Biology: The Science of Life
Dr. Stephen Nowicki is Bass Fellow and Professor of Biology at Duke University. He is also Dean and Vice Provost of Undergraduate Education at Duke, and holds appointments in the Department of Psychological and Brain Sciences and in the Neurobiology Department at Duke University Medical Center. Prior to taking his position at Duke, he was a post-doctoral fellow and assistant professor at The Rockefeller University. Professor Nowicki earned his undergraduate degree and a master's degree at Tufts University, and his Ph.D. from Cornell University. He is the recipient of the Robert B. Cox Distinguished Teaching Award from Duke University. He has been awarded fellowships from the Mary Flagler Cary Charitable Trust, the Alfred P. Sloan Foundation, and the John Simon Guggenheim Foundation. Professor Nowicki has published more than 65 scholarly articles in academic journals and is coauthor of the book The Evolution of Animal/Communication: Reliability and Deceit in Signaling Systems.
01: The Scope of "Life"
The first lecture gives an overview of biology, raising key questions about the nature of life and the origin of living things, and concludes with an outline of the structure of the course.
02: More on the Origin of Life
This lecture outlines the challenges of evolution for living entities such as we recognize today, and reviews experimental data suggesting how these challenges might have been met. The process of reproduction identifies the concept of information in biology, and introduces the connecting theme for the first third of the course.
03: The Organism and the Cell
Professor Nowicki outlines the hierarchical nature of biological systems and introduces two fundamental levels of the hierarchy: the organism and the cell.
04: Proteins—How Things Get Done in the Cell
This lecture describes the four major classes of biomolecules—lipids, carbohydrates, nucleic acids, and proteins—and discusses the role of proteins in the life of the cell.
05: Which Molecule Holds the Code?
Key experiments in the first half of the 20th century led to the conclusion that DNA is the information-carrying molecule.
06: The Double Helix
Experiments by Rosalind Franklin, Maurice Wilkins, and others led to the discovery by James Watson and Francis Crick of the double helix structure of DNA, suggesting a mechanism by which the information in DNA can be replicated.
07: The Nuts and Bolts of Replicating DNA
After describing how the theory of DNA replication was confirmed, Professor Nowicki summarizes the process, which has been the key to understanding and manipulating biological systems.
08: The Central Dogma
We are introduced to the "central dogma" of molecular biology: Genetic information flows in one direction only—from DNA to RNA to proteins, not in reverse.
09: The Genetic Code
How is protein structure coded in DNA? This lecture describes the experiments that cracked the code and examines the code's defining properties.
10: From DNA to RNA
Step one in the journey of genetic information from DNA to proteins is the process of transcription, by which messenger RNA is made from a DNA template.
11: From RNA to Protein
Completing the description of how genetic information finds its way to functional proteins, this lecture covers the process of translation, which is the synthesis of proteins based on an RNA template.
12: When Mistakes Happen
We learn the causes for errors that creep into DNA during copying and the mechanisms that have evolved to detect and repair those errors.
13: Dividing DNA Between Dividing Cells
Moving from the molecular level to the level of cells and organisms, this lecture addresses the question: When a new being is produced, how does it acquire DNA from its parents?
14: Mendel and His Pea Plants
The first of two lectures on Gregor Mendel's 19th-century experiments on the genetics of pea plants shows how this work anticipated the modern understanding of genes, chromosomes, and the formation of gametes during meiosis.
15: How Sex Leads to Variation
This lecture continues the discussion of Mendel's contributions to genetics, turning to subsequent experiments in which he looked at the transmission of more than one trait.
16: Genes and Chromosomes
We explore the understanding of the cellular and molecular basis of genetics that emerged after Mendel at the turn of the 20th century.
17: Charles Darwin and "The Origin of Species"
At almost the same time that Mendel was working on his laws of inheritance, Charles Darwin was completing his theory of natural selection, which sought to explain the change of species over time.
18: Natural Selection in Action
This lecture presents several examples that demonstrate natural selection in action, including data from both field studies and laboratory experiments.
19: Reconciling Darwin and Mendel
The apparent conflict between Mendel and Darwin was resolved through the "modern synthesis," which models gene frequency changes in populations.
20: Mechanisms of Evolutionary Change
Natural selection is not the only cause of evolution. Other factors can produce changes in the gene pool of a population, the most notable being genetic drift.
21: What Are Species and How Do New Ones Arise?
