Plant Kingdom - Past Notes

A Debate with an Atheist: The Story of Creation (14) -- Plants Evolution, Plants Kingdom, Wheat, Palms in the Holy Quran.https://www.chegg.com/homework-help/refer-figure-231-trace-evolutionary-history-land-plants-trai-chapter-23-problem-1rc-solution-9780077350611-exc **[Non-vascular Plants]** Horn...

A Debate with an Atheist: The Story of Creation (14) -- Plants Evolution, Plants Kingdom, Wheat, Palms in the Holy Quran.https://www.chegg.com/homework-help/refer-figure-231-trace-evolutionary-history-land-plants-trai-chapter-23-problem-1rc-solution-9780077350611-exc **[Non-vascular Plants]** Hornworts, liverworts, and mosses are seedless, non-vascular plants that likely appeared early in land plant evolution. **Phylum Anthocerophyta -- Hornworts** Hornworts are the smallest group of bryophytes. They have colonized a variety of habitats on land, although they are never far from a source of moisture. The short, blue-green gametophyte is the dominant phase of the lifecycle of a hornwort. The narrow, pipe-like sporophyte is the defining characteristic of the group. The sporophytes emerge from the parent gametophyte and continue to grow throughout the life of the plant. **Example: *Anthoceros*** **Phylum Hepaticophyta -- Liverworts** Liverworts** **are viewed as the plants most closely related to the ancestor that moved to land. Liverworts have colonized every terrestrial habitat on Earth and diversified to more than 7,000 existing species. Some gametophytes form lobate green structures. The shape is similar to the lobes of the liver, and hence provides the origin of the name given to the phylum. Liverworts can reproduce asexually and sexually. They reproduce asexually via fragmentation. Liverworts are dioecious (separate male and female plants) **Example: *Marchantia*** **Phylum Bryophyta -- Mosses** More than 10,000 species of mosses have been catalogued. Their habitats vary from the tundra, where they are the main vegetation, to the understory of tropical forests. In the tundra, the mosses' shallow rhizoids allow them to fasten to a substrate without penetrating the frozen soil. Mosses slow down erosion, store moisture and soil nutrients, and provide shelter for small animals as well as food for larger herbivores, such as the musk ox. Mosses are very sensitive to air pollution and are used to monitor air quality. Mosses can reproduce asexually and sexually. They reproduce asexually via fragmentation. Liverworts are dioecious (separate male and female plants) Mosses form diminutive gametophytes, which are the dominant phase of the lifecycle. Green, flat structures---resembling true leaves, but lacking vascular tissue---are attached in a spiral to a central stalk. The plants absorb water and nutrients directly through these leaf-like structures. Some mosses have small branches. Some primitive traits of green algae, such as flagellated sperm, are still present in mosses that are dependent on water for reproduction. Other features of mosses are clearly adaptations to dry land. For example, stomata are present on the stems of the sporophyte, and a primitive vascular system runs up the sporophyte's stalk. Additionally, mosses are anchored to the substrate---whether it is soil, rock, or roof tiles---by multicellular rhizoids. These structures are precursors of roots. They originate from the base of the gametophyte, but are not the major route for the absorption of water and minerals. The lack of a true root system explains why it is so easy to rip moss mats from a tree trunk. **[Vascular Plants]** The vascular plants are the dominant and most conspicuous group of land plants. More than 260,000 species of tracheophytes represent more than 90 percent of Earth's vegetation. Several evolutionary innovations explain their success and their ability to spread to all habitats. Bryophytes may have been successful at the transition from an aquatic habitat to land, but they are still dependent on water for reproduction, and absorb moisture and nutrients through the gametophyte surface. The lack of roots for absorbing water and minerals from the soil, as well as a lack of reinforced conducting cells, limits bryophytes to small sizes. Although they may survive in reasonably dry conditions, they cannot reproduce and expand their habitat range in the absence of water. Vascular plants, on the other hand, can achieve enormous heights, thus competing successfully for light. Photosynthetic organs become leaves, and pipe-like cells or vascular tissues transport water, minerals, and fixed carbon throughout the organism. **Vascular tissue** The simplest arrangement of conductive cells shows a pattern of xylem at the center surrounded by phloem.  **Xylem** is the tissue responsible for the storage and long-distance transport of water and nutrients, as well as the transfer of water-soluble growth factors from the organs of synthesis to the target organs. **Phloem** transports sugars, proteins, and other solutes throughout the plant. Phloem cells are divided into sieve elements (conducting cells) and cells that support the sieve elements. **[Seedless, Vascular Plants]** **Phylum Pterophyta -- Ferns, Horsetails, and Whisk ferns** **Ferns** Ferns are the most readily recognizable seedless vascular plants. They are considered the most advanced seedless vascular plants and display characteristics commonly observed in seed plants. More than 20,000 species of ferns live in environments ranging from tropics to temperate forests. Although some species survive in dry environments, most ferns are restricted to moist, shaded places. **Horsetails** The single genus ***Equisetum*** is the survivor of a large group of plants, which produced large trees and entire swamp forests in the Carboniferous. The plants are usually found in damp environments and marshes. The stem of a horsetail is characterized by the presence of joints or nodes, hence the name Arthrophyta (arthro- = \"joint\"; -phyta = \"plant\"). Leaves and branches come out as whorls from the evenly spaced joints. The needle-shaped leaves do not contribute greatly to photosynthesis, the majority of which takes place in the green stem. Example: *Equisetum* **Wisk ferns** The whisk ferns lack both roots and leaves, probably lost by reduction. Photosynthesis takes place in their green stems, and small yellow