LEARNING OBJECTIVES In this section, you will explore the following questions: Connection for AP® Courses The first organisms that originated about 3.5 billion years ago were prokaryotes that possessed the structures and metabolic processes associated with cells (refer to the Cell…
Figure 21.1 The tobacco mosaic virus (left), seen here by transmission electron microscopy, was the first virus to be discovered. The virus causes disease in tobacco and other plants, such as the orchid (right). (credit a: USDA ARS; credit b: modification of…
Organizing Life on Earth Scientists continually gain new information that helps understand the evolutionary history of life on Earth. Each group of organisms went through its own evolutionary journey, called its phylogeny. Each organism shares relatedness with others, and based…
In this section, you will explore the following questions: Connection for AP® Courses Newer technologies have uncovered surprising discoveries with unexpected relationships among organisms, such as the fact that humans seems to be more closely related to fungi than fungi are…
LEARNING OBJECTIVES Connection for AP® Courses To build phylogenetic trees, scientists must collect accurate information that allows them to make evolutionary connections among organisms. Using morphological and molecular data, scientists identify both homologous and analogous characteristics and genes. (In a prior…
LEARNING OBJECTIVES In this section, you will explore the following questions: Connection for AP® Courses In prior chapters we explored how all organisms on Earth, extant and extinct, evolved from common ancestry. Supporting this claim are core features and processes, such…
Figure 20.1 The life of a bee is very different from the life of a flower, but the two organisms are related. Both are members of the domain Eukarya and have cells containing many similar organelles, genes, and proteins. (credit: modification of…
Population Evolution The modern synthesis of evolutionary theory grew out of the cohesion of Darwin’s, Wallace’s, and Mendel’s thoughts on evolution and heredity, along with the more modern study of population genetics. It describes the evolution of populations and species,…
In this section, you will explore the following questions: Connections for AP® Courses As we have learned, natural selection acts on the level of the individual, selecting those with a higher overall fitness (reproductive success) compared to the rest of the population. In…
LEARNING OBJECTIVES In this section, you will explore the following questions: Connection for AP® Courses Take a look at your classmates. Individuals of a population often display different phenotypes, or express different alleles of a particular gene. These differences are called polymorphisms.…