Life 103 4th Week
Life 103 4th Week LIFE 103
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This 2 page Class Notes was uploaded by Caroline Hurlbut on Friday February 12, 2016. The Class Notes belongs to LIFE 103 at Colorado State University taught by Jennifer L Neuwald; Tanya Anne Dewey in Fall 2016. Since its upload, it has received 23 views. For similar materials see Biology of Organisms-Animals and Plants in Biology at Colorado State University.
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Date Created: 02/12/16
Seed Plants • a seed consists of an embryo and nutrients surrounded by a protective coat and provide energy for the embryo • seeds are —resistant to harsh environments, prevents desiccation (drying out) —can be dormant until environment is favorable —allow for wide dispersal • gymnosperms - “naked” + “seed” -seed are exposed on sporophylls that form cones • derived traits common to all seed plants —*reduced gametophytes (microscopic) —*heterospory —*pollen (air-borne) —ovules —seeds • gametophytes develop in the walls of spores retained within tissues of parent sporophyte seed plants’ life cycles are dominated by the sporophyte • • most gymnosperms are cone-bearing plants called conifers • seedless plants are homosporous, which produce one type of spore that develops into bisexual gametophyte • seed plants are heterosporous, which produce two types of spores, each of which develops into a male or female gametophyte • gymnosperm female anatomy —an ovule consists of a diploid megasporangium, a haploid megaspore (produced by megasporangium), and the integument (protective coating) —megaspore develops into female gametophyte • gymnosperm male anatomy —consists of a diploid microsporangium, a haploid microspore (produced by microsporangium), and pollen —microspore develops into pollen grains, which contains the male gametophyte • pollination - transfer of pollen to the part of a seed plant containing the ovules —released pollen grain reaches ovule and germinates —pollen tube formed, digesting through megasporangium and discharging sperm nucleus into egg nucleus 3 major features of gymnosperm life cycle • —miniaturization of gametophytes —development of seeds from fertilized ovules —transfer of sperm into ovules by pollen • life cycle of a pine —pine tree=sporophyte and produces sporangia in male and female cones —small cones produce microspores called pollen grains—>male gametophyte —large cones produce megaspores in ovules—>female gametophytes —takes nearly 3 years from cone production to mature seed • 4 gymnosperm phyla —coniferophyta: cone plants (largest group) —cycadophyta: palm-like leaves with large cones —gnetophyta: oddballs —gingkophyta: 1 living species coniferophyta • —sequoia —ﬁr —larch —juniper —pine
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