4.3 Taxonomy and the Diversity of Life Flashcards
Taxonomy
Names and organizes species based on their similarities
Biological systematics
Field that incorporates taxonomy, variation among populations, and relationships among organisms over time, to provide insight into evolutionary history of life
Morphology
Branch of biology that studies the form of organisms and relationships between their structures
Historical taxa
From largest to smallest taxon
- Kingdom
- Phylum (phyla)
- Class
- Order
- Family
- Genus (genera)
- Species
Recently added taxa
Domain (above kingdom)
Superfamily or subspecies (below species)
Binomial nomenclature
Combination of genus and species
Genus names are unique but may be used once in each kingdom
Species epithet can be used once per genus
Species epithet
Second word in the scientific name of binomial nomenclature
Biological species concept
Developed by Theodorakis Dobzhansky a Russian-American geneticist, and Ernst Mayr, a German evolutionary biologist in separate publications in 1937 and 1942
Species is a reproductive community of populations (reproductively isolated from others) that occupies a specific niche in nature
Criticism of biological species concept
- Doesn’t address extinct species
- no way to identify changes in lineage over time
- No way of separating a living species from its ancestors
- Excludes asexually reproducing species
- Reproductive isolating mechanisms can disappear over time and allow two closely related species to interbreed
Evolutionary species concept
- Doesn’t address extinct species
- no way to identify changes in lineage over time
- No way of separating a living species from its ancestors
- Excludes asexually reproducing species
- Reproductive isolating mechanisms can disappear over time and allow two closely related species to interbreed
Phylogenetic species concept
Similar to evolutionary species concept but considers two genetically similar populations as different species when they are geographically isolated from one another and each population carries unique morphological differences
Homologous characters
Derived from a common ancestor
Homoplastic characters
Analogues that evolve independently, usually through convergent evolution due to similar selective pressures
Don’t represent shared ancestry
Clade
(Or branch)
Group of species that share a derived character
A group containing a common ancestor and all of its descendants, monopyhyletic group
Derived character
Trait that differs from the ancestral state
Synapomorphies
Shared, derived characters
Cladogram
Used to depict the evolutionary relationships among different species or groups
Lesser derived clades are basal groups of lower taxa placed nearer to root
Sister taxa
Neighboring groups, closely related
Outgroup
Single species/group that’s related to all the others in the tree but still distinct
Used to determine ancestral character states
Phylogram
(Or phylogenic tree) conceptually and visually similar to a cladogram but the lengths of its branches correspond with time
Monophyletic taxon
Includes all the members of a group as well as their most recent common ancestor, a clade
Paraphyletic taxon
Contains a common ancestor but leaves out some of its descendants
Polyphyletic taxon
Doesn’t include the common ancestor to all of its members
Willi Hennig
(1913-1976) pushed for the use of cladistics
Cladistics
(or phylogenetic systematics) Idea that all recognized taxa should be monophyletic
Traditional taxonomies
Continue to accept some paraphyletic groupings as valid taxa on top of monophyletic taxon
Molecular systematics
The use of DNA and proteins in the identification and classification of species
DNA barcoding
Method of identifying species based on sequence of a standard section of DNA
Mitochondrial gene for cytochrome c oxidase subunit 1, frequently used
Morphometric studies
Constructing phylogenies using morphology
Cryptic species
Appear identical to one another but are different at a genetic level and unable to breed with each other
Autotrophs
Produce own food using photosynthesis or chemosynthesis (chemical energy)
Heterotrophs
Ingest other organisms for their nutrition
Bacillus
Rod-shaped bacteria
Coccus
Ball-shaped bacteria
Spirillum
Spiral-shaped bacteria
Gram-positive bacteria
Have thick outer cell wall, mostly made of cross-linked peptidoglycan along with a small amount of lipoteichoic acids that anchor the cell wall to the plasma membrane, stain purple
Gram-negative bacteria
Cell wall contains a thinner layer of peptidoglycan surrounded by an outer membrane of lipopolysaccharides and lipoproteins structurally similar to lipid bilayer of plasma membrane but chemically distinct, stain pink
