What types of evidence allow scientists to infer that single-celled life likely existed 3.8 billion years ago? Select all that apply. A. transitional fossils in ancient rocks
B. certain forms of carbon in ancient rock
C. fossil evidence, such as stromatolites
D. evidence of extinction events

How does pregnancy begin? a) a placenta forms in the uterus b) a sperm reaches an egg in the fallopian tubec) the blastocyst differentiates into two cell types d) contractions begin in the uterine wallapex

Next pretest: evolution select the correct answer in a laboratory population of flies, the female flies are gray and the males are yellowish gray. biologists observed that all the male flies had an equal chance for reproduction, but the male flies with the brightest colors were more likely to successfully reproduce. what phenomenon could explain such a change? a sexual selection b. disruptive selection c. stabilizing selection d. directional selection

What is the difference between an igneous, sedimentary and metamorphic rock