theory

Examples of theory in the following topics:

• Cell Theory

  • Cell theory states: living things are composed of one or more cells; the cell is the basic unit of life; cells arise from existing cells.
  • By the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory.
  • Rudolf Virchow later made important contributions to this theory.
  • The generally accepted portions of the modern Cell Theory are as follows:
  • The cell is the basic unit of life and the study of the cell led to the development of the cell theory.

• Chromosomal Theory of Inheritance

  • The Chromosomal Theory of Inheritance identified chromosomes as the genetic material responsible for Mendelian inheritance.
  • Together, these observations led to the development of the Chromosomal Theory of Inheritance, which identified chromosomes as the genetic material responsible for Mendelian inheritance.
  • The Chromosomal Theory of Inheritance was consistent with Mendel's laws and was supported by the following observations:
  • It was only after several years of carrying out crosses with the fruit fly, Drosophila melanogaster, that Thomas Hunt Morgan provided experimental evidence to support the Chromosomal Theory of Inheritance.
  • (a) Walter Sutton and (b) Theodor Boveri are credited with developing the Chromosomal Theory of Inheritance, which states that chromosomes carry the unit of heredity (genes).

• Misconceptions of Evolution

  • Critics of the theory of evolution dismiss its importance by purposefully confounding the everyday usage of the word "theory" with the way scientists use the word.
  • Scientists have a theory of the atom, a theory of gravity, and the theory of relativity, each of which describes understood facts about the world.
  • In the same way, the theory of evolution describes facts about the living world.
  • A theory in science has also survived significant efforts to discredit it by scientists.
  • The theory of evolution explains how populations change over time.

• Theories of Life History

  • Modern theories of life history incorporate life and survivorship factors with ecological concepts associated with r- and K-selection theories.
  • The r- and K-selection theory, although accepted for decades and used for much groundbreaking research, has now been reconsidered.
  • Over the years, several studies attempted to confirm the theory, but these attempts have largely failed.
  • Furthermore, the theory ignored the age-specific mortality of the populations which scientists now know is very important.
  • New demographic-based models of life history evolution have been developed which incorporate many ecological concepts included in r- and K-selection theory, as well as population age structure and mortality factors.

• The Cambrian Explosion of Animal Life

  • There are many theories that attempt to answer this question.
  • Yet other theories claim genetic and developmental reasons for the Cambrian explosion.
  • Theories that attempt to explain why the Cambrian explosion happened must be able to provide valid reasons for the massive animal diversification, as well as explain why it happened when it did.
  • There is evidence that both supports and refutes each of the theories described above.
  • The answer may very well be a combination of these and other theories.

• What is Evolution?

  • Evolution, the unifying theory of biology, describes a mechanism for the change and diversification of species over time.
  • The theory of evolution is the unifying theory of biology, meaning it is the framework within which biologists ask questions about the living world.
  • This theory contrasted with the predominant view of the time: that the geology of the planet is a consequence of catastrophic events that occurred during a relatively brief past.

• Scientific Method - The Practice of Science

  • A Theory is a statement well-supported by experimental evidence and widely accepted by the scientific community.
  • One of the most enduring, tested theories is of course the theory of evolution.
  • Even though theories are more generally thought of as "fact," they are still subject to being tested, and can even be overturned!
  • Teach. 35:125-129) and Gould, SJ (2002, The Structure of Evolutionary Theory.
  • Scientific Laws are even closer to ‘fact’ than theories!

• Endosymbiosis and the Evolution of Eukaryotes

  • The endosymbiotic theory was first articulated by the Russian botanist Konstantin Mereschkowski in 1905.
  • These theories were initially dismissed or ignored.
  • The endosymbiotic theory was advanced and substantiated with microbiological evidence by Lynn Margulis in 1967 .

• Altruism and Populations

  • Selfish gene theory has been controversial over the years and is still discussed among scientists in related fields.
  • According to evolutionary game theory, a modification of classical game theory in mathematics, many of these so-called "altruistic behaviors" are not altruistic at all.

• Endosymbiotic Theory and the Evolution of Eukaryotes

  • This mechanism is an aspect of the Endosymbiont Theory, which is accepted by a majority of biologists as the mechanism whereby eukaryotic cells obtained their mitochondria and chloroplasts.
  • The theory that mitochondria and chloroplasts are endosymbiotic in origin is now widely accepted.