Chapter 1 Notes: The Nature of Science
The Nature of Science
Science is a body of knowledge (data) about the natural world and an evidence-based process for acquiring that knowledge.
It deals with aspects of the natural world that can be detected, observed, and measured.
It is based on evidence that can be demonstrated through observations and/or experiments.
Science is subject to independent validation and peer review and is open to challenge by anyone at any time based on evidence.
It is a self-correcting enterprise.
Science cannot:
Tell us what is morally right or wrong.
Address the existence of God or other supernatural beings.
Decide what is beautiful or inspiring in poems, paintings, etc.
Distinctions to remember:
A scientific fact is a direct and repeatable observation of the natural world.
A scientific hypothesis: is a proposed explanation for observations that is testable and falsifiable; it can be supported but not proven with complete certainty.
A scientific theory: is a well-supported explanation that has been repeatedly tested and corroborated by diverse lines of evidence; it is different from the everyday use of the word "theory".
The scientific method (the process of science) produces knowledge through repeated testing and validation.
The Scientific Method
Core activities include:
Gathering observations and forming a hypothesis.
Making predictions based on that hypothesis.
Designing and conducting experiments with appropriate variables, treatments, and controls.
Interpreting data and drawing conclusions.
Revising hypotheses and/or experimental designs in light of new evidence.
Real-world context example: How to Survive a Mass Extinction – case study of Tahitian snails and the rosy wolf snail.
Two initial examples from the transcript:
Observation that certain Tahitian snails (e.g., P. hyalina) survived predation by a new predator (rosy wolf snail) while others did not, prompting hypotheses about why.
Hypotheses about how shell color and sun exposure might influence distribution and predation risk.
Key problem areas addressed by the method:
How to test an observation with a reliable, repeatable procedure.
How to distinguish facts, hypotheses, and theories in scientific claims.
Observations, Hypotheses, and Predictions
An observation is a description, measurement, or record of any object or phenomenon.
Example: Crampton (1916) noted that some Tahitian snails (P. clara and P. hyalina) had larger clutch sizes than other tree snails.
Implication: Production of more offspring might help a species withstand predators and environmental challenges.
Scientific hypotheses are informed, logical explanations for observations that are testable and falsifiable.
Bick’s hypotheses in the narrative:
Hypothesis 1: Producing more offspring improves predation survival.
Hypothesis 2: P. hyalina’s broader distribution (relative to P. clara) may be due to its white shell, which could heat up less in the sun.
A hypothesis must be:
Testable
Falsifiable
Precise enough to make predictions in the form of if… then statements.
Example structure: From Observation to Hypothesis to Testable Prediction (Figure 1.4)
Observation/Question: Why has P. hyalina survived where others have not?
Hypothesis: Pale shell allows survival in sunnier forest areas, reducing predation.
Predictions: If P. hyalina is less preyed upon due to sunnier habitats, then it should be found in areas with higher solar radiation.
Hypotheses, Predictions, and Proving Theories
Hypotheses can be supported by data but cannot be proven with 100% certainty; testing can increase confidence but cannot guarantee truth.
Advertising and other everyday claims often resemble scientific hypotheses but are not always supported by robust evidence.
Practice questions illustrate how to identify hypothesis, predictions, and testability in everyday statements.
Types of Hypotheses and Approaches to Testing
Hypotheses can be tested via:
Observational studies (descriptive): report data found in nature.
Observational studies (analytical): look for patterns and address how/why they exist.
Experimental studies: manipulate conditions to test cause-effect relationships.
Example: Multiple approaches to testing snails’ survival and predation:
Descriptive data collected on snail numbers in Tahitian valleys over decades (Trevor Coote).
Analytical data on solar exposure of snails using tiny computers (Cindy Bick).
Experimental data where rosy wolf snails were exposed to mucus trails from various prey snails to see following behavior.
Figure 1.6 illustrates these three data-collection approaches and how they complement one another.
Experimental Design and Variables
An experiment is a repeatable manipulation of one or more aspects of the natural world designed to test a hypothesis.
Variables:
Independent variable: the factor deliberately changed by the experimenter.
Dependent variable: the factor that responds to the change in the independent variable.
If the independent variable is the cause, the dependent variable is the effect.
Example: A prediction about rosy wolf snails following mucus trails from prey snails of different ranges;
Independent variable: type of mucus trail (native species vs non-native species).
