Chapter 1 Themes in the Study of Life 1 1 The Themes of this book make connections across different areas of biology Evolution the process of change that has transformed life on Earth from its earliest beginnings to the diversity of organisms living today Biology the scientific study of life Eight Themes 1 New Properties Emerge at Each Level in the Biological Hierarchy emergent properties reductionism new properties that arise with each step upward in the hierarchy of life the approach of reducing complex systems to simpler components that are more manageable to study Systems biology an approach that attempts to model the dynamic behavior of whole biological systems based on a study of the interactions among the system s parts this enables biologists to predict how a change in one or more variables will affect other components and the whole system Levels of Biological Organization 1 Molecules 2 Organelles 3 Cells 4 Tissues 5 Organs and Organ Systems 6 Organisms 7 Populations 8 Communities 9 Ecosystems 10 The Biosphere 2 Organisms Interact with Other Organisms and the Physical Environment global climate change global warming or cooling 3 Life Requires Energy Transfer and Transformation Consumers organisms that feed on producers and other consumers 4 Structure and Function are Correlated at all Levels of Biological Organization 5 The Cell is an Organism s Basic Unit of Structure and Function All cells share certain characteristics enclosed by a membrane that regulates the passage of materials between the cell and its surroundings every cell uses DNA as its genetic information There are two main types of cells 1 Prokaryotic cells bacteria and archae the DNA is not separated from the rest of the cell by a nucleus no membrane enclosed organelles 2 Eukaryotic cells all other forms of life subdivided by internal membranes into membrane enclosed organelles the largest organelle is the nucleus contains the DNA cytoplasm the region between the nucleus and the outer membrane that contains the other organelles much larger than prokaryotic cells 6 The Continuity of Life is Based on Heritable Information in the Form of DNA Chromosomes have almost all of the cell s genetic material its DNA DNA is the substance of genes the units of inheritance that transmit information from parents to offspring each chromosome contains one very long DNA molecule each DNA molecule is made up of two long chains called strands in a double helix each chain is made up of 4 kinds of chemical building blocks called nucleotides abbreviated A T C and G DNA provides the blueprint for making proteins proteins are the main players in building and maintaining the cell and carrying out its activities Gene expression the process by which the information in a gene directs the production of a cellular product the entire library of genetic instructions that an organism inherits studying whole sets of genes of a species as well as comparing genomes Genome Genomics between species Bioinformatics the use of computational tools to store organize and analyze the huge volume of data that result from high throughput methods 7 Feedback Mechanisms Regulate Biological Systems Feedback regulation the output or product of a process regulates itself Negative Feedback Positive Feedback the output slows the process the end product speeds up its own production ex clotting of the blood 8 Evolution the Overachieving Theme of Biology 1 2 The Core Theme Evolution accounts for the unity and diversity of life Domains 1 Bacteria 2 Archae 3 Eukarya Charles Darwin includes the kingdoms Plantae Fungi and Animalia wrote the book The Origin of Species which articulated two main points 1 contemporary species arose from succession of ancestors 2 natural selection three observations individuals in a population vary in their traits a population can produce far more offspring than can survive to produce offspring of their own species adapt to their environment 1 3 In studying nature scientists make observations and then form and test hypotheses data recorded observations qualitative descriptions quantitative measurements inductive reasoning we derive generalizations from a large number of specific observations deductive reasoning used after the hypothesis has been developed and involves logic that flows in the opposite direction from the general to the specific if then controlled experiment Theory one that is designed to compare an experimental group with a control group a theory is much broader than a hypothesis a theory is general enough to spin off many new specific hypotheses that can be tested a theory is generally supported by a much greater body of evidence Chapter 2 The Chemical Context of Life 2 1 Matter Matter consists of chemical elements in pure form and in combinations called compounds Organisms are composed of matter matter is anything that takes up space matter is made up of elements an element is a substance that cannot be broken down to other substances by chemical reactions A compound is a substance consisting of two or more different elements combined in a fixed ratio a compound has different characteristics than its elements 20 25 of the natural elements are essential elements elements that an organism needs to live a healthy life and reproduce there is some variation humans need 25 plants need just 17 Oxygen Carbon Nitrogen and Hydrogen make up 96 of living matter calcium phosphorus potassium and sulfur make up the rest Trace elements elements that are required by an organism in only minute quantities ex Iron that is needed by all forms of life 2 2 An element s properties depend on the structure of its atoms Each element consists of a certain type of atom that is different from the atoms of any other element an atom is the smallest unit of matter that still retains the properties of an element Subatomic Particles neutrons neutral charge protons positive charge electrons negative charge Protons and neutrons are located in a dense core called the atomic nucleus protons give the nucleus a positive charge the electrons form a cloud of negative charge around the nucleus and their attraction to the nucleus that keeps them close The neutron and proton are almost identical in mass amu is the measurement for them also called Dalton or atomic mass number the mass of an electron is about 1 2000 the mass of a proton or neutron Atoms of the various elements differ in their number of subatomic particles all atoms of a particular element have the same
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