white matter

Examples of white matter in the following topics:

• Spinal Cord

  • A cross-section of the spinal cord looks like a white oval containing a gray butterfly-shape .
  • Myelinated axons (the part of neurons that send signals) compose the "white matter," while neuron and glial cell bodies (neuronal "support" cells) compose the "grey matter."
  • Grey matter is also composed of interneurons, which connect two neurons, each located in different parts of the body.
  • A cross-section of the spinal cord shows grey matter (containing cell bodies and interneurons) and white matter (containing axons).

• Nutrients from Other Sources

  • This may occur with plants that are parasitic or saprophytic: ingesting and utilizing dead matter as a food source.
  • A saprophyte is a plant that does not have chlorophyll, obtaining its food from dead matter, similar to bacteria and fungi.
  • Most saprophytes do not directly digest dead matter.
  • Saprophytes, like this Dutchmen's pipe (Monotropa hypopitys), obtain their food from dead matter and do not have chlorophyll.
  • Note that the vines of the dodder, which has white flowers, are beige.

• Fungi Cell Structure and Function

  • Fungi are unicellular or multicellular thick-cell-walled heterotroph decomposers that eat decaying matter and make tangles of filaments.
  • The poisonous Amanita muscaria (fly agaric) is recognizable by its bright red cap with white patches .
  • Fungi are mostly saprobes (saprophyte is an equivalent term): organisms that derive nutrients from decaying organic matter.
  • They obtain their nutrients from dead or decomposing organic matter, mainly plant material.

• White Blood Cells

  • White blood cells, also called leukocytes (leuko = white), make up approximately one percent, by volume, of the cells in blood.
  • The role of white blood cells is very different from that of red blood cells.
  • White blood cells are formed continually; some live only for hours or days, while some live for years.
  • The morphology of white blood cells differs significantly from red blood cells.
  • The different types of white blood cells are identified by their microscopic appearance after histologic staining.

• Soil Composition

  • Soil is a mix of varying amounts of inorganic matter, organic matter, water, and air.
  • inorganic mineral matter, about 40 to 45 percent of the soil volume
  • The four major components of soil are shown: inorganic minerals, organic matter, water, and air.

• Phenotypes and Genotypes

  • When true-breeding plants in which one parent had white flowers and one had violet flowers were cross-fertilized, all of the F1 hybrid offspring had violet flowers .
  • However, we know that the allele donated by the parent with white flowers was not simply lost because it reappeared in some of the F2 offspring.
  • First, Mendel confirmed that he had plants that bred true for white or violet flower color.
  • Regardless of how many generations Mendel examined, all self-crossed offspring of parents with white flowers had white flowers, and all self-crossed offspring of parents with violet flowers had violet flowers.
  • In the F2 generation, approximately three-quarters of the plants had violet flowers, and one-quarter had white flowers.

• Garden Pea Characteristics Revealed the Basics of Heredity

  • First, Mendel confirmed that he had plants that bred true for white or violet flower color.
  • Regardless of how many generations Mendel examined, all self-crossed offspring of parents with white flowers had white flowers, and all self-crossed offspring of parents with violet flowers had violet flowers.
  • Instead, Mendel's results demonstrated that the white flower trait in the F1 generation had completely disappeared.
  • This was a ratio of 3.15 violet flowers per one white flower, or approximately 3:1.
  • For this same characteristic (flower color), white-colored flowers are a recessive trait.

• Fungi Habitat, Decomposition, and Recycling

  • Fungi are the major decomposers of nature; they break down organic matter which would otherwise not be recycled.
  • The food web would be incomplete without organisms that decompose organic matter .
  • The action of fungi releases these elements from decaying matter, making them available to other living organisms.
  • Trace elements present in low amounts in many habitats are essential for growth, but would remain tied up in rotting organic matter if fungi and bacteria did not return them to the environment via their metabolic activity.

• Biogeochemical Cycles

  • The elemental components of organic matter are cycled through the biosphere in an interconnected process called the biogeochemical cycle.
  • However, the matter that makes up living organisms is conserved and recycled.
  • Because geology and chemistry have major roles in the study of this process, the recycling of inorganic matter between living organisms and their environment is called a biogeochemical cycle.
  • It is important for leaching certain components of organic matter into rivers, lakes, and oceans, and is a reservoir for carbon.

• Sex-Linked Traits

  • In fruit flies, the wild-type eye color is red (XW) and is dominant to white eye color (Xw).
  • Now, consider a cross between a homozygous white-eyed female and a male with red eyes.
  • Half of the F2 females would be red-eyed (XWXw) and half would be white-eyed (XwXw).
  • Clockwise from top left are brown, cinnabar, sepia, vermilion, white, and red.
  • Red eye color is wild-type and is dominant to white eye color.