Dependent variable: whether the snail follows the trail (and how strongly).
Controlled experiments:
Include a control group kept under standard conditions where the independent variable is not changed.
Include treatment groups where the independent variable is manipulated.
Example (Figure 1.7): Rosy wolf snails choosing between following a water trail vs a mucus trail from different snails; includes multiple experimental groups and a control group.
The Rosy Wolf Snail Case Study: How to Survive a Mass Extinction
Timeline and problem:
In the early 1970s, Tahiti and nearby Pacific islands struggled to control the giant African land snail, introduced as a food source.
It became a major pest, decimating crops.
To control it, authorities released the North American rosy wolf snail, which preys on other snails, including its own species.
Ecological consequences:
Rosy wolf snails devoured nearly all the 61 native snail species (per slide data) and contributed to extinctions; these native snails supported forest ecosystems and held cultural importance to locals.
Worldwide, the rosy wolf snail has eaten an estimated 134 snail species to extinction.
Mass extinctions context:
There have been 5 mass extinctions on Earth.
Biologists think we are likely in the early stages of a 6th mass extinction, with human activities as the catastrophe this time (habitat alteration, poaching, expansion, pollution, global warming, invasive species).
Human-driven drivers of current extinctions:
Habitat alteration (farming, logging, mining, etc.)
Poaching
Road and city expansion
Pollution
Global warming
Invasive species (e.g., rosy wolf snail)
Conservation and study efforts:
Scientists study species that have avoided extinction to understand what differs in their survival.
Cindy Bick studies Partula hyalina, a white-shelled snail that survived the rosy wolf snail, to identify protective traits or conditions.
Relevance to science:
Helps illuminate how certain factors influence extinction risk and how targeted interventions might aid conservation.
The Biological Hierarchy
Biological hierarchy: levels from atoms to biosphere, illustrating how losing one component can ripple through ecosystems.
Levels (from atoms upward):
Atom → Molecule → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biome → Biosphere
Key concepts:
Cells form tissues; tissues form organs; organs form organ systems in organisms.
A population is a group of individuals of the same species in a shared environment.
A community consists of populations of different species interacting in a given area.
An ecosystem includes the community plus the physical environment.
Biomes are large regions defined by climate and characteristic communities; all biomes are part of the biosphere.
Quiz-style prompts:
Q1: Give examples of other kinds of organs that some animals have. (e.g., brain, heart, lungs, gills, kidneys, digestive organs, etc.)
Q2: Are Tahitian land snails part of the Kansas snail community if they are the same species? (No; they are separate populations in different ecosystems though they belong to the same species.)
Q3: Is soil part of the snails’ population, community, or ecosystem? (Soil is part of the ecosystem; it is the environment in which populations live and interact.)
Saving Species and the Sixth Extinction
Intensive efforts to stop extinctions:
Bans on hunting (e.g., humpback whales and elephant seals).
Bans on DDT.
Breeding programs (e.g., peregrine falcons and bald eagles in North America).
Partula snails case and reintroduction:
Fifteen American and European zoo curators bred 11 species of Partula snails to reintroduce them into the wild.
Rosy wolf snail populations declined in Polynesia as a result of conservation actions.
Since 2015, over 19{,}000 snails from 14 species have been reintroduced to their natural home ranges in Polynesia, including some placed in predator-proof preserved areas on Tahiti.
The Sixth Extinction: Context and Examples
The Sixth Extinction concept:
Past mass extinctions were caused by climate change, volcanic eruptions, sea level changes, etc.
The current extinction event is largely driven by human activities.
Ghosts of species past (examples of extinct or extinct-in-the-wild species since 1500):
Passenger Pigeon (extinct in 1914; last wild bird 1900, last captive 1914)
Xerces Blue Butterfly (extinct in 1943; habitat destroyed by urban development)
Caribbean Monk Seal (last sighted 1952; extinct due to overhunting and overfishing)
Golden Toad (not seen since 1989; pollution and global warming implicated)
Taxonomic counts of known extinctions since 1500 (illustrative):
Arachnids: 9
Crustaceans: 12
Reptiles: 22
Amphibians: 36
Insects: 58
Fishes: 71
Mammals: 79
Plants: 134
Birds: 145
Mollusks: 324
Visual summary: The Sixth Extinction underscores the rate and scale of current biodiversity loss and the urgency of conservation actions.
