Diversity of Life

Taxonomy

The science of classifying organisms based on their shared characteristics

Taxonomic hierarchy (broad to specific)

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species (Mnemonic: Dear King Phillip Came Over For Good Soup)

Prokarya

Informal domain of organisms that includes the domains Bacteria and Archaea; unicellular, lack membrane-bound organelles, circular chromosome, reproduce asexually

Binary fission

Asexual reproduction occurring in prokaryotic organisms; DNA replication and cytoplasmic division occur simultaneously

Bacteria

Prokaryotes with cell walls made of peptidoglycan; classified as Gram-positive or Gram-negative

Peptidoglycan

Rigid polymer that protects bacterial cells

Gram-negative bacteria

Thin layer of peptidoglycan, lipopolysaccharides (LPS) in outer membrane, stain pink, no teichoic acids

Gram-positive bacteria

Thick layer of peptidoglycan, teichoic acids present, no outer membrane, stain purple

Endospore

Dormant protective structure formed by certain bacteria to survive harsh conditions

Bacilli

Rod-shaped bacteria

Cocci

Sphere-shaped bacteria

Spirilli

Spiral-shaped bacteria

Strepto-

Prefix meaning linear chains (e.g. streptococcus)

Staphyl-

Prefix meaning clusters (e.g. staphylococcus)

Nitrogen-fixing bacteria

Bacteria that have a mutualistic relationship with plants

Cyanobacteria

Blue-green algae; photosynthetic bacteria

Archaea

Domain of prokaryotes that have similarities to both Bacteria and Eukarya; most are extremophiles

Methanogens

Obligate anaerobes that produce methane (CH4); found in GI tract, mud, swamps

Thermophiles

Heat-loving archaea found in hot springs and volcanoes; their enzymes are ideal for PCR (e.g. Taq polymerase)

Halophiles

Salt-loving archaea found in environments with high salt concentration

Phototrophs

Organisms whose primary source of energy is light

Chemotrophs

Organisms whose primary source of energy is chemical reactions

Heterotrophs

Consumers; organisms that consume organic compounds and cannot produce them on their own

Autotrophs

Producers; organisms that produce their own organic compounds from inorganic sources

Aerobic metabolism

Series of oxygen-dependent reactions that harness ATP from organic substrates; O2 acts as final electron acceptor

Anaerobic metabolism

Series of oxygen-independent reactions that harness ATP; a molecule other than O2 acts as final electron acceptor

Obligate aerobes

Must live in the presence of oxygen

Obligate anaerobes

Cannot live in the presence of oxygen; majority of bacteria in human intestine

Facultative anaerobes

Grows in presence of oxygen, but undergoes anaerobic metabolism if oxygen is absent; majority of bacteria in mammal bodies

Microaerophiles

Thrive in environments with low saturation of oxygen; found slightly below water surface

Eukarya

Domain of organisms with larger, more complex cells than prokaryotes; membrane-bound organelles, linear DNA, reproduce sexually or asexually

Protists

Eukaryotic organisms with wide variety of ecological roles; unicellular or multicellular, autotrophs or heterotrophs, found in moist environments

Plant-like protists

Contain chloroplasts and perform photosynthesis; lack plant structures; e.g. seaweeds, dinoflagellates, euglenoids

Animal-like protists (Protozoa)

Motile, single-celled heterotrophs that perform phagocytosis; categorized based on motility

Amoebas

Use pseudopodia for movement and food capture; perform phagocytosis

Pseudopodia

Transient cytoplasmic projections that emerge toward the direction of movement

Flagellates

Use flagella for movement (e.g. T. vaginalis)

Ciliates

Use cilia for movement (e.g. Paramecium); acquire genetic variation via conjugation

Sporozoans

Gliding movement, parasitic, reproduce using spores (e.g. Plasmodium causes malaria)

Fungus-like protists

Slime and water molds; resemble fungi, reproduce using spores, heterotrophic decomposers (saprobes), do not contain chitin

Algae

Informal taxonomic group functioning as primary producers; prokaryotic or eukaryotic, photoautotrophs, lack true plant structures

Green algae (Chlorophyta)

Kingdom Plantae or Protista; found in freshwater habitats; evolutionary ancestor to terrestrial plants; contain chlorophyll

Red algae

Kingdom Plantae or Protista; mostly multicellular; found in marine habitats

Brown algae

Kingdom Protista; multicellular; found in marine habitats (e.g. seaweeds, kelp)

Cyanobacteria (blue-green algae)

Kingdom Bacteria (Gram-negative); contain chlorophyll; precursor to chloroplasts (endosymbiotic theory)