Bacteria phyla
- Chlamydia
- Proteobacteria
- Cyanobacteria
- Spirochetes
- Gram-positive bacteria
Archaea
Prokaryotic microorganisms
lack membrane-bound organelles and nuclear envelope
Cell walls lack peptidoglycan, cell membranes have a different structure
Some of their genes have introns
differ in DNA replication and gene expression
known for living in extreme or inhospitable environments
Archaea phyla
- euryarchaeota
- crenarchaeota
- nanoarchaeota
- korarchaeota
Methanogens
Type of euryarchaeota, live in anaerobic conditions
Metabolize hydrogen and carbon dioxide into methane gas
Halobacteria
Type of eurychaeota, live in very salty environments
Crenarchaeota
Bacteria phylum, includes many thermophiles, some are sulfur-based autotrophs
Nanoarchaeota
Bacteria phylum, only one identified species Nanoarchaeum equitans
Korarchaeota
Bacteria phylum, thought to be one of the most primitive types of organisms
Traditional eukaryotic kingdoms
- Animals
- Plants
- Fungi
- Protists
Protista
Eukaryotic kingdom, definition debated by scientists
Contains mostly unicellular and less complex eukaryotes
Possess a nucleus and specialized organelles
Paraphyletic, invalid taxon
Historically defined as any eukaryote that isn’t plant, animal, of fungus
Can be autotrophic, heterotrophic, saprotrophic or mixotrophic
Live in wet environments
Can form colonies that have simple division of labor among different cell types
Many can switch between asexual and sexual reproduction
Sexual reproduction can be associated with the formation of protective cysts that are resistant to environmental extremes
Saprotrophic
Acquiring dissolved nutrients from their surroundings
Mixotrophic
Can be autotrophic or heterotrophic depending on availability of nutrients
Protist groups
- Cliliates
- Flagellates
- Amoebas
Ciliate protisits
Move by waving hair-like cilia to propel through water
Flagellate protists
Move by rotating one or more long flagella
Amoeboid protists
Move using pseudopods
Pseudopods
Fingerlike projections of cytoplasm
Plantae
Eukaryotic kingdom, include red and green algae, bryophytes, and vascular plants
Fungi
Eukaryotic kingdom, include both unicellular and multicellular organisms
Can reproduce both sexually or asexually
Non-vascular and non-moving
Heterotrophic, typically saprobes/saprophytes
Can break down cellulose or lignin,
Some can even break down jet fuel and useful in bioremediation
Possess cell wall composed of chitin
More closely related to animals than plants
Some posses accessory genomic structure analogous to bacterial plasmids
Traditional fungi groups
- Ascomycota (sac fungi)
- Basidiomycota (club fungi)
- Chytridiomycota (chytrids)
- Zygomycota (zygomycetes)
*the last two “lower fungi” are not monophyletic
Mycologists
Scientists who study fungi
Fungi seven monophyletic groups
Updated in 2007
- Microsporidia
- Blastocladiomycota
- Neocallimastigomycota
- Chytridiomycota
- Glomeromycota
- Basidiomycota
- Ascomycota
Microsporidia
Used to be considered protists buy are now understood to be fungi
Group of obligate intracellular parasites of animals, frequently insects
Lack mitochondria but retain mitochondrial genes in genome
Typically only cause disease in immunocompromised individuals.
Blastocladiomycota, Neocallimastigomycota, Chytridiomycota
Fungi previously classified as chytrids
Share ancestral trait of motile, flagellated zoospores
Some have been linked to mass die-offs of amphibians
Some are plant pathogens
Glomeromycota
Small group of asexual plant symbiont fungi
Form mutualisms with many species of trees and herbaceous plants
Most form arbuscular mycorrhizae
Hyphae associate with plant roots and exchange nutrients
Plants provide fungus with carbon and fungus provides plant with minerals from soil
Basidiomycota, Ascomycota
Often called the Dikaryka or higher fungi
Contain morels, truffles, mushrooms, toadstools, rusts, and shelf fungi
Animalia
Eukaryotic kingdom, multi-cellular heterotrophs
Except for sponges, animal cells are organized into tissues
Muscle tissue, nervous tissue, and lack of cell walls allow for active movement
Most reproduce sexually
Unique embryonic development, zygote produces a blastula then a gastrula
About 35 recognized animal phyla
Most are invertebrates
Chordata
Animal phylum
Contains vertebrate animals
About 56,000 species
Arthropoda
Most diverse animal phylum
Contains more that 1 million species of insects, crustaceans, and arachnids
Mollusks
Second-most diverse animal phylum, consists of about 110,000 species
Micrognathozoa
Smallest animal phylum, contains a single species discovered in 1994 on Disko Island in Greenland
