Plantae-gymnosperms

= = Gymnosperms - Kingdom plantae =Compiled by Rohit Krishnan =



__General characteristics of Gymnosperms__
==== Gymnosperms (from Greek //gymnos,// naked, and //sperma// seed) are vascular plants that are the first plants to have the presence of a seed to increase the productivity of reproduction. The seeds develop on the surface of the reproductive organs of the plants (which is why they are called the "naked-seed" plants).(SP) Early forms of Gymnosperms, similar to Conifers, evolved over 360 million years ago near the end of the Devonian period. Gymnosperms are defined particularly by their lack of a chamber (ovaries) for hosting the seed. This differs from the typical angiosperm. However, the Gymnosperms hold their ovules and seeds in specialized leaves called Sporophylls. They evolved form seed ferns that went extinct in the early Cretaceous period. As they fell other gymnosperms rose in dominance. (rj) ====

In gymnosperms, the gametophyte generation is greatly reduced, and the tree is the sporophyte. (MR; Source 13) The bulk of today’s world-wide coal and oil deposits are as a result of gymnosperm remains. (MR; Source 13)


 * ====Phylum Ginkgophyta ====
 * Commonly known as the Gingko
 * Approximately 1 existent specie found as a shrub in the American desert region
 * They are mostly only found in temperate zones, that too because of horticultural inventions (almost extinct.) (SP)
 * Gingko plants are dioecious, meaning that they have genders; there are male plants and female plants. (SP)


 * ====Phylum Cyadophyta ====
 * Commonly known as Cyads
 * Approximately 100 existent species resembles palm trees
 * Reproduce using pollen bearing sacs (in tube shape) (MM)
 * Most of them superficially resemble ferns or palms, having a cluster of long pinnate (rarely bipinnate) fronds growing from a central stalk, but they differ in developing distinctive male and female cones. (RW)
 * All species have coralloid roots, which support symbiotic cyanobacteria capable of nitrogen fixation.(RW)

A tropical cyad! (LPE)
 * ====Phylum Gnetophyta====
 * Commonly known as Gnetae
 * Only type of gymnosperm that undergoes double fertilization. (MM)
 * Approximately 70 existent species consists of three genera
 * //Welwitschia// - Large strap-like leaves
 * an example would be Welwitschia mirabilis of the southwestern African deserts where leaves arise from a woody trunk above the ground that extends below the ground into a large taproot (IL)
 * //Gnetum// - Grow in the tropics as trees or vines
 * //Ephedra -// A shrub of the American deserts
 * often called joint firs or Mormon tea in North America (IL)
 * examples include Ephedra viridis and Ephedra funerea, both of which have green stems and are found in the Death Valley region of California although one has scale-like leaves at the nodes and the other is leafless, respectively (IL)
 * ====<span style="font-family: "Trebuchet MS",Helvetica,sans-serif; font-size: 14px; line-height: 21px;">Phylum Coniferophyta ====
 * ====<span style="font-family: "Trebuchet MS",Helvetica,sans-serif; font-size: 14px; line-height: 21px;">Commonly known as Conifers ====
 * ====<span style="font-family: "Trebuchet MS",Helvetica,sans-serif; font-size: 14px; line-height: 21px;">The largest of the four gymnosperm phyla ====
 * ====Over 550 existent species, **the most typical being cedars, firs, junipers, spruces, and pines (MB)**====
 * Conifers are not just plants with needles instead of leaves but are defined as any plant that bears cones. A common misconception is that conifers must have needles. (JS)
 * <span style="font-family: "Arial Black",Gadget,sans-serif;">Well-represented in fossil record, and date back to the mesozoic era. (PS Source 11)

The image above shows the life cycle of a gymnosperm (CP source 5)

__Anatomy and Reproductive structures__

 * ====Gymnosperms are part of an umbrella group called **Vascular Plants.** Although there are similar characteristics, vascular plants do differ from bryophytes.This specific characteristic is the vascular tissue. In this tissue, a group of cells serve as a path to transport the water and nutrients acquired throughout the body of the plant.====
 * ====A characteristic that differentiates Gymnosperms from many other plantae is the use of **Seeds** to improve reproductive selection. A seed consists of a plant embryo[[image:http://occawlonline.pearsoned.com/bookbind/pubbooks/campbell6e_awl/medialib/assets/e-book/fig/big/fig30-2.jpg width="360" height="131" align="right" caption="From ovule to seed"]]and a layer of food and nutrients necessary for the embryo to survive. Approximately 360 million years ago, the first vascular plants with seeds were the Gymnosperms. These early Gymnosperms make way for today's conifers.====




 * ====**Pollination** is the transfer of pollen to the ovules. In a Gymnosperm and other seed-bearing plants, this process is critical to the development of the zygote. If a pollen grain lands in the vicinity of an ovule, the grain will extrude a tube which is used as a method of transferring the male sperm(s) into the female gamete in the ovule. In most Gymnosperm, the sperm cell does not have flagella. This means that they do not have an active transport mechanism through the tube. They are often carried through using air and wind. However, some Gymnosperms' sperm need the presence of a thin film of water to aid in the transport. The use of air, promotes the diversity of Gymnosperm offspring due to the large variation in environmental conditions.====

