explain the adaptations of bryophytes to the terrestrial environment

Living in the water provides a number of advantages compared to life on land: If life on land presents so many challenges, why did any land plants evolve to live on land? Leaves capture more sunlight with their increased surface area by employing more chloroplasts to trap light energy and convert it to chemical energy, which is then used to fix atmospheric carbon dioxide into carbohydrates. Figure 3. Over evolutionary time, land plants evolved strategies to survive in increasing degrees of dryness: The phylogenetic tree below shows the evolutionary relationships between modern plants, as well as the origins of adaptations in each plant lineage: As we’ve previously discussed, all eukaryote life cycles include a haploid stage and a diploid stage. The restoration of natural places encroached on by human intervention, such as wetlands, also requires the expertise of a landscape designer. The tissue consists of conducting cells, known as tracheids, and supportive filler tissue, called parenchyma. Adaptations to Terrestrial Life There is fossil evidence of land plants and fungi at about 480 million years ago, during the Ordovician period, and vascular plants were well established on land by the time terrestrial animals show up in the fossil record at about 420 million years ago. In seedless vascular plants, the diploid sporophyte is the dominant phase of the lifecycle. Figure 2. Silica collects in the epidermal cells, contributing to the stiffness of horsetail plants. In the mycorrhizal relationship, the fungal network of filaments increases the efficiency of the plant root system, and the plants provide the fungi with byproducts of photosynthesis. Figure 25. They produce the compounds lignin and sporopollenin, and form plasmodesmata that connect the cytoplasm of adjacent cells. Four major adaptations are found in all terrestrial plants: the alternation of generations, a sporangium in which the spores are formed, a gametangium that produces haploid cells, and apical meristem tissue in roots and shoots. Fossilized cells, cuticles, and spores of early land plants have been dated as far back as the Ordovician period in the early Paleozoic era. In the club mosses such as Lycopodium clavatum, sporangia are arranged in clusters called strobili. With their rigid cell walls, the xylem cells provide support to the plant and allow it to achieve impressive heights. Land plants evolved before land animals; therefore, no predators threatened early plant life. Know the plant adaptations required for terrestrial life. h) Magnifying lens- This is used to enlarge small objects.A hand lens is a common magnifying lens used in the laboratory. Hornworts developed … Explain in your own words why sexual reproduction can be useful if a protist’s environment changes. Plants have been enlisting animals to be their helpers in this way for hundreds of millions of years. Preface Some bryophyte species are specifically adapted to specific micro-environments and can be used as environmental and ecological indicators as they react to slight changes to their environmental conditions. Because of the lack of lignin and other resistant structures, the likelihood of bryophytes forming fossils is rather small. Most seedless plants still require a moist environment. Both adaptations were required for the colonization of land begun by the bryophytes and their ancestors. The carbohydrates are exported to the rest of the plant by the conductive cells of phloem tissue. More than 25,000 species of bryophytes thrive in mostly damp habitats, although some live in deserts. Landscape layout can encompass a small private space, like a backyard garden; public gathering places, like Central Park in New York City; or an entire city plan, like Pierre L’Enfant’s design for Washington, DC. Mosses and liverworts are often the first macroscopic organisms to colonize an area, both in a primary succession—where bare land is settled for the first time by living organisms—or in a secondary succession, where soil remains intact after a catastrophic event wipes out many existing species. Algae, which are aquatic, photosynthetic eukaryotes, are also typically considered to be plants (though obviously not land plants); however, the term “algae” refers to a large and diverse group of photosynthetic eukaryotes that includes green, brown, and red algae that do not have a single common photosynethic ancestor (in other words, the term “algae” is not monophyletic). Most ferns produce the same type of spores and are therefore homosporous. Bryophyte Definition. On the underside of its mature fronds, sori (singular, sorus) form as small clusters where sporangia develop (Figure 24). The first type of leaf is the microphyll, or “little leaf,” which can be dated to 350 million years ago in the late Silurian. The transition from an aquatic to a terrestrial environment occurred as a result of a number of specific adaptations to the above challenges to survival on land. Water filters out a significant amount of ultraviolet-B (UVB) light, which is destructive to DNA. This illustration shows the life cycle of mosses. In water or near it, plants can absorb water from their surroundings with no need for any special absorbing organ or tissue to prevent desiccation (drying out). These features are widely distributed among bryophytes generally, and cannot be regarded as specific adaptations to polar conditions. The sporophyte stage is barely noticeable in nonvascular plants. 