BIO 103 Chapter 1 Overview
Zoology and Evolutionary Theory
Biology is the scientific study of life. Zoology, a branch of biology, is the scientific study of animals. One theme in biology is the scientific Theory of Evolution. Evolutionary Theory states that populations genetically change over time. Natural selection is a mechanism that causes or drives evolution. Natural selection is the idea that individuals in a population show differential survival and reproduction due to environmental influences that act on that population. In accordance with natural selection, those individuals that have traits that provide advantages for survival and reproduction will survive the longest and reproduce the most, and therefore contribute more offspring with their traits for future generations. That is what causes a change in the genetics of the population over time (evolution). Remember, according to Evolutionary Theory, the population evolves not the individual.
Charles Robert Darwin and Alfred Russell Wallace are credited with independently developing the Theory of Evolution. Contributing to their ideas of evolutionary change were concepts developed by others. Examples include the idea that fossils were evidence of past life and that the earth was potentially hundreds of millions of years old with processes that have occurred over long periods of geologic time. Some of Darwin’s ideas were also influenced by his time aboard the Beagle. Darwin’s Theory of Evolution is often presented as five major components: perpetual change of the living world, common decent among life, multiplication of species as populations change over time, gradualism relative to changes in species, and natural selection. The scientific discipline must use evidence to support ideas. The following are considered some of the scientific evidences supporting evolution: fossils and the fossil record, comparative morphology including homology (i.e. example of vertebrate limb bones) and adaptive radiation, and DNA. Additionally, although gradualism is considered one of Darwin’s five components of evolution, sometimes evolution can occur more rapidly, relatively speaking for a geologic time scale. Examples may potentially include some insects’ resistances to pesticides, industrial melanism in peppered moths, and antibiotic resistant bacterial strains. Darwin was unable to accurately identify the mechanism for generational inheritance of traits. However, Gregor Mendel’s work provided the genetic basis for the chromosomal theory of inheritance. Microevolution and macroevolution play a role in how a population changes over time. Genetic drift, migration, mutations, and natural selection pressures interact as factors of evolutionary change in allelic frequencies in populations.
Macroevolution and microevolution also affect speciation. Speciation and extinction processes have occurred throughout geologic time. Scientists have identified at least five major mass extinction events throughout earth’s history. The fossil record suggests that adaptive radiation of species that survive mass extinctions is not uncommon. (This will be addressed again in chapter 2.)
The process of “doing science” as certain requirements, and zoology is a scientific discipline. Sciences must use the scientific method. The steps of the scientific method include an observation, formation of a question from that observation, formation of a hypothesis related to the observation (including a null hypothesis), an experiment to test the hypothesis, and formation of a conclusion based on the data collected from the experiment that will support or negate the hypothesis. Experimental results can then be published in peer reviewed scientific journals. Repeated sampling and testing are important in science, and sometimes hypotheses may eventually lead to scientific theories or laws.
Controlled experiments typically include at least one control group and at least one experimental group. A control group lacks the variable being tested (i.e. lacks the experimental or independent variable). The experimental group has the experimental variable. The dependent variable will be the result measured in the experiment. The experimental data will determine whether or not the hypothesis will be rejected or supported. Sometimes comparative methods are also utilized in science.
Reference: Hickman, C.P. Jr., et al., Animal Diversity