differences.
Taxonomy: The science of naming and classifying organisms.
Taxon: A group of organisms in a classification system.
Carolus Linnaeus developed the scientific naming system used today.
Binomial Nomenclature: A 2-part scientific naming system.
- Uses Genus and species names.
- Scientific name is always written in italics.
- Two parts are the genus and species names.
  - Ex: Human = Homo sapiens
A Genus includes one or more similar species.
- Species in the same genus are thought to be closely related.
- Genus name is always capitalized.
A Species name is the second part of a scientific name.
- Always lowercase.
- Always follows genus name; never written alone
Scientific names help scientists to communicate.
- Example: Scientific name: Canis familiaris, Common name: Dog
Linnaeus’ classification system has seven levels.
- Each level is included in the level above it.
- Levels get increasingly specific from kingdom to species.

A dichotomous key is a series of paired statements that describe alternative characteristics of different organisms.
Each pair divides the objects to be classified into two exclusive characteristics.
Organisms must fit into one category or the other.

Linnaean system based only on physical similarities and differences, but they are not always the result of close relationships.
Classification changes as discoveries are made
Modern classification systems apply Darwin’s ideas about evolution.

The most recent classification system divides life into three domains, which include six kingdoms.
Three Domains:
- Bacteria
- Archaea
- Eukarya
Six Kingdoms:
- Archaea
- Bacteria (Eubacteria)
- Protista
- Fungi
- Plantae
- Animalia

Feature	Domain Bacteria	Domain Archaea	Domain Eukarya
Kingdom	Eubacteria	Archaea	"Protista", Fungi, Plantae, Animalia
Cell Type	Prokaryote	Prokaryote	Eukaryote
Cell Structure	Cell walls with peptidoglycan	Cell walls without peptidoglycan	Some have cell walls (cellulose in plants, chitin in fungi), some have chloroplasts, animals have no cell walls
Number of Cells	Unicellular	Unicellular	Most multicellular; some unicellular
Mode of Nutrition	Autotroph or heterotroph	Autotroph or heterotroph	Autotroph or heterotroph
Examples	Streptococcus, Escherichia coli	Methanogens, halophiles	Amoeba, Paramecium, mushrooms, ferns, mosses, flowering plants, sponges, worms, insects, fishes, mammals, slime molds, yeasts, giant kelp

Modern classification is based on evolution.
Phylogeny: The evolutionary history for a group of species.
Evolutionary classification groups species into larger categories that reflect lines of evolutionary descent, rather than overall similarities and differences.
Can be shown in a branching tree diagram called a cladogram.

Cladistics: Classification based on common ancestry.
A cladogram is an evolutionary tree made using cladistics.
Species placed in order that they descended from common ancestor
The more categories organisms share, the more recently related they are (they will have more characteristics in common).
If two species share many of the same taxonomic categories, this indicates they have a recent common ancestor
A clade is a group of species that shares a common ancestor.
- Each species in a clade shares some traits with the ancestor.
- Each species in a clade has traits that have evolved.
- Nodes represent the most recent common ancestor of a clade.
Derived characters are traits shared in different degrees by clade members.
- Basis of arranging species in cladogram
- More closely related species share more derived characters
- Represented on cladogram as branches

A true clade must contain an ancestor and all of its descendants
Many traditional taxonomic groups do form clades (ex: Class Mammalia = clade Mammalia)
Some traditional groups do not form valid clades (ex: Class Reptilia – not a clade because it excludes birds, which evolved from reptiles)

A wide range of organisms share a number of genes
All genes mutate over time
Shared genes that contain differences can be treated as derived characters
The mutated gene may be passed to each generation thereafter
DNA analysis can be used to determine which species are more closely related by comparing the different forms of genes present in each species

This tree of life shows evolutionary relationships among the taxa within the three domains of life
All of the organisms in each domain share a common ancestor

Domain Bacteria
- Prokaryotic and unicellular
- Thick cell wall containing peptidoglycan
- Corresponds to kingdom Eubacteria
Domain Archaea
- Prokaryotic and unicellular
- Cell wall without peptidoglycan
- Live in extreme environments (ex: volcanic hot springs)
- Corresponds to kingdom Archaea
Domain Eukarya
- All eukaryotes
- Made up of kingdom Protista, Fungi, Plantae, and Animalia