Chapter 8 Life Histories (Ecology The Economy Of Nature 8th Edition) Flashcards Preview

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Flashcards in Chapter 8 Life Histories (Ecology The Economy Of Nature 8th Edition) Deck (44)
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Which group of organisms is most likely to be semelparous?



An individual with a slow life history strategy would generally NOT possess _________.

Low parental investment


Om a scatterplot, the coefficient of determination tells you _________.

how well the data fit to a regression line


You are studying the life history of plant species occupying habitats that differ in amounts of competition, stress, and disturbance. You discover an old field that is dominated by a single herbaceous plant species. As you are working in a Mediterranean climate with plenty of precipitation and moderate temperatures, stress is not a major ecological factor in this ecosystem. However, the ecosystem does undergo low-intensity fires every few years, an interval that is too frequent for competitively dominant species to take over but too infrequent for ruderal species to take over. Instead, the herbaceous plant species you discover in this old field possesses a perfect mixture of the life history traits of a competitor species and ruderal species. Most likely this species has _____ growth, _____ sexual maturity, and _____ energy expended on seeds.

fast; early; intermediate


A plant individual that reproduces twice in its lifetime and lives for 1 year is a(n) _____.

iteroparous annual


You are walking through a mixed evergreen–deciduous forest where approximately 10 percent of the trees are eastern hemlocks, a species of evergreen tree that casts very deep shade on the forest understory. Interestingly, under every eastern hemlock, you find the same small herbaceous plant species. However, you never observe this species anywhere else, even though a healthy diversity of other species live throughout the forest understory. You expect the small herbaceous species to have _____ growth, _____ sexual maturity, _____ energy expended on seeds, and _____ reproduction.

slow; late; low; vegetative


In freshwater aquatic ecosystems, invertebrates called giant water bugs are common predators. Giant water bugs reach sexual maturity relatively rapidly (in only a few months) and produce large numbers of offspring. Once fertilized, the female lays her eggs, usually numbering in the dozens to hundreds, on the dorsal surface of her mate's carapace so that he will aerate them as he swims and approaches the water surface to breathe. Once hatched, each giant water bug will live for approximately a year. What is unusual about the giant water bugs' reproductive biology, given the rest of its life history traits?

Males exhibit a high parental investment in offspring.


You are studying the effects of global climate change on the breeding dates of a certain wild animal species that inhabits parts of the North American, African, and Australian continents. Over the time span of 20 years, you record the dates breeding is initiated in the populations that live on each of the three continents. You also gather temperature and precipitation data for each site for the same 20-year period. At the end of the 20-year period, you examine the relationships between average dates of breeding initiation and the climate data. Your results indicate that in North America, changes in temperature and precipitation have had no influence on breeding dates. However, relationships between changes in climate and breeding dates existed on the other two continents. In Africa, the average date of breeding initiation was two weeks earlier, and in Australia, the average date of breeding initiation was one week earlier. What do these results suggest?

The impacts of global climate change can vary among different regions of the world.


Suppose a species exhibits the growth rate of a stress tolerator plant species and the age at sexual maturity of a ruderal plant species. It uses the same proportion of energy on seeds and places the same importance on sexual reproduction as a competitor species. The life history traits of this species are likely to be _____ growth, _____ sexual maturity, ____ proportion of energy used to make seeds, and _____ importance of vegetative reproduction.

slow; early; low; high


White-tailed deer hunters will oftentimes not shoot small deer. Instead they try to kill only the largest deer, and give the smaller deer more time to grow larger. Based on the hunters' preference to kill only larger white-tailed deer, over many generations evolution will most likely favor which life history traits?

smaller adult sizes, shorter life span, higher fecundity, and earlier times to maturity


A semelparous yucca plant variety will produce 900 seeds. Since the yucca delays reproduction for many years, these seeds are large and contain a relatively large amount of resources for germination. As a result, 23 percent of the semelparous yucca seeds actually germinate and reach reproductive age themselves. In contrast, an iteroparous yucca plant variety will reproduce five times during its life span, producing 250 seeds during each reproductive event. However, the iteroparous yuccas allocate less energy to each seed, so only 15 percent will actually germinate and reach reproductive age. Under equivalent environmental conditions, the _____ yucca variety produces _____ more successful seeds than the _____ variety.

semelparous; 19.5; iteroparous


In manipulative experiments examining optimal brood size in birds, why do experimental subjects fledge fewer offspring than controls when eggs are experimentally removed and added to other nests?

There are fewer offspring present to fledge.


You are performing an analysis of the long-term benefits of reproductive strategies employed by cicada species. Individuals of one species reproduce once every year and produce an average of 150 offspring per year. Because predators can easily predict when these cicadas will reproduce, they have evolved to efficiently hunt the yearly cicada offspring. Thus, only 5 percent of these offspring will survive to reproduce. Individuals of the 13-year cicada species produce an average of 250 offspring during their single mating every 13 years, and approximately 45 percent of the offspring survive to reproduce. Finally, 17-year cicadas produce an average of 350 offspring per individual during their single mating every 17 years, and approximately 50 percent of the offspring survive to reproduce. Over 100 years, which strategy will produce the most new cicadas? Assume the 13-year and 17-year cycles all begin at year 1; that is, the first 13-year cicada reproductive event is on year 13.

the 17-year cicadas


Select the statements that describe how selection for greater longevity affects time to maturity and body size at maturity.

time to sexual maturity increases
body size at sexual maturity increases


Which factor might have favored the evolution of semelparity over iteroparity in different species of salmon?

breeding significantly decreases parental survival rates


What factors make it unlikely that a mammal, such as an African elephant or a deer mouse, will give birth to numerous large offspring in a single reproductive event?

In mammals, the mother's uterus has a limited amount of available space.
Mammalian fetuses absorb all of the nutrients they need from their mother's blood.


How might caring for offspring increase a parent's current reproductive success, but decrease the parent's overall evolutionary fitness?

When a parent expends extra energy to ensure the survival of a brood of offspring, the parent may not have enough energy to reproduce again.


Why might an organism use the photoperiod to predict the state of its environment?

Annual photoperiod patterns are consistent from year to year, so changes in daily sunlight duration reliably indicate seasonal transitions for a particular geographic location.


How might global warming affect reproductive timing in some flowering plant species?

Species that flower in response to changing temperatures may begin flowering earlier in the year than usual.


All of the factors explain why trade-offs among life history traits are common EXCEPT

the lack of constant environments.


Using Grime's categorization, which method of dispersal would be expected from ruderals?

wind-dispersed seeds


Which would you expect from an organism with low annual survival?

reproduction beginning at an early age


Why do organisms face a trade-off between growth and fecundity?

limited energy


An organism that only reproduces once is known as



Why might natural selection act more strongly on traits that improve reproductive success early in life rather than later in life?

Many organisms do not survive to reach the age when the later-in-life traits increase survival.


Two reasons for the trade-off between offspring size and offspring number are

physical limitations and nutrient availability.


Why might an increased number of offspring with high parental care be selected against?

Increased parental care can decrease the subsequent fitness of the parent.


Which is NOT a common environmental cue?

population size


Why do some species of plants flower earlier, in warmer spring temperatures, when other spring plants do not?

The plants that flower earlier are more sensitive to temperature.


The number of offspring produced by an organism per reproductive event is termed