1 Principles of Life

Chapter 1 Principles of Life Key Concepts 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow 1.2 Genetic Systems Control the Flow, Exchange, Storage, and Use of Information 1.3 Organisms Interact with and Affect Their Environments

Chapter 1 Principles of Life 1.4 Evolution Explains Both the Unity and Diversity of Life 1.5 Science Is Based on Quantifiable Observations and Experiments

Biology—the scientific study of living things Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Biology—the scientific study of living things “Living things”—All the diverse organisms descended from a single-celled ancestor (a single common ancestor)

Characteristics shared by all living organisms: Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Characteristics shared by all living organisms: Composed of a common set of chemical components and similar structures • Contain genetic information that uses a nearly universal code • Convert molecules obtained from their environment into new biological molecules • Extract energy from the environment and use it to do biological work

Regulate their internal environment Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Regulate their internal environment • Replicate their genetic information in the same manner when reproducing • Share sequence similarities among a fundamental set of genes • Evolve through gradual changes in genetic information

Earth formed between 4.6 and 4.5 billion years ago. Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Earth formed between 4.6 and 4.5 billion years ago. It was some 600 million years or more before the earliest life evolved.

Figure 1.1 Life’s Calendar

Critical step for evolution of life—formation of nucleic acids Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Complex biological molecules possibly arose from random associations of chemicals in the early environment. Experiments that simulate conditions on early Earth show that this was possible. Critical step for evolution of life—formation of nucleic acids

Fatty acids were important in forming membranes. Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Biological molecules were enclosed in membranes, to form the first cells. Fatty acids were important in forming membranes.

For 2 billion years, organisms were unicellular prokaryotes. Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow For 2 billion years, organisms were unicellular prokaryotes. Early prokaryotes were confined to oceans, where they were protected from UV light. There was little or no O2 in the atmosphere, and hence no protective ozone (O3) layer.

Figure 1.2 The Basic Unit of Life is the Cell

Photosynthesis evolved about 2.7 billion years ago. Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Photosynthesis evolved about 2.7 billion years ago. The energy of sunlight is transformed into the energy of biological molecules. Earliest photosynthetic cells were probably similar to cyanobacteria. O2 was a byproduct of photosynthesis, and it began to accumulate in the atmosphere. VIDEO 1.1 Cyanobacteria

Figure 1.3 Photosynthetic Organisms Changed Earth’s Atmosphere (Part 1)

Figure 1.3 Photosynthetic Organisms Changed Earth’s Atmosphere (Part 2)

O2 was poisonous to many early prokaryotes. Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow O2 was poisonous to many early prokaryotes. Organisms that could tolerate O2 evolved aerobic metabolism (energy production using O2), which is more efficient than anaerobic metabolism. Organisms were able to grow larger. Aerobic metabolism is used by most living organisms today.

O2 also produced a layer of ozone (O3) in the upper atmosphere. Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow O2 also produced a layer of ozone (O3) in the upper atmosphere. This layer absorbs UV light, and its formation allowed organisms to move from the ocean to land.

Some cells evolved membrane-enclosed compartments called organelles. Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Some cells evolved membrane-enclosed compartments called organelles. Example: The nucleus contains the genetic information. These cells are eukaryotes. Prokaryotes lack nuclei and other internal compartments.

Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Some organelles may have originated by endosymbiosis, when larger cells engulfed smaller ones. Mitochondria (site of energy generation) probably evolved from engulfed prokaryotic organisms. Chloroplasts (site of photosynthesis) probably evolved from photosynthetic prokaryotes.

Multicellular organisms arose about 1 billion years ago. Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Multicellular organisms arose about 1 billion years ago. Cellular specialization—cells became specialized to perform certain functions.

Mutations are introduced when a genome is replicated. Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Evolution of species: Mutations are introduced when a genome is replicated. Some mutations give rise to structural and functional changes in organisms, and new species arise.

Each species has a distinct scientific name, a binomial: • Genus name Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Each species has a distinct scientific name, a binomial: • Genus name • Species name Example: Homo sapiens

A phylogenetic tree documents and diagrams evolutionary relationships. Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Evolutionary relationships of species can be determined by comparing genomes. A phylogenetic tree documents and diagrams evolutionary relationships.

