Figure 12.1 Although they look different, this bee and flower are distantly related. (credit: modification of work by John Beetham) Chapter Outline 12.1 Organizing Life on Earth 12.2 Determining Evolutionary Relationships This bee and Echinacea flower could not look more different, yet they are related, as…
Discovering How Populations Change Evolution by natural selection arises from three conditions: individuals within a species vary, some of those variations are heritable, and organisms have more offspring than resources can support. The consequence is that individuals with relatively advantageous…
Learning Objectives By the end of this section, you will be able to: Although the theory of evolution initially generated some controversy, by 20 years after the publication of On the Origin of Species it was almost universally accepted by biologists, particularly younger…
Learning Objectives By the end of this section, you will be able to: The biological definition of species, which works for sexually reproducing organisms, is a group of actually or potentially interbreeding individuals. According to this definition, one species is…
Learning Objectives By the end of this section, you will be able to: The evidence for evolution is compelling and extensive. Looking at every level of organization in living systems, biologists see the signature of past and present evolution. Darwin…
Learning Objectives By the end of this section, you will be able to: The Hardy-Weinberg equilibrium principle says that allele frequencies in a population will remain constant in the absence of the four factors that could change them. Those factors…
Learning Objectives By the end of this section, you will be able to: The theory of evolution by natural selection describes a mechanism for species change over time. That species change had been suggested and debated well before Darwin. The…
Figure 11.1 The diversity of life on Earth is the result of evolution, a continuous process that is still occurring. (credit “wolf”: modification of work by Gary Kramer, USFWS; credit “coral”: modification of work by William Harrigan, NOAA; credit “river”: modification of…
Cloning and Genetic Engineering Nucleic acids can be isolated from cells for the purposes of further analysis by breaking open the cells and enzymatically destroying all other major macromolecules. Fragmented or whole chromosomes can be separated on the basis of…
Learning Objectives By the end of this section, you will be able to: The study of nucleic acids began with the discovery of DNA, progressed to the study of genes and small fragments, and has now exploded to the field…