Hypothesis Theory Law Review Hypothesis A prediction based
Hypothesis, Theory, Law Review
Hypothesis • A prediction based on knowledge. • Used to perform experiments • Must be testable • Must test variables
Theory • An explanation of observations or events based on proven hypotheses and confirmed many times. • Can be modified if proven incorrect • Example: theory of evolution
Scientific Law • Statement of how things work in nature that seems to be true all the time. • Cannot be changed • Explains what happens but not why • Example : law of gravity
Changes Over Time
Darwin 1835 – Beagle reached the Galapagos Islands Observations: – Diversity of living things – Remains of ancient organisms – Characteristics of organisms
Theory of evolution • Is the gradual change in a species over time • Darwin's Reasoning's – Plants and animals faced different conditions so they gradually changed
Natural Selection • Organisms with traits best suited to their environment are more likely to survive and reproduce.
Adaptations • Any variation that makes an organism better suited to its environment. • Ex: color, shape, etc. (camouflage)
• Variation: any difference between individuals of the same species • Different colors, eat different things, etc.
Overproduction – insects lay thousands of eggs but they do not all survive (not enough food, water, living space)
Competition • Compete to survive –Can’t find enough food –Caught by predators
Environmental Change • Can affect an organism ability to survive
Genes and Natural Selection • Darwin did not know what caused these variations • Now we know that it is in our genes
Unanswered Questions about evolution
Mass extinctions • Not sure what caused extinction, but believed it was a sudden climate changed • asteroid
Example of Adaptation Many disease causing bacteria species were once easily killed by antibiotics but now they are not harmed by them. The bacteria that had the antibiotic resistant variation survived to reproduce and pass this trait to their offspring.
The story of the peppered moth • The darkening of color that occurred in a number of species of insects following the Industrial Revolution. This change appears to be related to the increase in pollutants in the environment. Before the Industrial Revolution, moth species were predominantly white with black speckles. By the end of the 1800 s, they were predominantly charcoal grey. This change was due to pollution - stained trees affected the camouflage potential of the moths. After anti-pollution laws took effect and the bark lightened, the moth populations in formerly polluted areas returned to previous color distributions.
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