Study Guide for Science Test Definition of Key Terms 1. Meiosis - meiosis produces sperm and eggs for sexual reproduction. In this process, chromosome duplication is followed by two divisions that result in a set of four cells, each of which has half the normal complement of DNA (Trefill and Hazen 465). Crossing over between pairs of chromosomes results in the shuffling/mixing of genetic material; and this process results in chromosomes with a new genetic makeup (Trefill and Hazen 463). 2. X and Y chromosome – A chromosome is a specific length of an organisms DNA that encloses a protein core (Trefill and Hazen 503). The X chromosome is associated with female characteristics and the Y chromosome is associated with male characteristics. The...The end:
..... are born than can possibly survive. Natural selection also provides a mechanism for a species to change its traits in response to changes in the environment. It is neither controlled nor rapid like artificial selection - the process of breeding controlled by humans. Thus natural selection is a process that operates over long time periods to produce gradual changes in populations, not a process that can explain short term variations in a few individual traits. So, natural selection relates to changes in populations over time (Trefill and Hazen 541-542). Works Cited Trefil, James S. Encyclopedia of science and technology. Taylor & Francis, 2001. Trefill, James and Robert Hazen. The Sciences: An Integrated Approach 6 Edition, Wiley, 2010.