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Population and Community Ecology
Terms in this set (42)
Which of the following is an example of a population of organisms?
o all of the students in a classroom
o all of the plants in a garden
o all of the animals in a zoo
o all of the plants and animals in a rainforest
All of the students in the classroom, because a population must consist of the same type of organism.
All of the following explain a clumped distribution of individuals in a population except
o soil nutrients available to a species of plant.
o territoriality in a species of bird.
o oxygen levels in a pond, where an oxygen-dependent bacterial species lives.
o food availability for humans living in a certain geographic area.
Territoriality in a species of bird.
What type of distribution pattern describes the evenly spaced distribution of stalks of corn planted in an agricultural field? (clumped, random, or uniform)
Birds tend to have which type of survivorship curve? What type usually describes humans and other animals?
Birds tend to have a type II survivorship curve, humans and other animals have a type I survivorship curve.
How do ecologists measure population size?
They sample a representative portion of each habitat and use the sample to make inferences on the population as a whole.
Name and define three patterns of population distribution
Population distribution can be clumped, uniform [evenly spaced], or random.
Name and define three survivorship curves, then provide an example of population that matches each one.
Type I curve; mortality is low in the early and middle years and occurs mostly in older individuals. Organisms exhibiting a type I survivorship typically produce few offspring and provide good care to the offspring increasing the likelihood of their survival. Humans and most mammals exhibit a type I survivorship curve.
Type II curve; mortality is relatively constant throughout the entire life span, and mortality is equally likely to occur at any point in the life span. Many bird populations provide examples of an intermediate or type II survivorship curve.
Type III curve; In type III survivorship curves, early ages experience the highest mortality with much lower mortality rates for organisms that make it to advanced years. Type III organisms typically produce large numbers of offspring, but provide very little or no care for them. Trees and marine invertebrates exhibit a type III survivorship curve because very few of these organisms survive their younger years, but those that do make it to an old age are more likely to survive for a relatively long period of time.
What is a population?
a group of individuals belonging to the same species, living in the same geographical area
What is a community?
is composed of many different species living in an area
What is a demography?
The statistical study of populations; it is the statistical study of population changes over time: birth rates, death rates, and life expectancies. These population characteristics are often displayed in a life table.
What is a life table?
Life tables detail the life expectancy of individuals within a population and are a mathematical tool designed to describe populations and investigate how they change.
What is the difference between population size and population density?
Population size is the total number of individuals in a population, while population density is the number of individuals per. unit area.
Are population density and organism mass proportional or inversely proportional?
They are inversely proportional, because smaller organisms tend to be more densely dispersed whereas larger organisms are more sparsely dispersed. For example, a lot of ants can exist in one area [small], but you wouldn't find the same amount of bobcats in the same area [large].
What is a quadrat and when is it used?
A quadrat is a wood, plastic, or metal square that is randomly located on the ground and used to count the number of individuals that lie within its boundaries. To obtain an accurate count using this method, the square must be placed at random locations within the habitat enough times to produce an accurate estimate. This counting method will provide an estimate of both population size and density. The number and size of quadrat samples depends on the type of organisms and the nature of their distribution. It is used for very small or slow-moving organisms.
What is the mark and recapture technique and when is it used?
This is used for smaller mobile organisms. This method involves marking a sample of captured animals in some way and releasing them back into the environment to mix with the rest of the population; then, a new sample is captured and scientists determine how many of the marked animals are in the new sample. This method assumes that the larger the population, the lower the percentage of marked organisms that will be recaptured since they will have mixed with more unmarked individuals. For example, if 80 field mice are captured, marked, and released into the forest, then a second trapping involving the capture of 100 field mice shows that 20 of them are marked, the population size (N) can be determined
What equation is used to determine the population size when using the mark and recapture technique?
[number marked first catch x total number second catch]/number marked second catch = N
What is a survivorship curve?
a graph of the number of individuals surviving at each age interval versus time
What type of growth is represented by a "J curve?" Which looks like an S curve?
Exponential growth is represented by a J curve. An example of exponential growth is bacteria doubling by binary fission. A graph of the logistic growth equation will give us an S-curve.
In the population growth equations, how is "r" calculated?
B [birth rate] - D [death rate] = r. R can be positive, negative, or 0. It is used in the equation population growth = rN to calculate pop. growth.
In the logistic growth equation, what is "K"?
K is the carrying capacity, which is the maximum population size an environment can sustain. It is used in the equations K-N = the number of individuals that may be added to a population at a given time and [K-N]/K = the carrying capacity available for further growth. Note that N is population size. The LOGISTIC GROWTH EQUATION IS: Population Growth = rN [(K-N)/K]
Give an example of a density-independent factor.
Affects the size of the population regardless of how many individuals ex. Fire, freezing weather, pesticides etc.
Define intraspecific competition. Is it a density-dependent or density-independent factor?
The resulting competition for resources among population members of the same species. It is density dependent, because the density of the population affects the growth and mortality rate.
