The Evolution and Diversity of Modern Gymnosperms

Flashcards about gymnosperms and their evolution

What is a plant embryo?

A young sporophyte that develops from a zygote, is multicellular and diploid, retained in maternal tissue, and depends on the mother plant for nutrients.

What is the function of placental transfer tissue?

To promote the movement of solutes from the gametophyte to the embryo, found in gametophyte tissues closest to embryos and in the embryos themselves

What are lycophylls?

The simplest, most ancient leaves produced by lycophytes, also called microphylls

What are euphylls?

Leaves with extensively branched veins found in other vascular plants, also called megaphylls. Larger size provides considerable advantage and evolved in a series of steps.

Describe the origin of seeds.

Ovule consists of a sporangium with a single spore and a small egg-producing gametophyte inside, enclosed by integuments. Seed plants produce microspores (male) and megaspores (female).

What happens during double fertilization?

One sperm fertilizes the egg to become an embryo, and the other sperm fuses with gametophyte tissue to form endosperm. The ovule's integument develops into a protective seed coat.

What are the ecological advantages of seeds?

Key adaptation to reproduction in a land habitat, able to remain dormant, have adaptations to improve dispersal, store food, and allow sperm to reach the egg without water.

What are some major critical innovations shared by all seed plants?

Pollen, ovules, seeds, and wood

What are the two functions of wood?

Allows woody tissue to transport water upward for great distances and provides structural support

What is the vascular cambium?

Produces a thick layer of wood and a thin layer of inner bark, inner bark used for transporting watery solutions of organic compounds

What are progymnosperms?

First wood, vascular tissue in a ring (eustele), produces vascular cambium and wood, reproduced by means of spores (not seeds)

Describe Phylum Cycadophyta.

300 cycad species, primarily tropical/subtropical, many species are rare, nonwoody stems may emerge like tree trunks or be underground, leaves palm-like

What are corraloid roots?

Roots are above ground and resemble corals, harbor cyanobacteria for nitrogen fixation, can produce toxins to deter herbivorous animals.

Describe reproduction in Phylum Cycadophyta.

Conelike structures bearing ovules and seeds or pollen, cones emit odors that attract beetles, beetles carry pollen to ovules

Describe Phylum Ginkgophyta.

Ginkgo biloba is the single remaining species, nearly extinct in the wild, widely planted along city streets (only males), individual trees produce either ovules and seeds or pollen, flagellate sperm, long-lived trees.

Describe Phylum Coniferophyta.

Named for seed cones, 500 species in 50 genera, common in mountain and high-latitude forests, simple pollen cones, more complex ovule-bearing cones, mature pollen released to wind.

How are seeds dispersed in Phylum Coniferophyta?

Some seed coats have wings for wind dispersal, others produce seeds or cones with brightly colored, fleshy coatings to attract birds for dispersal.

What are some cold climate adaptations of Phylum Coniferophyta?

Conical shape, flexible branches, scale-like or needle-shaped leaves, thick waxy cuticle; most are evergreens.

Name the three orders of Gnetales.

Gnetum, Ephedra, and Welwitschia

Describe Genus Gnetum.

Has broad leaves similar to tropical plants, vines, shrubs or trees in tropical Africa or Asia

Describe Genus Ephedra.

Native to arid SW US, produces ephedrine

Describe Genus Welwitschia.

One living species, coastal Namib Desert in SW Africa, long taproot and 2 very long leaves, obtains water from coastal fog

Describe the origin and characteristics of Phylum Gnetophyta.

Comprises only three genera, with uncertain relationships; some traits resemble angiosperms, such as vessel elements in xylem. This suggests convergent evolution.

What is the importance of 'vessel elements'?

Efficient water conduction, also found in angiosperms.

Describe angiosperms.

Flowering plants. The most diverse and successful plant group; defined by flowers, fruits, endosperm, and vessels.

What is the function of flowers?

Specialized for efficient pollination; key innovation leading to angiosperm success.

Describe the function of fruits.

Develop from ovaries after fertilization, aid in seed dispersal, and can be fleshy or dry.

Describe the process of endosperm formation.

A nutritive seed tissue with high-energy content. Formed when a second sperm nucleus fuses with the polar nuclei in the ovule.

Describe the structure and function of vessel elements.

Specialized water-conducting cells; more efficient than tracheids found in gymnosperms and other vascular plants.

What are the two major clades of angiosperms?

Monocots and eudicots.

Describe the characteristics of monocots.

One cotyledon, include grasses, palms, and orchids.

Describe the characteristics of eudicots.

Two cotyledons, vast majority of flowering plants.