Figure 1.4 The Tree of Life

• Bacteria (prokaryotes) • Archaea (prokaryotes) Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Relationships in the tree of life are determined by fossil evidence, structures, metabolic processes, behavior, and molecular analyses of genomes. Three domains of life: • Bacteria (prokaryotes) • Archaea (prokaryotes) • Eukarya (eukaryotes)

Concept 1.1 Living Organisms Share Common Aspects of Structure, Function, and Energy Flow Because all life is related, discoveries made using one type of organism can be extended to other types. Biologists use model systems for research, such as the green alga Chlorella to study photosynthesis.

DNA consists of repeating subunits called nucleotides. Concept 1.2 Genetic Systems Control the Flow, Exchange, Storage, and Use of Information Genome—the sum total of all the information encoded by an organism’s genes DNA consists of repeating subunits called nucleotides. Gene—a specific segment of DNA that contains information for making a protein Proteins govern chemical reactions in cells and form much of an organism’s structure. VIDEO 1.2 Deoxyribonucleic acid: A three-dimensional model

Figure 1.5 DNA Is Life’s Blueprint

Mutations are the raw material of evolution. Concept 1.2 Genetic Systems Control the Flow, Exchange, Storage, and Use of Information Mutations alter nucleotide sequences of a gene, and the protein is often altered as well. Mutations may occur during replication, or be caused by chemicals and radiation. Most are harmful or have no effect, but some may improve the functioning of the organism. Mutations are the raw material of evolution.

Complete genome sequences have been determined for many organisms. Concept 1.2 Genetic Systems Control the Flow, Exchange, Storage, and Use of Information Complete genome sequences have been determined for many organisms. Genome sequences are used to study the genetic basis of everything from physical structure to inherited diseases, and evolutionary relationships.

Concept 1.3 Organisms Interact with and Affect Their Environments Biological systems are organized in a hierarchy. Traditionally, biologists concentrated on one level of the hierarchy, but today much biology involves integrating investigations across many levels. VIDEO 1.3 Levels of complexity in volvocalean organisms

Figure 1.6 Biology Is Studied at Many Levels of Organization (Part 1)

Figure 1.6 Biology Is Studied at Many Levels of Organization (Part 2)

Concept 1.3 Organisms Interact with and Affect Their Environments Living organisms acquire nutrients from their environments. Nutrients supply energy and materials for biochemical reactions. Some reactions break nutrient molecules into smaller units, releasing energy for work.

Concept 1.3 Organisms Interact with and Affect Their Environments Examples of cellular work: Synthesis—building new complex molecules from smaller chemical units Movement of molecules, or the whole organism Electrical work of information processing in nervous systems

Concept 1.3 Organisms Interact with and Affect Their Environments Metabolism is the sum total of all chemical transformations and other work done in all cells of an organism. The reactions are integrally linked—the products of one are the raw materials of the next.

Concept 1.3 Organisms Interact with and Affect Their Environments In multicellular organisms, cells are specialized, or differentiated. Differentiated cells are organized into tissues. Tissue types are organized into organs, and organ systems are groups of organs with interrelated functions.

Concept 1.3 Organisms Interact with and Affect Their Environments Multicellular organisms have an internal environment that is acellular—an extracellular environment of fluids. Homeostasis—maintenance of a narrow range of conditions in this internal environment Regulatory systems maintain homeostasis in both multicellular organisms and in individual cells.

Concept 1.3 Organisms Interact with and Affect Their Environments Population—group of individuals of the same species that interact with one another A community—populations of all the species that live in the same area and interact Communities plus their abiotic environment constitute an ecosystem. VIDEO 1.4 A community: A coral reef in the Philippines

Concept 1.3 Organisms Interact with and Affect Their Environments Individuals may compete with each other for resources, or they may cooperate (e.g., in a termite colony). Plants also compete for light and water, and many form complex partnerships with fungi, bacteria, and animals.

Concept 1.3 Organisms Interact with and Affect Their Environments Interactions of plants and animals are major evolutionary forces that produce specialized adaptations. Species interaction with one another and with their environment is the subject of ecology.

