Parental Care by Frogs
Only an estimated 10 percent of anuran (frog and toad) species provide any kind of parental care. But within this 10 percent there is very great diversity of caregiving behaviors. The behaviors are of five basic types. The most common type is attendance of eggs. In most cases, terrestrial eggs are attended. The other four types of parental care are transporting the eggs, attending young frogs or tadpoles (the immature stage of a frog’s development), transporting the tadpoles or young frogs, and feeding the tadpoles.
The term parental care is generally used for any type of parental investment in offspring after the eggs have been deposited or the young have been born. Only a few studies have investigated the costs and benefits of parental care in amphibians, so, while parental care presumably increases the survivorship of the young, and usually entails a cost to the caregiver, the costs and benefits for the vast majority of frog species that provide care to their offspring are unknown.
How does parental care increase the survivorship of offspring? The parents may protect the eggs from predators or disease, or they may aerate aquatic eggs. Because the terrestrial environment is not hospitable to the porous jelly- covered eggs of amphibians or to tadpoles, parental behaviors may be particularly beneficial in preventing drying out. In some species the parent releases water from its bladder onto the eggs. Parents may turn the eggs, thus preventing developmental abnormalities. In New Guinea, male frogs of some species transport young on their backs. The tiny frogs hop off at different places in the habitat. Thus, the young may benefit from reduced competition for food, lower predator pressure, and reduced levels in inbreeding.
The benefits of egg attendance are best known in the Puerto Rican coqui frog. Female coquis lay eggs in a sheltered retreat within the male’s territory, and the male attends the eggs. To determine the benefits of egg attendance, Daniel Townsend and his colleagues removed attending males from some clutches (groups of eggs produced at the same time) to determine the fates of attended and unattended eggs. Unattended clutches failed more frequently than attended clutches. The main causes of mortality of unattended clutches were being eaten by other male coquis and drying out. Male coquis are important predators of the eggs of other coquis, and attending males aggressively defend their retreats from intrusion by other males. Attending males also protect their clutches from drying out.
Most amphibians do not exhibit parental care. This observation suggests that parental care has costs to the parents that may outweigh the enhanced survival of offspring. Reduced reproductive output is one cost of parental care. Species that exhibit parental care usually produce fewer eggs per clutch than related species that do not have parental care. Furthermore, time and energy spent on parental care may limit opportunities for additional matings. Another cost may be decreased food intake for the caring parent. Parents typically do not eat when they are guarding nests or eggs, and females that remain with their clutch produce fewer clutches overall than do females that do not remain with their clutch. Reduced rates of parental survival are another potential cost of parental care. Remaining with the eggs could increase an individual’s vulnerability to predation. Because most amphibians are small and have ineffective defenses against vertebrate predators, parental care could increase the risk of the parents’ death and might not save their eggs or young.
What circumstances would favor the evolution of parental care? We would expect parental care to evolve if a parent is able to increase offspring survival enough to offset the costs involved. If environmental conditions are harsh, or if predation pressure on the eggs or larvae is high, the benefits might outweigh the costs. There are some circumstances where the costs of parental care might be minimal. For example, cost might be minimal where parents attend offspring in hidden nest sites not readily accessible by predators. For females, if reproductive output is already limited for other reasons, the cost of parental care might be minimal. If females generally only produce one clutch per season, caring for that clutch might not reduce reproductive output appreciably. Costs might be minimal for a male if he can provide care for his offspring and at the same time defend territory and attract additional females.
1
Only an estimated 10 percent of anuran (frog and toad) species provide any kind of parental care. But within this 10 percent there is very great diversity of caregiving behaviors. The behaviors are of five basic types. The most common type is attendance of eggs. In most cases, terrestrial eggs are attended. The other four types of parental care are transporting the eggs, attending young frogs or tadpoles (the immature stage of a frog’s development), transporting the tadpoles or young frogs, and feeding the tadpoles.
According to paragraph 1, which of the following is true of parental care in anuran species?
Factual Information Questions事实信息题
AMost anuran species provide a wide variety of parental care.
BAttendance of eggs laid on land is the most common form of parental care.
CTadpoles receive parental care more frequently than young frogs do.
DParental care is provided according to the various stages of development of offspring.
