Which of the following must occur in order for a photon to excite an electron in a pigment molecule?
a. The photon must match the energy difference between the ground state and one of the excited states.
b. The photon must have lower energy than the electron at the ground state.
c. The photon must have lower energy than the energy of the electron at the excited state.
d. The photon must have higher energy than the electron at the ground state.
Ans: a. The photon must match the energy difference between the ground state and one of the excited states.
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Male deer have large antlers that are used to challenge each other in fights for territory and females. The females of this group actively choose the strongest males. Which type of sexual selection is occurring with the deer population?
A. Stabilizing selection. B. negative frequency-dependent selection. C. Intersexual selection. D. Intrasexual selection. E. Intersexual and intrasexual selection are both occurring.
Protruding from the inner membrane of the mitochondria into the matrix are knoblike spheres called ________ complexes, which are attached by a short protein stalk to a(n) ________ complex. Together these complexes are referred to as the ________ complex.
Fill in the blank(s) with the appropriate word(s).
In sexual reproduction in ciliates the sequence of events is
A. (1) In the pair of conjugating cells, the micronuclei undergo mitosis to produce four diploid micronuclei. All but one of these micronuclei disintegrate. (2) The remaining micronucleus undergoes meiosis to produce two. (3) One micronucleus stays in the parent cell and the other moves to the opposite cell while the macronucleus in each cell disintegrates. (4) The cells separate, each with two nuclei. (5) One haploid micronucleus in each cell forms a new haploid macronucleus and the other divides mitotically to form eight new haploid micronuclei. (6) The two haploid macronuclei fuse to form a diploid one and the eight haploid micronuclei fuse by pairs into four diploid micronuclei. B. (1) In each conjugating cell, the micronucleus undergoes meiosis to produce four haploid micronuclei, of which three disintegrate. (2) The remaining micronucleus undergoes mitosis to produce two. (3) One micronucleus stays in the parent cell and the other moves to the opposite cell while the macronucleus in each cell disintegrates. (4) The cells separate, each with two nuclei, one of its own and one from its conjugant. (5) The two haploid micronuclei in each cell fuse to form a diploid micronucleus. (6) The diploid micronucleus divides mitotically, producing four diploid macronuclei and four micronuclei. C. (1) In each conjugating cell, the macronucleus and micronucleus undergo meiosis. One haploid macronucleus and micronucleus disintegrate in each cell. (2) The remaining nuclei undergo mitosis to produce two macronuclei and two micronuclei. (3) One set of nuclei stays in the parent cell and the other moves to the opposite cell. (4) The cells separate, each with two sets of nuclei, one of its own and one from its conjugant. (5) The two haploid micronuclei in each cell fuse to form a diploid micronucleus, and the two macronuclei fuse to form a diploid macronucleus. (6) The diploid nuclei mitotically, producing four diploid macronuclei and four micronuclei.
Muscle cramps are helped by massage and stretching, which increase blood flow to the affected area.
a. true b. false