Seed Plants and Evolution

This set of vocabulary flashcards covers the evolution, reproductive adaptations, and classification of seed plants, including gymnosperms and angiosperms.

Seed

A structure consisting of an embryo and nutrients surrounded by a protective coat, originating about $360\,million$ years ago.

Gymnosperms

A clade of seed plants that appeared about $305\,million$ years ago, characterized by "naked seeds" exposed on sporophylls that usually form cones.

Angiosperms

Seed plants with reproductive structures called flowers and fruits; they began to replace gymnosperms near the end of the Mesozoic era.

Mesozoic

A geological era lasting from $251-65.5\,million$ years ago, during which gymnosperms dominated terrestrial ecosystems.

Heterospory

The production of two different types of spores: megaspores that give rise to female gametophytes and microspores that give rise to male gametophytes.

Megasporangia

Structures that produce megaspores, which eventually give rise to female gametophytes.

Microsporangia

Structures that produce microspores, which eventually give rise to male gametophytes.

Ovule

A structure consisting of a megasporangium, megaspore, and one or more protective integuments.

Integument

A layer of sporophyte tissue that surrounds the megasporangium/embryo; gymnosperms typically have one, while angiosperms usually have two.

Pollination

The transfer of pollen to the part of a seed plant containing the ovules, eliminating the need for a film of water for sperm transfer.

Pollen grain

Developed from microspores, these structures contain the male gametophytes and can be dispersed by wind or animals.

Endosperm

A supply of stored food found within a seed that supports the embryo.

Conifers

The largest group of gymnosperms, consisting of cone-bearing plants such as pine, fir, and redwood.

Phylum Cycadophyta

A phylum of gymnosperms often mistaken for palms due to their leaf shape; they currently face extinction.

Phylum Ginkgophyta

A gymnosperm phylum represented by only one living species: Ginkgo biloba.

Phylum Gnetophyta

A diverse gymnosperm phylum consisting of the three genera: Gnetum, Ephedra, and Welwitschia.

Sepals

Modified leaves of a flower that function to enclose and protect the flower before it opens.

Petals

Brightly colored floral organs that serve to attract pollinators to the flower.

Stamens

The pollen-producing reproductive organs of a flower, consisting of a stalk (filament) and a pollen sac (anther).

Carpels

The ovule-producing reproductive organs of a flower, consisting of an ovary at the base, a style, and a stigma.

Complete flower

A flower that contains all four floral organs: sepals, petals, stamens, and carpels.

Perfect (Bisexual) flowers

Flowers that possess both functional stamens and functional carpels.

Fruit

A structure formed when the ovary wall thickens and matures, functioning to protect seeds and aid in their dispersal.

Monocots

A group of angiosperms (forming more than one-quarter of species) characterized by one cotyledon, parallel leaf veins, and scattered vascular tissue.

Eudicots

A group of angiosperms (forming more than two-thirds of species) characterized by two cotyledons, netlike leaf veins, and vascular tissue arranged in a ring.