Gymnosperms Lecture Review

Flashcards covering key vocabulary related to Gymnosperms, including their characteristics, reproduction, and specific examples like the pine lifecycle.

Gymnosperms

A group of seed plants that includes cycads, ginkgo, conifers, and gnetophytes, characterized by 'naked' seeds not enclosed within an ovary.

Seed Plants

Arose ca. 350 MYA; their gametophyte and sporophyte develop within the sporophyte, fertilization is no longer aquatic, and the next generation sporophyte can delay growth within a seed.

Gametophyte (in seed plants)

The haploid generation that develops within the sporophyte.

Sporophyte (in seed plants)

The dominant diploid generation within which both the gametophyte and the next generation sporophyte (embryo within a seed) develop.

Seed

A structure in seed plants that provides protection and food storage for the embryo, allowing it to wait for favorable conditions before growth.

Cycads (Cycadophyta)

The most ancient lineage of gymnosperms, including trees and 'shrubs' (ca. 140 species).

Ginkgo (Ginkgophyta)

A lineage of gymnosperms with only one living species, Ginkgo biloba, a tree.

Conifers (Pinophyta)

The most common lineage of gymnosperms, including trees and shrubs (ca. 700 species), such as pine, spruce, and juniper.

Gnetophytes (Gnetophyta)

A lineage of gymnosperms exhibiting convergent evolution of angiosperm-like traits, including trees, shrubs, and woody vines (ca. 96 species).

Monoecious

Describes plants like pines and most conifers, which have both male cones and female cones on the same sporophyte.

Microsporangiate Cones

Also known as male cones, pollen cones, or male strobili, they produce pollen grains containing male gametophytes.

Megasporangiate Cones

Also known as female cones or seed cones, they contain ovules where megaspores and female gametophytes develop.

Pollen Grain

The male microgametophyte, typically released from male cones and consisting of cells (e.g., 4 or 5 cells at dispersal in pine) that will produce sperm.

Microsporogenesis

The process within the microsporangium where microsporocytes undergo meiosis to produce haploid microspores.

Microgametogenesis

The process where a microspore undergoes mitosis and cellularization to develop into a mature pollen grain (microgametophyte), which will eventually produce sperm cells.

Ovule

A structure within the female cone consisting of integuments surrounding the nucellus (megasporangium) and an opening called the micropyle.

Nucellus

The central part of the ovule, considered the megasporangium, where the megaspore mother cell forms.

Micropyle

An opening in the integuments of an ovule through which pollen is drawn and the pollen tube grows towards the egg.

Megaspore Mother Cell (Megasporocyte)

A diploid cell in the nucellus of the ovule that undergoes meiosis to produce four haploid megaspores.

Megasporogenesis

The process within the ovule where a megaspore mother cell undergoes meiosis to produce megaspores, typically with three of the four dying.

Megagametophyte

The female gametophyte that develops from a surviving megaspore inside the ovule, consuming the nucellus and forming archegonia with eggs.

Archegonia

Flask-like structures formed on the megagametophyte, each containing a single egg cell.

Pollen Tube

A tube formed from the germinating pollen grain after landing on the micropyle, which grows towards an egg to deliver sperm.

Fertilization (in pine)

The process where sperm delivered by the pollen tube fuses with an egg, forming a diploid zygote, after which the integuments close and unfertilized structures decompose.

Pine Seed

A mature ovule containing a diploid embryo (offspring sporophyte), a haploid megagametophyte (food storage from maternal genome), and a diploid seed coat (protective layer from maternal integuments).

Seed Coat

The protective outer layer of a seed, developed from the integuments of the maternal sporophyte.

Embryo (in seed)

The next generation pine tree (sporophyte), which develops from the zygote and is contained within the seed, ready for germination.