Integrating Concepts in Biology IIAnswer Key for Sample Exam covering Chs 19-21 on Evolution of populations/ecological systems

1. (CH19) Explain why the data shown below support the hypothesis that flower color is being selected for in the plant “desert snow.” Elaborate in no more than 3 sentences and support using the data in the figures.Flower color changes across the ravine, quite dramatically. None of the other four genetic loci (those not associated with flower color) change across the ravine, as evidenced by the frequency of the most common allozyme of each, suggesting no selection at those loci. The figure on the right shows that white plants on the white side of the ravine, at least in one year, have higher reproduction than blue plants on the white side, and in a different year the opposite was true. Even though there is variation among years, this is still evidence of selection and may have led to the pattern seen in the left figure, given enough time.

2. (CH19) Use data from Data Gallery #1 to explain how natural populations contain both drab and

bright guppy males. Limit your answers to a maximum of 4 sentences.

Figure 19.3A: drab males inspect less when females are present, suggesting they hang back with the females. Figure 19.4: Females choose bold males no matter their coloration and there is not a perfect correspondence between boldness and color (FIGURE 19.3B).

3. (CH19) Use data from Data Gallery #1 to explain why someone could logically predict that only drab males would survive in a wild population. Limit your answers to a maximum of 2 sentences.

Figure 19.1 shows that timid (which is correlated with drab) fish survive longer.

4. (CH19) Does boldness depend on presence of females? What evidence do you use to support your conclusion? Use data from Data Gallery #1 to support your answer.

In the presence of female guppies, bright guppies are more likely than drab guppies to swim toward and inspect potential predators and bright guppies tend to be more bold (FIGURE 19.3).

5. (CH19) Why do drab males inspect as much as bright males in the absence of females? Use data from Data Gallery #1 to support your answer.

Drab males spent less time inspecting predators when females were present, because they spent more time near those females (FIGURE 19.3). These males may be more bold because they are paired with another male.

6. (CH19) Is boldness correlated with color? What is your evidence, and what can you conclude about the strength of the relationship? Use data from Data Gallery #1 to support your answer.FIGURE 19.3B shows a strong correlation between color index and inspection frequency. While there is a fair amount of scatter in the relationship, the P-value < 0.005, indicating a significant relationship.

7. (CH20) Of the two hypotheses constructed to explain the pattern of diversity in orchids, which is better supported? Use Data Gallery #1 to choose the data testing each hypothesis and indicate how each hypothesis is well or poorly supported by the available data. Answer in no more than 2 sentences for each hypothesis.Living in trees hypothesis is better supported than pollinator specialization.

The pollinator specialization hypothesis predicts that diversity arose through the process of specialization of pollinators. Subfamilies with higher numbers of species ought to have a lower mean number of pollinators/orchid species. The figure shows that there is not a conclusive relationship between the number of pollinator per species for a subfamily and the diversity of that subfamily. Subfamily A had the fewest number of pollinators per species but also the lowest species diversity, while subfamily E had a higher mean number of pollinators per species, and yet extremely high diversity. The hypothesis that highly specific pollinators would lead to higher species diversity is poorly supported (FIGURE 20.6).

The living in trees hypothesis predicts that the epiphytic condition of living in trees has led to diversity through an adaptive radiation. That is, an ancestral orchid evolved to live above ground and that allowed descendant species to further evolve to live in the wide variety of microhabitats that exist in the trees. The figure above on the left shows that, both among orchids and non-orchid plants, there were fewer genera with only 1 species per genus for tree-dwelling plants. There were several genera with more than 300 species per genus among the tree-dwelling orchids compared to no genera with more than 300 species for orchids on the ground. These data indicate that orchids living in trees have higher species diversity, supporting the hypothesis. The figures on the right merely show that that there are multiple microhabitats, some of which have more species, in the trees. It is not evidence for or against the “living in trees leads to diversity” hypothesis (FIGURES 20.4 and 20.5).

