Biology and Society: Biology All Around Us

Transcription

1 Biology and Society: Biology All Around Us We are living in a golden age of biology. Scientists are studying questions that are relevant to our lives. How can errors in cell growth lead to cancer? How do plants trap solar energy? How do living creatures form ecological networks and how do human activities disrupt them? How did the great diversity of life on Earth evolve from the first microbes and how does such evolution have an impact on human health? How do mutations in genes lead to disease? How can DNA the molecular basis of heredity be used in forensic investigations?

2 Biology Scientific study of life Lays the foundation for asking basic questions about life and the natural world What Are the Characteristics of Living Things? 1. Living Things Are Both Complex and Organized 2. Living Things Maintain Relatively Constant Internal Conditions Through Homeostasis 3. Living Things Grow 4. Living Things Acquire and Use Materials and Energy 5. Living Things Respond to Stimuli 6. Living Things Reproduce Themselves 7. Living Things As a Whole Have the Capacity to Evolve

3 Why Study Biology? To learn how organisms are constructed, how they function, where they live, and what they do To help develop, modify, and refine ideas about life Biology helps you understand your body Biology helps you become an informed citizen Biology can enrich your appreciation of the world

4 Life s Underlying Unity Life s organization extends from the molecular level to the biosphere Shared features at the molecular level are the basis of life s unity Ecosystems Each organism interacts continuously with its environment. Organisms interact continuously with the living and nonliving factors in the environment. All the living organisms in a specific area, along with all of the nonliving factors with which they interact, form an ecosystem.

5 Energy Flow Usually starts with energy from the sun Transfers from one organism to another Flows in one direction Eventually flows back to the environment Interdependencies among Organisms Producers Make their own food Consumers Depend on energy stored in tissues of producers Decomposers Break down remains and wastes

6 Unity of Life All organisms Consist of one or more cells Have the capacity to reproduce based on instructions in DNA Engage in metabolism Sense and respond to the environment

7 Cells and Their DNA The cell is the level at which the properties of life emerge. Cells are the lowest level of structure that can perform all activities required for life. All organisms are composed of cells. Cells are the subunits that make up multicellular organisms such as humans and trees. We can distinguish two major types of cells: 1. The prokaryotic cell is simpler and usually smaller and characteristic of bacteria. 2. The eukaryotic cell is subdivided by internal membranes into different functional compartments called organelles and found in plants and animals.

8 Prokaryotic Organisms Single cells No nucleus Smaller, less complex Archaebacteria, eubacteria Eukaryotic Organisms Single- or multicelled Nucleus Larger, more complex Fungi, protistans, plants, animals

9 Diversity is a hallmark of life. Life in Its Diverse Forms The diversity of known life includes about 1.8 million species that biologists have identified and named. Estimates of the total number of species range from 10 million to over 100 million. Biodiversity can be beautiful but overwhelming. Categorizing life into groups helps us deal with this complexity. Taxonomy is the branch of biology that names and classifies species. It formalizes the hierarchical ordering of organisms into broader and broader groups.

10 The Three Domains of Life The three domains of life are Bacteria, Archaea, and Eukarya. Bacteria and Archaea have prokaryotic cells. Eukarya have eukaryotic cells. Eukarya include Kingdom Plantae, Kingdom Fungi, Kingdom Animalia, and Protists (multiple kingdoms). Most plants, fungi, and animals are multicellular. Protists are generally single-celled.

11 The Three Domains of Life These three multicellular kingdoms are distinguished by how they obtain food. Plants produce their own sugars and other foods by photosynthesis. Fungi are mostly decomposers, digesting dead organisms. Animals obtain food by ingesting (eating) and digesting other organisms. Underlying the diversity of life is a striking unity, especially at the lower levels of biological organization. For example, all life uses the genetic language of DNA. Biological evolution accounts for this combination of unity and diversity.

