Transcript chapter1
Invitation to Biology Chapter 1 1.1 Life’s Levels of Organization Nature has levels of organization Unique properties emerge at successively higher levels Organization Within An Organism Atoms are organized into molecules In multicelled species, cells are organized into tissues, organs, and organ systems All organisms consist of one or more cells Emergent properties: Life emerges at the cellular level Organization of Groups of Organisms Population • All individuals of one species in a specific area Community • All populations in a specific area Ecosystem • A community interacting with its environment Organization of Life on Earth Biosphere • All regions of Earth that hold life • Land, water, and atmosphere Levels of Organization Levels of Organization molecule cell tissue organ organ system atom Fig. 1.3a, p. 4 multicelled organism population community ecosystem biosphere Fig. 1.3b, p. 4 KEY CONCEPTS: LEVELS OF ORGANIZATION We study the world of life at different levels of organization, from atoms and molecules to the biosphere “Life” emerges at the level of cells 1.2 Overview of Life’s Unity Organisms require energy and materials to sustain their organization and activities • Nutrients are required for growth and survival • Producers make their own food • Consumers eat other organisms Ecosystem: Energy Flow and Material Cycling Energy input, from sun Producers Nutrient cycling Consumers energy output (mainly metabolic heat) Fig. 1.4, p. 6 Overview of Life’s Unity Organisms sense change • Receptors respond to stimulation • Responses keep internal conditions within ranges that cells can tolerate (homeostasis) Response to Stimulus Overview of Life’s Unity Organisms grow and reproduce • Based on information encoded in DNA • Inheritance transmits DNA from parents to offspring through reproduction mechanisms • Development transforms first cell into an adult Instructions Assemble Materials Development Fig. 1.7a, p. 7 Fig. 1.7b, p. 7 Fig. 1.7c, p. 7 Fig. 1.7d, p. 7 Fig. 1.7e, p. 7 KEY CONCEPTS: LIFE’S UNDERLYING UNITY All organisms are alike in key respects: • Consist of one or more cells • Live through inputs of energy and raw materials • Sense and respond to changes in their external and internal environments • Cells contain DNA (molecule that offspring inherit from parents; encodes information necessary for growth, survival, and reproduction) 1.3 So Much Unity, So Many Species The world of life, past and present, shows great diversity Classification systems organize species in ever more inclusive groups Genus and Species Species: One kind of organism Each species has a two-part name • First part: Genus name • Combined with the second part, it designates one particular species Domains Current classification groups all species into three domains • Bacteria (single-celled prokaryotes) • Archaea (single-celled prokaryotes) • Eukarya (protists, plants, fungi, and animals) Bacteria and Archaea Bacteria Archaea Eukarya Eukarya Eukarya Eukarya Life’s Three Domains KEY CONCEPTS: LIFE’S DIVERSITY The world of life shows great diversity Many millions of kinds of organisms (species) have appeared and disappeared over time Each species is unique in at least one trait—in some aspect of its body form or behavior 1.4 An Evolutionary View of Diversity Life’s diversity arises from mutations • Changes in molecules of DNA which offspring inherit from their parents In natural populations, mutations introduce variation in heritable traits among individuals Variation in Heritable Traits Some trait forms are more adaptive than others • Bearers are more likely to survive and reproduce Over generations, adaptive forms of traits tend to become more common in a population • Less adaptive forms of the same traits become less common or are lost Evolution Populations evolve • Traits that help characterize a population (and a species) can change over generations Evolution • Change which occurs in a line of descent Selection Natural selection • In natural populations • Differential survival and reproduction among individuals that vary in one or more heritable traits Artificial selection • Breeding of captive populations • Traits selected are not necessarily adaptive Artificial and Natural Selection KEY CONCEPTS: EXPLAINING UNITY IN DIVERSITY Theories of evolution (especially a theory of evolution by natural selection) help explain why life shows both unity and diversity Evolutionary theories guide research in all fields of biology 1.5 Critical Thinking and Science Critical thinking is a self-directed act of judging the quality of information as one learns Science is a way of looking at the natural world • Helps minimize bias in judgments • Focuses on testable ideas about observable aspects of nature Evidence-Based Thinking 1.6 How Science Works Researchers generally • Observe something in nature • Form hypotheses (testable assumptions) about it • Make predictions about what might occur if the hypothesis is not wrong • Test their predictions by observations, experiments, or both Experiments Tests used to support or falsify a prediction • Variable characteristic is measured and changed • In the control group, variables do not change A Scientific Approach Scientific Theory A well-tested hypothesis • Explains a broad range of observations • Can be used to make useful predictions about other phenomena Opinion and belief are not scientific theory Some Scientific Theories 1.7 The Power of Experiments Biological systems have many variables Experiments simplify observations of nature • Focus on cause, effect, or function of one variable at a time Researchers design experiments to minimize potential bias in interpreting results A Controlled Experiment Hypothesis Olestra® causes intestinal cramps. Prediction People who eat potato chips made with Olestra will be more likely to get intestinal cramps than those who eat potato chips made without Olestra. Experiment Results Control Group Experimental Group Eats regular potato chips Eats Olestra potato chips 93 of 529 people get cramps later (17.6%) 89 of 563 people get cramps later (15.8%) Conclusion Percentages are about equal. People who eat potato chips made with Olestra are just as likely to get intestinal cramps as those who eat potato chips made without Olestra. These results do not support the hypothesis. Fig. 1.11, p. 14 Hypothesis Olestra® causes intestinal cramps. Prediction People who eat potato chips made with Olestra will be more likely to get intestinal cramps than those who eat potato chips made without Olestra Experiment Control Group Eats regular potato chips Experimental Group Eats Olestra potato chips Results Control Group Eats regular potato chips Experimental Group Eats Olestra potato chips Conclusion Percentages are about equal. People who eat potato chips made with Olestra are just as likely to get intestinal cramps as those who eat potato chips made without Olestra. These results do not support the hypothesis. Stepped Art Fig. 1-11, p. 14 a Wing spots painted out b Wing spots visible; wings silenced c Wing spots painted out; wings silenced d Wings painted but spots visible e Wings cut but not silenced f Wings painted but spots visible; wings cut but not silenced Stepped Art Fig. 1-14, p. 18 Butterflies and Birds: A Behavioral Experiment Butterflies and Birds: Results 1.8 Sampling Error in Experiments Small sample size increases the likelihood of sampling error in experiments In such cases, a subset may be tested that is not representative of the whole Experiment: Sampling Error KEY CONCEPTS: HOW WE KNOW Biologists make systematic observations, predictions, and tests in the laboratory and field They report their results so others may repeat their work and check their reasoning Animation: Building blocks of life CLICK HERE TO PLAY Animation: Insect development CLICK HERE TO PLAY Animation: Life's diversity CLICK HERE TO PLAY Animation: Life's levels of organization CLICK HERE TO PLAY Animation: One-way energy flow and materials cycling CLICK HERE TO PLAY Animation: Sampling error CLICK HERE TO PLAY Animation: Three domains CLICK HERE TO PLAY