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33 Cards in this Set
- Front
- Back
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From 1860 to 1991, the human population _____ in size and the energy consumption increased ____ - fold. |
Quadrupled; 93 |
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How many people do we add to the population every 13 years |
1 Million
Recall that in 1825, we only had 1 billion people |
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Describe each type of survivorship curve and give examples of organisms that fall within each curve type. |
Type I: Most organisms live to an old age bc offspring are very well cared for
Type II: Constant mortality rate
Type III: Example: Oysters; Rapid death when young, but if they survive for long enough to produce a hard shell, they will live |
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In which scenarios can survivorship curves vary? |
*Within populations *Between sexes *Among cohorts that experience different environmental conditions |
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Discuss the components of age structure. |
*Uses charts to show how many individuals of each age are present in a population *The number of individuals at reproductive age can predict future population growth *Age structure does not change - environmental factors can alter the survival rates or fecundity and can change the population rate, however *Can be used to determine where to increase survival rates in certain species *For example, to protect a species of turtles, scientists originally thought to protect them at the tadpole stage. In reality, life tables suggest that the best area of protection is juvenile and adult stages (likely that these areas faced the highest mortality levels) |
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This is a type of growth that occurs when a population reproduces in synchrony at discrete time periods and growth rate DOES NOT CHANGE. Increases by constant proportions but the number of individuals added is larger every time.
Ex: N*2 each time N = 1 N = 2 N = 4 N = 8 N = 16 |
Geometric Growth |
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This type of growth is occurs when a population reproduces continuously and the generations may overlap.
Ex: N^2 every time N = 2 N = 4 N = 16 N = 256 N = 65536 |
Exponential growth |
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Explain exponential growth using this equation:
dN/dT = rN
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This equation allows you to calculate the growth rate and/or number of individuals that will be added to a system. It does not factor in limiting factors. The rate of the change in population size at each instant in time (dN/dT) determines the growth rate times each individual in the system currently. Exponential growth CANNOT continue indefinitely.
When: r = 0, there is no growth r < 0, N will decrease and pop. will possibly go extinct r > 0, N is increasing |
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Describe density independent and density dependent factors and how they affect population growth. |
Density independent -tornadoes, temperature extremes, floods, etc. -Can kill random organisms in a population, leaving only non-reproductive organisms or only one sex (Demographic stochasticity)
Density dependent -Lack of resources (food, water, space), competition, disease, parasitism, predation, disease -Density dependent factors encourage growth when density is low and population decrease when density is high -High population densities mean that food, space, and/or other resources are in short supply, forcing a decrease in N (organisms die because the environment can no longer support them. K has been reached.)
**** Death rates will increase as density increases. r will eventually equal zero when K is reached, and the population will stop growing. If r gets below zero, the population will begin to decline. |
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What are some behavioral population regulators? |
-Mating dances/rituals that encourage more species to enter a particular area -Competition -Winners will stay -Losers will leave the area and disperse to an area of lower competition
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Explain logistic growth with the below equation: |
This equation is the same as the exponential growth equation, only this equation factors in limits (Carrying capacity, uninhabited areas, etc.) The population will increase rapidly (exponential growth), then stabilize at a carrying capacity (K), which is the maximum population size that can be supported "indefinitely". At the carrying capacity, the growth rate equals zero. Assume that dN/dt declines as N increases. At low densities, logistic and exponential growth will be similar.
1-N/K is also referred to as the "unused portion of K", because when N < K, there is unoccupied space within the possible living space. There are several reasons that an organism may not occupy these areas, such as the inability to reproduce (biologically incapable, not enough mates, fellow organisms are all the same sex as you), competition keeps them out of the area, predators keep them out of the area, or the organisms simply cannot find the area, possibly because it is too small or there is a physical barrier. |
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Why would a carrying capacity (K) be exceeded? |
When resources are scarce, K is maintained. However, an unexpected event can occur, increasing the amount of resources previously available to the area. For example, a whale dies and falls to the bottom of a certain area. Benthic detritivores and scavengers suddenly have a lot more food and K will skyrocket. If a system exceeds its carrying capacity, there will not be enough resources to support that many organisms, so deaths will occur as a result. There will be an ebb and flow around the K Selective pressures will favor organisms that can survive in low resource conditions. The more fit organism will survive.
