History of Life, Biodiversity, and Organismal Groups – Review

Vocabulary flashcards covering major theories, evolutionary events, taxonomy concepts, microbial groups, plant life cycles, and fungal biology as outlined in the lecture notes.

Nebular Theory

Astronomical model stating that the solar system formed from a rotating cloud of gas and dust (nebula) about 4.6 billion years ago.

Plate Tectonic Theory

Geological concept that Earth’s lithosphere is divided into moving plates whose interactions shape continental positions, mountains, earthquakes, and volcanic activity.

Reducing Atmosphere Hypothesis

A theory suggesting that early Earth had a reducing atmosphere rich in hydrogen, ammonia, and methane, facilitating the formation of organic compounds, possibly leading to the origin of life.

Hydrothermal-Vent Hypothesis

Proposal that life originated in mineral-rich, warm water vents on the ocean floor; limitation: extreme conditions may destroy delicate organic molecules.

Tidal-Pool (Primordial Soup) Hypothesis

Idea that life began in shallow pools subject to evaporation and concentration of organics; limitation: UV radiation and desiccation could degrade molecules.

Panspermia Hypothesis

Speculation that life’s building blocks (or microbes) arrived on Earth via meteorites or comets; limitation: survival through space and atmospheric entry is uncertain.

Protocell Formation

Stepwise process in which organic monomers polymerize, self-assemble into lipid vesicles, trap biomolecules, and gain rudimentary metabolism and replication.

RNA World Hypothesis

Model suggesting RNA was the first self-replicating genetic material before DNA evolved, because RNA can both store information and act as a catalyst.

Transition from RNA to DNA

Evolutionary shift where more stable, double-stranded DNA replaced RNA for long-term information storage, while proteins took over most catalytic roles.

Radiometric Dating

Technique that determines absolute ages of rocks or fossils by measuring decay of radioactive isotopes (e.g., 14C, 40K).

Fossil

Preserved remains or impressions of ancient organisms, providing evidence of past life and evolutionary transitions.

Age of the Earth

Approximately 4.54 billion years, determined by radiometric dating of meteorites and Earth rocks.

Oxygen Revolution

Increase in atmospheric O₂ about 2.4 billion years ago due to photosynthetic cyanobacteria, leading to aerobic metabolism and ozone formation.

Eukaryotic Cell Formation

Origin of cells with membrane-bound organelles (~1.8 billion years ago), likely via endosymbiosis of prokaryotes such as mitochondria and chloroplasts.

Endosymbiotic Theory

The hypothesis that eukaryotic cells arose from the symbiotic relationship between prokaryotic organisms, particularly through the incorporation of mitochondria and chloroplasts.

Cambrian Explosion

Rapid diversification of animal body plans ~541 million years ago, documented in fossil record.

Plant Colonization of Land

Transition (~470 million years ago) when bryophyte-like plants adapted to terrestrial environments with cuticles and protected embryos.

Animal Colonization of Land

Movement of arthropods and later vertebrates onto land (~450–360 million years ago) following development of limbs, lungs, and supportive skeletons.

Pros and Cons of Colonizing Land

The advantages of transitioning from aquatic to terrestrial environments include access to new food sources and reduced competition, while disadvantages involve desiccation, gravity challenges, and reliance on new reproductive strategies.

Mass Extinction Event

Period when ≥75 % of species are lost in geologically short time, e.g., Permian or Cretaceous extinctions.

Adaptive Radiations

Rapid evolutionary diversification of a lineage into various forms to fill different ecological niches after a mass extinction event or the colonization of new habitats. .

Binomial Nomenclature

Two-part scientific naming system (genus + species epithet) introduced by Linnaeus.

Taxonomic Hierarchy

Nested classification levels: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Cladogram

Branching diagram depicting hypotheses of evolutionary relationships based on shared derived traits (synapomorphies).

Derived Trait

A novel feature unique to a clade, used to infer common ancestry in cladistics.

Outgroup

Taxon outside the group of interest, used to determine ancestral versus derived character states in a cladogram.

Prokaryote

Unicellular organism lacking a nucleus; includes Bacteria and Archaea.

3 Primary Bacterial Morphologies

Cocci, bacilli, and spirilla.

Gram-Positive Bacteria

Bacteria with thick peptidoglycan cell wall, stain purple, generally less resistant to antibiotics but may produce exotoxins.

Gram-Negative Bacteria

Bacteria with thin peptidoglycan and outer membrane containing lipopolysaccharide; stain pink and often more virulent or antibiotic-resistant.

Bacterial Capsule

Polysaccharide layer outside cell wall that aids adhesion, evades host immune response, and prevents desiccation.

Biofilm

Community of microorganisms embedded in extracellular matrix attached to surfaces, enhancing survival and antibiotic resistance.

Plasmid

Small, circular DNA molecule independent of chromosome; can carry antibiotic-resistance or metabolic genes and transfer between cells.

Proteobacteria

Large bacterial phylum including nitrogen fixers and pathogens like Yersinia pestis (plague), Vibrio cholerae (cholera), and some E. coli strains.

