Until recently, the human population grew slowly
a. true
b. false
Ans: a. true
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This illustration shows
a. cytoplasmic division in an animal cell. b. a contractile ring mechanism. c. how chromosomes are dragged to the poles. d. cytoplasmic division in an animal cell and a contractile ring mechanism. e. cytoplasmic division in an animal cell and how chromosomes are dragged to the poles
Trisomy 21, or Down syndrome, occurs when there is a normal diploid chromosomal complement but one (extra) chromosome 21. Although fertility is reduced in both sexes, females have higher fertility than males. Van Dyke et al
(1995; Down Syndrome Research and Practice 3[2]:65—69 ) summarize data involving children born of Down syndrome individuals. Given the fact that conceptuses with 48 chromosomes (four chromosome 21's) are not likely to survive early development, what percentage of surviving offspring would be expected to have Down syndrome if both parents have Down syndrome? A) One-half of the surviving offspring would be expected to have Down syndrome. B) All the children would be expected to have Down syndrome. C) One-third of the surviving offspring would be expected to have Down syndrome. D) None of the surviving offspring would be expected to have Down syndrome. E) Two-thirds of the surviving offspring would be expected to have Down syndrome.
What is the correct order of events that occur during muscle contraction?
1) muscle shortens 2) calcium binds to troponin 3) filaments slide 4) T tubules are depolarized 5) acetylcholine is released 6) ATP molecule is split a. 4 ? 5 ? 2 ? 1 ? 3 ? 6 b. 4 ? 2 ? 5 ? 6 ? 1 ? 3 c. 5 ? 2 ? 4 ? 1 ? 6 ? 3 d. 6 ? 2 ? 5 ? 4 ? 3 ? 1 e. 5 ? 4 ? 2 ? 6 ? 3 ? 1
Suppose you are a botanist and you discover a plant that has a dominant gametophyte, but no xylem or phloem. Into which group should you classify this plant?
a. angiosperms b. gymnosperms c. seedless vascular plants d. bryophytes