Transcript Chapter 1
Invitation to Biology Chapter 1 1.1 Impacts/Issues: The Secret Life of Earth Biology The systematic study of life We have encountered only a fraction of the organisms that live on Earth Scientists constantly discover new species Extinction rates are accelerating Video: Lost worlds and other wonders Exploring New Guinea A rare golden-mantled tree kangaroo 1.2 Life’s Levels of Organization The building blocks (atoms) that make up all living things are the same ones that make up all nonliving things The unique properties of life emerge as certain kinds of molecules become organized into cells Life’s Levels of Organization Atom Fundamental building block of all matter Molecule An association of two or more atoms Cell Smallest unit of life Organism An individual; consists of one or more cells Life’s Levels of Organization Population Group of individuals of a species in a given area Community All populations of all species in a given area Ecosystem A community interacting with its environment Biosphere All regions of Earth that hold life Nature and Life Nature Everything in the universe, except what humans have manufactured Emergent property A characteristic of a system that does not appear in any of a system’s component parts Levels of Organization in Nature Animation: Life’s levels of organization Active Figure: Levels of organization 1.3 Overview of Life’s Unity All living things have similar characteristics Require energy and nutrients Sense and respond to change Reproduce with the help of DNA Energy Sustains Life’s Organization One-way flow of energy through the biosphere and cycling of nutrients among organisms sustain life’s organization Energy The capacity to do work Nutrient Substance that is necessary for survival, but that an organism can’t make for itself Organisms and Energy Sources Producers Organisms that make their own food using energy and simple raw materials from the environment Example: plants Consumers Organisms that get energy and carbon by feeding on tissues, wastes, or remains of other organisms Example: animals Energy Flow and Material Cycling sunlight energy A Producers harvest energy from the environment. Some of that energy flows from producers to consumers. PRODUCERS plants and other self-feeding organisms B Nutrients that become incorporated into the cells of producers and consumers are eventually released by decomposition. Some cycle back to producers. CONSUMERS animals, most fungi, many protists, bacteria C All energy that enters the world of life eventually flows out of it, mainly as heat. Stepped Art Fig. 1-3a, p. 6 Fig. 1-3b, p. 6 Animation: One-way energy flow and materials cycling Organisms Sense and Respond to Change Organisms sense and respond to change to keep conditions in their internal environment within a range that favors cell survival (homeostasis) Homeostasis Set of processes by which an organism keeps its internal conditions within tolerable ranges Receptor Molecule or structure that responds to a stimulus Response to Stimuli Organisms Grow, Develop and Reproduce Organisms grow, develop, and reproduce based on information encoded in DNA, which they inherit from their parents Growth Increase in size, volume, and number of cells in multicelled species Development Multistep process by which the first cell of a new individual becomes a multicelled adult Organisms Grow, Develop and Reproduce Reproduction Process by which parents produce offspring Inheritance Transmission of DNA from parents to offspring DNA (Deoxyribonucleic acid) Molecule that carries hereditary information about traits 1.4 Introduction to Life’s Diversity The millions of species on Earth vary greatly in details of body form and function Each species is given a unique two-part name that includes genus and species names Species A type of organism Genus Group of species that share a unique set of traits Classification Systems Classification systems group species according to traits and organize information about species One system sorts all organisms into one of three domains: Bacteria, Archaea, and Eukarya The eukaryotes include plants, protists, fungi and animals Life’s Diversity: Three-Domain Classification System Animation: Life’s diversity Prokaryotes Prokaryotes Single celled organisms in which DNA is not contained in a nucleus Bacterium A member of the prokaryotic domain Bacteria Archaeans A member of the prokaryotic domain Archaea Eukaryotes Eukaryotes Organisms whose cells typically have a nucleus Fungus Eukaryotic consumer that obtains nutrients by digestion and absorption outside the body Protists Eukaryotes that are not plants, animals, or fungi Eukaryotes Plant Typically a multicelled, photosynthetic producer Animal Multicelled consumer that develops through a series of embryonic stages and moves about during all or part of the life cycle Animation: Three domains break 1.5 The Nature of Scientific Inquiry Critical thinking Mental process of judging the quality of information before deciding whether or not to accept it The Scope and Limits of Science Science is a way of looking at the natural world which helps us to communicate our experiences without bias by focusing only on testable ideas about observable phenomena Science does not address the supernatural Science The systemic study of nature 1.6 How Science Works Researchers make and test potentially falsifiable predictions about how the natural world works Generally, scientific inquiry involves forming a hypothesis (testable assumption) about an observation then making and testing predictions based on the hypothesis A hypothesis that is not consistent with the results of scientific tests is modified or discarded Common Research Practices 1. Observe some aspect of nature 2. Frame a question about your observation 3. Propose a hypothesis (a testable explanation of the observation) Common Research Practices 4. Make a prediction – a statement based on a hypothesis, about some condition that should exist if the hypothesis is not wrong 5. Test the accuracy of the prediction by experiments or gathering information (tests may be performed on a model) Common Research Practices 6. Assess the results of the tests (data) to see if they support or disprove the hypothesis 7. Conclusions: Report all steps of your work and conclusions to the scientific community Making Observations: A Field Study A Scientific Theory Scientific theory A hypothesis that has not been disproven after many years of rigorous testing Useful for making predictions about other phenomena Laws of Nature Law of nature Generalization that describes a consistent and universal natural phenomenon for which we do not yet have a complete scientific information Example: gravity Examples of Scientific Theories Animation: An example of the scientific method 1.7 The Power of Experiments Natural processes are often influenced by many interacting variables Variable A characteristic or event that differs among individuals The Power of Experiments Experiments simplify interpretations of complex biological systems by focusing on the effect of one variable at a time Experiment A test to support or falsify a prediction Experimental and Control Groups Experimental group A group of objects or individuals that display or are exposed to a variable under investigation Control group A group of objects or individuals that is identical to an experimental group except for one variable Potato Chips and Stomachaches 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 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. Stepped Art Fig. 1-10, p. 14 Example: Butterflies and Birds Question Why does a peacock butterfly flick its wings? Two hypotheses Exposing wing spots scares off predators Wing sounds scare off predators Two predictions Individuals without spots are eaten more often Individuals without sounds are eaten more often Peacock Butterfly Defenses Experiments and Results Four groups of butterflies were exposed to predators (birds) Butterflies without spots Butterflies without sounds Butterflies without spots or sounds Control group Test results support both original hypotheses Results: Peacock Butterfly Experiment Sampling Error Biology researchers experiment on subsets of a group, which may result in sampling error Sampling error Difference between results derived from testing an entire group of events or individuals, and results derived from testing a subset of the group Sampling Error Probability Researchers try to design experiments carefully in order to minimize sampling error Statistically significant Refers to a result that is statistically unlikely to have occurred by chance Animation: Sampling error 1.8 Impacts/Issues Revisited Biologists constantly discover new species Mouse lemur (Microcebus lehilahytsara), discovered in Madagascar in 2005 Digging Into Data: Peacock Butterfly Predator Defenses