1. 1 Which statement best describes one of the stages represented in the diagram below? (1) The mature forest will most likely be stable over a long period of time. (2) If all the weeds and grasses are destroyed, the number of carnivores will increase. (3) As the population of the shrubs increases, it will be held in check by the mature forest community. (4) The young forest community will invade and take over the mature forest community.   1   2   3   4   Hint Half-n-half Clue   2. 2 Which organ system in humans is most directly involved in the transport of oxygen? (1) digestive (3) excretory (2) nervous (4) circulatory   1   2   3   4   Half-n-half Clue   3. 3 Which cell structure contains information needed for protein synthesis?   1   2   3   4   Half-n-half Clue   4. 4 The human liver contains many specialized cells that secrete bile. Only these cells produce bile because (1) different cells use different parts of the genetic information they contain (2) cells can eliminate the genetic codes that they do not need (3) all other cells in the body lack the genes needed for the production of bile (4) these cells mutated during embryonic development   1   2   3   4   Half-n-half Clue   5. 5 Although identical twins inherit exact copies of the same genes, the twins may look and act differently from each other because (1) a mutation took place in the gametes that produced the twins (2) the expression of genes may be modified by environmental factors (3) the expression of genes may be different in males and females (4) a mutation took place in the zygote that produced the twins   1   2   3   4   Half-n-half Clue   6. 6 Which hormone does not directly regulate human reproductive cycles? (1) testosterone (3) insulin (2) estrogen (4) progesterone   1   2   3   4   Half-n-half Clue   7. 7 Owls periodically expel a mass of undigested material known as a pellet. A student obtained several owl pellets from the same location and examined the animal remains in the pellets. He then recorded the number of different prey animal remains in the pellets. The student was most likely studying the (1) evolution of the owl (2) social structure of the local owl population (3) role of the owl in the local ecosystem (4) life cycle of the owl   1   2   3   4   Half-n-half Clue   8. 8 Which sequence best represents the relationship between DNA and the traits of an organism?   1   2   3   4   Half-n-half Clue   9. 9 A sequence of events associated with ecosystem stability is represented below. sexual reproduction → genetic variation → biodiversity → ecosystem stability The arrows in this sequence should be read as (1) leads to (3) prevents (2) reduces (4) simplifies   1   2   3   4   Half-n-half Clue   10. 10 In some people, the lack of a particular enzyme causes a disease. Scientists are attempting to use bacteria to produce this enzyme for the treatment of people with the disease. Which row in the chart below best describes the sequence of steps the scientists would most likely follow?   1   2   3   4   Half-n-half Clue   11. 11 What will most likely occur as a result of changes in the frequency of a gene in a particular population? (1) ecological succession (2) biological evolution (3) global warming (4) resource depletion   1   2   3   4   Half-n-half Clue   12. 12 The puppies shown in the photograph below are all from the same litter. The differences seen within this group of puppies are most likely due to (1) overproduction and selective breeding (2) mutations and elimination of genes (3) evolution and asexual reproduction (4) sorting and recombination of genes   1   2   3   4   Half-n-half Clue   13. 13 Carbon dioxide makes up less than 1 percent of Earth’s atmosphere, and oxygen makes up about 20 percent. These percentages are maintained most directly by (1) respiration and photosynthesis (2) the ozone shield (3) synthesis and digestion (4) energy recycling in ecosystems   1   2   3   4   Half-n-half Clue   14. 14 Which sequence represents the order of some events in human development? (1) zygote → sperm → tissues → egg (2) fetus → tissues → zygote → egg (3) zygote → tissues → organs → fetus (4) sperm → zygote → organs → tissues   1   2   3   4   Half-n-half Clue   15. 15 A variety of plant produces small white fruit. A stem was removed from this organism and planted in a garden. If this stem grows into a new plant, it would most likely produce (1) large red fruit, only (2) large pink fruit, only (3) small white fruit, only (4) small red and small white fruit on the same plant   1   2   3   4   Half-n-half Clue