(AR) =__Transport of Materials__=

=__Reproduction__=
 * Gymnosperms are intrinsically characteristic for their use of a vascular tissue to deliver nutrients and water to the whole plant or tree. This efficient form of distribution of resources is done using a layer of tissue surrounding a cavity which allows for transfer of water or nutrients using capillary action. Although it is quite simple of a design (similar to that of straws), it has been naturally selected for optimal transport. This method is also used by several other plants, including Angiosperms.
 * In order to transport nutrients gymnosperms depend on two vascular tissues, xylem and phloem. The xylem is a vascular tissue that is used by plants to transport water from the roots to the shoots. Gymnosperms have xylem that are composed of tracheids which are long tapered cells specifically designed for water transport. The phloem is a vascular tissue that is used by plants to transport food (sugar) to the rest of the plant. Unlike the one way travel of water in the xylem, the phloem transports sugar to both the roots and the shoots of the plant; the phloem is predominately composed of companion and sieve cell types.[[image:http://image.absoluteastronomy.com/images/encyclopediaimages/s/st/stem-cross-section2.jpg caption="Cross section of an Asperagus Stem (MS 10)"]]

As shown in the diagram to the right, the reproductive process of a typical gymnosperm plant (in this example, the fern) involves the fertilization of an egg and a sperm to form a new cell. This process starts with a mature sporophyte, the structure which produces spores. This structure then develops a sporangium, which is the enclosure for the spores. The spores inside the soprangium, after Meiosis, then develop outside the sporangium to become a young gametohyte (which produces gametes). The Antheridium and the Archegonium later form the male and female gametes respectively and the gametes meet to fertilize as a zygote. This zygote undergoes the process of Mitosis to form a new sporophyte and a new gametophyte to continue this process of sexual reproduction.

=__Environmental Adaptations__=

> > > Read more: [|Gymnosperms & Adaptation | eHow.com] [|http://www.ehow.com/facts_7349023_gymnosperms-adaptation.html#ixzz1dePeEFts]
 * One very important terrestrial adaptation that is not specific to Gymnosperms is the development of **Apical Meristems**. These are areas in the roots and shoots involving high productivity and growth. This environmental "adaptation" is naturally selected for its ability to use resources more efficiently.
 * Conifers' leaves are needle-shaped to conserve water, which is why angiosperms can survive in areas which are drier and have harsher conditions than ferns can tolerate. (SP)
 * <span style="background-color: #ffffff; color: #000000; display: block; text-align: left; text-decoration: none;">Many conifers are evergreen, which means they maintain their leaves throughout the year. In some ecosystems this gives them an advantage over deciduous trees that must shut down photosynthesis operations when their leaves drop. Conifers often excel in harsh conditions such as arid hills or high mountain environments. (RW)

__**Review Questions**__ 1. Explain how reproduction in gymnosperms is analogous to internal fertilization of land dwelling animals. (TB) 2. What are some adaptions that the gymnosperm has to live on land? (AR) 3. Discuss the differences and similarities between the four different gymnosperm phylum. (VN) 4. Identify and discuss the major types of gymnosperms. (CM) 5. Where are Ginkgophyta mostly found? (MP) 6. How does the transport of materials happen in a gymnosperm? Explain how water and nutrients (sugars) travel to different parts of the plant. (SP)

<span style="color: #0004ff; font-family: "Times New Roman",Times,serif; font-size: 120%;">__**Sources**__ <span style="font-family: "Times New Roman",Times,serif;">Campbell, Neil A., and Jane B. Reece. __Biology__. Sixth Edition. Boston: Benjamin-Cummings Company, 2002.

Carter, Stein J. "Gymnosperms." //Biology at Clermont College - University of Cincinnati//. 2 Nov. 2004. Web. 30 Oct. 2011. <http://biology.clc.uc.edu/courses/bio106/gymnospr.htm>. (SP)

[] (JS)

4. [|http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookplantanat.html#Xylem]

5. "Gymnosperm Life Cyle." //<span style="background-color: #ffffff; font-family: "Times New Roman",Times,serif; font-size: 16px;">Memorial University //. Web. 06 Nov. 2011. <http://www.mun.ca/biology/scarr/Gymnospermae.html>. (CP) 6. Cyadophyta 06 Nov. 2011 [|http://www.esu.edu/~milewski/intro_biol_two/lab_3_seed_plts/Cycadophyta.html] (MM) Gnetophyta 06 Nov. 2011 [] (MM)

<span style="font-family: "Times New Roman","serif"; font-size: 16px;">< [] > (RW)

<span style="font-family: "Times New Roman","serif"; font-size: 16px;"> [] (RW)

<span style="font-family: "Times New Roman","serif"; font-size: 16px;">Source 9 http://botit.botany.wisc.edu/Resources/Botany/Gymnosperms/Old%20Collection/Ginkgophyta/Ginkgo%20Leaf%20MC%20.jpg (Matt B)

http://www.kentschools.net/hmcclure/files/2010/04/gymnosperm.jpg (cone image) [] (LPE) [|http://www.ehow.com/facts_7349023_gymnosperms-adaptation.html(RW]) 10. //Stem-cross-section//. Digital image. //Http://image.absoluteastronomy.com//. Web. <http://image.absoluteastronomy.com/images/encyclopediaimages/s/st/stem-cross-section2.jpg>.// //(MS)//

//[] (JP)//

//11. []//

//12. "Welwitschia and Ephedra: Remarkable Genera of Gymnosperms."// WAYNE'S WORD//. Web. 14 Nov. 2011. <http://waynesword.palomar.edu/welwit.htm>. (IL) 13. "Gymnosperm." The Gale Encyclopedia of Science. Ed. K. Lee Lerner and Brenda Wilmoth Lerner. 4th ed. Detroit: Gale, 2008. Gale Science In Context. Web. 3 Dec. 2011.