UNIT 1 QUIZ 2 CELL THEORY

BIOLOGY

IV. Biology

Biology - bio- means life, -logy means study of therefore biology is study of life

A. Three unifying theories of biology - CELL theory, genetic theory, theory of evolution.

Form the foundation of biology. Do not exist or function independently, rather interact with + influence one another, allowing life to exist



  1. Cell Theory - a three component theory (developed between 1839 and 1858)

1) All living organisms are composed of one or more cells

2) Cells are the fundamental unit of structure, function, and organization in living organisms

3) Cells arise only from pre-existing cells



Current (modern) interpretations of cell theory include three additional components:

4) cells contain genetic material DNA and RNA that is passed to new generations of cells through cell division

5) all cells essentially same in chemical composition

6) metabolism (transfer of energy from chemical bonds of molecules into form that cells can use, ATP) and biochemistry (chemical reactions that sustain life) utilized by living organisms occur only within cells



  1. Genetic Theory (1865-1915)

Using mathematical analysis of offspring of pea plants. Gregor Mendel was able to deduce principles that explain patterns of inheritance (1865). Both Mendel and Darwin independently recognized that:

  1. There had to be a “factor” (genes) that determined traits and characteristics

  2. These factors (genes) could be passed from parents to offspring

  3. These factors (genes) could vary

  4. Chromosomes transfer genes from parents to offspring

Mendel and Darwin predicted existence of genes decades before DNA was isolated. 1915, Thomas Hunt Morgan demonstrated genes carried on chromosomes (chromosome theory of inheritance). These 4 concepts form foundation of genetics



3. Theory of evolution (Darwin, 1859)

A five component sequential theory that provides scientific mechanism and explanation for how life evolved from a common ancestor

  1. Common Descent: all life arose from single common ancestor that gave rise to ALL life seen today

  2. Variation: individuals within population differ from one another. It is now known these variations are result of random mutations in DNA

  3. Natural selection/Adaption: Some variations (mutations) more beneficial in particular environment than others. Individuals possessing beneficial variations more likely to survive in that environment. Those individuals that survive more likely to reproduce and pass their favorable variations (from mutations) on to future generations. This component is highly dependent on environment; a mutation that is beneficial in one environment may be detrimental or even fatal in another.

  4. Survival of the fittest: species produce far more offspring than necessary to maintain the population. Therefore, only individuals that are most fit, and those fortunate enough to survive until reproduction, are likely to reproduce and pass their favorable variations to next generation.

  5. Speciation: over thousands of generations (often millions of years), adaptations accumulate within population. As these adaptations accumulate, population gradually changes until it becomes new species. This process is known as speciation.



B. Integration of the Unifying Theories