Explain the characteristics of and differences between exponential and logistic growth patterns
Exponential and logistic growth patterns both use deterministic equations to describe the rate of change in the size of a population over time and neither account for random factors. Exponential growth is a scenario in which resources are unlimited, while logistic growth accounts for an environment's carrying capacity.
Give examples of exponential and logistic growth in natural populations
Bacteria multiplying via binary fission. Sheep are an example of logistic growth, because the population grows and exceeds the carrying capacity for a short period of time, and then falls beneath the carrying capacity over and over again.
Give examples of how the carrying capacity of a habitat may change
A fire might burn a lot of the plants that were used as shelter or food. A drought might make water scarce.
Compare and contrast density-dependent growth regulation and density-independent growth regulation, giving examples of each
A DD would be intraspecific competition [comp. with other species], interspecific competition [competition in the same population], parasites, and predation. DI would be earthquakes, wildfires, drought, and pollution.
What are k-selected species?
are adapted to stable, predictable environments. Populations of K-selected species tend to exist close to their carrying capacity. These species tend to have larger, but fewer, offspring and contribute large amounts of resources to each offspring. Elephants would be an example of a K-selected species
What are r-selected species?
are adapted to unstable and unpredictable environments. They have large numbers of small offspring. Animals that are r-selected do not provide a lot of resources or parental care to offspring, and the offspring are relatively self-sufficient at birth. Examples of r-selected species are marine invertebrates such as jellyfish and plants such as the dandelion.
At the start of 2015, approximately how many humans were on the planet?
It was well over 7 billion.
What sorts of advances during the last century have led to the extreme exponential growth of human beings on Earth?
They've created shelters, domesticated animals, developed agriculture, developed language to communicate, migrated to new areas, and developed public health the survive in greater numbers and live longer.
How have humans expanded the carrying capacity of their habitat?
Advancements in science and using fossil fuels have given us more resources.
How does the economic level of countries impact the population growth and age structure?
Underdeveloped countries have rapid growth [a pointy triangle] because old people don't live long and there is a high birth rate, but with infant mortality being high, the largest population is young adults of reproductive age. Developed countries can have a slow growth model, with a regular shaped triangle, so less young breeders and more old people. Very developed countries that have a 0% population growth, like Italy, is conical, with more middle-aged and elderly people. A decreasing has a conical curve but at the bottom juts in on both sides, like the corners were cut.
What are the implications of long-term unchecked human population growth?
Famine, disease, and large-scale death; as well as social consequences like increased crime.
What is age structure?
the proportion of a population in different age classes. Models that incorporate age structure allow better prediction of population growth, plus the ability to associate this growth with the level of economic development in a region.
Why is the Pisaster ochraceus sea star considered to be a keystone species in the intertidal habitat?
A keystone species is one whose presence has inordinate influence in maintaining the prevalence of various species in an ecosystem, the ecological community's structure, and sometimes its biodiversity. Pisaster ochraceus, the intertidal sea star, is a keystone species in the northwestern portion of the United States (figure 14D-11). Studies have shown that when this organism is removed from communities, mussel populations (their natural prey) increase, which completely alters the species composition and reduces biodiversity.
What are pioneer species?
The first species to populate an area
What is the predator-prey cycle?
This cycle is based on trapping data from the past 100 years in North America. The lynx, predator, population goes up into response to a larger hare population. They increase in lynxes causes the hare population to drop. The lack of hares to eat causes the lynx population to drop, and, because there aren't as many predators, the hare population flourishes, and the cycle starts anew.
Name four examples of defenses against predation and herbivory and define each.
There are four defenses; mechanical, chemical, physical, or behavioral.
Mechanical defenses are like physical barriers that protect prey from predators. Examples include armor on animals and thorns on plants.
Chemical defenses are when plants or animals produce compounds that discourage predation. Examples include the toxic compounds in foxgloves and animals that are toxic use warning coloration to ward off predators, such as the monarch butterfly and fire-bellied toad.
What is the competitive exclusion principle?
The competitive exclusion principle states that two species cannot occupy the same niche in a habitat: in other words, different species cannot coexist in a community if they are competing for all the same resources.
Name three examples of symbiotic relationships between species.
Symbioses may be commensal, in which one species benefits while the other is neither harmed nor benefited; mutualistic, in which both species benefit; or parasitic, in which the interaction harms one species and benefits the other.
What is community structure and succession?
Succession describes the sequential appearance and disappearance of species in a community over time after a severe disturbance. In primary succession, newly exposed or newly formed rock is colonized by living organisms; in secondary succession, a part of an ecosystem is disturbed and remnants of the previous community remain. In both cases, there is a sequential change in species until a more or less permanent community develops.
What are foundation species?
Foundation species are considered the "base" or "bedrock" of a community, having the greatest influence on its overall structure. They are often primary producers, and they are typically an abundant organism. For example, kelp, a species of brown algae, is a foundation species that forms the basis of the kelp forests off the coast of California.
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