Note that K is assumed to be constant. At k, births and deaths are equal. This happens rarely, and because births and deaths vary over time, we expect K to fluctuate. |
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If the world used resources like the US uses resources, the K would be _____
If the world used resources like India used resources, the K would be ____ |
1.3 billion; 14 billion |
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Describe the ecological footprint system. |
The "Ecological footprint" is the total area of productive ecosystem that is required to support a population. It uses data on agricultural productivity, production of goods, resource usage, N, and pollution. It can be used to estimate the area required to support these activities. |
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Ecologists once predicted the carrying capacity of earth. Humans have currently exceeded that prediction by 40%. Give at least three examples of how humans have been able to increase the global carrying capacity. Also provide at least two possible explanations as to why the population is still increasing, even though the world growth rate is declining. |
Humans have been able to increase the global carrying capacity by increasing agriculture (we are better at feeding ourselves. Animals have been domesticated and used for farming.), increasing medical technology (vaccines prevented us from dying from dumb stuff), increasing sanitation practices (creating sewage systems), being able to live more comfortably in less space (heating, air conditioning, planes to increase transportation). Some possible explanations as to why the growth rate has decreased is that we have less of a economic need for kids. Since most lifestyles do not require more kids for more farming, we simply do not need them. Kids do not start bringing in money until much later in life. Women are choosing a second career over staying at home and having more kids. Birth control accessibility is preventing more unwanted children. |
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Explain population dynamics created by the introduction of Mnemiopsis leidyi to the Black Sea. |
The comb jelly (Mnemiopsis leidyi) was introduced into the Black Sea accidentally. The Black Sea was already "in trouble" because nutrient inputs caused Eutrophication (excess nutrients causing excessive plant growth). Phytoplankton populations were increased because zooplankton were being eaten (their population crashed), and the decreased predation of phytoplankton resulted in their increase. The increased amount of phytoplankton decreased the water clarity. The dead phytoplankton provided food for aerobic decomposers who used up LOTS of oxygen. Oxygen concentrations began to decrease from not enough light being able to penetrate the water. The lack of oxygen resulted in a massive die off of fish. Mnemiopsis can reproduce VERY quickly and continues to feed even when its full, then spits out a mucus ball. The population EXPLODED. The area later recovered when a different type of comb jelly arrived that ate Mnemiopsis.
Recall this equation: Nt + 1 = Nt + Births - Deaths + Immigrants - Emigrants |
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Explain delayed density dependence |
Delayed density dependence causes populations to fluctuate in size. These are delays on the effect that density has on population size. Fluctuations in N, growth rate, and chance events can affect a population's risk of extinction. The number of individuals born in a given time period is influenced by population densities present several time periods ago. |
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____% of the populations with less than 10 breeding pairs went extinct. ____ extinctions occurred in populations with over 1000 breeding pairs. |
39; 0
Bottom Line: Extinctions are much more common in small populations. Chance events (genetic, demographic, environmental can play a role in extinctions) |
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These are chance events that influence which alleles are passed. How does this impact small populations? |
Genetic Drift -Reduced genetic variation reduces the ability of populations to respond to environmental change -Harmful alleles occur in high frequencies -High frequency of inbreeding |
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Explain different types of stochasticity and give examples of each. |
Demographic stochasticity - chance events that affect survival and reproduction of individuals Ex: In populations of 10 individuals, a storm wipes out 6 of the 10. A 40% chance of survival may be MUCH lower than the average rate for that species and the survivors may all be post-reproductive, or all one sex. For larger populations, the risk of extinction from demographic stochasticity is very low. The allee effect comes into play here, and at low densities, individuals of some species may have difficulty finding mates or engaging in breeding behaviors, so the growth rate decreases as the population density decreases, making an already small N even smaller. Although the birth and death rates would other wise be constant, age or gender of individuals in a population will influence success and survivorship, which can be predicted by age structure charts indicating the number of species remaining at each age.
Environmental stochasticity is when changes in the average birth or death rates from year to year occur as a result of environmental changes. Example: Weather, disease, competition, predation, anything external.