12 Two-part name Scientific Names First part- genus (genera) group of species with distinct traits for common ancestor Second part particular species within a genus Humphead parrotfish is Scarus gibbus First part (Scarus) Second name gibbus Midnight parrotfish is S. coelestinus

13 SCIENCE The word science is derived from a Latin verb meaning to know. Science is a way of knowing, based on inquiry. Science developed from our curiosity about ourselves and the world around us. There are two main scientific approaches: Discovery science is mostly about describing nature. Hypothesis-driven science is mostly about explaining nature.

14 Discovery Science Science seeks natural causes for natural phenomena. This limits the scope of science to the study of structures and processes that we can observe and measure directly or indirectly. The dependence on observations that people can confirm demystifies nature and distinguishes science from belief in the supernatural. Verifiable observations and measurements are the data of discovery science. In biology, discovery science enables us to describe life at its many levels, from ecosystems down to cells and molecules. Discovery science can stimulate us to ask questions and seek explanations and uses a process of inquiry called the scientific method, consisting of a series of steps that provide a loose guideline for scientific investigations.

15 Hypothesis-Driven Science Most modern scientific investigations can be described as hypothesis-driven science. A hypothesis is a tentative answer to a question an explanation on trial. Although we don t think of it in those terms, we use hypotheses in solving everyday problems, like figuring out why a TV remote fails. Once a hypothesis is formed, an investigator can use logic to test it. A hypothesis is tested by performing an experiment to see whether results are as predicted. This deductive reasoning takes the form of If then logic.

16 Scientific Method Observe phenomenon Develop hypotheses Make predictions Devise test of predictions Carry out test and analyze results Role of Experiments Study a phenomenon under known conditions Allow you to predict what will happen if a hypothesis is not wrong Can never prove a hypothesis 100% correct

17 Experimental Design Control group A standard for comparison Identical to experimental group except for variable being studied Sampling error Nonrepresentative sample skews results Can be minimized by using large samples Biological Therapy Experiments Can viruses that attack bacteria (bacteriophages) fight infections in mice? Minimizing Variables All mice were same age and sex, reared under same conditions Each mouse in each test group received exact same treatment All mice in control group received same amount of saline Variable tested was antibiotic treatment versus bacteriophage treatment

18 Hypothesis: Bacteriophages will kill E.coli in infected mice Prediction: Lab mice injected with bacteriophage will not die after being injected with E.coli Experimental Test: Researchers establish populations of bacteriophage and E.coli; they select a specific strain of laboratory mice 15 mice injected with E.coli Control group 15 mice injected with E.coli and bacteriophage Experimental group Test results All mice die within 32 hours All mice live

19 Another Prediction: Bacteriophage will be more effective than a single dose of antibiotics against E.coli Experimental Test: Researchers inject 48 mice with E.coli; eight hours later: Control: 12 mice injected with saline All die Expt Group 1: 12 mice injected with bacteriophage Expt Group 2: 12 mice injected with streptomycin 60 micrograms/gram 11 of 12 survive 3 of 12 survive Test results Expt Group 3: 12 mice injected with streptomycin 100 micrograms/gram 5 of 12 survive

20 Scientific Theory An explanation of the causes of a wide range of related phenomena Has wide-ranging explanatory power Still open to testing Example - Darwin s theory of evolution by natural selection What is a scientific theory, and how is it different from a hypothesis? A scientific theory is much broader in scope than a hypothesis. Theories only become widely accepted in science if they are supported by an accumulation of extensive and varied evidence.

21 Science, Technology, and Society Science and technology are interdependent. New technologies advance science. Scientific discoveries lead to new technologies. For example, the discovery of the structure of DNA about 60 years ago led to a variety of DNA technologies. Limits of Science Scientific approach cannot provide answers to subjective questions Cannot provide moral, aesthetic, or philosophical standards May conflict with supernatural beliefs

22 The Culture of Science Science has two key features that distinguish it from other forms of inquiry. Science depends on observations and measurements that others can verify and requires that ideas (hypotheses) are testable by experiments that others can repeat. The external world, not internal conviction, must be the testing ground for scientific beliefs