Theme 4: CONTINUITY & CHANGE
Explanation: All species tend to maintain themselves from generation to generation using the same genetic code. However, there are genetic mechanisms that lead to change over time, or evolution.
Clarification: You would post here examples of how organisms reproduce while maintaining the same genetic information from generation to generation AND also examples of how organisms reproduce while accumulating changes to their genetic information from generation to generation.
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When organisms reproduce, they transfer their genes from generation to generation. In sexual reproduction an organism always gives have of its DNA code to its offspring. This ensures that the genes of that organism are passed down. Since an offspring receives half of its genetic code from one parent and the other half from another parent, their is always change in genetic recombination. Different genes can be obtained from both parents.
An example of continuity and change is meiosis. Meiosis occurs in all eukaryotic life cycles involving sexual reproduction. It is the process by which one diploid eukaryotic cell divides to generate four haploid cells,called gametes. In sexual reproduction half the genes of one parent and half of the other parents go into making a zygote and in this process of genetic recombination different genes occur.
An example of change in genetic information while being passed from one generation to the next is through mutation. A mutation can occur when a copying error in the the DNA is caused by ultraviolet or ionizing radiation, chemical mutagens, or viruses, or other enviornmental factors.
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