Fill in the blank A biological community and its physical environment including both biotic and abiotic factors is called a(n) _ .

If an organ has six haploid chromosomes,how many chromosomes are present. 6 12

Which of the following is the earliest era of earth's geologic time scale? cenozoic mesozoic precambrian paleozoic

Ihave no idea how to solve these. plus there's another question that is 2) a 10 kilogram meteorite is collected in space and brought back to earth. it is composed of 1.25 kg of uranium-238 and 8.75 kg of lead-206. how many u-238 half lives have passed? what is the approximate age of the meteorite?