Practice and Practice-questions from the Slides
Topics appropriate for scientific study (NOT appropriate in some cases):
a) Do women make the same amount of money for the same job as men? (appropriate; can be studied with careful data)
b) Is Anne really in love with Andy? (not appropriate; subjective/personal)
c) Does drinking coffee raise blood pressure? (appropriate)
d) Do Lucky Strike cigarettes contain fewer carcinogens than other brands? (appropriate if measurable)
Answer key (as provided in the slides): NOT appropriate example is b).
Hypothesis formation and testing for a tomato plant sun-exposure scenario:
Question: If tomato plants are exposed to more sun, they will grow more tomatoes.
Which statement is the hypothesis? The intended answer is that either B or C could be the hypothesis, depending on framing:
B: Increased sun exposure leads to more tomatoes. (predictive, but not explicitly an if-then form)
C: Amount of sun exposure affects tomato quantity. (describes a relation, could be used as a hypothesis in a broader sense)
The most precise hypothesis would typically be an explicit if–then form, so selecting D (Either B or C could be the hypothesis) captures the ambiguity in how a hypothesis might be framed in this context.
Controlled experiments and independent variable identification:
A controlled experiment must include experimental and control groups to isolate the effect of the independent variable.
The independent variable is the factor deliberately changed (e.g., type of exercise in a fitness study).
The dependent variable is the outcome measured (e.g., heart rate).
Quick checks for understanding (answers summarized):
Q1 (which topics are not appropriate for the scientific method): b) Is Anne really in love with Andy?
Q2 (hypothesis framing for tomato sun exposure): D) Either B or C could be the hypothesis.
Q3 (independent variable): c) Type of exercise.
Q4 (word replacement for “theory”): c) Hypothesis.
Q5 (independent variable in Dr. Jones’s exercise study): c) Type of exercise.
Key Terms and Concepts (Glossary)
Science: the body of knowledge about the natural world and the evidence-based process used to acquire it.
Observation: a description, measurement, or record of an object or phenomenon.
Hypothesis: a testable, falsifiable, and precise explanation that can be stated in an if–then format.
Prediction: a specific, testable consequence derived from a hypothesis.
Independent variable (IV): the factor deliberately changed by the experimenter.
Dependent variable (DV): the factor observed and measured in response to the IV.
Control group: a group kept under standard conditions to serve as a baseline.
Treatment group(s): experimental groups where the IV is manipulated.
Descriptive data: data that summarize observations in nature.
Analytical data: data used to identify patterns or relationships.
Experimental data: data collected from controlled experiments designed to test causality.
Peer review: evaluation of a study by independent experts to ensure quality and reduce bias.
Scientific fact vs hypothesis vs theory:
Fact: a direct, repeatable observation.
Hypothesis: a testable explanation.
Theory: a well-supported, comprehensive explanation that integrates many hypotheses and lines of evidence.
Biological hierarchy: the organization of life into levels from atoms to biosphere, and the relationships between populations, communities, ecosystems, and biomes.
Mass extinctions: events where a large proportion of species go extinct in a relatively short period; there have been at least five documented before the current era.
The Sixth Extinction: the ongoing mass extinction largely driven by human activities, with widespread biodiversity loss.
Conservation strategies: bans on hunting, pesticide restrictions (e.g., DDT), breeding programs, and predator-proof reintroduction zones.
Predator–prey dynamics and ecological roles: extinction of one group can destabilize ecosystems that rely on them for ecological services.
Notes on LaTeX and Numerical References
Use of LaTeX syntax for numbers and formulas when presenting data:
Mass extinctions: 5
Native snail species affected: 61
Snail species extinct worldwide due to rosy wolf snail: 134
Reintroduced snails: 19{,}000
Reintroduced snail species: 14
Trial counts: 18/20, 15/20
Conceptual formula structures:
Hypothesis structure: ext{If } A ext{ then } B
Relationship statements: ext{Increased sun exposure correlates with increased tomato yield}
Quick Reference: Key Figures and Concepts from the Transcript
The science curriculum emphasizes real-world applications, e.g.,: surviving a mass extinction and conserving endangered species.
The Rosy wolf snail case demonstrates unintended ecological consequences when introducing a predator as a biological control.
The biological hierarchy illustrates how loss at one level can cascade through ecosystems.
The Sixth Extinction framework links past mass extinctions to current human-driven biodiversity loss and informs conservation priorities.