Group 1 - BryophytesReading A - Evolution

The earliest known moss fossil is from the early Carboniferous period, about 320 million years ago. Mosses are not well-represented in the fossil record because their soft tissue is not well preserved. An examination of extant species indicates that bryophytes are a polyphyletic group. They appear to have evolved from more than one ancestral line.

Most botanists believe that mosses evolved from aquatic ancestors but there is debate about their evolutionary ancestry. It is commonly accepted by most botanists that mosses evolved from a simpler filamentous green alga. Although bryophytes appear intermediate in complexity between algae and vascular plants, they are unlikely to be an evolutionary "missing link" between these two groups.

Read more: Moss - Evolution - Mosses, Evolved, Appear, and Evolutionary - JRank Articles http://science.jrank.org/pages/4459/Moss-Evolution.html#ixzz2PPNwkQH4

Group 1 - BryophytesReading B - Examples

Group 1 - BryophytesReading B - Life Cycle

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http://upload.wikimedia.org/wikipedia/commons/1/10/Lifecycle_moss_svg_diagram.svg

Group 1 - BryophytesReading C - Distinguishing Characteristics

There are several characteristic features of bryophytes. First, the green tissue that makes up most of the plant body is not vascularized; it does not have xylem and phloem cells. This absence of specialized tissues for transporting water and dissolved food throughout the organism limits terrestrial forms to being very short plants, since the only way to move substances through the plant body is by osmosis and diffusion from surface moisture.

Second, bryophytes do not have roots, but have rhizoids, which are relatively simple, sometimes multicellular filaments of thin-walled cells that extend from the photosynthetic tissue into the soil or other substrate. They anchor the plant somewhat and in some cases facilitate water and nutrient uptake.

Mosses, liverworts, and hornworts lack complex vascular tissue for transporting water and nutrients. Some mosses have simple vascular tissue. 

The lack of an extensive system of  vascular tissue restricts their size. The largest are less than 20 cm (8 in.).

Rhizoids are root-like structures that absorb water and nutrients. They do not have true roots, stems, or leaves because they lack vascular tissue.

Bryophytes are generally restricted to moist areas because the sperm are flagellated and therefore require at least a film of water to swim to the egg.

The sporophyte of bryophytes is dependent on the gametophyte, that is, it derives its nutrition from the gametophyte. The gametophyte is independent.

Read more: http://www.biologyreference.com/Bl-Ce/Bryophytes.html#ixzz2PPK1GxEf

Group 2 – Seedless Vascular PlantsReading A - Evolution

The earliest vascular plants lacked seeds. Members of four phyla of living vascular plants lack seeds, as do at least three other phyla known only from fossils. As we explore the adaptations of the vascular plants, we focus on both reproductive strategies and the advantages of increasingly complex transport systems. We will begin with the most familiar phylum of seedless vascular plants, the ferns.

Ferns (Pterophyta)

Ferns are the most abundant group of seedless vascular plants, with about 12,000 living species. Recent research indicates that they may be the closest relatives to the seed plants. The fossil record indicates that ferns originated during the Devonian period about 350 million years ago and became abundant and varied in form during the next 50 million years. Their apparent ancestors had no broad leaves and were established on land as much as 375 million years ago.

Today, ferns flourish in a wide range of habitats throughout the world; about 75% of the species, however, occur in the tropics.

Source: http://www.mhhe.com/biosci/genbio/tlw3/eBridge/Chp16/16_3.pdf

Group 2 – Seedless Vascular PlantsReading B – Examples

Group 2 – Seedless Vascular PlantsReading B - Life Cycle

Group 2 – Seedless Vascular PlantsReading C - Distinguishing Characteristics

Seedless vascular plants include ferns, whisk ferns, club mosses, and horsetails.

The plants do not produce seeds so, like bryophytes, they are dispersed (spread) by windblown spores.

The gametophyte and sporophyte are independent.

They are vascular plants and therefore have true roots, stems, and leaves.

The sperm are flagellated and require water for reproduction. These plants are therefore limited to moist areas.

Many of the seedless vascular plants were once tree-sized. During the carboniferous period (near the end of the Paleozoic), these plants were so abundant that in some areas, their remains accumulated faster than they decomposed. These accumulations produced our fossil fuels.

The earliest known vascular plants had a pattern of branching that increased the number of sporangia.

Leaves of later plants probably evolved from webbing between the branches.

Group 3 – GymnospermsReading A – Evolution

Gymnosperms are seed-bearing plants that lack the combination of specialized features that characterize the flowering plants. The name gymnosperm, means naked seed. (e.g. gymnasium); that is, the seeds are not enclosed within fruits.

Gymnosperms, then, are all fruitless seed plants. And they are made up of a heterogeneous group of plants characterized by the production of naked seeds. Estimates form fossil records indicate that gymnosperms must have evolved approximately 300 million years ago from non-seed producing ancestors of the extinct division of Progymnospermophyta, which were fern-like in appearance.

1. They lack the folded, marginally-sealed carpels that characterize the flowering plants.2. The pollen-receptive structures are the ovules rather than the stigmatic portion of the carpels.3. Most gymnosperms lack vessels in their xylem (unlike flowering plants which have both vessels and tracheids), except for the gnetophytes, which have vessels.

 Considering the relatively small number of living gymnosperms (about 720 species in 65 genera), they are remarkably diverse in their reproductive structures and leaf types.

Gymnosperms, like angiosperms (the flowering plants), differ from seedless plants (like mosses and ferns) in not requiring water for sperm to swim in to reach the egg. This means that the movement of pollen (male gamete) to ovule (female gamete) in seed plants relies on airborne transport, not water transport. Consequently, most gymnosperms produce huge amounts of pollen.

Group 3 – GymnospermsReading B - Examples

Group 3 – GymnospermsReading B - Life Cycle

Group 3 – GymnospermsReading C - Distinguishing Characteristics

The gymnosperm is a seed-bearing vascular plant that does not bear flowers. The gymnosperm is either woody plant, trees, shrubs, but seldom vines. Many of them are very large in size. Gymnosperms are borne upon seed scales arranged in cones.

Gymnosperms are the most ancient seed plants that we know of. The gymnosperms appear to have arisen from the fern ancestors in the Devonian Period.

They are arranged in four different phyla: Cycadophyta, Ginkgophyta, Pinophyta, and Gnetphyta. The Cycads and the Gnetophytes are mainly tropical to subtropical. Although the Cycad and Gingko are now extinct relatives.

To help conserve water evergreens have needles ( flat leaves) with a waxy coating. An evergreen is known as a confier. Which are trees or shrubs that bear seeds in cones. 

Below is a picture of a pine cones inside. If you look closely at picture (A) you can see the seeds.

A.) A pine cones insides

Group 4 – AngiospermsReading A - Evolution

Angiosperms (flowering plants) appeared about 130 million years ago and today dominate the plant world, with approximately 235,000 species.

In early Devonian-age rocks, approximately 363- 409 million years old, fossils of simple vascular and nonvascular plants can be seen. Ferns, lycopods, horsetails, and early gymnosperms became prominent during the Carboniferous period (approximately 290-363 million years ago).

The gymnosperms were the dominant flora during the Age of Dinosaurs, the Mesozoic era (65-245million years ago). More than 130 million years ago, from the Jurassic period to early in the Cretaceous period, the first flowering plants, or angiosperms (phylum Anthophyta), arose. Over the following 40 million years, angiosperms became the world’s dominant plants.

The angiosperms show high species diversity, and they occupy almost every habitat on earth, from deserts to high mountain peaks and from freshwater ecosystems to marine estuaries. Angiosperms range in size from eucalyptus trees well over 100 meters (328 feet) tall with trunks nearly 20 meters (66 feet) in circumference to duckweed, simple floating plants barely 1 millimeter (0.003 inch) long.

Group 4 – AngiospermsReading B - Examples

Group 4 – AngiospermsReading B - Life Cycle

Group 4 – AngiospermsReading C - Distinguishing Characteristics

Some of the defining characteristics of angiosperms involve their physical appearance or morphology and internal anatomy: the presence of flowers and fruits containing seeds, stamens with two pairs of pollen sacs, a microgametophyte (the male, haploid stage of the life cycle contained in the pollen) with three nuclei, a megagametophyte (the female, haploid stage of the life cycle enclosed in the ovary) with eight nuclei, companion cells, and sieve tubes in the phloem (vascular tissue important in the transport of organic molecules).

Some of these characteristics involve life-cycle features, such as double fertilization, that are distinct from almost all other members of the plant kingdom.

Because angiosperms possess so many unique features, plant taxonomists have long believed that angiosperms originated from a single common ancestor. Because the first flowers and pollen grains appear in fossils from the early Cretaceous period, up to about 130 million years ago, it is probable that angiosperms actually arose more than 130 million years ago.

As the findings of paleobotanists (botanists who study plants in the fossil record) have been combined with more recent knowledge from evolutionary genetics and biochemistry, a clearer picture of angiosperm evolution has emerged.