Natural catastrophes can eliminate or greatly reduce even large populations and play a role in extinction. For example: a subspecies of hen was reduced to one population out of a previous fifty when a series of bad weather, fires, diseases and predators drove most of these populations to extinction. |
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Explain what metapopulations are. Be sure to include source and sink populations and Levin's meta population work focuses, as well as habitat fragmentation. |
For many species, suitable habitat space exists in a series of spatially isolated patches, resulting in isolated populations. A metapopulation is a set of spatially isolated subpopulations linked by the dispersal of individuals or gametes, characterized by repeated extinction and colonization of the individual subpopulations and overall metapopulation persistence. In a source population, births will exceed deaths. In a sink population, deaths exceed births, and will eventually become extinct unless this area is "rescued". For a metapopulation to persist, the extinction/colonization rates must be greater than one. Some patches will be occupied as long as the colonization exceeds the extinction rate, otherwise all populations within the metapopulation would go extinct.
Levin's metapopulation work focused on factors that influenced the patch, the importance of the spatial arrangement, the landscape between the patches, and whether or not the empty patches were actually suitable habitats.
Habitat fragmentation occurred in which large patches of habitat were convered into isolated patches, resulting in a metapopulation structure. As patches get smaller, they can become more isolated from one another, reducing the rate of colonization and therefore extinction. There are two types of isolation created by habitat fragmentation: isolation by distance (habitats are too far apart) and isolation by patch size: (patches may be too small and hard to find; high extinction rates bc they are not saved).
The "rescue effect" is when a patch near an occupied patch repeatedly receives immigrants. A high rate of immigration protects the population from extinction.
Nonrandom factors may affect metapopulations. With pool frogs, over time, some ponds will fill in with sediment and vegetation, shrinking the pond and increasing extinction. |
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Explain the difference between bottom up and top down control. |
Bottom up control occurs from a lower trophic level to a higher trophic level. Population abundance is driven by primary [roducers and nutrients. Increased nutrients induces lots of plant growth. There is increased phytoplankton biomass, which are eaten by aerobic organisms. These organisms use up a lot of oxygen, leaving a reduced amount for fish, causing them to die.
Top down control occurs from higher trophic levels to lower trophic levels. Top predators drive abundance of populations. For example: Overfishing results in top predators being removed. Plankton-eating fish then increase because they are not being eaten. Zooplankton decrease because they are consumed by the non-eaten fish. Phytoplankton increases because zooplankton are not there to eat them. |
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Why do some plants eat animals? |
Plant competition can be intense where soil nutrients are scarce, so organisms find nutrients elsewhere so they do not have to compete for that particular resource. Carnivory in plants evolved in nutrient-poor environments (unconfirmed?) For example, noncarnivorous competitor plants were removed from areas near pitcher plants, and their growth rates increased. Some pitcher plants were covered to prevent prey capture, but that did not reduce their growth rate. It was later discovered that pitcher plants will compete for light, but not soil nutrients. Low light means little growth, so few nutrients are needed, and little prey has little effect. High light means that more nutrients are required to grow more, so more prey must be consumed. |
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This is an interaction between individuals in which each is harmed by their shared use of a limiting resource. Explain four types of this. |
Competition
Interspecific competition - Interactions between two different species in which each is harmed when they both use the same limiting resource
Intraspecific competition - as above, but in a single species
Exploitative competition - Species compete indirectly and reduce the availability of a resource as they use it. For example: Resources used by pitcher plant are unavailable for use by the other species because they have already been exploited
Interference competition - Species compete for direct access to a resource. Individuals may perform antagonistic actions (2 predators fighting for 1 prey item)
Recall that resources are environmental features that can be consumed to the point of depletion - food, water, space, etc.
