Chapter 7 Flashcards
How should selection for greater longevity (life expectancy) affect time to maturity and size at maturity?
Time to sexual maturity increases. Body size at sexual maturity increases.
These include the time required to reach sexual maturity; fecundity, which is the number of offspring produced per reproductive episode; parity, which is the number of episodes of reproduction; parental investment, which is the amount of time and energy given to offspring; and longevity, or life expectancy, which is the life span of an organism.
What factors might favor the evolution of semelparity versus iteroparity in different species of salmon?
Some organisms reproduce only once, a phenomenon known as semelparity, as we saw in the earlier example of sockeye salmon, or they may reproduce multiple times throughout their life, a phenomenon known as iteroparity, as in the case of oak trees that produce acorns every year. Semelparity example in salmon is shortly after reproducing for the first time, both the male and female salmon rapidly lose strength and physiological abilities, and they both die. The factor that may favor the evolution of semelparity versus iteparity is breeding significantly decreases parental survival rates. Breeding multiple times hurts parents
Compare and contrast the two leading arguments regarding why temperate bird species lay one or two more eggs than closely related tropical bird species.
In short, tropical birds produce a smaller number of higher-quality offspring not because they are unable to feed more offspring but because they have a different overall strategy, which is to provide more food per nestling as a way to produce offspring with higher survival rates when they leave the nest. In contrast, the temperate birds’ strategy is to produce more nestlings at the cost of each nestling being of lower fitness.
Given your knowledge of how predators and resources can affect life history traits, hypothesize how the four combinations of high resources, low resources, predator presence, and predator absence would affect the size at maturity of a prey species.
- high resources & predator present: juveniles grow quickly, allow them to metamorphose and escape their aquatic habitat earlier
- high resources & predator absent: juveniles grow quickly and metamorphose when they reach the optimal body size for metamorphosis.
- low resources & predator present: juveniles grow slowly and may not have time to reach even minimum size needed for metamorphosis
- low resources & predator absent: juveniles grow slowly but likely have plenty of time to reach the optimal body size for metamorphosis.
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 where the traits increase survival.
Give two reasons why a mammal such as a gray wolf could face a trade-off between offspring number and offspring size.
It’s limited by energy and nutrients. They can have many kids but offspring can be small due to too many to feed. Food competition. Not enough energy.
the number of offspring in any given pregnancy can only increase if the size of each individual offspring decreases. The trade-off between offspring number and offspring size for a given reproductive event can also be limited by energy and nutrients. An example of this can be seen in Figure 7.5, which illustrates the relationship between seed size and seed number in plants of the goldenrod genus (Solidago). The goldenrod plant is an example of negative correlation, a phenomenon that can be seen across both populations and species: Plants that produce more seeds also produce smaller seeds.
The number of offspring produced in a single reproductive event can also cause a trade-off with the amount of parental care that can be provided. As the number of offspring increases, the efforts of the parents to provide food and protection will be increasingly spread thin.
What is the mechanism by which parental care can increase current fitness but decrease future fitness?
Because parental care for offspring that are large and care for large numbers of offspring is costly to the parent and the offspring, so trade-offs are favored.
The number of offspring produced in a single reproductive event can also cause a trade-off with the amount of parental care that can be provided. As the number of offspring increases, the efforts of the parents to provide food and protection will be increasingly spread thin.
Why might an organism use cues such as photoperiod to predict the future state of its environment?
Virtually all organisms sense the amount of light that occurs each day, known as the photoperiod. Many can distinguish whether the photoperiod is getting shorter or longer. Organisms use cues such as photoperiod to predict the future state of its environment. Some organisms need to hibernate during certain temperatures. The sensitivity of individuals to these cues has been adjusted by natural selection so that the individual’s response to an environmental cue is well matched to the environmental condition.
In terms of environmental cues, hypothesize why some, but not all, species of plants flower earlier in association with warmer spring temperatures.
Plants use two different cues to bloom, they can use temperature or photoperiod cues. If they use temperature cues when it hits a certain temperature they bloom but those who use photoperiod they only bloom when there is a certain number of hours in a day. That is why those plants that use temperature bloom first because it gets warmer quicker but those who use length of day have to wait until the day hits a certain number of hours and global warming does not affect time of day
Compare and contrast the concept of a regression versus a coefficient of determination
The difference between these two statistical measurements is that correlation measures the degree of a relationship between two variables (x and y), whereas regression is how one variable affects another. correlation does not show cause and effect while regression does