8. (CH20) What might be the advantage to an epiphytic plant living in any one of the microhabitats found on a large tree? What might be a disadvantage that prevents more species and individuals from surviving in the microhabitat you chose? Use data from Data Gallery #1 to support your answer.Advantage of living further out or higher up in the tree is that the epiphyte can obtain more light (FIGURE 20.4). Possessing adaptations that allow small plants to live in trees provides them with high light conditions, as opposed to being small and living in the shade on the ground. Orchids and other plants with this adaptation are able to compete successfully for light, which may be limiting in forests. Although living at the very tops of trees might provide orchids with the highest light conditions, very few species live there. The disadvantages caused by high wind conditions, extreme daily temperature variations, and lack of support from weak branches may outweigh the advantages of high light. However, living high enough to gather light but gaining protection through a strong attachment to branches or trunks appears to be of benefit to individuals and their descendants.

9. (CH20) Discuss one mechanism by which mosquitoes have been shown to evolve resistance to insecticides. Use Data Gallery #1 to choose the data that supports your answer. Explain the

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mechanism and how the data illustrate evolution of the mechanism in mosquitoes. Answer in no more than 3 sentences.There are two mechanisms that we discussed. One is the modification, through adaptation, of a detoxification enzyme, and the other is modification, through adaptation, of a target site. TABLE 20.3 shows that Tanzanian mosquitoes are more resistant to DDT than Gambian mosquitoes. When examined for the mechanism of resistance, it was found that some variants of the enzyme GST was found in greater quantities in Tanzanian mosquitoes and that some of those variants were much more active in breaking down DDT than those in the Gambian mosquitoes. This latter point is important in concluding that evolution had occurred, and was probably caused by exposure to DDT (FIGURE 20.24).

TABLE 20.4 shows that a population of mosquitoes known to be resistant to permethrin had both altered detoxification enzyme and altered target site. When the enzyme that breaks down permethrin was inhibited by PBO, there was some increase in susceptibility to permethrin. However, that can’t be the only mechanism here, as they did not become as susceptible as the susceptible population. Permethrin and DDT have the same target site (but different detoxification enzymes break them down), so demonstrating that permethrin-resistant mosquitoes were also resistant to DDT is strong evidence that the target site has been modified.

10. (CH20) Are A. gambiae from Gambia more susceptible to DDT than A. gambiae from Tanzania? What data support your conclusion? Use Data Gallery #1 to choose the data that supports your answer. TABLE 20.3 shows that Tanzanian mosquitoes are more resistant to DDT than Gambian mosquitoes. The concentration that kills 50% or 90% of the population from Gambia is much lower than the concentration that kills 50% or 90% of the Tanzanian population.

11. (CH19) Using data from Data Gallery #1, describe the evidence that evolution occurred in wild mustard due to a change in the climate. Support your answer with data and elaborate in no more than 3 sentences.Focus on the data comparing plants from 1997 to those from 2004, especially in the plants from the wet soil population. Those plants, when exposed to dry conditions in the experiment, flowered earlier and had higher survival than their ancestral plants from 1997. During the drought between 2000 and 2004, the plant population evolved. There was less of a response in the 04 to 97 comparison of plants from the dry soil site, but it was still there. Plants growing there were already adapted to dry conditions, so were pre-adapted to the drought. The changes were adaptations for surviving and reproducing in a short wet season, and we also see that the changes are heritable. All this indicates that the drought placed selective pressure on the plants, causing them to adapt through natural selection to survive and reproduce in a dry climate (FIGURES 19.10 and 19.11 and TABLE 19.1).

DATA GALLERY #1Figure 19.1 Figure 19.2

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Figure 19.3 Figure 19.4

Figure 20.1 Figure 20.2

Figure 20.3

Figure 20.5

Figure 20.4 Figure 20.6

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Table 20.3

Table 20.4

Figure 20.23

Figure 20.24 Figure 19.9

Figure 19.10 Figure 19.11

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Table 19.1

12. (CH20) What are the implications to susceptibility and resistance of differences in the mass of each GST variant? Would you predict some variants to play a larger role in resistance than others, and if so, which ones? Use Data Gallery #1 to choose the data that supports your answer.

Scientists discovered that the GST family of genes was responsible for conferring resistance to this population of mosquitoes. In the Tanzanian population, there was a greater amount of almost every GST enzyme, and some of those enzymes had much higher activity in the resistant than the susceptible population. Exposure to toxic chemicals can lead to increased expression of genes, as is evident for several variants, but the higher activity for the same variant in the Tanzanian population than the Gambian population indicates a mutation changed the allele to one that detoxifies DDT faster and may play a larger role in resistance (FIGURE 20.24).

