Science Concepts: Theory, Hypothesis, Evolution, and Ecology (Last-Minute Review)

Not all science uses controlled experiments; predictions from hypotheses test ideas when experiments aren’t feasible.
A good hypothesis yields a testable prediction; example: if dinosaurs gave rise to birds, then some fossils should show bird-like features or transitional skulls.
Fossil evidence can test predictions about evolutionary transitions (e.g., dinosaur traits overlapped with early birds).
Science is powerful but flexible: theories can be revised with new data; well-established ideas can change (e.g., algae once classified as plants).
Science has limitations: human activity, bias, errors, and fraud are possible; science does not dictate ethics or spiritual guidance.
Ethics in science matter: “Just because we can do it, doesn’t mean we should.”

Theory has two meanings: common English (a conjecture) vs. scientific usage (a coherent, well-tested set of propositions with broad explanatory power).
In science, a theory (e.g., gravity, cell theory, evolution) is an overarching framework that explains many observations and has withstood repeated testing.
Data are observable facts; they are the evidential basis for hypotheses and theories.
Facts are observations; hypotheses/theories are explanations of those facts.
Evolution is both a fact (observable changes in populations) and a theory (the unifying framework explaining those changes).

Evolution as a fact: allele frequencies in populations change over time; observed repeatedly across organisms.
Microevolution: change within a population over time due to allele frequency shifts.
Population: a group of interacting individuals of the same species.
Key evidence examples:
- Bacteria (E. coli) experiments: many lineages evolved larger cell size/ density; citrate utilization evolved in one lineage after many generations, illustrating mutation and selection.
- Lizard island study (Pod Mrčaru, Croatia, 1971): introduced lizards; within ~ $4 ext{0 years}$ , populations evolved larger heads/jaws and a diet shift toward more plant matter due to ecological pressures; shows natural selection and rapid allele-frequency changes.
Evolution as theory and fact: widely accepted; evolution by natural selection is the core scientific explanation for biodiversity.

Biological organization hierarchy (start small, build up): atoms → molecules → macromolecules → cells → tissues → organs → organisms → populations → communities → ecosystems → biosphere.
Ecology focuses on interactions among organisms and between organisms and their environment.
Ecological levels:
- Population: group of individuals of a single species.
- Community: multiple populations living in the same area.
- Ecosystem: living components plus abiotic factors (soil, water, etc.).
- Biosphere: all ecosystems on Earth.
Global ecology looks at energy and material flows across the globe; climate and geography shape ecosystems.

Weather vs. climate:
- Weather: short-term conditions (today, tomorrow).
- Climate: long-term prevailing conditions (typical over years).
Four main climate components: $T$ (temperature), $P$ (precipitation), $S$ (sunlight), $W$ (wind).
Sunlight and latitude:
- Direct overhead sunlight at the equator yields high intensity per unit area.
- As latitude increases, solar angle decreases, reducing intensity and temperature range changes.
- Earth’s tilt: $23.5^ op$ tilt causes seasons by shifting direct solar radiation between hemispheres.
Hadley cells and global circulation:
- Hadley cells drive major wind/rain patterns between the equator and ~ $30^ op$ latitude.
- Rising warm air near the equator causes heavy rainfall (tropics); dry air descends around $30^ op$ , creating deserts.
Wind and climate patterns:
- Winds move weather systems (e.g., storms moving west to east in some regions).
- Global circulation and air patterns influence regional climates and biodiversity.

Sunlight, temperature, precipitation, and wind determine which biomes and habitats occur where.
Seasonal changes in day length and solar radiation become more pronounced at higher latitudes.
Conceptual goal: graph and compare $T$ and $P$ over time to understand climate effects on ecosystems.

Science is a human activity with potential for error, bias, and fraud; it’s not a moral or spiritual guide.
Ethical oversight and committees help govern what research should or should not be done.
As you move through units, connect learning objectives to the core ideas: hypotheses/tests, theory vs fact, evolution, ecology, and global climate patterns.