Ploidy: the number of sets of chromosomes in an organism

Diploid: two sets of chromosomes, 2n

Haploid: one set of chromosomes, n

Gametophyte: the haploid form of an organism which gives rise to the male and female gametes

Sporophyte: the diploid form of an organism which gives rise to haploid spores

Alternation of Generations

• The sporophyte undergoes meiosis forming haploid spores

• Those haploid spores undergo mitosis to become haploid gametophytes

• Those gametophytes undergo mitosis again to form the haploid gamete

• Those gametes combine during fertilization to form a diploid zygote

• The diploid zygote grows into a new sporophyte and the process repeats

Bryophytes

• Bryophyte: non vascular plants

• Three phyla of bryophytes:

  1. Hepatophyta - liverworts

  2. Bryophyta - mosses

  3. Anthocerophyta - hornwarts

• Nonvascular plants lack specialized conducting tissues to transport water and nutrients through the plants body

• They lack “true” roots, stems, and leaves

• They only produce one type of spore

Phylum Hepatophyta:

• Liverworts

• Produce both asexually and sexually

• Asexually via gemmae and gemma cups, sexually via gametophores producing gametes

• Key anatomical features:

• Thallus: the body of a liverwort

• Rhizoids: hairlike structures that anchor the thallus

• Two distinct types:

  1. Thalloid Liverworts

• Possess thalli: flat, leaflike lobed bodies

• Commonly found along creek banks or in moist soil

  2. Leafy Liverworts

• Resemble mosses

• Commonly found on tree barks in tropical and subtropical environments

Liverwort Lifecycle

Phylum Bryophyta:

• Also called the true mosses

• Found in temperate zones growing on trees, rocks, and the sides of buildings

• Serves as a pioneer species to help form soil

• Key anatomical features:

• Operculum: lid-like structure on the tip of the capsula

• Peristome: teeth like structures that lock the operculum to the capsule

• Protonema: developed from immature spores and will eventually develop into the “leafy” gametophyte

Moss Lifecycle

Vascular Plants

• Possess tissues for conducting water and nutrients throughout the plant

• Xylem: conducts water and dissolved minerals

• Phloem: conducts nutrients, hormones, and other molecules

• Vascular plants possess true roots, stems, and leaves

• Separated into seedless vascular plants and seed plants

Phylum Lycophyta:

• Club mosses, quillworts, and spike mosses

• Homosporous — only produce one type of spore

• Key anatomical features:

• Rhizome: produces aerial stems and underground roots

• Sporophyllus: reproductive sporangia located on the surface of leaves

• Strobilus: cone-shaped structure that contains spores

Phylum Psilotophyta:

• Known as whisk ferns

• Homosporous — only produce one type of spore

• Does not have leaves or roots

• Has a photosynthetic stem that contains bright yellow synangia

• Horizontal rhizome gives rise to the aerial stem

Phylum Sphenophyta:

• Known as horsetails

• The aerial stems of horsetails are ribbed, and stomata occur in the grooves between the ribs

• Rhizomes run horizontally across ground and gives rise to aerial stem and roots

• Key Anatomical structures:

• Microphylls: small, scalelike leaves arranged in a whorl at the nodes

• Pith: the center of the stem, hollow in horsetails

• Sporangiophores: make up the strobili at the tip of the stem, contains sporangia that produce spores

Phylum Pterophyta:

• Also known as ferns

• Key anatomical features:

• Fronds: the leaves of ferns, arise from rhizomes

• Fiddlehead: tightly rolled up and coiled structure consisting of immature fronds

• Pinnae: ornate leaflets possessed by compound frond ferns

• Petiole: attaches the pinnae to the rhizome, sometimes called stalk

• Sori: the sporangia of ferns that appear as distinct brown spots on the underside of the frond

• Indusium: colorless flap that protects the sori

• Annulus: fuzzy region of the sorus that catapults mature spores

Fern Life Cycle: