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The Return of the Elephant Seals
Female elephant seals reach sexual maturity at 3 to 4 years of age and produce one pup each year. Elephant seals breed harem-style, with a single large bull typically monopolizing and inseminating 30 to 100 females. Although males reach sexual maturity at 5 to 7 years of age, few are powerful enough to acquire a harem until 7 to 10 years of age; some are never able to compete. Further, although the maximum life span is about 20 years for females and 15 for males, only about 1 in 5 survives beyond 5 years of age. These factors combine to produce a biotic potential of about 12% per year. But elephant seal populations virtually never reproduce at their biotic potential. Why not?
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Chapter 27 Solutions
Biology: Life on Earth with Physiology Plus Mastering Biology with Pearson eText -- Access Card Package (11th Edition)
- High testosterone is often associated with shorter lifespan in mammals. However, you find a new species of mouse in which males live longer than females under field conditions. Which of the possible explanations below would NOT predict this pattern? Male-male competition often injures the participants. Females suffer costs of reproduction caused by the burden of milk production. Males, but not females, provide territorial guarding that improves the survival of their grandchildren. Females enter menopause and stop reproducing at age five, while males can reproduce until death.arrow_forwardLynx mate in March and have litters of 3 to 5 kittens in May. Lynx kittens are born blind and naked. Their eyes open after 10 days. In 12 weeks, the kittens travel with their mother. They watch and learn how to hunt for hares. Their eyesight is more acute than their hearing or sense of smell. Lynx are active at night (nocturnal). Hares have litters of 2 to 4 offspring, with up to 4 litters over a summer. Hares are born with their eyes open and bodies fully haired. Birth weight doubles in 8 days. Hares use their good hearing and supersensitivity to ground vibrations, as well as speed and coordination, to escape lynx. Hares are active at night and spend the day grooming and resting. Classify the lynx as a r- or K-selected species. Provide evidence from the information given to support your choice.arrow_forwardIn human population, males are in general larger than females. This observation can be seen as an example of sexual dimorphism. True Falsearrow_forward
- Sexual behavior in animals is largely controlled by estrogen levels in the female and the occurrence of estrus in the male. T or F?arrow_forwardAccording to the graphs on the right (a) (b) (c) Number fledged Mean calves per year Mean eggs per day 2 (378) (184) (73) (26) (39) *** 2.0 1.0- 0.5- 0 1 2 3 4 5 Age (years) 1 3 36- 12 5 Stags Hinds 7 9 11 13 15 17 Age (years) 0 8 16 24 32 40 48 Age from start of assay (days) Probability of survival 1,000 750 500 Number of survivors 0.6 (365) (177) (73) (18) (33) 0.5- 0.4- 0.3- 0.2 Number alive 250 100 50 60 40 20 1 0 2 Age (years) 3 4 5 Stags Hinds 0 2 4 6 8 10 12 14 Age (years) 20 40 60 80 Adult age (days) survivorship increases with age when young but then decreases w/age reproductive ability increases with age when young but then decreases w/age survivorship declines with age reproductive ability declines with agearrow_forwardConsider the temperature effect in the sex determination of a turtle species represented in the graph below. 100 What effect would a decrease in temperature below the epivotal temperature have on sex ratios of these turtles? 50 FT MT Temperature Fewer males and females will result. None of the other answers is correct. No difference in the proportion of females to males will result as only colder temperatures will alter the sex ratio in the offspring. More males than females will result. More females than males will result. To Percent female O O O Oarrow_forward
- Female mammals undergo continuous reproductive cycles during their reproductive life. In the sense of offspring production, what is the benefit of these continuous cycles?arrow_forwardBoth men and women produce testosterone, but levels of testosterone are generally higher in men than women. However, levels of testosterone in some XX females fall within the range of testosterone levels of XY men. This overlap has created controversy within women’s sports. Testosterone is known to increase muscle mass and enhance some types of athletic performance, so some people have suggested that women with naturally high testosterone have an unfair competitive advantage. In 2011, the International Association of Athletics Federations (IAAF) adopted a policy that limits levels of testosterone in women athletes, saying that women athletes must not have a blood testosterone concentration greater than 10 nanomoles per liter (nmol/L), a level typically seen in men. Some elite women athletes have natural testosterone levels above this limit and have challenged the policy. Do you think that it is fair for XX females with naturally high testosterone (levels typically found in XY males) to…arrow_forwardMale California sea lion mating success is determined by the number of mates they can acquire. Larger males are more successful at maintain larger territories. Females remain in one territory for the duration of the mating season and larger territories support more females than smaller territories. Additionally, the most successful males will fast during mating season to remain present in their territory at all times. If they leave to hunt they risk loss of their territory and access to all the females present in it. Which of the following best describes sexual selection in this species? a. Males likely engage in male-male combat to maintain territories. b. Intersexual selection is likely stronger than intrasexual selection. c. Sexual selection on the females is stronger than on the males. d. Females will mate with smaller males at a higher frequency than larger malesarrow_forward
- Polygyny is a common mating system in nature. Which one of the following scenarios is LEAST likely to result in a polygynous mating system? Male stalk-eyed flies form leks where receptive females come visit Male Neotropical giant damselfly defend water-filled tree holes, which are the oviposition sites for females. Suitable tree holes for oviposition are rare and females must mate with the resident male in exchange for access to the oviposition sites. Male Bengal tigers defend large territories that contain food sources. Female Bengal tigers visit male territories to mate. The density of the Bengal tiger is extremely low that male tigers rarely encounter more than one female in their lifetime. In the bumblebee-wolf Philanthus bicinctus, females are unreceptive until they finish constructing the long underground burrow as nest sites. Males search for locations containing a number of newly constructed burrows and attempt to control these sites against the intruders. Your cousin Peter…arrow_forwardWhen the fitness increment of increased male function results in a small cost in fitness of female function, would a population evolve hermaphrodites?arrow_forwardAccording to the figure for oppossums Birth Age (months): 0 Energy source: Energy used for: Baby Juvenile Maturity Adult Killed by predator 1st litter 2nd litter Independence (8 pups) (7 pups) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Mother Gathered by self Growth, metabolism, and repair Metabolism, repair, and reproduction delayed maturation = longer growth = larger litters early maturation = shorter growth = larger litters early maturation = shorter growth = fewer litters delayed maturation = longer growth = more littersarrow_forward
- Case Studies In Health Information ManagementBiologyISBN:9781337676908Author:SCHNERINGPublisher:Cengage