Seed Plants (29)
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•Late in the ______, some plants developed secondary
Devonian (~400 mya)
thickened woody stems of xylem
Alternation of generations differs between nonvascular plants, vascular non-seed plants, and seed plants
The evolution of seeds provided a means for plants to:
Tolerate severe ecological conditions that could not support an independent gametophyte stage.
Withstand variation in climate that included unfavorable periods of drought or cold.
Develop mechanisms for both animal and wind dispersal into new habitats
Seed plants dominate on land during the___a___ era
Gymnosperms were dominant during the ___a___, until about ______.
Angiosperms also appear later in the ___a___
era during the ________ period (oldest fossils from _____)
Angiosperm radiation was explosive; they became dominant in _____ in the_______ era.
- 65 Mya
- Cretaceous/140 mya
- ~60 million yrs/Cenozoic [remain dominant plants]
Factors that contributed to the success of seed plants include:
- -reduction of the size of thegametophyte
produce 2 types of spores (seed plants do this)
One becomes female gametophyte, one becomes male gametophyte.
- The female gametophyte that arises from a megaspore of a heterosporous plant.
- A plant structure in which megaspores are formed, such as those of the female cones of pines
when a pollen grain lands near a female gametophyte and a pollen tube is produced that digests its way through the sporophyte tissue to the megagametophyte.
(“naked seeds”): ovules and seeds are not protected by ovary or fruit tissue
- •4 major groups of living Gymnosperms
- §Cycads (Cycadophyta): 300 spp,
- §Ginkgos (Ginkgophyta): only 1 species survives
- §Gnetophytes (Gnetophyta): 90 spp.
- §Conifers (Coniferophyta): 700 spp.,
300 spp, appear palm-like, but w/o flowers; mostly tropical.
§Ginkgos (Ginkgophyta): only 1 species survives, Ginkgo biloba.
90 spp., restricted to deserts and the tropics.
700 spp., the cone bearers, includes the pines, firs, junipers; aredominant trees in northern climates; include oldest living organisms on earth(e.g. bristlecone pines that germinated ~4,800 ya).
Cone vs Strobilus
A cone is a modified stem, bearing a tight cluster of scales (reduced branches), specialized for reproduction. Megaspores are produced here.
- cone-like structure; scales are modified leaves. Microspores are produced here.
The oldest angiosperm fossils are_______, ______ old. Radiation was explosive during the Tertiary. Over _______ species exist today.
Jurassic, 150 million years
5 Synapomorphies in Angiosperms include:
Double fertilization with a diploid zygote and triploid endosperm.
Endosperm—nutritive tissue in seeds
Ovules and seeds enclosed in a carpel
Flower develops as a reproductive structure
Fruits (mature ovary) protects ovule and aid in dispersal.
- Xylem with vessel elements and fibers, phloem with
- companion cells
-Microgametophyte has two male gametes. Nucleus of one combines with egg.
-The other nucleus combines with two haploid nuclei of female gametophyte to form a triploid nucleus—becomes the endosperm.
-Endosperm nourishes developing sporophyte.
•Enclose ovules and seeds; that’s why Angiosperms mean “enclosed seed”:
-provide protection, and may interact with pollen to prevent self-pollination.
Anther, Carpel, Filament, Ovary, Ovule, Petal, Receptacle, Sepal, Stamen, Stigma, Style
Stamens bear______: consist of ____and_____.
Carpels bear______. One or more carpels form the_____ = _______.
Petals and sepals are modified leaves. Often play a role in attracting pollinators.
microsporangia/filament and anther
megasporangia/ pistil/stigma, style, ovary
•have large and variable # of sepals and petals.
“one-housed”; male and female flowers occur on the same plant.
“two-housed”;male and female flowers on different plants. Inflorescence: grouping offlowers.
Angiosperms are _____sporous
•_______ fruits develop from one carpel (e.g. cherry).
•_______ fruits develop from several carpels (e.g. rasberry).
•_______ fruits form from a cluster of flowers (e.g. pineapple).
•_______ fruits develop from parts other than carpels (strawberry, apple).
Most Angiosperms are in two clades:
Monocots and Eudicots
one cotyledon (generally have leaves with parallel veins ); mostly wind pollinated. Monocots include grasses, cattails, lilies, orchids, and palms
two cotyledons (usually have leaves with netlike veins); mostly animal pollinated (e.g. most flowering plant species). Eudicots include most of the seed plants, including most herbs (nonwoody plants), vines, trees, and shrubs.
Other 4 Angiosperm clades include:
Amborella trichopoda: the most primitive living angiosperm (found only on New Caledonia, an island in the south pacific).
“Water lilies”: the most primitive of the widely distributed Angiosperm groups.
Star anise (Illicium floridanum) and relatives.
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