CHAPTER 1 Introduction: The Scientific Study of Life Modules 1.4 – 1.6

1.4 The diversity of life can be arranged into three domains EVOLUTION, UNITY, AND DIVERSITY 1.4 The diversity of life can be arranged into three domains Grouping organisms by fundamental features helps make the vast diversity of life manageable for study Scientists classify organisms into a hierarchy of broader and broader groups

Most classification schemes group organisms into three domains: Domain Bacteria Domain Archaea Figure 1.4A, B

Domain Eukarya Figure 1.4C-F

1.5 Unity in diversity: All forms of life have common features All organisms share a set of common features, signs of unity in life’s vast diversity All are made of cells All have DNA as their genetic blueprint These orchids show the variety possible within one species Figure 1.5A

DNA is made of chemical units called nucleotides Each species has its own nucleotide sequence Figure 1.5B

The genetic information in DNA underlies all of the features that distinguish life from nonlife Order and regulation Growth and development Use of energy from the environment Response to environmental stimuli Ability to reproduce Evolutionary change

1.6 Evolution explains the unity and diversity of life Charles Darwin is a central figure in biology He synthesized the theory of evolution by natural selection A theory in science is a comprehensive idea with broad explanatory power Evolution is the core theme of biology Figure 1.6A

The theory of natural selection explains the main mechanism whereby all species of organisms change, or evolve (1) Population with varied inherited traits (2) Elimination of individuals with certain traits Figure 1.6B (3) Reproduction of survivors

Evolution happens when populations of organisms with inherited variations are exposed to environmental factors that favor the success of some individuals over others Natural selection is the editing mechanism Evolution is based on adaptations Figure 1.6C