13. (CH20) If the enzyme that detoxifies permethrin is inhibited by PBO, what would you expect to observe in the permethrin w/ PBO treatment in Table 20.4? What do you conclude regarding the mechanism of resistance in this population of permethrin-resistant mosquitoes? Use Data Gallery #1 to choose the data that supports your answer.

There was evidence that PBO inhibition led to an increased rate of mortality and shorter time for 50% or 90% mortality, which suggested that the detoxification enzyme was inhibited (TABLE 20.4).

14. (CH19) Interpret the p-values for Part A of the Figure 19.4, explaining what the p-values mean both statistically and biologically:

A p-value of 0.058 above the left pair of bars is above the cutoff of 0.05 used conventionally to reject a null hypothesis of no difference, thus we must conclude that while there may be a trend towards females choosing bright males that are simulated to be bold, we cannot conclude that females are displaying a preference here. For the right two bars the p-value is <0.01, and so we can reject the null hypothesis and conclude with pretty high confidence that females are selecting drab males when drab males are simulated to be bold and when a predator is present.

15. (CH19) Using at least one of the figures below, discuss one consequence to genetic diversity for a species that has widely distributed, isolated, numerous, or small populations. Elaborate in no more than 2 sentences and support with data.

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Populations that are small and isolated have greater genetic distance as geographic distance (Fig. 19.20) and as a consequence of that population structure, heterozygosity has decreased (Figs. 19.19 and 19.22) and alleles may be lost (Fig. 19.22). In small, isolated populations, genetic diversity often decreases through the processes of genetic drift or natural selection. Figures 19.19 and 19.20 are from the study of small plants widely distributed in the Swiss Alps, and Figure 19.22 is from the black grouse populations in Europe, where one population in the Netherlands has experienced a population bottleneck, in which alleles were lost due to random chance during a population crash. Combine that with isolation from other populations, and genetic diversity declines. The consequence of the types of population structures seen here is that genetic diversity can be lost, and that can lead to other consequences.

Figure 19.19 Figure 19.22

Figure 19.20

16. (CH20) Compare the dates of existence of Paranthropus and Homo, using the horizontal widths of the colored boxes in the evolutionary tree below, with the mammalian communities in Africa at 2 and 1.5 million years ago, shown in Figure 20.21. In what type of habitat was each of these hominid species living? Incorporate one of the following two themes of the Evolution Big Idea: Organisms can be linked by lines of descent from common ancestry, and natural selection is a mechanism of evolution that accounts for adaptation, into your answer.

Based on fossil evidence, scientists hypothesize that Paranthropus evolved about 3 MYA, followed by Homo around 2.5 MYA. The evolutionary tree shows that Paranthropus lived from approximately 2.8 to 1.3 million years ago (MYA), while Homo lived from 2.5 MYA to the present. Both coexisted for a period of time, but Paranthropus species went extinct about 1.6 MYA. Around 2 MYA, when multiple hominid species coexisted, the habitats in southern and eastern Africa included growing proportions of grazing mammals and declining proportions of tree-dwelling and fruit-eating mammals. This is evidence that the environment was changing from a more forested habitat to open grassland. If Paranthropus had evolved to live in trees or in forests, then the changing environment could have caused their extinction. Homo species might have lived in more open areas already, and when these habitats expanded as conditions became drier, these hominid species would have been favored by natural selection. Thus, a grassland environment likely favored Homo, as they survived and Paranthropus died off during this

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environmental transition. Natural selection acts as a mechanism of evolution, accounting for the adaptations (such as bipedalism and large brain).

Figure 20.21 Figure 20.20

17. (CH19) Choose three different scales-of-distance examples that illustrate a single mechanism of evolution that slows the rate of speciation. To get full credit, you must describe in general or name the species and how each figure is connected to this mechanism. Use Data Gallery #2 to choose the data that supports your answer. Limit your answers to a maximum of 2 sentences each.a. FIGURES 19.12 and 19.13: on the scale of 10s or 100s of meters this fungus can disperse to different

rotting logs. Gene flow is the mechanism that slows the rate of speciation.

b. FIGURE 19.17: on the scale of 10s of km this annual flowering plant can disperse to different geographic areas. Gene flow is the mechanism that slows the rate of speciation.

c. FIGURE 19.18: on the scale of 1000s of km, European starlings can disperse across the country. Gene flow is the mechanism that slows the rate of speciation.