Concept 1.4 Evolution Explains Both the Unity and Diversity of Life Evolution is a change in genetic makeup of biological populations through time—a major unifying principle of biology. Charles Darwin proposed that all living organisms are descended from a common ancestor by the mechanism of natural selection.

Concept 1.4 Evolution Explains Both the Unity and Diversity of Life Natural selection leads to adaptations— structural, physiological, or behavioral traits that enhance an organism’s chances of survival and reproduction VIDEO 1.5 Animal adaptation: Prey capture by a kingfisher

Figure 1.7 Adaptations to the Environment (Part 1)

Figure 1.7 Adaptations to the Environment (Part 2)

Figure 1.7 Adaptations to the Environment (Part 3)

Figure 1.7 Adaptations to the Environment (Part 4)

Concept 1.4 Evolution Explains Both the Unity and Diversity of Life In science, a theory is a body of scientific work in which rigorously tested and well-established facts and principles are used to make predictions about the natural world. Evolutionary theory is: (1) a body of knowledge supported by facts (2) the resulting understanding of mechanisms by which populations have changed and diversified over time, and continue to evolve

Concept 1.4 Evolution Explains Both the Unity and Diversity of Life Evolution can be observed and measured by: Changes in genetic composition of populations over short time frames The fossil record—population changes over very long time frames

Concept 1.5 Science Is Based on Quantifiable Observations and Experiments Scientific investigations are based on observation and experimentation. Understanding the natural history of organisms—how they get food, reproduce, behave, regulate internal environments, and interact with other organisms—facilitates observation and leads to questions.

Concept 1.5 Science Is Based on Quantifiable Observations and Experiments Observation is enhanced by technology: microscopes, imaging, genome sequencing, and satellites. Observations must be quantified by measurement and mathematical and statistical calculations.

The scientific method (hypothesis–prediction (H–P) method): Concept 1.5 Science Is Based on Quantifiable Observations and Experiments The scientific method (hypothesis–prediction (H–P) method): Observations Questions Hypotheses Predictions Testing

Figure 1.8 Scientific Methodology

Inductive logic leads to tentative explanations called hypotheses. Concept 1.5 Science Is Based on Quantifiable Observations and Experiments Inductive logic leads to tentative explanations called hypotheses. Deductive logic is used to make predictions. Experiments are designed to test these predictions. ANIMATED TUTORIAL 1.1 Using Scientific Methodology

Independent variable—the variable being manipulated Concept 1.5 Science Is Based on Quantifiable Observations and Experiments Controlled experiments manipulate the variable that is predicted to cause differences between groups. Independent variable—the variable being manipulated Dependent variable—the response that is measured

Figure 1.9 Controlled Experiments Manipulate a Variable (Part 1)

Figure 1.9 Controlled Experiments Manipulate a Variable (Part 2)

Concept 1.5 Science Is Based on Quantifiable Observations and Experiments Comparative experiments look for differences between samples or groups. The variables cannot be controlled; data are gathered from different sample groups and compared.

Figure 1.10 Comparative Experiments Look for Differences among Groups (Part 1)

Figure 1.10 Comparative Experiments Look for Differences among Groups (Part 2)

Concept 1.5 Science Is Based on Quantifiable Observations and Experiments Statistical methods help scientists determine if differences between groups are significant. Statistical tests start with a null hypothesis— that no differences exists. Statistical methods eliminate the possibility that results are due to random variation.

Not all forms of inquiry into nature are scientific. Concept 1.5 Science Is Based on Quantifiable Observations and Experiments Not all forms of inquiry into nature are scientific. Scientific hypotheses must be testable, and have the potential of being rejected. Science depends on evidence that comes from reproducible and quantifiable observations.

Science and religion are nonoverlapping approaches to inquiry. Concept 1.5 Science Is Based on Quantifiable Observations and Experiments Religious or spiritual explanations of natural phenomena are not testable and therefore are not science. Science and religion are nonoverlapping approaches to inquiry.

Concept 1.5 Science Is Based on Quantifiable Observations and Experiments Scientific advances that may contribute to human welfare may also raise ethical questions. Science describes how the world works; it is silent on the question of how the world “ought to be.” Contributions from other forms of human inquiry may help us come to grips with such questions.