Professor Nowicki discusses problems with the biological species concept, introduces alternate definitions, and describes the process of allopatric speciation.
22: More on the Origin of New Species
Continuing the discussion of how new species arise, this lecture looks at sympatric speciation, which occurs in the absence of physical separation of populations.
23: Reconstructing Evolution
How do biologists organize the enormous diversity of living things? We learn about phylogenetic systematics as an approach for reconstructing evolutionary history.
24: The History of Life, Revisited
This lecture takes a final look at the concept of information and evolution in biology by returning to the question of how an original, primordial life form might have given rise to the complex biodiversity observed today.
25: From Cells to Organisms
This lecture recaps material presented to this point and introduces the second major section of the course, "Development and Homeostasis," by looking at the mystery of complex, multicellular, self-regulating organisms.
26: Control of Gene Expression I
What makes cells different? We look at the mid 20th-century experiments of Jacques Monod and François Jacob in search of the mechanisms of gene regulation.
27: Control of Gene Expression II
We continue our investigation of how the proteins in a cell are determined by mechanisms that turn on and off the expression of specific genes.
28: Getting Proteins to the Right Place
Producing the right proteins at the right time is only the first step. This lecture explains how proteins find themselves in the right places inside or outside a cell.
29: Genetic Engineering and Biotechnology
The mechanisms cells use to replicate and transcribe DNA have shown researchers how to modify genes, transfer genetic material, and sequence genes.
30: How Cells Talk—Signals and Receptors
This lecture is the first of two that explore how molecular messages control cell function, focusing on how signals outside the cell get their message to the inside of the cell.
31: How Cells Talk—Ways That Cells Respond
Continuing the discussion of extracellular signals and cell function, this lecture focuses on the molecular mechanisms by which signals can change the way cells work.
32: From One Cell to Many in an Organism
How does a single cell develop into a fully formed organism? This lecture outlines the major questions surrounding development.
33: Patterns of Early Development
Professor Nowicki describes the four earliest stages of animal development - fertilization, cleavage, gastrulation, and organogenesis—outlining the processes involved in each.
34: Determination and Differentiation
Developmental processes cause cells to differentiate into many different types of cells. One such mechanism is cytoplasmic segregation.
35: Induction and Pattern Formation
The second major mechanism involved in differentiation is induction, in which cells stimulate each other to develop in different ways.
36: Genes and Development
This lecture examines the development of the Drosophila melanogaster (fruit fly) as an example of the influence of specific genes on pattern formation.
Homeostasis refers to an organism's ability to maintain a constant internal environment. We explore the nature of this mechanism and look at examples such as the regulation of body temperature.
38: Hormones in Animals
Homeostasis requires the different parts of a complex organism to communicate with each other. This lecture focuses on the endocrine system, which uses chemical signals called hormones to transmit physiological information.
39: What is Special about Neurons?
This lecture begins a discussion of the nervous system by examining neurons and the properties that enable them to transmit information over long distances at high speeds.
40: Action Potentials and Synapses
We review the initiation of action potentials and discuss how the anatomy of the neuron allows action potentials to propagate along the axon.
41: Synaptic Integration and Memory
In addition to transmitting information, the nervous system must also be able to process it. This lecture covers how inputs to a typical neuron are processed and stored.
42: Sensory Function
This lecture looks at the basic principles underlying sensory function—the mechanism by which animals obtain information from their environment.
43: How Muscles Work
Turning to the output side of cell function, Professor Nowicki examines muscles, describing the molecular basis for how muscle cells change their shape and exert force in doing so.
44: The Innate Immune System
How do animals defend themselves from injury or infection? We see how the nonspecific, or innate, immune response provides a general defense.
45: The Acquired Immune System
What happens if an infection can't be handled by nonspecific defenses? This is where the more specifically targeted and more efficient mechanisms associated with acquired immunity come into play.
46: Form and Function in Plants I
This lecture begins an examination of plant structure, development, and physiology, illustrating similarities and differences with analogous processes in animals.
47: Form and Function in Plants II
We continue our study of plant form and function by looking at how homeostasis is maintained in plants and by examining the ways plants respond to the external environment.
48: Behavior as an Adaptive Trait
This lecture discusses the adaptive significance of the ways organisms respond to stimuli. Why are some behaviors inflexible and others not?
