lesson17 - 17 Doing it, Comparatively Key Terms and...

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17 Doing it, Comparatively Key Terms and Concepts o Secret knock hypothesis o Spontaneous ovulation o Induced ovulation o Implantation o Cryptic sexual selection o Mate choice o Single male mating systems o Dispersed monogamy o Single male polygyny o Colonial monogamy o Promiscuity o Scramble competition o Allometry o Testicular quotient o Sperm competition o First- vs. last-male advantage o Sperm lottery o Vaginal plug o Seminal fluid o Female sequestration o Sexual jealousy o Anovulatory estrus o Copulatory pattern The union of male and female gametes can take place externally, as it does in many amphibians and fish that release their eggs and sperm into the water, or it can occur internally as it does in mammals, birds, and many fish and insects. Both forms require precisely timed movement patterns to assure that fertilization occurs. This lesson will focus on the copulatory behavior of mammals. We will begin by describing the various movement patterns involved in copulation and how these patterns vary among species. Then we will review ideas concerning the reasons for the enormous variability that exists. Lesson 17 199
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Patterns of Copulation Male behavior . The diversity of mammalian copulatory behavior is illustrated by a classification scheme for the copulatory behavior of male mammals developed by Donald Dewsbury of the University of Florida. The classification is based on four features that are either present or absent in copulatory behavior, resulting in 16 categories of behavior, as shown in the following figure. They are: (1) Lock: Some species, such as domestic dogs, exhibit a vaginal lock following ejaculation. The penis swells, making withdrawal difficult or impossible. (2) Thrusting: In some species, such as humans, the penis is repetitively thrust back and forth in the vagina. In others, there is no intra-vaginal thrusting. (3) Intromission frequency: In some mammals, such as rats, the male mounts the female, intromits the penis into the vagina, and then quickly dismounts. Rats must intromit several times before an ejaculation can occur. Other species need intromit only once. (4) Ejaculation frequency: In some species, such as baboons, the male typically ejaculates several times per copulation episode. Others usually ejaculate only once. PSYC 373 200
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Each species is classified according to its performance on each of the four variables. Although 11 of the 16 possible categories have been discovered in at least one species, even closely related species may fit into different slots in this system. For example, seven of the 16 categories were found in a survey of 31 species of small rodents. Primates are less diverse than rodents in their copulatory patterns, with only three of the 16 patterns known so far. Why these species differences exist is not yet known. No ecological correlation of any note has been discovered, and the finding that there is no evolutionary pattern makes the whole thing even more puzzling. Obviously, more data are necessary to enlighten this issue. Female behavior
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This note was uploaded on 05/27/2010 for the course BIOS 373 B02 taught by Professor Dr.danielleger during the Spring '10 term at UNL.

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lesson17 - 17 Doing it, Comparatively Key Terms and...

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