knobs form at the tip of the branch stem and contain the sporangia. Whisk ferns were considered an early pterophytes. However, recent comparative DNA analysis suggests that this group may have lost both vascular tissue and roots through evolution, and is more closely related to ferns. **Examples: *Psilotum* and *Tmesipteris*** **Phylum Lycophyta -- Club mosses** The club mosses are the earliest group of seedless vascular plants. They dominated the landscape of the Carboniferous, growing into tall trees and forming large swamp forests. Today's club mosses are diminutive, evergreen plants consisting of a stem (which may be branched) and microphylls. The phylum consists of close to 1,200 species, including the quillworts (*Isoetales*), the club mosses (*Lycopodiales*), and spike mosses (*Selaginellales*), none of which are true mosses or bryophytes. **Examples:** Isoetales*,* Lycopodiales*,* and Selaginellales **[Seeded, Vascular Plants]** **[Gymnosperms]** Gymnosperms are heterosporous seed plants that produce naked seeds. They appeared in the Paleozoic period and were the dominant plant life during the Mesozoic. Modern-day gymnosperms belong to four phyla. **Phylum Cycadophyta -- Cycads** Cycads** **thrive in mild climates, and are often mistaken for palms because of the shape of their large, compound leaves. Cycads bear large cones, and may be pollinated by beetles rather than wind: unusual for a gymnosperm. They dominated the landscape during the age of dinosaurs in the Mesozoic, but only a hundred or so species persisted to modern times. Example: **Phylym Gingkophyta -- Ginkgo** The single surviving species of the phylum is the *Gingko biloba*. Its fan-shaped leaves---unique among seed plants because they feature a dichotomous venation pattern---turn yellow in autumn and fall from the tree. For centuries, *G. biloba *was cultivated by Chinese Buddhist monks in monasteries, which ensured its preservation. It is planted in public spaces because it is unusually resistant to pollution. Male and female organs are produced on separate plants. Example: *Ginkgo biloba* **Phylum Coniferophyta -- Conifers** Conifers** **are the dominant phylum of gymnosperms, with the most variety of species. Most are typically tall trees that usually bear scale-like or needle-like leaves. Water evaporation from leaves is reduced by their thin shape and the thick cuticle. Snow slides easily off needle-shaped leaves, keeping the load light and decreasing breaking of branches. Conifers include familiar evergreen trees such as pines, spruces, firs, cedars, sequoias, and yews. **Phylum Gnetophyta -- Gnetophytes** **Gnetophytes** are the closest relative to modern angiosperms, and include three dissimilar genera of plants: *Ephedra*, *Gnetum*, and *Welwitschia*. Like angiosperms, they have broad leaves. In tropical and subtropical zones, gnetophytes are vines or small shrubs. *Ephedra* occurs in dry areas of the West Coast of the United States and Mexico. Like angiosperms, but unlike other gymnosperms, all gnetophytes possess vessel elements in their xylem. Examples: *Ephedra*, *Gnetum*, and *Welwitschia*  **[Angiosperms]** Without seed plants, life as we know it would not be possible. Plants play a key role in the maintenance of terrestrial ecosystems through stabilization of soils, cycling of carbon, and climate moderation. Large tropical forests release oxygen and act as carbon dioxide sinks. Seed plants provide shelter to many life forms, as well as food for herbivores, thereby indirectly feeding carnivores. Plant secondary metabolites are used for medicinal purposes and industrial production. Angiosperm diversity is due in part to multiple interactions with animals. Herbivory has favored the development of defense mechanisms in plants, and avoidance of those defense mechanism in animals. Pollination (the transfer of pollen to a carpel) is mainly carried out by wind and animals, and angiosperms have evolved numerous adaptations to capture the wind or attract specific classes of animals. The angiosperms (flowering plants) have evolved to dominate most terrestrial ecosystems. With more than 250,000 species, the angiosperm phylum (Anthophyta) is second only to insects in terms of diversification. The success of angiosperms is due to two novel reproductive structures: flowers and fruit. **The function of the flower is to ensure pollination.** Flowers also provide protection for the ovule and developing embryo inside a receptacle. **The function of the fruit is seed dispersal**. They also protect the developing seed. Different fruit structures or tissues on fruit, such as sweet flesh, wings, parachutes, or spines that grab---reflect the dispersal strategies that help spread seeds.  https://www.sciencefacts.net/parts-of-a-flower.html Flowers are modified leaves organized around a central stalk. Although they vary greatly in appearance, all flowers contain the same structures: sepals, petals, carpels, and stamens. The peduncle attaches the flower to the plant. A whorl of **sepals** (collectively called the calyx) is located at the base of the peduncle and encloses the unopened floral bud. Sepals are usually photosynthetic organs, although there are some exceptions. **Petals** (collectively the corolla) are located inside the whorl of sepals and often display vivid colors to attract pollinators. Flowers pollinated by wind are usually small, feathery, and visually inconspicuous. Sepals and petals together form the perianth. The sexual organs (carpels and stamens) are located at the center of the flower. **Styles, stigmas,** and **ovules** constitute the female organ: the **carpel**. Flower structure is very diverse, and carpels may be singular, multiple, or fused. Multiple fused carpels comprise a pistil. The megaspores and the female gametophytes are produced and protected by the thick tissues of the carpel. A long, thin structure called a **style** leads from the sticky **stigma**, where pollen is deposited, to the **ovary**, enclosed in the **carpel**. The ovary houses one or more ovules, each of which will develop into a seed upon fertilization. The male reproductive organs, the **stamens** (collectively called the androecium), surround the central carpel. **Stamens** are composed of a thin stalk called a **filament** and a sac-like structure called the **anther**. The