Chapter 30: Plant Diversity II: The Evolution of Seed Plants
Concept 30.1: Seeds and pollen grains are key adaptations for life on land •Name five terrestrial adaptations that contributed to the success of seed plants. 1) Seed
2) Reduction of gametophyte generation (dominant is sporophyte) -tiny gametophytes can develop in sporangia of the parental sporophytes which protect them from UV and from drying out 3) Heterospory (mega and micro)
-mega- female, part of ovule
-micro- male that develops into pollen grain and enters ovule 4) Ovules
have integument which protects
enter ovules with female megaspores and germenate
•Compare the size and independence of the gametophytes of bryophytes with those of seed plants. oSeedless vascular plants have tiny gametophytes that are visible to the naked eye --- The gametophytes of seed plants are microscopically small and develop from spores in the sporangia of the parental sporophyte. oThe gametophytes of seed plants obtain nutrients from their parents, while the gametophytes of seedless vascular plants must fend for themselves
•Describe the ovule of a seed plant.
An ovule of a seed plant consists of the megasporangium, megaspores, and integuments
•Explain why pollen grains were an important adaptation for successful reproduction on land.
Pollen grains were an important adaptation because the evolution of pollen allowed for pollination and contributed to the diversity of seed plants Basically like pollen allowed for sexual reproduction so there could be diversity •Explain how a seed can be said to include contributions from three distinct generations. 1) Seeds can survive harsh conditions through dormancy
2) Distributed far from their parent sporophyte (or close depending) 3) Multicellular.
Concept 30.2: Gymnosperms bear “naked” seeds, typically on cones
•List and distinguish the four phyla of gymnosperms.
1) Phylum Ginkgophyta
Phylum Ginkgophyta consists of only a single extant species, Ginkgo biloba This popular ornamental species has fanlike leaves that turn gold before they fall off in the autumn. 2) Cycadophyta
Cycads (phylum Cycadophyta) have large cones and palm like leaves. Cycads flourished in the Mesozoic era. (look like palms with cone) 3) Phylum Gnetophyta
Phylum Gnetophyta consists of three very different genera.
Weltwitschia plants have strap like leaves that are among the largest known leaves. (desert plant that looks like dried sea weed) Gentum species are tropical trees or vines.
Ephedra is a shrub of the American deserts. (look like Welt but have little cones) 4) Coniferophyta
The conifers belong to the largest gymnosperm phylum, the phylum Coniferophyta. The term conifer comes from the reproductive structure, the cone, which is a cluster of scale like sporophylls. (large trees, juniper berries, pines, sequoia)
•Describe the life history of a pine. Indicate which structures are part of the gametophyte generation and which are part of the sporophyte generation. •
oIn most conifer species, each tree has both ovulate and pollen cones. The pine tree is the sporophyte. Each ovulate cone contains megasporangium. Microsporangium undergoes meiosis, producing haploid micropsores that develop into pollen grains. A pollen grain enters through the micropyle and germinates, forming a pollen tube that digests through the megasporangium. By meiosis, four haploid cells are produced. One survives as a megaspore. Female egg develops. Fertilization occurs as sperm and egg nuclei unite. The ovule becomes a seed. oWhich does not apply to gymnosperms or angiosperms?
3.Single spore type (because they have micro- and megaspores) 4.Cuticle with stomata
oIn seed bearing plants, microspores develop into ____.
oHow many generations are represented in the seed of a gymnosperm? 1.1