18. (CH19) A loss of genetic diversity is a form of evolution. Use data from Data Gallery #2 to support your answer.a. Give one example of a bottleneck effect. Explain why bottlenecks reduce genetic diversity.

Support your answer with data. Limit your answer to a maximum of 2 sentences.

FIGURE 19.21 illustrates a bottleneck, where a population drops dramatically in abundance in a short time period. A bottleneck can be a form of genetic drift, where alleles are randomly lost from a population. TABLE 19.2 shows that genetic distance can be high when one population goes through a bottleneck compared to populations that have not experienced a bottleneck. FIGURE 19.22 shows that heterozygosity can be low and alleles can be lost in populations experiencing a bottleneck.

b. Give an example of random loss of genetic diversity that is not the consequence of natural selection. Support your answer with data. Limit your answer to a maximum of 2 sentences.

TABLE 19.2 shows that genetic distance can be high when one population goes through a bottleneck compared to populations that have not experienced a bottleneck. FIGURE 19.22 shows that heterozygosity can be low and alleles can be lost in populations experiencing a bottleneck. While not known to be subject to a bottleneck, the plant species in FIGURE 19.19 have low heterozygosity, and these populations are small and isolated. While not known to be subject to a bottleneck, the plant species in FIGURE 19.19 have low heterozygosity, and these populations are small and isolated.

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19. (CH19) How does a “bottleneck effect” contribute to evolution? Use one specific example, name the mechanism of evolution, and support your example with at least two data sets. Use data from Data Gallery #2 to support your answer. Limit your answers to a maximum of 4 sentences.

A bottleneck contributes to evolution by changing frequencies of alleles in a population, the definition of biological evolution. FIGURE 19.21 illustrates a bottleneck, where a black grouse population drops dramatically in abundance in a short time period. A bottleneck can be a form of genetic drift, where alleles are randomly lost from a population. TABLE 19.2 shows that genetic distance can be high when one population goes through a bottleneck compared to populations that have not experienced a bottleneck. FIGURE 19.22 shows that heterozygosity can be low and alleles can be lost in populations experiencing a bottleneck.

20. (CH19) Predict the genetic and evolutionary consequences for populations of plants that are pollinated predominantly by bumble bees. Now predict the genetic and evolutionary consequences for populations of plants that are pollinated predominantly by butterflies. Use data from Data Gallery #2 to support your answer.

In populations where bumblebees are the primary pollinator, you might conclude that population clusters would be small, both in numbers of individuals and area occupied. Bumble bees, once in a flower patch, fly very short distances from flower to flower (FIGURES 19.15 and 19.16). When butterflies are the pollinator, populations are predicted to be more spread out and to be more highly connected genetically, because gene flow and mating between widely separated individuals would be much more substantial due to higher flight distances between flower visits (FIGURES 19.15 and 19.16).

DATA GALLERY #2Figure 19.13 Figure 19.12

Figure 19.18 Figure 19.19

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Figure 19.7 Figure 19.5

Figure 19.6 Figure 19.17

Figure 19.15 Figure 19.16

Figure 19.20

Table 19.2

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Figure 19.21 Figure 19.22

Figure 21.3 Figure 21.2 Figure 21.4

21. (CH21) What are two adaptations in yucca moths which may have been selected for by yucca plants? Support your answer with data from Data Gallery #2 and elaborate in no more than 2 sentences per adaptation.

The adaptations that you identify must be adaptations that are beneficial to the plant. They would probably also be beneficial to the moth, too, but you must discuss from the plant’s perspective. Adaptations that are acceptable include the moth’s habit of pollinating after laying an egg (laying an egg first as an adaptation is not acceptable). Pollinating after egg-laying is shown in the positive correlation in the middle figures below – this positive correlation suggests that moths that lay more eggs also pollinate more. This benefits the plant and the moth. It is beneficial to the yucca plant, which ultimately produces more fruits and more viable offspring when pollinated with lots of pollen, especially from other plants. Other adaptations include moths flying immediately after collecting pollen. That is one that directly benefits the plant, as it helps prevents self-pollination and facilitates spreading of pollen to other plants. Pollinating unvisited flowers more than visited flowers also benefits the plants, as moths have a limited supply of pollen, so they would both benefit by pollinating only when necessary (FIGURES 21.2-21.4).