2
The term parental care is generally used for any type of parental investment in offspring after the eggs have been deposited or the young have been born. Only a few studies have investigated the costs and benefits of parental care in amphibians, so, while parental care presumably increases the survivorship of the young, and usually entails a cost to the caregiver, the costs and benefits for the vast majority of frog species that provide care to their offspring are unknown.
Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
Sentence Simplification Questions句子简化题
AA few investigations have been carried out that show the benefits of parental care in amphibians, and presumably parental care increases the survivorship of young frogs in most cases.
BPresumably parental care benefits the offspring and has costs for the parents, but the costs and benefits are not known for the great majority of frog species.
CWhether there are costs and benefits of providing parental care is unknown for the vast majority of frog species that provide parental care.
DBecause there have been few investigations of parental care in amphibians, and in frogs in particular, the vast majority of frog species that provide parental care have not been investigated.
3
How does parental care increase the survivorship of offspring? The parents may protect the eggs from predators or disease, or they may aerate aquatic eggs. Because the terrestrial environment is not hospitable to the porous jelly- covered eggs of amphibians or to tadpoles, parental behaviors may be particularly beneficial in preventing drying out. In some species the parent releases water from its bladder onto the eggs. Parents may turn the eggs, thus preventing developmental abnormalities. In New Guinea, male frogs of some species transport young on their backs. The tiny frogs hop off at different places in the habitat. Thus, the young may benefit from reduced competition for food, lower predator pressure, and reduced levels in inbreeding.
Why does the author mention that in some frog species “Parents may turn the eggs”?
Rhetorical Purpose Questions修辞目的题
ATo illustrate a behavior of parent frogs that can prevent damage to eggs from drying out
BTo support the idea that the terrestrial environment is not hospitable to amphibian offspring
CTo give an example of parental care that can increase the survivorship of offspring
DTo explain what happens when a parent releases water onto the eggs
4
How does parental care increase the survivorship of offspring? The parents may protect the eggs from predators or disease, or they may aerate aquatic eggs. Because the terrestrial environment is not hospitable to the porous jelly- covered eggs of amphibians or to tadpoles, parental behaviors may be particularly beneficial in preventing drying out. In some species the parent releases water from its bladder onto the eggs. Parents may turn the eggs, thus preventing developmental abnormalities. In New Guinea, male frogs of some species transport young on their backs. The tiny frogs hop off at different places in the habitat. Thus, the young may benefit from reduced competition for food, lower predator pressure, and reduced levels in inbreeding.
It can be inferred from paragraph 3 that adult males of some New Guinea frog species help their offspring survive by transporting them to locations where
Inference Questions推理题
Asome other animals eat the same foods that the offspring eat
Bthe offspring are already familiar with the types of predators around
Cplentiful supplies of water are available
Dfew or no other offspring from the same parents live
5
The benefits of egg attendance are best known in the Puerto Rican coqui frog. Female coquis lay eggs in a sheltered retreat within the male’s territory, and the male attends the eggs. To determine the benefits of egg attendance, Daniel Townsend and his colleagues removed attending males from some clutches (groups of eggs produced at the same time) to determine the fates of attended and unattended eggs. Unattended clutches failed more frequently than attended clutches. The main causes of mortality of unattended clutches were being eaten by other male coquis and drying out. Male coquis are important predators of the eggs of other coquis, and attending males aggressively defend their retreats from intrusion by other males. Attending males also protect their clutches from drying out.
According to paragraph 4, what is true about unattended coqui eggs?
Factual Information Questions事实信息题
AThey usually take more time to hatch.
BThey can be removed easily from sheltered retreats.
CThey can become too dry to survive.
DThey may be eaten by female coquis from other territories.
6
Most amphibians do not exhibit parental care. This observation suggests that parental care has costs to the parents that may outweigh the enhanced survival of offspring. Reduced reproductive output is one cost of parental care. Species that exhibit parental care usually produce fewer eggs per clutch than related species that do not have parental care. Furthermore, time and energy spent on parental care may limit opportunities for additional matings. Another cost may be decreased food intake for the caring parent. Parents typically do not eat when they are guarding nests or eggs, and females that remain with their clutch produce fewer clutches overall than do females that do not remain with their clutch. Reduced rates of parental survival are another potential cost of parental care. Remaining with the eggs could increase an individual’s vulnerability to predation. Because most amphibians are small and have ineffective defenses against vertebrate predators, parental care could increase the risk of the parents’ death and might not save their eggs or young.