49: Energy and Resources in Living Systems
Starting with a review of previous material, Professor Nowicki sets the stage for the third major theme of the course, "Energy and Resources," which moves from the level of molecules to global ecosystems.
50: How Energy is Harnessed by Cells
We look at the process by which cells obtain energy from a molecule called adenosine triphosphate (ATP).
51: Enzymes - Making Chemistry Work in Cells
Activation energy is the initial "push" required for a chemical reaction to proceed. This lecture examines the role and function of enzymes in facilitating chemical reactions in cells, which they do by effectively lowering this activation energy.
52: Cellular Currencies of Energy
We explore the chemical nature of ATP that allows it to serve as an energy "currency" for cells, and learn how energy is stored in glucose and other organic molecules, which allow them to act as a cellular "fuel" for making more ATP.
53: Making ATP - Glycolysis
This lecture introduces the three energy-producing metabolic processes in the cell - glycolysis, the Krebs cycle, and the electron transport chain - and looks in depth at glycolysis.
54: Making ATP - Cellular Respiration
Glycolysis extracts relatively little of the energy available in glucose. The complete harvest of this energy involves several additional processes, including the Krebs cycle and the electron transport chain.
55: Making ATP - The Chemiosmotic Theory
The electron transport chain is the process that ultimately uses the energy extracted from the breakdown of organic molecules such as glucose to drive the production of ATP, but how this worked was a mystery for decades. This lecture outlines the radical theory that finally solved this puzzle.
56: Capturing Energy from Sunlight
Living things require fuel to generate ATP. Some organisms generate fuel by converting the energy of sunlight into high-energy organic compounds through the process of photosynthesis.
57: The Reactions of Photosynthesis
Where does the added mass come from when a plant grows? The answer leads us to consider the reactions of photosynthesis and the Calvin cycle.
58: Resources and Life Histories
Many organisms have the capacity for the kind of explosive population growth associated with bacteria. Asking why such unchecked growth is rare provides a transition to considering energy and resources at higher levels of biological organization.
59: The Structure of Populations
Our survey of energy and resources moves to the level of populations, in which we define the term population and outline the characteristics of a population from an ecological perspective.
60: Population Growth
This lecture looks at population growth under the ideal conditions of exponential growth and under the more realistic assumptions of logistic growth.
61: What Limits Population Growth?
Does the logistic growth model describe the growth of real populations? The answer is "yes and no." We look at the factors that actually regulate population growth.
62: Costs and Benefits of Behavior
The behavior of an individual changes in a way that maximizes the difference between the costs and benefits that are accrued by that particular behavior.
63: Altruism and Mate Selection
Altruistic interactions are quite common, yet difficult to understand from an evolutionary perspective. An expanded definition of reproductive fitness provides an explanation.
64: Ecological Interactions Among Species
The interaction between predators and their prey is one of the most important in nature. We examine examples of these interactions and the principles that can be derived from them.
65: Predators and Competitors
This lecture looks in more detail at cases in which one species benefits and the other is harmed, and then focuses on competition where both species might be affected adversely by the other's presence.
66: Competition and the Ecological Niche
Continuing the discussion of competition in communities, we look at studies of how a competitive interaction affects species, which leads to the concept of the ecological niche.
67: Energy in Ecosystems
Environments store and release critical resources to the species that live in them. This lecture explores the flow of one such resource - energy - showing how inefficiencies in energy transfer can influence the abundance of a species.
68: Nutrients in Ecosystems
Unlike energy, nutrients are recycled into and out of ecosystems. To illustrate the significance of this fact, we follow the cycles of three critical nutrient elements: carbon, nitrogen, and phosphorus.
69: How Predictable Are Ecological Communities?
Many aspects of the structure and composition of ecological communities have been shown to be unpredictable. As a result, ecologists now focus on patterns of disturbance in communities instead of trying to describe the end-state of ideal communities.
Biogeography is the branch of biology that attempts to account for the patterns of distribution of populations, species, and ecological communities on a global scale. We look at examples that illustrate key points.
71: Human Population Growth
For most of history, human population size was limited by the amount of resources available naturally in the environment. But humans have repeatedly redefined ways many resources can be obtained and used, an ability that has led to a dramatic increase in world population.
72: The Human Asteroid
The increasing loss of biodiversity means that species diversity is decreasing at the very moment of our greatest strides in biological understanding. Professor Nowicki closes with reasons for alarm and hope.