Biological Diversity, Phylogenetics, and Evolutionary Mechanisms

Vocabulary flashcards covering key terms and concepts in fungal biology, prokaryotes, protists, phylogenetics, population genetics, and speciation mechanisms.

Fungal Hyphae

Thread-like filaments that make up the cellular structure of a fungus.

Mycelium

A mass composed of interconnected fungal hyphae.

Plasmogamy

The stage in fungal sexual reproduction where haploid cells from two different mycelia fuse to form a heterokaryotic cell with two or more nuclei.

Karyogamy

The fusion of haploid nuclei in fungi to form a diploid ($2n$) zygote.

Batrachochytrium dendrobatidis (Bd)

An amphibian chytrid fungus responsible for the extinction of $125$ to $500$ frog species and widespread local extirpations.

Endomycorrhiza

A mycorrhizal plant-fungus association where hyphae form arbuscular vesicles inside plant root cells.

Ectomycorrhiza

A mycorrhizal association where fungal mycelia surround root hairs but do not invade plant root cells.

Ascomycota

A fungal phylum known as sac fungi that includes most yeasts, truffles, puff balls, and important crop pathogens.

Basidiomycota

A fungal phylum known as club fungi that includes mushrooms and toadstools and characteristically lacks an asexual phase.

Endosymbiosis

An evolutionary association in which a symbiont lives permanently inside a host organism, explaining the origins of mitochondria and chloroplasts.

Giardia lamblia

A diplomonad protist responsible for causing beaver fever.

Trypanosoma brucei

A euglenozoan parasite transmitted by the tsetse fly that causes sleeping sickness in humans.

Trypanosoma cruzi

A euglenozoan parasite transmitted through the feces of kissing bugs or assassin bugs that causes Chagas' disease.

Zooxanthellae

Photosynthetic dinoflagellates that live as mutualistic endosymbionts inside coral tissues.

Plasmodium

An apicomplexan protist transmitted by mosquitoes that causes malaria, causing $700{,}000$ to $2{,}700{,}000$ deaths each year.

Diatomaceous Earth

A powdery substance composed of the fossilized silica skeletons of dead diatoms.

Entamoeba histolytica

An amoebozoan protist that causes amoebic dysentery, infecting approximately $500$ million people and causing $100{,}000$ deaths per year.

Mitosis

Cell division for growth and asexual reproduction resulting in genetically identical daughter cells without changing the number of different DNA molecules.

Meiosis

Cell division that reduces the chromosome number set by half ($2n \rightarrow n$) to produce genetically non-identical gametes for sexual reproduction.

Microevolution

Evolutionary change consisting of small, incremental shifts in allele frequencies within a population over time.

Macroevolution

Evolutionary change on a large scale where novel innovations open new lines of diversification and form entirely new taxonomic groups.

Monophyletic

A taxonomic taxon or clade containing a single common ancestral species and all of its descendant species.

Paraphyletic

A phylogenetic grouping that includes an ancestral species but lacks some of its descendant species.

Polyphyletic

A phylogenetic grouping that lacks a recent common ancestor uniting all member species.

Genotype

The complete genetic makeup and specific set of alleles contained within an organism's genome.

Phenotype

The expressed physical and physiological traits of an organism upon which natural selection directly acts.

Stabilizing Selection

Natural selection that favors intermediate phenotypic variants by selecting against extreme expressions of a trait.

Directional Selection

Natural selection that favors individuals at one extreme end of the phenotypic distribution spectrum.

Diversifying Selection

Natural selection that favors individuals at both phenotypic extremes over intermediate traits.

Genetic Drift

Random shifts in population allele frequencies caused by chance events, which are especially pronounced in small populations.

Paedomorphosis

A heterochronic evolutionary process where adult descendants retain juvenile physical traits of their ancestors.

Adaptive Radiation

The rapid speciation and diversification of multiple ecologically distinct species from a single common ancestral lineage.

Reinforcement

A process in a hybrid zone where natural selection strengthens reproductive barriers because hybrid offspring are less fit than purebred species.

Fusion

A process in a hybrid zone where reproductive barriers weaken over time until two diverging species merge back into one.