Algae bloom

Rapid increase in algae or cyanobacteria from nitrogen and phosphorous accumulation; produces toxins, blocks sunlight, decreases oxygen

Eutrophication

Process by which water bodies accumulate nutrients from fertilizer, wastewater, and stormwater runoff

Fungi

Kingdom of eukaryotic organisms; often decomposers and symbionts; cell walls contain chitin

Decomposers

Organisms that digest dead or decaying organic matter

Saprophytes

Decomposers that anchor to substance they digest and digest by releasing enzymes extracellularly

Hypha

Filaments that form the body of filamentous fungi; cells surrounded by continuous tubular cell wall

Mycelium

Network of hyphae that connect fungi together; mushrooms arise asexually from mycelium

Septate hyphae

Have cell walls (septa) that separate hyphae

Coenocytic hyphae

Multinucleated hyphae with no septa

Yeast

Non-filamentous unicellular fungi; reproduce asexually by budding

Molds

Specific type of filamentous fungi that can be diploid or haploid; grow in moist environments

Spores (fungi)

Haploid reproductive cells that can disperse and form new mycelia; not gametes because they develop on their own

Sporangium

Multicellular organ where spore formation occurs

Rhizoids

Branching hyphae that anchor structures to ground; not composed of plant tissues

Plasmogamy

Fusion of cytoplasm during fungal sexual reproduction

Karyogamy

Fusion of nuclei after plasmogamy, forming a diploid zygote

Lichens

Mutualistic relationship between fungi and algae; algae provides food via photosynthesis, fungi provides protection and anchoring

Plantae

Kingdom of eukaryotic organisms; multicellular, photoautotrophic (contain chlorophyll), cell walls contain cellulose

Alternation of generations

Life cycle between multicellular gametophyte and sporophyte forms

Sporophyte

Multicellular diploid plant stage (2n) that produces haploid spores via meiosis

Spores (plants)

Haploid dispersal units (n) that divide via mitosis to produce the gametophyte

Gametophyte

Multicellular haploid plant stage (n) that produces gametes via mitosis

Gametes

Haploid reproductive cells (n); male (sperm) and female (egg) gametes fuse to form a zygote (2n)

Tracheophytes

Plants with differentiated structures and vascular system (xylem and phloem); includes all plants except Thallophytes and Bryophytes

Pterophytes

Seedless, vascular plants with flagellated sperm; predominantly sporophyte

Flowers

Reproductive structures found in flowering plants (angiosperms)

Pistil

Female reproductive structure; includes stigma, style, and ovary

Stigma

Sticky tip of pistil that receives pollen

Style

Stalk-like structure that connects stigma to ovary

Ovary

Structure at base of pistil that surrounds ovules; eventually forms fruit

Ovules

Structures inside ovary that eventually form seeds

Stamen

Male reproductive structure; includes anther and filament

Anther

Tip of stamen that produces pollen

Filament

Stalk-like structure that supports and elevates the anther

Petals

Brightly colored modified leaves that attract pollinators

Sepals

Modified leaves that enclose and protect developing flower buds

Hermaphroditic plants

Produce flowers with both male and female reproductive structures

Monoecious plants

Produce both male and female flowers, but individual flowers don't contain both structures

Dioecious plants

Produce either male or female flowers, but not both

Fruit

Mature flower ovary that forms after fertilization to protect seed and aid in dispersal; can be fleshy or dry

Seeds (angiosperms)

Mature flower ovules containing embryo and nutrients; diploid structures produced from double fertilization

Germination

Process by which a seed or spore becomes active and develops into a new organism

Angiosperms

Flowering plants that bear seeds enclosed by fruit; undergo double fertilization

Megasporocytes

Diploid cells (2n) that undergo meiosis to produce four megaspores (n)

Microsporocytes

Diploid cells (2n) that undergo meiosis to produce four microspores (n)

Embryo sac

Female gametophyte; formed when one megaspore undergoes three mitotic divisions

Pollen grain

Male gametophyte; formed when microspore undergoes mitosis; contains generative cell and tube cell

Double fertilization

One sperm fertilizes egg (forming 2n zygote), another sperm fuses with central cell (forming 3n endosperm)

Endosperm

Nutrient-rich tissue (3n) that nourishes the developing embryo

Synergid cells

Flank the egg cell and guide pollen tube into embryo sac

Antipodal cells

Three nuclei in embryo sac that degenerate after fertilization

Cotyledon

Transfers nutrients from endosperm to embryo

Monocots

One cotyledon

Dicots

Two cotyledons

Ground tissue

Plant tissue that carries out most metabolic functions