If there are 20 units of hormone in the bloodstream and it's half life is 2 hours how much will be left after 4 hours

Match the following. match the items in the left column to the items in the right column. 1. foreshocks process used to locate the epicenter of an earthquake 2. magnitude newer magnitude scale that measures the amount of moved (displaced) rock along a fault to determine the strength of an earthquake 3. mercalli intensity scale measure of the total amount of energy released during an earthquake 4. moment magnitude scale areas on active faults where a major earthquake hasn't occurred in a long time 5. richter scale mini-quakes that usually occur before a major earthquake 6. seismic gaps scale that measures the effects or severity of an earthquake 7. triangulation scale of magnitude based on the size of seismic waves produced by an earthquake

Rachel ate a piece of fruit and happened to drop the seeds in her backyard. after a few weeks, she saw a small plant with flowers growing in the backyard. which group does this plant belong to? a. angiosperms b. gymnosperms c. pteridophytes d. bryophytes e. chytrids

Is there any species that went extinct in recent years due to natural causes (not caused by human interaction). if so, what caused it?