Nitrogen Fixation

Conversion of atmospheric N₂ into ammonia by bacteria, making nitrogen available to living organisms.

Cyanobacteria

Photosynthetic, oxygen-producing bacteria often called “blue-green algae,” pivotal in the Oxygen Revolution.

Spirochetes

Helical Gram-negative bacteria; some cause diseases such as Lyme disease (Borrelia burgdorferi).

Yersinia pestis

The bacterium responsible for the infectious disease known as the plague, transmitted through fleas and rodents.

Protist

Any eukaryote that is not a plant, animal, or fungus; diverse group including algae and protozoa.

Primary Producer (Protist Role)

Photosynthetic protists (e.g., diatoms) that form the base of aquatic food webs and fix significant carbon.

Plasmodium

Protist genus causing malaria; alternates between mosquito vector and human host, producing cyclic fevers (paroxysms).

Malaria Symptoms

Periodic fever, chills, sweating, anemia, and possible organ failure.

Malaria Vector

Anopheles mosquito transmitting Plasmodium parasites.

Paroxysm (Malaria)

Recurrent bout of fever and chills corresponding to synchronous rupture of infected red blood cells.

Trypanosoma

Protist genus causing African sleeping sickness (T. brucei) via tsetse fly and Chagas disease (T. cruzi) via kissing bug.

Sleeping Sickness Symptoms

Fever, lymph swelling, neurological impairment, disrupted sleep cycles; endemic to sub-Saharan Africa.

Chagas Disease Symptoms

Fever, swelling at bite, chronic heart and digestive system damage; prevalent in Latin America.

Alternation of Generations

Life cycle alternating between multicellular haploid (gametophyte) and diploid (sporophyte) stages.

Moss Gametophyte

Dominant, photosynthetic, haploid stage producing gametes by mitosis in bryophytes.

Moss Sporophyte

Diploid, dependent stage that grows from gametophyte and produces haploid spores by meiosis.

Spore

Haploid reproductive cell capable of developing into a new organism without fusion with another cell.

Moss Adaptations to Land

Cuticle, protected embryos, rhizoids for anchorage.

Moss Limitations

Lack vascular tissue and true roots; require water for sperm motility; limited height.

Fern Sporophyte

Dominant diploid stage with vascular tissue and fronds; produces spores in sori.

Fern Gametophyte (Prothallus)

Small, free-living haploid structure producing gametes; requires moist habitat.

Fern Adaptations

Vascular tissue (xylem & phloem), true roots, leaves (fronds).

Fern Limitations

Dependence on water for fertilization; no seeds, limiting dispersal distance.

Pollen

Male gametophyte of seed plants encased in protective wall, enabling water-independent dispersal of sperm.

Gymnosperm Sporophyte

Coniferous or cycadal diploid tree/shrub that produces cones containing gametophytes.

Seed

Embryo + food supply + protective coat, allowing dormancy and dispersal in seed plants.

Pollen Dispersal (Gymnosperms)

Primarily wind-borne, enabling fertilization without water.

Seed Dispersal (Gymnosperms)

Often by wind (winged seeds) or animals (food caches).

Pollination

Transfer of pollen from anther/stamen to receptive stigma (angiosperms) or ovule surface (gymnosperms).

Fertilization (Plants)

Fusion of sperm nucleus with egg cell to form zygote after successful pollination.

Stigma

Sticky tip of carpel that captures and germinates pollen in angiosperms.

Style

Slender stalk connecting stigma to ovary, through which pollen tube grows.

Ovary (Plant)

Basal portion of carpel housing ovules; matures into fruit after fertilization.

Ovule

Structure within ovary containing female gametophyte; develops into seed after fertilization.

Stamen

Male floral organ composed of anther (pollen production) and filament.

Petal

Colorful flower part attracting pollinators.

Fungal Extracellular Digestion

Secretion of enzymes outside the body to break down organic matter, followed by absorption of nutrients.

Hypha

Microscopic filament making up a fungus; collective network forms mycelium.

Mycelium

Interwoven mass of hyphae providing extensive surface area for absorption.

Plasmogamy

Fusion of cytoplasm from two fungal hyphae without nuclear fusion.

Karyogamy

Fusion of nuclei from two haploid fungal cells, producing a diploid nucleus.

Dikaryotic Cell

Fungal cell containing two genetically distinct haploid nuclei (n+n) following plasmogamy, preceding karyogamy.

Fungi in Nutrient Cycling

Decompose organic matter, releasing carbon, nitrogen, and other elements back into ecosystems.

Fungi in Food Production

Yeasts ferment bread, beer, wine; molds produce cheeses and soy products.

Chytrid Fungus

Batrachochytrium dendrobatidis pathogen causing global amphibian declines by infecting skin.

White-Nose Syndrome

Fungal disease (Pseudogymnoascus destructans) decimating North American bat populations.

Zombie-Ant Fungus

Cordyceps species manipulate ant behavior before killing the host, facilitating spore dispersal.