9. Some paleobotanists are skeptical of the conclusions drawn from the analysis of molecular fossils. Some gametophytes develop underground and form mycorrhizal associations with fungi. Physiological evolution of lower embryophytes: adaptations to the terrestrial environment John A Raven and Dianne Edwards CONTENTS Introduction 17 The ancestors of embryophytes 18 Water, carbon dioxide and energetics of land plants 19 Desiccation tolerance, desiccation intolerance, poikilohydry and homoiohydry 22 Poikilohydry of algae and early-evolving embryophytes 22 … (credit: modification of work by “Smith609”/Wikimedia Commons based on original work by Mariana Ruiz Villareal). Things to Remember. All nonvascular embryophytes are bryophytes. Archesporium 12. Mosses and ferns can be used as fuels and serve culinary, medical, and decorative purposes. The first bryophytes (liverworts) probably appeared in the Ordovician period, about 450 million years ago. All land plants (and *some* green algae) reproduce via the alternation of generations life cycle, where both the haploid and the diploid stage of an organism are multicellular: the haploid multicellular form, known as a gametophyte, is followed in the life cycle sequence by a multicellular diploid form: the sporophyte. Habitat 5. The organism is also subject to bombardment by mutagenic radiation, because air does not filter out ultraviolet rays of sunlight. However, some adaptations to the symbiotic state were observed. Current evolutionary thought holds that all plants—green algae as well as land dwellers—are monophyletic; that is, they are descendants of a single common ancestor. Stomata appear in the hornworts and are abundant on the sporophyte. The plants absorb water and nutrients directly through these leaf-like structures. Water also provides buoyancy to organisms. Meristem cells at the base of the plant keep dividing and adding to its height. Throughout plant evolution, there is an evident reversal of roles in the dominant phase of the lifecycle. Once the ovary is fertilized the carpel and some surrounding tissues develop into a fruit, another opportunity for angiosperms to increase their domination of the terrestrial ecosystem with evolutionary adaptations … They have colonized a variety of habitats on land, although they are never far from a source of moisture. Megaphylls most likely appeared independently several times during the course of evolution. 23.14. These structures are precursors of roots. The common ancestry with green algae places plants on the phylogenetic tree of life as seen below: A more simplified tree of life, which does not show protist lineages, would look like this: The information below was adapted from OpenStax Biology 25.1. In fact, modern land plants have an array of adaptations to life on land, but they did not evolve all at once. Some primitive traits of green algae, such as flagellated sperm, are still present in mosses that are dependent on water for reproduction. Studying Biology as a science helps to leverage human life in a lot of ways. Bryophytes are the group of plants that are the closest extant relative of early terrestrial plants. Adaptations: Bryophytes. To biologists who cast a broad net over living things that share a common characteristic (in this case, photosynthetic eukaryotes), all algae are plants. Under ice . Sample Released SOL Test Items. Which of the following statements about the moss life cycle is false? This conclusion is consistent with the fact that most members of the polar bryophyte floras range widely in boreal forest, and in many cases also temperate regions. One example of the use of analytical chemistry and molecular biology is the identification of oleanane, a compound that deters pests. These toxic compounds can also cause severe diseases and even death, thus discouraging predation. Cells in green algae divide along cell plates called phragmoplasts, and their cell walls are layered in the same manner as the cell walls of embryophytes. Hornworts grow a tall and slender sporophyte. However, the Permian period at the end of the Paleozoic era saw much drier climates, and the dry climate provided gymnosperms an advantage over seedless plants because plants with seeds are better able to survive dry periods due to reproduction with pollen and seeds. The image below shows a simplified version of the alternation of generations life cycle: Though all plants display an alternation of generations life cycle, there are significant variations in different lineages of plants, consistent with their evolutionary history and order of origination: The video below describes the features of nonvascular plants (mosses, liverworts, hornworts), and their alternation of generations life cycle: The video below describes the features of vascular plants and their alternation of generations life cycle: Before we discuss evolution of plant lineages over geologic time, first let’s briefly review the relevant eras and periods of the Phanerozoic. However, the cuticle also prevents intake of carbon dioxide needed for the synthesis of carbohydrates through photosynthesis. The gametophyte gives rise to the gametes (reproductive cells) by mitosis. Figure 6. Water is still required for fertilization of seedless vascular plants, and most favor a moist environment. Liverworts (Hepaticophyta) are viewed as the plants most closely related to the ancestor that moved to land. The lifecycle of hornworts (Figure 13) follows the general pattern of alternation of generations. (credit: Myriam Feldman). Note that we are specifically referring to LAND plants throughout this reading, such as mosses, ferns, conifers, and flowering plants. They had to develop strategies to avoid drying out, to disperse reproductive cells in air, for structural support, and for capturing and filtering sunlight. Modern seedless vascular plants provide insights into plant evolution during the Carboniferous period, when vascular plants began to diversify, but most groups of seed plants had not yet evolved. The oldest-known vascular plants have been identified in deposits from the Devonian. The male organ (the antheridium) produces many sperm, whereas the archegonium (the female organ) forms a single egg. 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. Gymnosperms, the earliest seed plants, also first appeared in the fossil record during the Devonian. 182. Explain how bryophytes are still tied to water. Vascular plants, on the other hand, can achieve enormous heights, thus competing successfully for light. A few green algae even survive on soil, provided it is covered by a thin film of moisture in which they can live. Some reports indicate that bryophytes make the soil more amenable to colonization by other plants. This field seeks to find transitional species that bridge gaps in the path to the development of modern organisms. More than 260,000 species of tracheophytes represent more than 90 percent of Earth’s vegetation. Select the following plant adaptations for the terrestrial environment that are correctly listed by their function. Xylem conductive cells incorporate the compound lignin into their walls, and are thus described as lignified. The closed carpel of angiosperms also allows adaptations to specialized pollination syndromes and controls to prevent self-fertilization, thereby maintaining increased diversity. The first reliable record of gymnosperms dates their appearance to the Pennsylvanian … During the Carboniferous period, swamp forests of club mosses and horsetails—some specimens reaching heights of more than 30 m (100 ft)—covered most of the land. (credit: modification of work by Mariana Ruiz Villareal), Figure 15. The first vascular plants appeared in the late Ordovician and were probably similar to lycophytes, which include club mosses (not to be confused with the mosses) and the pterophytes (ferns, horsetails, and whisk ferns). #13 (1995) Energy transfer occurs in all cellular activities. Figure 24. The disappearance of mosses can be considered a bioindicator for the level of pollution in the environment. Green, flat structures—resembling true leaves, but lacking vascular tissue—are attached in a spiral to a central stalk. These adaptations are noticeably lacking in the closely related green algae—another reason for the debate over their placement in the plant kingdom. In seed plants, which use pollen to transfer the male sperm to the female egg, the toughness of sporopollenin explains the existence of well-preserved pollen fossils. Flowering plants. Elsevier Academic Press, … In the multicellular Ulva, a sporophyte grows by mitosis after fertilization. Both Chlamydomonas and Ulva produce flagellated gametes. Sphagnum bogs (Figure 27) are cultivated with cranberry and blueberry bushes. Seedless plants, like these horsetails (Equisetum sp. The gemmae then land nearby and develop into gametophytes. The remaining green algae, which belong to a group called Chlorophyta, include more than 7000 different species that live in fresh or brackish water, in seawater, or in snow patches. Water provides a sort of external structure and buoyancy to living things; living on land requires additional structural support to avoid falling over. As a result of this selective pressure by plant-eating animals, plants evolved adaptations to deter predation, such as spines, thorns, and toxic chemicals. Modern-day seedless tracheophytes include club mosses, horsetails, ferns, and whisk ferns. In seedless vascular plants, the sporophyte became the dominant phase of the lifecycle. Some green algae may already be familiar, in particular Spirogyra and desmids. Describe four problems associated with animal survival in terrestrial environments but not in aquatic environments. They are distinguished by large leaves called fronds and small sporangia-containing structures called sori, which are found on the underside of the fronds. Many mosses, for example, can dry out to a brown and brittle mat, but as soon as rain or a flood makes water available, mosses will absorb it and are restored to their healthy green appearance. (credit: Javier Martin). Bryophytes have been found in almost all terrestrial ... habit will require continuous and elaborate adaptations. Figure 17. Plants in this group are also called nontracheophytes because they lack the transport cells called this group are also called nontracheophytes because they lack the transport cells called Two different types of spores are produced in land plants, resulting in the separation of sexes at different points in the lifecycle. Openings that allow the movement of gases may be observed in liverworts. In the brown algae genus Laminaria , haploid spores develop into multicellular gametophytes, which produce haploid gametes that combine to produce diploid organisms that then become