ring of life

Examples of ring of life in the following topics:

• Web, Network, and Ring of Life Models

  • To more accurately describe the phylogenetic relationships of life, web and ring models have been proposed as updates to tree models.
  • The "ring of life" is a phylogenetic model where all three domains of life evolved from a pool of primitive prokaryotes .
  • This does not mean a tree, web, or a ring will correlate completely to an accurate description of phylogenetic relationships of life.
  • According to the "ring of life" phylogenetic model, the three domains of life evolved from a pool of primitive prokaryotes.
  • Describe the web, network, and ring of life models of phylogenetic trees

• Hydrocarbons

  • Hydrocarbons are important molecules that can form chains and rings due to the bonding patterns of carbon atoms.
  • As the backbone of the large molecules of living things, hydrocarbons may exist as linear carbon chains, carbon rings, or combinations of both.
  • This three-dimensional shape or conformation of the large molecules of life (macromolecules) is critical to how they function.
  • Another type of hydrocarbon, aromatic hydrocarbons, consists of closed rings of carbon atoms.
  • Ring structures are found in hydrocarbons, sometimes with the presence of double bonds, which can be seen by comparing the structure of cyclohexane to benzene .

• Primary and Secondary Growth in Stems

  • Some plants, especially those that are woody, also increase in thickness during their life span.
  • The activity of the vascular cambium gives rise to annual growth rings.
  • It results in the formation of an annual ring, which can be seen as a circular ring in the cross section of the stem .
  • The rate of wood growth increases in summer and decreases in winter, producing a characteristic ring for each year of growth.
  • Note how the rings vary in thickness.

• Class Scyphozoa

  • The defining characteristic of this class is that the medusa is the prominent stage in the life cycle, although there is a polyp stage present .
  • Scyphozoans live most of their life cycle as free-swimming, solitary carnivores.
  • These animals possess a ring of muscles lining the dome of the body, which provides the contractile force required to swim through water.
  • The life cycle of these animals can be described as polymorphic because they exhibit both a medusal and polypoid body plan at some point .
  • For jellyfish (a), and all other scyphozoans, the medusa (b) is the most prominent of the two life stages.

• The Structure and Sequence of DNA

  • The nitrogenous base can be a purine such as adenine (A) and guanine (G), characterized by double-ring structures, or a pyrimidine such as cytosine (C) and thymine (T), characterized by single-ring structures.
  • The sugars and phosphates of the nucleotides form the backbone of the structure, whereas the pairs of nitrogenous bases are pointed towards the interior of the molecule.
  • That is to say, at each point along the DNA molecule, the two sugar phosphate backbones are always separated by three rings, two from a purine and one from a pyrimidine.
  • The rapid speed of sequencing attained with modern technology has been instrumental in obtaining complete DNA sequences, or genomes, of numerous types and species of life, including the human genome and those of other animal, plant, and microbial species.
  • B is a cartoon model of DNA, where the sugar-phosphate backbones are represented as violet strands and the nitrogenous bases are represented as color-coded rings.

• Fungi as Plant, Animal, and Human Pathogens

  • The active ingredient of ergot is lysergic acid, which is a precursor of the drug LSD.
  • Similarly, more than a million bats in the United States have been killed by white-nose syndrome, which appears as a white ring around the mouth of the bat.
  • Dermatophytes are also called "ringworms" because of the red ring they cause on skin.
  • Patients in the late stages of AIDS suffer from opportunistic mycoses that can be life threatening.
  • (a) Ringworm presents as a red ring on skin; (b) Trichophyton violaceum, shown in this bright field light micrograph, causes superficial mycoses on the scalp; (c) Histoplasma capsulatum is an ascomycete that infects airways and causes symptoms similar to influenza.

• Types of Biological Macromolecules

  • Biological macromolecules, the large molecules necessary for life, include carbohydrates, lipids, nucleic acids, and proteins.
  • Biological macromolecules all contain carbon in ring or chain form, which means they are classified as organic molecules.
  • Each of these types of macromolecules performs a wide array of important functions within the cell; a cell cannot perform its role within the body without many different types of these crucial molecules.
  • All organisms are composed of a variety of these biological macromolecules.
  • Each different type of macromolecule, except lipids, is built from a different set of monomers that resemble each other in composition and size.

• The Origins of Archaea and Bacteria

  • When and where did life begin?
  • Prokaryotes were the first forms of life on earth, existing for billions of years before plants and animals appeared.
  • Microbial mats or large biofilms may represent the earliest forms of life on earth; there is fossil evidence of their presence starting about 3.5 billion years ago.
  • Fossilized microbial mats represent the earliest record of life on earth.
  • This (a) microbial mat, about one meter in diameter, grows over a hydrothermal vent in the Pacific Ocean in a region known as the "Pacific Ring of Fire."

• Protists as Human Pathogens

  • Members of the genus Plasmodium must colonize both a mosquito and a vertebrate to complete their life cycle.
  • Of the four Plasmodium species known to infect humans, P. falciparum accounts for 50 percent of all malaria cases and is the primary cause of disease-related fatalities in tropical regions of the world.
  • During the course of malaria, P. falciparum can infect and destroy more than one-half of a human's circulating blood cells, leading to severe anemia.
  • However, T. brucei has thousands of possible antigens; with each subsequent generation, the protist switches to a glycoprotein coating of a different molecular structure.
  • In this light microscopic image taken using a 100× oil immersion lens, the ring-shaped P. falciparum stains purple.

• Signaling Molecules

  • Important members of this class of ligands are the steroid hormones.
  • Steroids are lipids that have a hydrocarbon skeleton with four fused rings; different steroids have different functional groups attached to the carbon skeleton.
  • Steroid hormones include the female sex hormone, estradiol, which is a type of estrogen; the male sex hormone, testosterone; and cholesterol, which is an important structural component of biological membranes and a precursor of steriod hormones .
  • The binding of these ligands to these receptors results in a series of cellular changes.
  • NO has a very short half-life; therefore, it only functions over short distances.