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Scientific Investigation

Objectives

  • At the end of the lab activity, the students should be able to:
    1. Identify questions or problems that can be answered through scientific investigation.
    2. Discuss and explain the characteristics of a good hypothesis and distinguish between null and alternative hypotheses.
    3. Describe the essential components of a scientific experiment.
    4. Present and discuss results of an experiment and critique its merits.
    5. Convey the experimental results in a concise but clear manner for the whole class to understand and appreciate.

Introduction

  • Scientific inquiry is a basic and essential skill for beginning biology students, developed through either self-motivation or directed coursework under a faculty advisor.
  • The course provides the opportunity to learn the basic concepts of the scientific method, which is employed by scientists to investigate natural phenomena.
  • Biology aims to explain how the natural world functions, in contrast to beliefs rooted in religious, mythical, or traditional origins.
  • Key differences between science and alternative understandings:
    • Objectivity: Scientific explanations are not influenced by faith, authority, or opinion.
    • Testability: Scientific claims can be verified through laboratory experiments or field observations.
    • Consistency: Scientific results are reproducible in experiments.

Steps of the Scientific Method

  • The scientific method involves the following steps:
    1. Observations & Questions: Start by observing something biological and asking a relevant question.
    • Example: "The life cycle of a snail is about 30 days (at 29 degrees Celsius). How do changes in temperature affect the life cycle of a snail?"
    1. Hypothesis: Formulate a testable hypothesis.
    • A useful hypothesis is a testable statement:
      • Null Hypothesis (H₀): "Decreasing the temperature of a snail's environment will not increase the time it takes the snail to complete its life cycle."
      • Alternative Hypothesis (H₁): "Decreasing the temperature of a snail's environment will increase the time it takes the snail to complete its life cycle."
    1. Experiment: Design and conduct an experiment that tests the hypothesis. The experiment should produce results that either support or falsify the hypothesis.
    • Example: "Place 33 snails at 18 and 29 degrees Celsius for one generation. If the hypothesis is correct, then the snails at 18 degrees Celsius will complete their life cycle after those at 29 degrees Celsius. Those raised at 4 degrees Celsius may not develop at all."
    1. Analyze Results and State Conclusions:
    • Reject the null hypothesis if results are inconsistent; if results are consistent, accept the alternative hypothesis as possibly true.
    • Note that results do not prove a hypothesis; they may support it while other explanations may exist.
    • For instance, if snails at 18 degrees Celsius develop slower, it could be due to an inadequate algal diet rather than temperature alone.
    • If results do not support the hypothesis, modify the hypothesis and conduct more experiments.

Experimental Design

  • Key components of a well-designed experiment include:
    1. Independent Variable: The variable manipulated by the scientist.
    • Example: Temperature, which causes changes in outcomes.
    1. Dependent Variable: The outcome that changes as a result of the manipulation.
    • Example: Length of the snail's life cycle, which impacts development based on temperature.
    1. Experimental Group: The group subjected to a test variable.
    • Example: Snails raised at 18 degrees Celsius are the experimental group testing lower temperature effects.
    1. Control Group: The group that receives no experimental treatment or a standard level of treatment.
    • Example: Snails raised at 29 degrees Celsius serve as the control group for optimal temperature development.
    1. Positive Control: Designed to produce a positive result, demonstrating the experiment can indeed yield expected outcomes.
    2. Negative Control: Designed to produce a negative result, confirming that the experiment can yield negative results when appropriate.
    3. Sample Size: The study should include a sizable number of subjects to ensure reliability.

Lab: Systematics and Taxonomy

Objectives

  • At the end of the lab activity, students should be able to:
    1. Recognize the significance and applications of systematics and taxonomy in evolutionary biology.
    2. Demonstrate an understanding of binomial nomenclature and the hierarchical system of taxonomy.
    3. Discuss the basic concepts of organismal identification and classification using dichotomous keys.
    4. Design a functional dichotomous key and present it to the class for critique.
    5. Undertake online research to find a newly discovered species and submit a professional write-up about it.

Introduction

  • Systematics is the science of classifying organisms, aiding biologists in determining identities, relationships, and establishing evolutionary connections.
  • Biodiversity is vast, but systematics has organized it into hierarchical taxonomic groups (taxa): Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
  • A mnemonic for taxa: "Dear King Philip Came Over For Good Soup".
  • Taxonomy deals with naming organisms through the Linnean or binomial system.
    • Scientific names are always in Latin: Genus (capitalized) + specific epithet (lowercase, italicized).
    • Example: Gallus domesticus (domesticated chicken), Gallus bankiva (red jungle fowl).
  • Taxonomy is a subset of systematics, with possible divergence in interpretation; however, both facilitate proper communication regarding organisms’ diversity.
  • Phylogenetic systematics (cladistics) is based on evolutionary history.

Dichotomous Key

  • A dichotomous key is a classification tool consisting of paired statements describing physical characteristics of organisms.
  • At each stage, two choices lead toward identifying the organism—a method central to classification.
  • Cladistics provides a basis for reconstructing evolutionary patterns, focusing on derived characters to establish relationships among taxa.

Cladistics

Introduction to Cladistics

  • Cladistics analyzes evolutionary relationships among species, forming phylogenetic trees to illustrate these relationships.
  • Willi Hennig developed cladistics, focusing on shared derived characters (synapomorphies) rather than primitive characters (plesiomorphies).
  • A taxonomic clade consists of a common ancestor and all its descendants; these are illustrated in a cladogram.
  • The Occam's Razor Principle suggests that the simplest explanation is preferred when multiple hypotheses exist.
  • Derived characters (apomorphies) are unique to taxa, while shared derived characters (synapomorphies) help create monophyletic groups.

Anatomy of a Cladogram

  • Cladograms show branching hierarchical relationships, with non-primed (ancestral) and primed (derived) character states.
  • Sister taxa share a closest evolutionary