Chapter 1 Biology is the scientific study of life Biologists ask questions such as o How does a single cell develop into an organism o How does the human mind work o How do living things interact in communities Life defines a simple one sentence definition Life is recognized by what living things do Growth and development Order Energy processing Response to the environment Regulation Reproduction Evolutionary adaptation Concept 1 1 The study of life reveals common themes Biology is a subject of enormous scope There are five unifying themes o Organization o Information o Energy and matter Theme New Properties Emerge of Successive Levels of Biological Organization Life can be studied at different levels from molecules to the entire living planet This enormous range can be divided into different levels of biological organization o Interactions o Evolutions 1 The biosphere 2 Ecosystems 3 Communities 4 Populations 5 Organisms 6 Organs and organ systems 7 Tissues 8 Cells 9 Organelles 10 Molecules Emergent Properties Emergent properties result from the arrangement and interaction of parts within a system Emergent properties characterize non biological entities as well o For example a functioning bicycle emerges only when all of the necessary parts connect in the correct way Reductionism is the reduction of complex systems to simpler components that are more manageable to study o For example studying the molecular structure of DNA helps us to understand the chemical basis of inheritance To explore emergent properties biologists complement reductionism with systems biology analysis of the interactions among the parts of a biological system Structure and Function function At each level of the biological hierarchy we find a correlation between structure and The Cell An organism s basic unit of structure and function The cell is the lowest level of organization that can perform all activities required for life Every cell is enclosed by a membrane that regulates passage of materials between the cell and its environment A eukaryotic cell has membrane enclosed organelles the largest of which is usually the nucleus By comparison a prokaryotic cell is simpler and usually smaller and does not contain a nucleus or other membrane enclosed organelles Theme Life s Processes Involve the Expression and Transmission of Genetic Information Within cells structures called chromosomes contain genetic material in the form of DNA deoxyribonucleic acid DNA the genetic material Each chromosome has one long DNA molecule with hundreds or thousands of genes Genes encode information for building the molecules synthesized within the cell Genes are the units of inheritance DNA controls the development and maintenance of organisms Each DNA molecule is made up of two long chains arranged in a double helix Each chain is made up of four kinds of chemical building blocks called nucleotides and nicknamed A G C and T Genes control protein production indirectly DNA is transcribed into RNA which is then translated into a protein Gene expression is the process of converting information from gene to cellular product Genomics Large Scale Analysis of DNA Sequences The human genome and those of many other organisms have been sequenced An organism s genome is its entire set of genetic instructions Genomics is the study of sets of genes within and between species Proteomics is the study of whole sets of proteins encoded by the genome known as proteomes The genomics approach depends on o High throughput technology which yields enormous amounts of data o Bioinformatics which is the use of computational tools to process a large volume of data o Interdisciplinary research teams Theme Life Requires the Transfer and Transformation of Energy and Matter The input of energy from the sun and the transformation of energy from one form to another make life possible When organisms use energy to perform work some energy is lost to the surroundings As a result energy flows through an ecosystem usually entering as light and exiting as as heat heat Theme From Ecosystems to Molecules Interactions Are Important in Biological Systems Interactions between the components of the system ensure smooth integration of all the parts This holds true equally well for components of an ecosystem and the molecules in a cell Evolution the Core Theme of Biology Evolution is the one idea that makes logical sense of everything we know about living organisms The scientific explanation for both the unity and diversity of organisms is the concept that living organisms are modified descendants of common ancestors Many kinds of evidence support the occurrence of evolution Concept 1 2 The Core Theme Evolution accounts for the unity and diversity of life Nothing in biology makes sense except in the light of evolution Theodosius Dobzhansky Evolutionary mechanisms account for the unity and diversity of all species on Earth Charles Darwin published On the Origin of Species by Means of Natural Selection in 1859 Darwin made two main points o Species showed evidence of descent with modification from common ancestors o Natural selection is the mechanism behind descent with modification Darwin s theory explained the duality of unity and diversity The Three Domains of Life Organisms are divided into three domains o Bacteria o Archaea o Eukarya Domain Bacteria and domain Archaea compose prokaryotes Unity in the Diversity of Life A striking unity underlies the diversity of life for example o DNA is the universal genetic language common to all organisms o Unity is evident in many features of cell structure Concept 1 3 In studying nature scientists make observations and form and test hypotheses The word science is derived from Latin and means to know Inquiry is the search for information and explanations of natural phenomena The scientific process includes making observations forming logical hypotheses and testing them Making Observations Biologists describe natural structures and processes This approach is based on observation and the analysis of data Recorded observations are called data o Qualitative data often take the form of recorded descriptions o Quantitative data are generally expressed as numerical measurement organized into tables and graphs Forming and Testing Hypotheses In science a hypothesis is a tentative answer to a well framed scientific question It is usually a rational accounting for a set of observations It leads to predictions that can be tested by making additional
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