dispersal

Examples of dispersal in the following topics:

• Fruit and Seed Dispersal

  • Some fruits can disperse seeds on their own, while others require assistance from wind, water, or animals.
  • The fruit has a single purpose: seed dispersal.
  • Modifications in seed structure, composition, and size aid in dispersal.
  • Wind is used as a form of dispersal by lightweight seeds, such as those found on dandelions.
  • Summarize the ways in which fruits and seeds may be dispersed

• Species Distribution

  • Individuals of a population can be distributed in one of three basic patterns: they can be more or less equally spaced apart (uniform dispersion), dispersed randomly with no predictable pattern (random dispersion), or clustered in groups (clumped dispersion) .
  • Uniform dispersion is observed in plant species that inhibit the growth of nearby individuals.
  • Random dispersion occurs with dandelion and other plants that have wind-dispersed seeds that germinate wherever they happen to fall in a favorable environment.
  • Clumped dispersions may also result from habitat heterogeneity.
  • Plants with wind-dispersed seeds, such as dandelions, are usually distributed randomly.

• Angsiosperm Fruit

  • Regardless of how they are formed, fruits are an agent of seed dispersal.
  • The variety of shapes and characteristics reflect the mode of dispersal, whether it be wind, water, or animals .
  • Once eaten, tough, undigested seeds are dispersed through the herbivore's feces.
  • A fruit's distinctive shape and specialized characteristics will determine its dispersal mechanism.
  • The winged shape of Alsomitra macrocarpa's seeds allow them to use wind for dispersal.

• The Evolution of Seed Plants and Adaptations for Land

  • The evolution of seeds allowed plants to reproduce independently of water; pollen allows them to disperse their gametes great distances.
  • The lush palms on tropical shorelines do not depend upon water for the dispersal of their pollen, fertilization, or the survival of the zygote, unlike mosses, liverworts, and ferns of the terrain.

• Plant Reproductive Development and Structure

  • Seeds are the next generation, serving as the primary method in most plants by which individuals of the species are dispersed across the landscape.
  • Actual dispersal is, in most species, a function of the fruit (a structural part that typically surrounds the seed) .

• Liverworts and Hornworts

  • The spore-producing cells undergo meiosis to form spores, which disperse (with the help of elaters), giving rise to new gametophytes.
  • This sporophyte disperses spores with the help of elaters; the process begins again.
  • Liverworts also disperse their spores with the help of elaters, while hornworts utilize pseudoelaters to aid in spore dispersal.

• Allopatric Speciation

  • The nature of the geographic separation necessary to isolate populations depends entirely on the biology of the organism and its potential for dispersal.
  • Biologists group allopatric processes into two categories: dispersal and vicariance.
  • Dispersal occurs when a few members of a species move to a new geographical area, while vicariance occurs when a natural situation arises to physically divide organisms.
  • In some cases, a population of one species disperses throughout an area with each finding a distinct niche or isolated habitat.

• Basics of DNA Replication

  • There were three models of replication possible from such a scheme: conservative, semi-conservative, and dispersive.
  • In dispersive replication, after replication both copies of the new DNAs would somehow have alternating segments of parental DNA and newly-synthesized DNA on each of their two strands.
  • This suggested either a semi-conservative or dispersive mode of replication.
  • Dispersive replication would have resulted in exclusively a single band in each new generation, with the band slowly moving up closer to the height of the 14N DNA band.
  • Therefore, dispersive replication could also be ruled out.

• Early Plant Life

  • They had to develop strategies: to avoid drying out, to disperse reproductive cells in air, for structural support, and for capturing and filtering sunlight.

• Water’s High Heat Capacity

  • Due to its high heat capacity, water is used by warm blooded animals to more evenly disperse heat in their bodies; it acts in a similar manner to a car's cooling system, transporting heat from warm places to cool places, causing the body to maintain a more even temperature.