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Biological Evolution by Natural Selection

• WHAT IS BIOLOGICAL EVOLUTION?
• * The process whereby Earth´s life changes over time through changes in the genes of populations.
• * In 1858, naturalist Charles Darwin and Alfred Russell Wallace proposed the concept pf natural selection as a mechanism for biological evolution. They observed that organisms must constantly struggle to obtain resources to survive and reproduce, and they also observed that some individuals have specific advantages over other individuals that make them more likely to survive.
• * Darwin and Wallace concluded that their survival traits would become more prevalent with future generations.
• * A change in the genetic characteristics of a population from one generation to another is known as "Biological Evolution." According to this theory, life has evolved into 6 majors groups of species called kingdoms.

Fossil Record

• * Fossils are mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds or impressions of such items found in rocks. They provide physical evidence of ancient organisms and reveal what their internal structures looked like.
• * The world cumulative body of fossils found is called the "fossil record," this record is incomplete. The fossils found so far probably represent only 1% of all species that have ever lived.
• * The paleonteologists are the one is charge of trying to reconstruct the development of life.

Genetic Makeup of Populations Change

• * Populations evolve by becoming genetically different. The first step in this process is the development of genetic variability; this occurs through mutations. Most mutations result from random changes that occur in coded genetic instructions or sometimes its due to exposure to external agents.
• * Mutations can occur in any cell, but only those take place in reproductive cells are passed onto offspring, sometimes this new genetic trait might give better chances for survival and reproduction.

Beneficial Genetic Traits in Offsprings

• * The next step in biological evolution is "natural selection," which occurs when some individuals of a population have genetically based-- traits that enhance their ability to survive and produce offsprings.
• * An adaption or adapted trait is any inheritable trait that enables an individual to survive through natural selection and to reproduce. For natural selection to occur, a trait must be heritable, it must also lead to differential reproduction which enables individuals with trait to leave more offspring that other members of the population leave.
• * Genetic resistance is the ability of one or more organisms in a population to tolerate a chemical designed to kill it.
• * A remarkable example of evolution by this type of selection is human beings, we have evolved certain traits but have allowed us to take over must of the world.