VARIOUS NOTES: CHANGES OVER TIME / EVOLUTION
******CHANGES OVER TIME******
DARWIN’S VOYAGE
SPECIES- A GROUP OF SIMILAR ORGANISMS THAT CAN MATE WITH EACH OTHER AND PRODUCE FERTILE OFFSPRING.
ADAPTATION- A TRAIT THAT HELPS AN ORGANISM SURVIVE AND REPRODUCE.
PERHAPS, DARWIN THOUGHT, THE SPECIES GRADUALLY CHANGED OVER MANY GENERATIONS AND BECAME BETTER ADAPTED TO THE NEW CONDITIONS.
EVOLUTION- THE GRADUAL CHANGE IN A SPECIES OVERTIME.
SCIENTIFIC THEORY- A WELL-TESTED CONCEPT THAT EXPLAINS A WIDE RANGE OF OBSERVATIONS.
NATURAL SELECTION- THE PROCESS BY WHICH INDIVIDUALS THAT ARE BETTER ADAPTED TO THEIR ENVIRONMENT ARE MORE LIKELY TO SURVIVE AND REPROUCE THAN OTHER MEMBERS OF THE SAME SPECIES.
VARIATION- ANY DIFFERENCE BETWEEN INDIVIDUALS OF THE SAME SPECIES.
OVER A LONG PERIOD OF TIME, NATURAL SELECTION CAN LEAD TO EVOLUTION. HELPFUL VARIATIONS GRADUALLY ACCUMULATE IN A SPECIES, WHILE UNFAVORABLE ONES DISAPPEAR.
A NEW SPECIES CAN FORM WHEN A GROUP OF INDIVIDUALS REMAIN SEPERATED FROM THE REST OF ITS SPECIES LONG ENOUGH TO EVOLVE DIFFERENT TRAITS.
THE FOSSIL RECORD
MOST FOSSILS FORM WHEN ORGANISMS THAT DIE BECOME BURIED IN SEDIMENTS.
SEDIMENTARY ROCK- FORMED WHEN LAYERS OF SEDIMENT BUILD UP AND COVER THE DEAD ORGANISMS AND OVER MILLIONS OF YEARS THE LAYERS HARDEN.
PETRIFIED FOSSILS- GRADUALLY THE MINERALS REPLACE THE REMAINS, CHANGING THEM INTO ROCK.
MOLD- A HOLLOW SPACE IN SEDIMENT IN THE SHAPE OF AN ORGANISM OR PART OF AN ORGANISM.
CAST- IS SOMETIMES WHEN A MOLD BECOMES FILLED IN WITH HARDENED MINERALS.
SCIENTISTS CAN DETERMINE A FOSSILS AGE IN TWO WAYS: RELATIVE DATING AND ABSOLUTE DATING.
RELATIVE DATING- IS WHEN SCIENTISTS DETERMINE WHICH OF TWO FOSSILS IS OLDER.
ABSOLUTE DATING- ALLOWS SCIENTISTS TO DETERMINE THE ACTUAL AGE OF FOSSILS.
RADIOACTIVE ELEMENTS- UNSTABLE ELEMENTS THAT DECAY, OR BREAK DOWN, INTO DIFFERENT ELEMENTS.
HALF-LIFE- IN A RADIOACTIVE ELEMENT, THE TIME IT TAKES FOR HALF OF THE ATOMS IN A SAMPLE TO DECAY.
FOSSIL RECORD- THE MILLIONS OF FOSSILS THAT SCIENTISTS HAVE COLLECTED.
EXTINCT- WHEN NO MEMBERS OF A SPECIES ARE STILL ALIVE.
GRADUALISM- PROPOSES THAT EVELOUTION OCCURS SLOWLY BUT STEADILY.
PUNCTUATED EQUILIBRIA- SPECIES EVOLVE DURING SHORT PERIODS OF RAPID CHANGE.
OTHER EVIDENCE FOR EVOLUTION.
Scientists compare body structures, development before birth, and DNA sequences to determine the evolutionary relationships among organisms.
Homologous structures- Structures that related species have inherited from a common ancestor.
Branching Tree- Diagram that shows how scientists think different groups of organisms are related.