Chapter 8 Flashcards

Question

Iteroparity

Answer 1

when organisms reproduce multiple times during their life; common among birds, reptiles, mammals, and amphibians.

Answer 2

an organism that has a life span of one year.

Answer 3

an organism that has a life span of more than one year.

Answer 4

when there is a massive amount of energy required for reproduction. Examples: Bamboos are semelparous tropical plants that have few opportunities for seed germination. Once a bamboo germinates, it spreads vegetatively for years.

Answer 5

semelparous, arid plants that reproduce by growing a giant flowering stalk that produces a large number of seeds. Stalk growth is so rapid that it must steal water and nutrients from the leaves; the plant dies soon after reproduction.

Answer 6

are mostly iteroparous, but some varieties are semelparous. Semelparous varieties live in regions prone to fire, which may favor a single, large reproduction effort before fires kill adults. Iteroparous varieties live where there is less precipitation, but less chance of fire. Differences in breeding patterns lead to tradeoffs in flower and fruit numbers, and in germination rates.

Answer 7

spend the first part of their life underground where they obtain nutrients from xylem tissue of plant roots. Periodical cicadas spend 13 or 17 years underground as nymphs and then emerge from the ground in synchrony to mate. The long nymphal period gives larvae time to grow to adulthood on a diet of low nutritional quality.

Answer 8

the amount of light that occurs each day; provides a cue for many events in the life histories of virtually all organisms. Example: In Michigan, water fleas (Daphnia) enter diapause in mid-September when the photoperiod declines to less than 12 hours of sunlight. Related species in Alaska enter diapause in August when the photoperiod declines to less than 20 hours of sunlight. These photo-sensitivities are related to environmental temperature; the photoperiod is related to decline of temperatures below a hospitable threshold.

Answer 9

Fluctuations in resource availability often determine the timing of life history events. Example: Metamorphosis occurs when a larva changes into a juvenile or an adult. Like many amphibians, the barking treefrog undergoes metamorphosis. Individuals with high food resources can metamorphose at a relatively large mass and early age. Individuals with low food resources can metamorphose early and small, but this may reduce fecundity and increase predation risk.

Answer 10

Predation can affect many life history traits (e.g., time to and size at hatching, metamorphosis, and sexual maturity). Example: Many embryos can detect the presence of an egg predator and respond by speeding up their hatching time to avoid predation. The red-eyed tree frog of Central America lays eggs on leaves that overhang water. The embryos can sense the vibrations of a snake predator on the leaf, and hatch earlier than usual. This makes them hatch at a smaller size, and leaves them more prone to aquatic predators.

Answer 11

Small changes in temperature can have substantial impacts on an organism’s physiological processes. The increase in global temperature has changed the breeding times of many animals and plants. Example: Between 1959 and 1991, researchers found that an increase in average May temperatures was associated with earlier egg-laying dates of North American tree swallows. Many organisms (e.g., amphibians) respond to the duration of warm air temperatures, which is also influenced by global warming.

Answer 12

Changes in temperature can alter the initiation of flower production. As temperatures get warmer, flowering occurs earlier and earlier.

Answer 13

Problems can arise when a species depends on the environment to provide the necessary resources with an altered breeding season. Example: The pied flycatcher breeds in Europe each spring. In 1980, the date of egg hatching began a few days before the peak of caterpillar abundance, which is prey for the flycatchers. Over the next two decades, spring temperatures warmed and peak caterpillar abundance shifted to two weeks earlier. The pied flycatcher retained its normal breeding time. As a result, newly hatched chicks no longer have their major source of food and flycatcher populations have declined by 90%.

Answer 14

In addition to global warming, human activities can impose strong selection and have substantial impacts on organisms’ life histories. Example: Commercial fisheries impose selection pressure on fish size by harvesting only the largest individuals. Between the 1930’s and 1970’s, the average age at maturity of northeast Arctic cod decreased from 9–11 years to 7–9 years. This shift is likely associated with changes in fecundity and longevity.

Chapter 8 Flashcards

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