22. (CH21) Coevolution is not uncommon, but it is difficult to document. a. Give one example of diffuse coevolution and support your answer with data from Data

Galleries 2 or 3. Limit your answers to a maximum of 3 sentences.

TABLE 21.1 shows the changing nutritional value of fruits that are dispersed by birds. In both cases there are multiple species involved and the trees as a group change the nutritional status of their fruits as the seasons changes, reflecting what the birds need at certain times of the year (energy or water, e.g.).

b. Give one example of pairwise coevolution and support your answer with data from Data Galleries 2 or 3. Limit your answers to a maximum of 3 sentences.

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There are a couple of choices here, including the yucca moth and yucca plant or newts and garter snakes.

In most cases there is one or only a couple of species on each side of the interaction, although sometimes several yucca moths will interact with one yucca plant species or several plant species may interact with one or more yucca moth species. FIGURE 21.2 shows that moths have behaviors that benefit the plant – they are likely to pollinate a flower if they detect it has not been visited by another moth, for instance. They also have behaviors that benefit themselves – they lay an egg first, and often only lay one egg and then leave without pollinating a flower (FIGURE 21.3). But if they lay multiple eggs on a flower they often usually pollinate at least once. If they don’t possess pollen already there is a high likelihood they will collect pollen and then once collected, will immediately leave (FIGURE 21.4). Large pollen loads from non-self lead to higher fruit retention and germination frequency, relative to pollen from self (FIGURES 21.5 and 21.6).

FIGURE 21.7: Snakes that consumed a newt and did not survive had lower resistance than snakes that consumed a newt and survived. This would lead to natural selection against snakes with lower resistance – coevolution in action, as newts in areas with populations of snakes that have higher resistance, on average, might evolve to have higher levels of tetrodotoxin. Even when exposed to newts from a population with generally higher levels of tetrodotoxin, some garter snakes ought to be able to resist those higher levels, and some of those newts may have below average levels of tetrodotoxin. Garter snakes with higher resistance could handle a much longer exposure to toxic newts and could survive after eating a newt. For snakes that both consumed and rejected newts, recovery time seemed to be a function of exposure time. The longer a snake was exposed to a newt, the longer it took to recover from the exposure to tetrodotoxin.

23. (CH21) How does variation in resistance to tetrodotoxin affect the ability of garter snakes to utilize rough-skinned newts as prey? Support your answer with data from Data Gallery #3 and elaborate in no more than 2 sentences.

FIGURE 21.7: Snakes that consumed a newt and did not survive had lower resistance than snakes that consumed a newt and survived. This would lead to natural selection against snakes with lower resistance. Even when exposed to newts from a population with generally higher levels of tetrodotoxin, some garter snakes ought to be able to resist those higher levels, and some of those newts may have below average levels of tetrodotoxin. Garter snakes with higher resistance could handle a much longer exposure to toxic newts and could survive after eating a newt. For snakes that both consumed and rejected newts, recovery time seemed to be a function of exposure time. The longer a snake was exposed to a newt, the longer it took to recover from the exposure to tetrodotoxin.

24. (CH21) Summarize why coral with algae is an example of mutualism and not pathology or parasitism. How do endosymbiotic algae enter their coral hosts? Support your answer with data from Data Gallery #3 and elaborate in no more than 3 sentences.

Coral are not born with their symbiotic algae. Coral larvae eat the algae, some of which move from the digestive system to inside animal cells of their new hosts (Figure 21.9). The algae supply their animal hosts with energy derived from photosynthesis. The coral animal captures microscopic prey with their tentacles, and they share the consumed nutrients with their symbiotic algae. Algae are unicellular photosynthesizers that capture sunlight for energy and contain a range of different pigments that

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provide them with many different colors (Figures 21.8D and 21.9F). The photosynthetic pigment called chlorophyll fluoresces red when stimulated by UV light.

