Intro to Biology: Taxonomy & the Diversity of Life

Phylogeny

the branch of biology that studies the evolutionary history of organisms & refers to the evolutionary relationships among organisms.

Taxonomy

the branch of biology that names & organizes species based on their similarities.

Species that are closely related are placed in the same group, while species that are more distantly related are joined at higher levels of organization

Biological systematics

a field that incorporates taxonomy, variation among populations, & relationships among organisms over time to provide insight into the evolutionary history of life.

Morphology

branch of biology that studies the form of organisms & relationships between their structures.

Binomial nomenclature

Developed by Carl Linnaeus to name species using the combination of the names of the genus & species of the organism

Genus

references a specific group of closely related organisms.

e.x., genus Panthera (lions, tigers, jaguars, leopards)

Species epithet

the second word in the scientific name generated by binomial nomenclature. Epithets can be repeated to name organisms across many different genera, but only once per genus.

Evolutionary species concept

defines a species as a specific lineage evolving separately from others

Phylogenetic species concept

More commonly used than evo. species concept & similar, but considers 2 genetically similar populations as different species when they are geographically isolated from each other & each population carries unique morphological differences.

Phylogenetic tree

(a.k.a. phylogram) used to depict phylogeny, with branches to represent lineages, the lengths of which correspond with time, & nodes to depict common ancestors

Homology

Homologous traits are derived from a common ancestor— like the tail of a monkey and a cat

Homoplasy

Homoplastic traits are analogues that evolve independently, usually through convergent evolution because of similar selective pressures, so they don’t represent a shared ancestry.

e.g., the wings of a bird and the wings of a bat are homoplastic.

Clade

a monophyletic group; they share a derived character, a trait that differs from the ancestral state.

Synapomorphies

Shared, derived characteristics.

Outgroup

a single species that’s related to all the others in a tree but is still distant

Cladogram

shows the relationship between different groups of animals along w their derived characters. Cladograms are interpreted from left to right.

Monophyletic taxon

Includes all the members of a group as well as their more recent common ancestor.

Paraphyletic taxon

contains a common ancestor but leaves out some of its descendants

e.g., invertebrates & protists

Polyphyletic taxon

doesn’t include the common ancestor to all of its members

e.g., marine mammals & flying vertebrates

Molecular systematics

use of DNA & proteins in the identification & classification of a species

DNA barcoding

a method of identifying species based on the sequence of a standard section of DNA.

Cryptic species

species that appear identical but are different at a genetic level & unable to breed w each other

e.g., African elephants that live in forests (Loxodonta cyclotis) & African elephants that live in the savanna (Loxodonta africana)

Bacteria

sometimes called Eubacteria, “true bacteria”; a vast group of prokaryotes that play critical roles in cycling carbon, nitrogen, & sulfur, & have an important symbiotic relationship with other organisms.

Autotrophs

produce their own food from their surroundings using photosynthesis or chemosynthesis

Heterotrophs

Unable to produce their own food, they inject orher organism’s for nutrition.

Bacillus

Rod-shaped bacteria

Coccus

Ball-shaped bacteria

Spirillum

Spiral-shaped bacteria

Gram-positive bacteria

have a thick, complex outer cell wall, mostly made of peptidoglycan, stains a purple color after Gram staining.

Gram-negative bacteria

have a thinner layer of peptidoglycan in their cell wall & stain pink in Gram staining

Archaea

Diverse group of prokaryotes known for living in extreme or inhospitable environments.

Eukaryarchaeota

includes methanogens, which live in anaerobic conditions, like swamps or animal intestines, & metabolize hydrogen & carbon dioxide into methane gas.

Eukaryarcheota also includes halobacteria, which are halophiles & live in very salty environments

Crenarcheota

includes many thermophiles that live in extremely high temperatures of 140°-176°F.

Nanoarchaeota

has only one species, Nanoarckaeum equitans, which has been identified in a hydrothermal vent at Yellowstone, as well as at the bottom of the Atlantic ocean

Korarcheaota

thought to be one of the most primitive tikes of organisms & have only been found in hot springs at Yellowstone & in deep-sea vents.

“Protista”

**the definition of protists is often debated by scientists**

This kingdom us diverse, consisting of eukaryotes that are mostly unicellular & relatively less complex than most other eukaryotes.

This group is paraphyletic, making it an invalid taxon to non-traditionalists.

Protists can be autotrophic, heterotrophic, saprotrophic, or mixotrophic.

Saprotrophic

acquires dissolved nutrients from their surroundings

Mixotrophic

Can be autotrophic or heterotrophic, depending on nutrients availability.

Ciliates

move by waving large numbers of small, hair-like cilia to propel themselves through water.

Flagellates

move by rotating one or more long flagella— hair-like structure, whip-like appearance.

Amoeboids

move using pseudopods, which are finger-like projections of cytoplasm.

Plantae

Plants include red & green algae, bryophytes, & vascular plants; are multicellular & photosynthetic, & can reproduce sexually or asexually. Plants are autotrophs but several groups have separately evolved adaptations to nutrient-poor environments.

e.g. pitcher plants and venus flytraps obtain some nutrients from insects & other small organisms

Fungi

diverse group of eukaryotes both multicellular & unicellular.

Fungi reproduce both sexually & asexually; they are non-vascular, sessile, heterotrophic, & posses a cell wall made of chitin.

Some types of fungi cause disease, others produce chemicals like antibiotics.

The 7 Fungi groups

Microsporidia— used to be considered protists, now understood to be fungi.

Blastocladiomycota, Neocallimastigomycota, & Chytridiomycota— All preciously classified as chytrids.

Glomeromycota— Soil fungi that have mutualistic relationships w plants.

Basidiomycota & Ascomycota— Often called Dikaryka, or higher fungi.