The word “potential” in the passage is closest in meaning to
Vocabulary Questions词汇题
Aidentified
Bpossible
Ccommon
Dobvious
7
Most amphibians do not exhibit parental care. This observation suggests that parental care has costs to the parents that may outweigh the enhanced survival of offspring. Reduced reproductive output is one cost of parental care. Species that exhibit parental care usually produce fewer eggs per clutch than related species that do not have parental care. Furthermore, time and energy spent on parental care may limit opportunities for additional matings. Another cost may be decreased food intake for the caring parent. Parents typically do not eat when they are guarding nests or eggs, and females that remain with their clutch produce fewer clutches overall than do females that do not remain with their clutch. Reduced rates of parental survival are another potential cost of parental care. Remaining with the eggs could increase an individual’s vulnerability to predation. Because most amphibians are small and have ineffective defenses against vertebrate predators, parental care could increase the risk of the parents’ death and might not save their eggs or young.
According to paragraph 5, providing parental care is associated with which of the following?
Factual Information Questions事实信息题
AMore clutches produced per female
BLess danger to parents from predators
CMore food needed by caregiving parents
DFewer eggs produced per clutch
8
What circumstances would favor the evolution of parental care? We would expect parental care to evolve if a parent is able to increase offspring survival enough to offset the costs involved. If environmental conditions are harsh, or if predation pressure on the eggs or larvae is high, the benefits might outweigh the costs. There are some circumstances where the costs of parental care might be minimal. For example, cost might be minimal where parents attend offspring in hidden nest sites not readily accessible by predators. For females, if reproductive output is already limited for other reasons, the cost of parental care might be minimal. If females generally only produce one clutch per season, caring for that clutch might not reduce reproductive output appreciably. Costs might be minimal for a male if he can provide care for his offspring and at the same time defend territory and attract additional females.
The word “harsh” in the passage is closest in meaning to
Vocabulary Questions词汇题
Aunpredictable
Bsevere
Cunusual
Ddisturbed
9
Most amphibians do not exhibit parental care. This observation suggests that parental care has costs to the parents that may outweigh the enhanced survival of offspring.⬛ Reduced reproductive output is one cost of parental care. Species that exhibit parental care usually produce fewer eggs per clutch than related species that do not have parental care. ⬛Furthermore, time and energy spent on parental care may limit opportunities for additional matings.⬛ Another cost may be decreased food intake for the caring parent. ⬛Parents typically do not eat when they are guarding nests or eggs, and females that remain with their clutch produce fewer clutches overall than do females that do not remain with their clutch. Reduced rates of parental survival are another potential cost of parental care. Remaining with the eggs could increase an individual’s vulnerability to predation. Because most amphibians are small and have ineffective defenses against vertebrate predators, parental care could increase the risk of the parents’ death and might not save their eggs or young.
Look at the four squaresthat indicate where the following sentence could be added to the passage
Caring parents might experience difficulties in different areas of their lives.Insert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
10
In amphibians, any type of parental investment in offspring after the eggs have been deposited counts as parental care.
Prose Summary Questions概要小结题
Select 3 answers
AAmong the 10 percent of frog and toad species that provide parental care, there is a great variety of care involving the attending, guarding, and transporting of the eggs or young.
BThe benefits of parental care have been demonstrated in the case of the attending of eggs by male coqui frogs, but for most species the costs and benefits are unknown.
CBecause the survival rate of young is greater when the eggs and young are cared for, frogs that provide parental care do not need to have large clutches of eggs or to reproduce frequently.
DThe fact that few amphibians provide parental care suggests that the survival and reproductive costs of providing the care generally outweigh the evolutionary benefits of having more young survive.
ESince amphibian eggs lose water easily and would die if they were to dry out, covering the eggs to protect them is a major form of parental care among land-dwelling frogs.
FParental care has evolved in those frogs, coqui frogs for example, where there are few vertebrate predators, easily available food, and hiding places that parents can provide the young.