25. (CH21) Describe differences in the induction of photosynthesis response among plants. Explain why understory shrubs responded the way they did and how it relates to light availability patterns. Support with data from Data Gallery #3 and elaborate in no more than 3 sentences.FIGURES 21.15 and 21.16: The amount of light available to the various rainforest plants affected their response to the simulated pattern of light. The shrubs that live beneath trees in the forest understory had a higher percent induction after being kept in the shade before being exposed to bright light flashes. After 1 minute, these plants had achieved a higher percentage of their maximum photosynthesis rate than the other plants. In addition, their efficiency of use of these light flashes was extremely high. These are good adaptations for plants living mostly in the shade and exposed to brief, but frequent, flashes of bright light throughout the day. These plants and the plants living in the forest edge had somewhat similar responses as the time in low light increased (Figure 21.15B). The plant that lived in clearings did not respond well to light flashes and would not be predicted to in the understory or in shady areas because of its lower induction and light use efficiency. Plant distributions, or where plants are found, are affected by the adaptations that plants have to the amount and pattern of light available.

26. (CH21) The best working hypothesis for global coral bleaching is increased water temperature. Use one example of correlational data and one example of causal data that support the hypothesis that warm water is causing coral bleaching. Support your answer with data from Data Gallery #3 and elaborate in no more than 3 sentences.a. correlation: Figure 21.11 is correlational data that show that warmer sea surface temperatures are

associated with higher percentages of bleached coral cells.

b. causal: TABLE 21.3 shows that algal symbionts have altered photosynthetic capacity when exposed to different temperatures.

Data Gallery #3Figure 21.8 Figure 21.9

Figure 21.10 Figure 21.11

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Figure 21.12 Figure 21.13

Table 21.3

Figure 21.14 Figure 21.15

Figure 21.16 Figure 21.17

Table 21.4

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Figure 21.18 Figure 21.19

Figure 21.20 Figure 21.21

Figure 21.22 Figure 21.7

Figure 20.16 Figure 20.18

Table 21.1 Figure 20.19

27. (CH20) Analyze the evolutionary tree and the pattern of presence and absence of the three introns studied by Qui and colleagues. Which group is more closely related to land plants, green

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algae or red algae? Which group of bryophytes—liverworts, mosses, or hornworts—is most closely related to the algae? What evidence did you use to come to your conclusion?

Figure 20.15

Green algae are more closely related to land plants as suggested by the closer branching of the green algae lineage to the land plant lineages. Liverworts seem to be most closely related to algae, based not only on the branching pattern of the evolutionary tree but also based on the intron pattern, which is the same for both liverworts and algae.

28. (CH21) Populations must adapt to their environment as it changes. Support your answer to the following with data from Data Gallery #3.a. Give one example of plants that exhibit diffuse co-evolution. Support your answer with data.

Limit your answer to a maximum of 3 sentences.

Fruit trees may exhibit diffuse co-evolution with their bird dispersers. TABLE 21.1 shows the changing nutritional value of fruits that are dispersed by birds. In both cases there are multiple species involved and the trees as a group change the nutritional status of their fruits as the seasons changes, reflecting what the birds need at certain times of the year (energy or water, e.g.).

b. Give one example of an animal species that has evolved adaptations to a habitat that experiences frequent disturbances. Support your answer with data. Limit your answer to a maximum of 2 sentences.

The two mussel species in FIGURES 21.21 and 21.22 have different strategies for dealing with disturbances. The large, heavy California mussel release gametes throughout the year (FIGURE 21.20), has a higher shell weight per shell length than the blue mussel, and this allows the California mussel to live in a zone of the intertidal that is subject to more disturbance and predation. The large thick shell makes it more difficult for starfish and snails to prey upon it and waves to break it apart.Populations of blue mussels that live lower down in the intertidal zone are subject to more disturbance, predation, and competition. But access to more food resources may allow them to grow faster when submerged below the high tide. The blue mussel releases gametes once a year, spawning in the winter and early spring, which may also be a strategy for living in this area of frequent disturbance; the larvae may have a better chance of survival in the cooler winter and spring temperatures. Larvae settle on unoccupied rocks in winter, and because they grow more quickly than the California mussel at equal height above the tide, early on in development they have a good chance of maintaining themselves at least until they can reproduce once.

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