multicellular organisms with a different structure from the haploid form ( [link] ). The coding region includes the genes for the five tryptophan biosynthesis enzymes. Bodleian Libraries. The first bryophytes (liverworts) most likely appeared in the Ordovician period, about 450 million years ago. 12. Scientists who solely track evolutionary straight lines (that is, monophyly), consider only the Charophytes as plants. They are considered the most advanced seedless vascular plants and display characteristics commonly observed in seed plants. As organisms adapted to life on land, they had to contend with several challenges in the terrestrial environment. The egg, and later, the zygote, form in a protected chamber on the parent plant. Most biologists also consider green algae to be plants, although others exclude all algae from the plant kingdom. The ancestors to the green algae became photosynthetic by endosymbiosing a green, photosynthetic bacterium about 1.65 billion years ago. Figure 20. The sporophyte bears the sporangia (singular, sporangium): organs that first appeared in the land plants. Describe adaptations of bryophytes for terrestrial environments. The bryophytes exhibit adaptations to terrestrial life. Desiccation, or drying out, is a constant danger for an organism exposed to air. Then vegetation began to take on a taller profile with the evolution of vascular plants. While most ferns form large leaves and branching roots, the whisk ferns, Class Psilotopsida, lack both roots and leaves, probably lost by reduction. Figure 5. The most familiar structure is the haploid gametophyte, which germinates from a haploid spore and forms first a protonema—usually, a tangle of single-celled filaments that hug the ground. A structure called a peristome increases the spread of spores after the tip of the capsule falls off at dispersal. Landscape design also has strong roots in the United States’ tradition. The position of green algae is more ambiguous. The moss lifecycle follows the pattern of alternation of generations as shown in Figure 14. Vascular systems consist of xylem tissue, which transports water and minerals, and phloem tissue, which transports sugars and proteins. Figure 21. The single genus Equisetum is the survivor of a large group of plants, known as Arthrophyta, which produced large trees and entire swamp forests in the Carboniferous. Gametangia are prominent in seedless plants, but are very rarely found in seed plants. With the exception of Sphagnum (peat moss), bryophytes have little economic value except perhaps for erosion control and as a seedbed for trees. Fossil evidence indicates that flowering plants first appeared in the Lower Cretaceous, about 125 million years ago, and were rapidly diversifying by the Middle Cretaceous, about 100 million years ago. For example, the chemical materials of interest degrade rapidly when exposed to air during their initial isolation, as well as in further manipulations. The hornworts (Anthocerotophyta) belong to the broad bryophyte group. Shoots and roots of plants increase in length through rapid cell division in a tissue called the apical meristem, which is a small zone of cells found at the shoot tip or root tip (Figure 4). Their habitats vary from the tundra, where they are the main vegetation, to the understory of tropical forests. Being a more robust body a sporophyte can effectively meet the challenges of a terrestrial environment better than the gametophyte. 1. This situation changed as animals emerged from the water and fed on the abundant sources of nutrients in the established flora. In contrast, as plants co-evolved with animals, the development of sweet and nutritious metabolites lured animals into providing valuable assistance in dispersing pollen grains, fruit, or seeds. Paleobotanists trace the evolution of plants by following the modifications in plant morphology: shedding light on the connection between existing plants by identifying common ancestors that display the same traits. Describe adaptations of bryophytes for terrestrial environments. Key Differences Between Bryophytes and Pteridophytes. The ability to perform sexual reproduction allows protists to recombine their genes and produce new variations of progeny that may be better suited to the new environment. Some mosses have small branches. The environment changes suddenly and none of the white rabbits survive. Bryophytes were the prevalent vegetation for the first 100 million years that terrestrial communities existed. Coal is still a prime source of energy and also a major contributor to global warming. Humans are diplontic. More importantly, fiddleheads are a traditional spring food of Native Americans in the Pacific Northwest, and are popular as a side dish in French cuisine. A microphyll is small and has a simple vascular system. Aside from these two adaptations, seedless vascular plants are still tied to the water for reproduction: like Bryophytes, their sperm and eggs are sensitive to desiccation, and the sperm must swim through water to get to the egg. Lycophytes have tracheids. Spore-producing sacs called sporangia grow at the ends of long, thin stalks in this photo of the moss Esporangios bryum. Looking at the well-laid parterres of flowers and fountains in the grounds of royal castles and historic houses of Europe, it’s clear that the gardens’ creators knew about more than art and design.

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