Human Biology, Science, and Society Flashcards

The Characteristics of Life

Living things exhibit a specific set of characteristics that distinguish them from nonliving matter. The core attributes include:

• Molecular Composition: Living things have a different molecular composition than nonliving things.

• Requirement for Energy and Raw Materials: All living organisms require energy and raw materials to sustain life processes.

• Cellular Composition: All living things are composed of cells, which are the fundamental units of life.

• Homeostasis: Living things maintain a stable internal environment despite external changes.

• Environmental Response: Organisms respond to their external environment.

• Growth and Reproduction: Living things have the capacity to grow in size and produce offspring.

• Evolution: Populations of living things evolve over time.

Classification of Living Things

Living organisms are grouped according to shared characteristics using a hierarchical system.

• Three Domains of Life:

  • Domain Bacteria: Composed of unicellular organisms that lack a membrane-bound nucleus.

  • Domain Archaea: Composed of unicellular organisms that lack a membrane-bound nucleus; often found in extreme environments.

  • Domain Eukarya: Consists of organisms that possess a membrane-bound nucleus. This domain is subdivided into four kingdoms:

    • Kingdom Protista: Includes protozoans, algae, and slime molds. These are typically unicellular or simple multicellular eukaryotes.

    • Kingdom Animalia: Multicellular eukaryotes that are heterotrophic (obtain energy by consuming other organisms).

    • Kingdom Fungi: Eukaryotic decomposers, including molds, yeasts, and mushrooms.

    • Kingdom Plantae: Multicellular, eukaryotic organisms that are photosynthetic.

Fundamental Criteria for Classification

Scientists use several fundamental criteria to categorize organisms into the domains and kingdoms mentioned above:

• Presence or Absence of a Nucleus:

  • Prokaryotic: Domains Bacteria and Archaea lack a membrane-bound nucleus.

  • Eukaryotic: Domain Eukarya possesses a membrane-bound nucleus.

• Number of Cells:

  • Unicellular: Organisms composed of a single cell.

  • Multicellular: Organisms composed of many cells.

• Type of Metabolism: How the organism acquires and uses energy (e.g., photosynthetic vs. heterotrophic).

Human Classification and Defining Features

Humans, biologically identified as Homo sapiens, are classified within the following taxonomic hierarchy:

• Domain: Eukarya

• Kingdom: Animalia

• Phylum: Chordata

• Class: Mammalia

• Order: Primates

• Family: Hominidae

• Genus: Homo

• Species: sapiens

Defining Features of Humans: Humans possess four specific features that distinguish them from other primates:

• Bipedalism: The ability to stand upright and walk on two legs.

• Large Brain: A brain size that is large relative to total body size.

• Capacity for Complex Language: The ability to communicate through both spoken and written language.

• Opposable Thumbs: The ability to grasp objects between the thumb and the tips of the fingers.

Levels of Biological Organization

Human biology can be studied at various levels of complexity, ranging from microscopic components to the global environment:

• Atom: The smallest unit of an element; composed of protons, neutrons, and electrons.

• Molecule: Two or more atoms held together in a stable association with each other.

• Cell: The fundamental structural and functional unit of all living organisms.

• Tissue: A group of similar associated cells specialized to perform a specific function.

• Organ: A structure composed of two or more different tissues working together to perform a specific function.

• Organ System: A group of organs that work together to serve a broad function important to the survival of an organism or species.

• Organism: An individual living being composed of several organs or organ systems.

• Population: A group of individuals of the same species that occupy the same geographic area and interact with each other.

• Community: All the populations of different species that coexist and interact within the same environment.

• Ecosystem: All living organisms in a given area plus the physical environment and energy.

• Biosphere: The sum total of all ecosystems on Earth.

Issues and Controversies in Human Biology

Each level of biological organization presents unique ethical, social, and practical controversies:

• Atom and Molecule: Disposing of radioactive wastes; keeping drinking water free of toxins like lead and mercury; the role of free radicals in cancer and aging.

• Cell: Cloning adult organisms (plants, animals, and humans) from a single cell.

• Tissue: Using human fetal tissues in medical research.

• Organ: Increasing the supply of organs for transplantation; xenotransplantation (animal organs into humans); using stem cells to grow new organs.

• Organ System: Enhancing human performance through drugs or genetic modification.

• Organism: Testing for incurable heritable diseases; abortion; determining financial responsibility for behavior-related illnesses (e.g., smoking-related diseases).

• Population: Rationing medical care; distribution of scarce organs; mandatory vaccinations.

• Community: Human impact on species survival; genetic modification of plants/animals; animal testing in research and cosmetics.

• Ecosystem: Environmental pollution; destruction of ecosystems due to human activity.

• Biosphere: Global warming; climate change; destruction of the ozone layer.

The Nature of Science and the Scientific Method

Science is defined as both a body of knowledge about the natural world and the process—known as the scientific method—used to acquire that knowledge.

Steps in the Scientific Method:

1. Observe and Generalize: Use inductive reasoning to make generalizations based on specific observations. (Example: Observing that past winters were colder than summers leads to the generalization that winter is always colder than summer.)

2. Formulate a Hypothesis: Create a tentative statement about the natural world that can lead to testable deductions. (Example: "Drug X would be an effective treatment for high blood pressure.")

3. Make a Testable Prediction: Use deductive reasoning to create specific "if…then" statements. (Example: "If Drug X is effective, then a specific dose will lower blood pressure in people within one month.")

4. Experiment or Observe: Conduct a carefully planned procedure to test the prediction. A hypothesis cannot be proven true; it can only be supported or disproved.

5. Modify the Hypothesis: If the prediction is false, the hypothesis must be modified. If true, further testing is required to increase confidence.

Designing and Conducting a Controlled Experiment

A controlled experiment involves the manipulation of variables to test a hypothesis:

• Independent Variable: The component intentionally changed by the researcher (also called the manipulated variable).

• Dependent Variable: The observed change or response caused by the independent variable (also called the responding variable).

Example Experiment Structure (Drug X):

• Subjects: A large number of individuals with high blood pressure are selected.

• Groups: Subjects are randomly divided into an Experimental Group (receives Drug X) and a Control Group (receives a placebo).

• Controlled Variables: Factors like age, gender, and health status are equalized between groups.

• Comparison: Blood pressure (dependent variable) is measured after one month and compared to initial readings.

Communication and Scientific Theory

Scientific findings are disseminated through peer-reviewed journals. Experts must approve the documentation before publication to ensure accuracy and enable other scientists to repeat the experiment.

Defining a Scientific Theory: A hypothesis becomes a theory only if it meets the following criteria:

• It is broad.

• It has been extensively tested.

• It is supported over time.

• It explains a broad range of facts.

• It has a high degree of reliability.

• Examples: Evolution, Cell theory.

Critical Thinking and Information Quality

Sources of scientific information vary in reliability:

• High Reliability: Peer-reviewed journals.

• Moderate Reliability: Science magazines, nonfiction books, general news magazines, and reputable news websites.

• Lower/Variable Reliability: Social media platforms like Facebook, Twitter, and Instagram.

Assessing Internet Sources:

1. Author: Check academic or professional credentials and expertise.

2. Purpose: Determine if the site provides information or promotes an agenda/product.

3. Currency: Check if the information is recently updated.

4. References: Ensure the information is supported by cited sources.

Skills for Critical Thinkers:

• Maintain skepticism.

• Learn to read graphs and appreciate the value of statistics.

• Distinguish between anecdotes and scientific evidence.

• Separate facts from conclusions.

• Understand the difference between correlation (events occurring together) and causation (one event causing another).