Diverrsity of Plants
Plants evolved more than 430 million years ago from multicellular green algae. By 300 million years ago, trees had evolved and formed forests, within which the diversification of vertebrates, insects, and fungi occurred. Roughly
266,000 species of plants are now living.
The two major groups of plants are the bryophytes and the vascular plants; the latter group consists of nine divisions that have living members.
Bryophytes and ferns require free water so that sperm can swim between the male and female sex organs; most other plants do not. Vascular plants have elaborate water- and food conducting strands of cells, cuticles, and stomata; many of these plants are much larger that any bryophyte.
Seeds evolved between the vascular plants and provided a means to protect young individuals. Flowers, which are the most obvious characteristic of angiosperms, guide the activities of insects and other pollinators so that pollen is dispersed rapidly and precisely from one flower to another of The same species, thus promoting out crossing. Many angiosperms display other modes of pollination, including self-pollination.
Evolutionary Origins
Plants derived from an aquatic ancestor, but the evolution of their conducting tissues, cuticle, stomata, and seeds has made them progressively less dependent on water. The oldest plant fossils date from the Silurian Period, some 430 million years ago.
The common ancestor of plants was a green alga. The similarity of the members of these two groups can be demonstrated by their photosynthetic pigments
(chlorophyll a and b,) carotenoids); chief storage product (starch); cellulose- rich cell walls (in some green algae only); and cell division by means of a cell plate (in certain green algae only).
Major Groups
As mentioned earlier, The two major groups of plants are The bryophytes-
-mosses, liverworts, and hornworts--and The vascular plants, which make up nine other divisions. Vascular plants have two kinds of well-defined conducting strands: xylem, which is specialized to conduct water and dissolved minerals, and phloem, which is specialized to conduct The food molecules The plants manufacture. Gametophytes and Sporophytes
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... definite organs nor do they have definite target areas.
They stimulate or inhibit growth in response to environmental clues such as light, day length, temperature, touch, and gravity and thus allow plants to respond efficiently to environmental demands by growing in specific directions, producing flowers, or displaying other responses appropriate to their survival in a particular habitat.
Tropisms
Tropisms in plants are growth responses to external stimuli. A phototropism is a response to light, gravvitropism is a response to gravity, and thigmotropism is a response to touch.
Turgor Movement
Turgor movements are reversible but important elements in adaptation of plants to their environments. By means of turgor movements, leaves, flowers, and other structures of plants track light and take full advantage of it.
Dormancy
Dormancy is a necessary part of plant adaptation that allows a plant to bypass unfavorable seasons, such as winter, when the water my be frozen, or periods of drought. Dormancy also allows plants to survive in many areas where they would be unable to grow otherwise.
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How does the vegetation surface type affect the amount of runoff? Speculate why this happens.
Eukaryotic cells, whether from animals, plants, protists, or fungi, are the most structurally advanced of the major cell types. Eukaryote are single-celled or multicellular organism whose cells contain nucleus and any other structures (organelles) enclosed within the membrane that perform specific functions. The surface of the cell is covered with a thin film or plasma membrane, which is the boundary that separates the living cell from its nonliving surroundings. Plasma membranes are composed mostly of proteins and lipids (Simon, 02/2012, p. 59-60).
This article relates to this course about Biology within the cells. This article relates to
Cyanobacteria, also known as Blue-green algae, (Cyanophyta), (Myxophyta) and (Cyanochloronta) are difficult to classify, and there are numerous schools of thought on their Taxonomy. Cyanobacteria are prokaryotic organisms however posess many of the same qualities as algae and therefore were previously categorized as such, hence the name blue-green algae. They form a class greatly dissimilar from that of other algae, and possess many of the same characteristics of bacteria. They produce energy via the process of photosynthesis and posses photosynthetic pigments chlorophyll a, just as plants, and phycobilin which are responsible for the blue-green hue. The main distribution of Cyanobacteria is in aquatic environments such as fresh and saltwater, they are however, found in terrestrial habitats where there is sufficient moisture and can even occur in deserts. Cyanobacteria do not have a nucleus or chloroplasts, they’re DNA and chlorophyll float freely within the cytoplasm. They show a variety of movements, such as gliding, rotation, oscillation, jerking and flicking. In addition they possess gas vesicles, giving them buoyancy in water. Cyanobacteria reproduce exclusively by asexual means via binary fission and may form exo- or endospores as well.
By definition, a cell is life's basic unit. In practice, the cells share several mechanisms across different animals, plants, and microorganisms. Two fundamental differences exist between the architecture of cells for different classes of organisms (Jan, 2014). Lipids build and maintain both the plasma (the external bilayer) and the nuclear membrane within a cell. In addition, the thick filament of proteins (actin filaments and microtubes) confer rigidity to the cytoskeleton of the cell. Factors, such as physical forces acting on a cell as and the cell’s mechanical environment control gene regulation (the rate of production of proteins). In animals, the polymer filament gel (network) regulate the motility of cells. In fact, forces acting on the polymer gel tend to deform the cell membrane.
