Chapter 1 – Nature of Biology Sections 1.1, 1.3, 1.5, 1,6, 1.7, 1.8
1.3 Cells are the structural and functional units of life • Cell – Lowest level of structure the can perform all activities required for life. Basic unit of life. All cells are membrane bound and contain DNA. • Prokaryotic Cell – Cells lacking a nucleus. Lacks organization. No organelles?? Bacteria • Eukaryotic Cell – Cells containing a nucleus and organelles. Plants, Animals, Fungi. • Cells give rise to other cells. Basis for all reproduction
1.5 The diversity of life can be arranged into three domains • Taxonomy – Branch of biology responsible for classifying and naming species. • Species – term used for a particular type of organism. Binomial naming system • Homo sapiens (genus and species) • Kingdoms – classification scheme under which all organisms were organized (Animal, Plant, Fungi, Protista, Monera) • Domains – new scheme based on DNA sequencing. Based on the fact that there are two very distinct types of prokaryotes • Includes Bacteria, Archaea, Eukarya
1.5 Taxonomy (Domain Scheme) Bacteria and Archaea (all prokaryotes) Split from each other in ancient times and have distinct differences in DNA sequences and genes Includes Eukaryotes Plants Animals Fungi Protists Common Ancestor 3.5 bya Live in extreme conditions, reminiscent of ancient times. Use of sulfuric acid for energy What properties do you think this species had?
1.6 Evolution explains the unity and diversity of life • Charles Darwin (1859 On Origin of Species by Means of Natural Selection) • Diversity of life can be explained by natural selection – occurs when heritable variations are acted on by environmental factors that favor the reproductive success of some individuals over others.
1.6 Natural Selection (Darwin) • Observations (involves using one or more of the senses to gather information – data) • #1 Individual variation – Not all individuals are th same • #2 Overproduction and competition • Inference (logical interpretation of the data) • Unequal reproductive success. Those with the best heritable variations will have the best chance to reproduce and pass genes on to next generation.
1.6 Observations lead to Inferences Observation #1 – Variation Inference – Natural Selection Observation #2 – Overproduction and Competition
1.6 Theory • Darwin’s idea has become so well supported that it is now considered a theory. • Theory – well tested explanation that unifies a broad range of observations. • Similarity in DNA • Diversity of life • Fossil Record • Antibiotic Resistance
1.7 Discovery Science vs. Hypothesis Based Science • Science - Way of knowing. Seeks natural causes for natural phenomena. i.e. study of what we can observe, measure. • Discovery – Describing nature. Uses data gathered from observations (technology) to describe. • All living things are made of cells • All living things are based on the universal code of DNA. • Hypothesis Based – Explaining nature. Involves making and testing a hypothesis. • If all living things are made of cells, then plants are made of cells • If all living things contain DNA, then bacteria would contain DNA.
Hypothesis-based science uses and tests hypotheses • A scientific method of investigation involves the following steps: • Observe & identify a problem (make an inference) • State a hypothesis • Design & perform an experiment • Form conclusions • Replicate the work
Concept Map – Rough draft due tomorrow • Main Concept – Scientific Method • Sub Concepts • Observation • Inference • Hypothesis • Theory • Controlled Experiment • Control Group • Experimental Group • Manipulated Variable • Responding Variable • Independent Variable • Dependent Variable
Key Terms • Experimental group—group that is exposed to the experimental (independent/manipulated) variable. • Control group—group that is not exposed to the experimental variable. • Independent/manipulated variable—experimental variable, what you test on the experimental group to see if it makes a difference. What is new and novel. What is to be studied. • Dependent variable/responding variable—some factor you measure in both groups to see if it changes. • Hypothesis—a reasonable explanation supported by observation and/or research.
Criteria for Evaluating Hypotheses • A hypothesis should be a clear, concise statement that focuses on a specific well-defined problem. • It should be testable. • It should contain the independent and dependent variable and state a cause and effect relationship.
Formal Hypothesis Writing Step 1 • Form a question based on observations. For instance, if you notice your pet mice have more babies when you feed them corn rather than pellets, this is an observation. Your question, therefore, may be: Do mice produce more babies when fed corn? You can test this, but first you must form a hypothesis. Step 2 • Write down what you predict will happen in your experiment. For instance, you can predict that if you feed some of your mice corn, they will produce more babies than mice to which you feed pellets.
Formal Hypothesis Writing Step 3 • Determine your manipulated and responding variables. Both the manipulated and responding variables must be measurable and testable. Step 4 • State as If manipulated variable, is related to responding variable, then prediction (what you expect will happen in lab. • Example: If a corn fed diet increases mice offspring production, then those mice fed corn will produce more offspring than those fed pellets.
Example #1 Problem • Spontaneous Generation? Independent variable (manipulated) • Preventing flies from getting to meat Dependent Variable (Responding) • Maggots Hypothesis • If the absence of flies on meat (prevents) maggots, then the meat in the covered jars will lack maggots.
Redi’s Experiment PROCEDURE Uncovered jars Covered jars Controlled Variables: jars, type of meat, location, temperature, time Several days pass Manipulated Variables: gauze covering that keeps flies away from meat Responding Variable: whether maggots appear Maggots appear No maggots appear CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur.