Text Book Question

1a) Some of the consequences of having such a large population is that the demand for food will be very high, also they may dominate the food source causing other animals to have a lower number of food supplies.

1b) Allow people to hunt there geese and bring in animals that would eat geese.

2a) Some of the challenges for biologists are that when they migrate they travel very long distances and keeping up with them may be very hard. Another challenge is that because whales go underwater there are chances of have a miscount.

2b) The challenge with estimating the population of algae is due to their small size and their large number.

2c) The biggest challenge with Caribou is the environment they live in. The mountain terrain would be very difficult to estimate their population.

2d) When trying to estimate amphibians the challenges biologists run into are that they are very good at hiding and they are very fast. Another problem is that they can be very dangerous.

3a) Clumped

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1) Natality affects the increase in the population size while mortality affects the decrease in the population. immigration and emigration will affect the amount of people who come into and leave a population.

2) Density-dependent factors are those that influence population regulation, having a greater impact as population density increases or decreases. Density-independent factors are those that influence population regulation regardless of population density.

3a) Density Dependent
3b) Density independent
3c) Density independent

Applying Inquiry Skills 5. (a) density dependent
(b) The graph below illustrates what occurs when population density increases in the great tit population. As population density increases, food supply decreases. In the graph of average clutch size versus number of breeding pairs, it is evident that as the population increases (number of breeding pairs), clutch size decreases. This indicates that intraspecific competition in high. If this is the case, it makes sense that as the population increases, food decreases. There is not enough food to go around; therefore, clutch size decreases because there is not enough food to feed the young birds.

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Understanding Concepts 1. (a) Exploitative competition. As in Gause’s experiment with paramecium, one type of ant is using all the resources that another type of ant also needs, driving the second species of ant to low population levels. This would force the ants to move to a new area to find resources.
(b) Interference competition. Although plants releasing toxins does not seem like fighting, it is keeping other plants from growing in the area.
(c) Interference competition. This is actual fighting over resources and is therefore interference competition.
d) Resource partitioning. The owls and hawks feed on the same organisms, but they have evolved a method of hunting that allows both species to find enough food. Owls hunt at night and hawks hunt at day; therefore, they avoid competing with one another for resources.
2.Chthamalus barnacles are able to live throughout the entire intertidal zone, as shown by Joseph Connell when he removed
Balanus barnacles from the intertidal zone. Chthalamus’ fundamental niche is the entire intertidal zone. However, they are not able to compete with Balanus on rocks on the lower parts of the shore. Balanus crowds Chthalamus off the lower rocks; therefore, Chthamalus has a realized niche that is much smaller than its fundamental niche.
Balanus outcompetes Chthalamus on the lower rocks of the shore, but it is not able to survive in the upper areas of the shore that Chthalamus occupies. The fundamental niche for Balanus is therefore only the lower rocks of the shore, which it completely occupies. Balanus’ realized niche is the same as its fundamental niche. 3. • Pisaster is a predator of mussels. When the mussels are eaten, new rock surfaces are exposed for other organisms to inhabit. 4. Character displacement is the phenomenon of traits in a population of two species that occupy the same geographical range tending to be more divergent than traits in a population of the same species that are geographically isolated. When the two species of finch are together in the same area, they are competing for similar food sources. Rather than continuing to fight over the same resources, the species start to feed on other food sources, for instance the bird with the larger bill, Geospiza fortis, may begin to feed on larger, harder seeds, while the other species, Geospiza fuliginosa, may feed on smaller seeds. This phenomenon helps both species avoid competition, because they no longer feed on the same resources, an adaptive advantage is conferred to those birds with the large/small bills. This is similar to stabilizing selection (Chapter 12, section 12.4). The traits become more divergent because they are advantageous to the survival of the birds. However, when the birds are not on the same island, they are not competing for resources. There is no pressure to evolve a large or small bill size, so the sizes stay similar. G. fuliginosa still has a smaller bill size than G. fortis, but there is no pressure for it to become smaller still. 5. (a) camouflage (b) active chemical defence (toxins) 6. Predators quickly capture, kill, and consume their prey, while parasites feed on the bodies of their host organisms but generally do not kill their hosts. Parasites feed off the hosts but do not kill them because it would destroy their home and their food source. 7. This type of relationship is a mutualism

Chapter 14 Self-Quiz

1. True 2. True 3. False. In nature, species often exhibit clumped dispersal. 4. False. An organism facing interspecific competition always occupies its realized niche. 5. False. Similar species occupying the same niche can reduce competition by resource partitioning. 6. False. Population dynamics of predator–prey interactions show that, in the presence of a predator, prey species often decline but then rebound as predator levels decline in response to the reduced availability of prey. 7. True 8. (d) 9. (c) 10. (e) 11. (b) 12. (a) 13. (c) 14. (e) 15. (c

3. (i) random with no visible pattern, such as dandelions on a lawn (ii) clumped with areas of high and low densities, such as ant hills (iii) uniform with evenly spaced individuals, such as a cornfield 4. The quadrat method is fast and inexpensive, as it needs to be done only once. It is good for plants and slow moving small animals. It allows for multispecies sampling and is a good method for finding population sizes over a large area (as long as the total area is known). The mark–recapture method is suited to mobile animals. As it needs to be repeated, it tends to be more expensive, especially since it is best suited to one species at a time. Additionally, several conditions must be met to ensure the accuracy of mark–recapture samples. All organisms must have an equal opportunity of being captured; during the sampling period, the proportion of marked to unmarked individuals must stays constant; and the population size must remain constant. These conditions are rarely met in nature, because organisms are dying, reproducing, emigrating, and immigrating. It is very difficult to keep population sizes constant. Additionally, there is risk to the organism during mark–recapture experiments. The “mark” could cause damage to the organism and even hurt or kill it. The capturing of the animals is also traumatic. Some people are opposed to this method of sampling because of the potential harm it can cause organisms. 5. Crude density is the ratio of the entire population to the entire habitat area. However, many populations cannot use the entire habitat and are not spread evenly over it. Ecological density is the ratio of the population to the percentage of the habitat that can actually be used. For instance, the crude density of raccoons in Toronto may be 100 per hectare, but once one considers the unusable spaces (for a raccoon), such as bodies of water, the ecological density increases. 6. All habitats provide food resources for a limited number of each type of organism for a limited time. This number is the carrying capacity. This represents the maximum sustainable population for the species. The carrying capacity determines just how large a population can get before resources are used up and the population size crashes. As population size increases, the amount of resources per individual decreases. When populations change density, the new density may exceed the available amount of resources. If a population has high natality or immigration, the population may reach its carrying capacity more quickly. If the death rate or emigration is high, this may reduce the rate at which the carrying capacity is reached. 7. As resources in an ecosystem decline, population size declines as well. If food resources decline, less food is available to the population, so more starvation will occur, increasing the death rate. It may also increase emigration rates as organisms leave the ecosystem to find a new area with more plentiful resources. Similarly, if shelters are rare, many organisms may die or may not be able to reproduce (without available nests), which also decreases population size or slows the growth rate of the population. 8. The Allee effect is a density dependent phenomenon that occurs when a population cannot survive or fails to reproduce enough to offset mortality rates once the population density is too low. Populations like this generally do not survive. The most famous example of an organism that suffered the Allee effect is the passenger pigeon. 9. (a) camouflage (b) mimicry (c) toxic sting (d) camouflage 10. The loss of predators leads to a rapid increase in prey populations. This increase in prey population size can run out of control and can deplete resources for the prey population, causing a population crash and possibly extinction. 15.(a) Owls: the points show a population that rises and falls over time as measured in years. (b) Bacteria: in a lab bacteria are provided with ample food resources to support rapid population increases.

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Understanding Concepts 1. Human populations exhibit a mainly clumped distribution pattern. Humans tend to live in or around urban areas, leaving a lot of unoccupied land between high concentrations of the population. For instance, in Ontario, a huge percent of the population lives in the Greater Toronto Area, leaving much of the northern part of the province unoccupied.
2. Asia has the highest population densities. This region has a moderate climate and good water supplies. It has been inhabited for a long period to allow population growth. Additionally, most domesticated animals are from the Eurasian area, so the region had earlier access to domesticated animals, and therefore has had longer to allow population growth. 3. (a) Rice needs warm, moist conditions, with a long growing period. Rice grows best in Asia for these reasons. Wheat tolerates drier and cooler climates and therefore can be grown in places such as North America. (b) Rice is associated with high population densities, while wheat is associated with lower population densities. 4. (a) Large-scale food production allowed for an increase in the size of families and created a larger overall population size. Agriculture and livestock allowed larger population densities to be supported. (b) Large-scale food production allowed the hunter-gatherer society to stop moving around to find food. Only a small number of people were needed to tend to the farms, so many others were free to pursue other opportunities. People could pursue art or education and could become merchants. This led to urbanization and nonagricultural occupations. (c) Food production, processing, storage, and transport led to early technological advances. 5. The human populations that experienced the most rapid growth were able to spread around the globe. For instance, Eurasia had the highest number of domesticated animals and had the earliest domestication of plants, including rice and wheat. These societies were the ones that grew the fastest and were the first societies able to spread around the globe. They brought their domesticated animals and plants along with them and therefore introduced these species to new parts of the world, for instance, North America. These animals and plants were adopted into the new regions and then contributed to the rise of the new society. Europeans brought wheat, barley, and other crops, along with pigs and cattle, with them when they landed in North America. Europe had long been an established society because of their early use of domesticated plants and animals. When these species were brought to North America, they became the dominant food source for future generations.

Applying Inquiry Skills 6. (a) Corn. (b) The people were living in an isolated region. Mesoamericans had developed resistance to the pathogens that were present and therefore had a low rate of disease. When the Europeans came to Mesoamerica, they brought with them all of the pathogens that had developed in Europe. As the Mesoamericans had never been exposed to these diseases, they had no resistance to them and were therefore susceptible to them. Without resistance to the European pathogens, the population was quickly decimated by “European” diseases. 7. (a) Rice originated in China, wheat in the Southwest Asia. Wheat is currently grown in many areas of North America. North America has the cool, dry conditions needed to grow wheat. Rice is not grown in most of North America because the necessary wet and warm conditions are not generally available; the exceptions are some parts of Louisiana and California. Neither rice nor wheat is really grown substantially in Africa. Africa tends to be very hot and very dry, for the most part, and therefore does not have the conditions available to grow either wheat or rice. Africa depends on alternate crops, such as manioc, as their food source. (b) North America is a much richer region, based largely on industrial production. This has allowed North America to grow wheat in an intensive, mechanized manner. North Americans have plenty of surplus food supply. Africans have relied on subsistence agriculture, which does not allow for surpluses large enough to generate wealth.