Cyanobacteria are one of the largest and most important groups of bacteria on the earth. Often called ‘the blue-green algae’ Cyanobacteria is in fact, not an algae at all. Algae are eukaryotic, whereas cyanobacteria, is a bacteria, and is prokaryotic. The name algae is used to refer to any aquatic organisms capable of photosynthesis, so the term is considered general, though in this case, inaccurate. Being tiny and normally unicellular, cyanobacteria grow in large colonies, making them visible to the human eye, and often dominate aquatic habitats such as shorelines. Over their 3.5 billion year reign, Cyanobacteria have helped to successfully establish the earth’s atmosphere, making it possible for human life forms to thrive and some of the oldest known fossils in the world are cyanobacteria, earning it the title of one of the great survivors of all time.
Mitochondria and chloroplasts have the likenesses with microscopic organisms that prompted the endosymbiont hypothesis. This hypothesis expresses that an early a castor of eukaryotic cell inundated an ocygen utilizing nonphotosynthetic prokaryotic cell. In the long run, the overwhelmed cell shaped an association with the host cell in which it was en shut, turning into an endosymbiont. Through the span of advancement the host cell and its endosymbiont converged into a solitary living being, an eukaryotic cell with a mitochondrion. As opposed to being limited by a solitary layer like organelles of the endomembrane framework, mitochondria and common chloroplasts have two layers encompassing them. Evidence the hereditary overwhelmed prokaryotes
The outer layer of a reef consists of living animals, or polyps, of coral. Single-celled algae called zooxanthellae live within the coral polyps, and a skeleton containing filamentous green algae surrounds them. The photosynthetic zooxanthellae and green algae transfer food energy directly to the coral polyps, while acquiring scarce nutrients from the coral. The numerous micro habitats of coral reefs and the high biological productivity support a great diversity of other life.
to construct and or maintain the cell membrane. In a microscopic view of the cell membrane we can
Bacterial cells, like plant cells, are surrounded by a cell wall. However, bacterial cell walls are made up of polysaccharide chains linked to amino acids, while plant cell walls are made up of cellulose, which contains no amino acids. Many bacteria secrete a slimy capsule around the outside of the cell wall. The capsule provides additional protection for the cell. Many of the bacteria that cause diseases in animals are surrounded by a capsule. The capsule prevents the white blood cells and antibodies from destroying the invading bacterium. Inside the capsule and the cell wall is the cell membrane. In aerobic bacteria, the reactions of cellular respiration take place on fingerlike infoldings of the cell membrane. Ribosomes are scattered throughout the cytoplasm, and the DNA is generally found in the center of the cell. Many bacilli and spirilla have flagella, which are used for locomotion in water. A few types of bacteria that lack flagella move by gliding on a surface. However, the mechanism of this gliding motion is unknown. Most bacteria are aerobic, they require free oxygen to carry on cellular respiration. Some bacteria, called facultatibe anaerobes can live in either the presence or absence of free oxygen. They obtain energy either by aerobic respiration when oxygen is present or by fermentation when oxygen is absent. Still other bacteria cannot live in the presence of oxygen. These are called obligate anaerobes. Such bacteria obtain energy only fermentation. Through fermentation, different groups of bacteria produce a wide variety of organic compounds. Besides ethyl alcohol and lactic acid, bacterial fermentation can produce acetic acid, acetone, butyl alcohol, glycol, butyric acid, propionic acid, and methane, the main component of natural gas. Most bacteria are heterotrophic bacteria are either saprophytes or parasites. Saprophytes feed on the remains of dead plants and animals, and ordinarily do not cause disease. They release digestive enzymes onto the organic matter. The enzymes breakdown the large food molecules into smaller molecules, which are absorbed by the bacterial cells. Parasites live on or in living organisms, and may cause disease. A few types of bacteria are Autotrophic, they can synthesize the organic nutrients they require from inorganic substances. Autotrophic bacteria are either photosynthetic or Chemosynthetic. The photosynthetic bacteria contain chlorophyll that are different from the plant chlorophyll. In bacterial photosynthesis, hydrogen is obtained by the splitting of compounds other than water.
Formation of germ layers is the first step towards multicellular organisms. It establishes division of tissue types. Diploblastic organisms, such as coelenterates, have two germ layers (ectoderm and endoderm), whereas triploblastic organisms, which include all higher animals, have three germ layers (ectoderm, mesoderm and endoderm). These germ layers are often termed as leaves with ectoderm being the outer leaf, mesoderm being the middle leaf...
The secondary walls of sclerenchyma cells are thick and contain abundant lignin. This relatively indigestible strengthening polymer accounts for more than a quarter of the dry mass of wood. Lignin is present in all vascular plants, but not in bryophytes. Sclerenchyma cells stop growing in length when mature and cannot elongate any further. They are so specialized for support that many are dead at functional maturity, but they produce secondary walls before the protoplast (the living part of the cell) dies. In some cases, the rigid walls remain as a ‘skeleton’ that support the plant for hundreds of
Diatoms have a unique characteristic. They live in an outer cell wall, or a frustrule made of silica. This frustrule is not just for the physical appearance, it provides protection and even structure. On the cell wall, there are spikes, spines and pores which allow diatoms to be classified into different classes, the centric (Centrobacillariophyceae) and the pennate (...
When plants such as seaweeds or others that grow under water, their parts are supported on all sides by hydrostatic pressure. There is not much difference in the density between plant cells and their surrounding liquid environment. Aquatic plants do not require significant structural support; their cell walls only contain polysaccharides, c...