Physical factors are NOT consumed and are not considered resources, such as temperature, pH, and salinity
Competition reduces resource availability and it intensifies when resources are scarce. Competition effects are often unequal/asymmetrical and one species is harmed more than another, often resulting in extinction of the less successful one |
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If the ecological niches of competing species are very similar, the superior competitor may drive the other species to extinction. Explain the principle relating to this concept, and how this is handled in nature. |
The competitive exclusion principle states that two species that use the same limiting resource in the same way CANNOT coexist for a long period of generational time. This is resolved/handled through resource partitioning, in which species using a limiting resource coexist by using said resource in a different way. For example, red and green cyanobacteria and their use of light. They can survive when grown alone. When they are grown together, one will drive the other to extinction, depending on the wavelength of light they are grown in. Red will grow best in clear water and green will grow the best in turbid waters. Both will grow in intermediate water because they can partition the light resource, and both will grow under white light because it contains all wavelengths. |
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Sometimes an interior competitor in one habitat can become the superior competitor in another. Explain what this is called and how it occurs. |
Competitive reversal; disturbances such as fires and storms will kill some and create opportunities for others (consider disaster taxa). Forest plants that require sunlight are found only where the canopy has been damaged. As trees recolonize and create shade, the plants requiring sunlight will die. These are called fugitive species because they must disperse as conditions change, much like fugitives. |
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Natural selection can influence morphology of competing species and result in character displacement. Explain this. |
Phenotype, including behavior, of competing organisms will become more different over time. Differences between species whose distributions overlap geographically are accentuated where the species coexist (organisms evolved over time to increase survival chances) but are minimized in areas where the species do not overlap. |
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Most predators have broad diets (generalized) and most herbivores have more relatively narrow diets (dietarily specialized). Orgnaisms have evolved a wide range of adaptations that help them obtain food and avoid being eaten. Recall that feeding on other organisms is ALWAYS exploitative. Explain types of predation. |
Some organisms forage through their environments. Others are sit and wait predators that stay in one place until prey are close. Some will ambush. Sessile animals and carnivorous plants do this because they cannot move, but will nab prey. Some species will go to areas where prey are abundant and eat basically anything, and some will form a "search image" of what they want to eat. Predators exert strong selective pressures on their prey, and if they do not have strong enough defenses, they will die before they reproduce. |
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List some adaptive techniques and how they help a species to defend itself. Give at least 3 examples of each. (Physical, behavioral, plants, predator adaptations) |
Physical: -Large size scares smaller predators (elephants) -Rapid movement makes them harder to catch (gazelles) -Body armor protects the interior or can physically harm a predator (sea urchins) -Warning coloration makes them appear more dangerous than they actually are (poison dart frogs) -Camouflage to remain unseen (rabbits) -Mimicry to appear toxic or like a predator
Behavioral: -Not foraging in an open area to avoid predators -Keeping lookouts to alert the rest of the pack -Creating defensive circles to protect the young in the middle
Plants: Masting - releasing a LOT of seeds one year, then none in the next to force predators to relocate or die -Compensation - grow when they are eaten -Structural - growing tough leaves, spines, thorns, saw-like leaves, nearly invisible piercing hairs -Induced -produced post-attach (cacti form more spines) Chemical - Produce toxins that deter predators -Produce scents that attract predators that eat/hurt herbivores (Tobacco does/has both that are induced)
Predators: -Can counter prey adaptations -Using smell or touch to detect a camouflaged prey species -Subdue prey with venom -Use mimicry -Detoxify or tolerate toxins that prey species use -Herbivores have digestive systems that can tolerate toxins -Careful eating to avoid pressurized toxin release (beatles)
ALL Exploitative interactions have the potential to reduce prey growth, survival or reproduction |
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Recall the Paine experiment |
1974 Removed starfish predators from Rocky Intertidal Zone which led to the extinction of large vertebrates except one mussel species. When the starfish predator was present, inferior competitors persisted (inferior competitors, not inferior species) |
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Give examples of mutualism. |
-Fungus growing ants cultivating fungus 50 million years before human farmers. Ants nourish, protect and eat fungus they grow, forming a +/+ relationship with them. The ants cannot survive without the fungus and the fungus cannot survive without the ants. The benefits outweigh the costs. The ants scrape protective wax off of plants that the fungus wants to penetrate, and the fungus digests and detoxifies plants used to deter the ants.
-Mycorrhizae - roots and fungus interaction. The fungus increases the surface area to allow the plant to absorb more nutrients and water, protect the plant from pathogens by forming a protective layer around the roots, and improve the plant's growth and survival. The plant produces carbs to feed the fungus. |
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Recall the different types of species/species interactions. |
Mutualism (+/+) -Obligate mutualism - MUST OCCUR for both of the organisms to survive -Facultative -Only necessary for ONE organisms to survive (Adult plants shade other plants causing cooler, moister conditions. The seeds can only germinate in the shade. *When deer eat seeds and poops them out, the seeds are dispersed
**Trophic mutualism - mutualist receives energy or nutrients from the partner (mycorrhizae, ants and fungus)
**Habitat mutualism - one partner provides the other with shelter, living space, favorable habitat (desert plants) ***** NOT ALTRUISTIC***
**Service mutualism - one partner performs an ecological service for the other (Deer dispersing seeds, increases distribution)
Commensalism (+/0) Parasitism (+/-) |
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Give an example of commensalism: |
Lichens that grow on trees Bacteria on the skin Kelp forests - used as habitat with no damage to the kelp |
