Lecture 12: Population Dynamics over Space and Time, not growth

A population with an intrinsic growth rate of 0.34 and a time delay of 2.3 years will _____.

.34(2.3)=.782, undergo damped fluctuations, between .37 and 1.57?

In a metapopulation of squirrels where the probability that any squirrel subpopulation will go extinct within one year is 0.35 and the probability that any unoccupied patch could be colonized within one year is 0.45. What is the probability that any given patch in the metapopulation will be occupied in the next year?

1-.35/.45 0.22

Since its introduction in 2004, you have been tracking the population size of the invasive coquí frog in Hawaii, where the frog has no known predators. You have collected the following data:

2011-->had highest population

In a metapopulation, when colonization (c) and extinction (e) rates in habitat patches achieve an equilibrium, the following equation predicts the proportion of patches that will be occupied at any given time:

=1−e/c=phat

Select the examples that describe delayed density dependence.

A healthy herd of deer breeds in the fall. A harsh winter results in the loss of key food sources. Many fawns are born malnourished and do not recover. An abundant fall allows a large population of black bears to store enough fat reserves to survive hibernation in the winter, but a harsh winter causes food to be scarce in the spring when the bears wake up, causing many bears to die before reproducing. Changes in the environment can cause populations to grow or shrink. Delayed density dependence occurs specifically when a population's growth rate is a result of past environmental conditions. In the examples, the deer and bear populations both exhibited delayed density dependence. Both deer and bear species had favorable fall feeding conditions which allowed for more deer to reproduce successfully and more bears to survive hibernation. However, the harsh winters caused deer fawns conceived in the abundant fall to be born malnourished after the harsh winter. Similarly, the harsh winter caused more bears to starve after waking from hibernation. The past changes from fall to winter lead to density dependent conditions in the spring. NEWBORN FROM BAS CONDITIONS WILL NOT BE NOURSIHED In dry areas, mesquite seedlings do not grow near mature mesquite trees because roots of established trees outcompete the seedlings for limited water. As the density of mature trees increases, the population growth rate simultaneously slows-->The suppression of population growth by mature mesquite trees is an example of density dependence. However, the population growth rate responded to immediate environmental conditions, so this is not an example of delayed density dependence. Density‑independent factors affect the population growth rate regardless of the population density. For example, a fire in a pine forest will kill trees in its path, regardless of the density of trees.

Analyzing ecology: delayed density dependence in the flixweed

Abundances of flixweed fluctuate in a cyclical manner overtime; the population grows according to a delayed densitydependence model where K = 100, r = 1.1, and τ = 1. From surveys, we know that there were 10 plants per m3 in year 1, and 20 plants per m3 in year 2. Expected change in population size in year 3 dN/dt=rN2(1-N1/K), can use any past years Hence, year 3 will add 20 individuals to the population, and total population abundance will be 20 + 20 = 40 individuals.-->gives rate change year 4 uses N3 times r and 1-N2/K delayed build upon logistic , If tau r less than .37 smooth log growth up to K with sigmoid shape However, since this movement back to the center has momentum, the pendulum overshoots the stable center position and swings to the other side. Gravity then pulls it back toward the center, where momentum once again causes it to overshoot the stable center position. the momentum of population increases, and decreases causes populations to oscillate. dens dep or indep events can cause growth grow beyond its carrying capacity. We see this phenomenon when there is a delay between the initiation of breeding and the time that offspring are added to the population may be dif breeding conditions and when adding offspring to pop When a population experiences a large reduction in size during a die-off, it can undershoot its carrying capacity.

Successful use of metapopulationtheory

After settlement of farmers in westernUnited States, habitat loss substantiallyreduced the number of black-footedferrets Poisons and disease reduced numberseven further.Initial captive breeding programs failed Initial captive breeding programs failed.-->thought ferret extinct. In 1981, a small population in Wyomingwas discovered and a captive breeding program was very successful Using metapopulation theory, biologists conducted several reintroductions inlocations throughout western North America. This created a metapopulation thatwas resistant to complete extinction took them to a bunch, found suitable areas or areas near suitable areas, certain patches will still go extinct or colonize in certain year -wolves doing too, farmers don't like wolves

Population modelers have determined that the amount of cycling in a population experiencing delayed density dependence depends on the product of r and τ ,

As you can see in Figure 12.10a, when this product is a low value ( r τ < 0.37 ) , the population approaches the carrying capacity without any oscillations. If this product is an intermediate value oscillations=AMT OVER OR UNDERSHOOTING? ( 0.37 < r τ < 1.57 ) , as shown in Figure 12.10b, the population initially oscillates, but the magnitude of the oscillations declines over time, a pattern known as damped oscillations. When the product is a high value ( r τ > 1.57 ) , as shown in Figure 12.10c, the population continues to exhibit large oscillations over time, a pattern known as a stable limit cycle.

Basic model of metapopulations

Assume that habitat patches are of equal quality, each occupiedpatch has the same subpopulation size, and each subpopulationsupplies the same number of dispersers to other patches p = the fraction of habitat patches that is occupied e = the probability of each patch becoming unoccupied (i.e., goingextinct) c = the probability of a patch becoming colonized The proportion of occupied patches when colonization and extinctionhave reached an equilibrium () is represented as phat=1-e/c wanna decrease e increase c We can increase the number of occupied habitat (p) patches by providing corridors between patches to increase the rate of colonization (c)-->fig out what causing extinct We can also increase the number of occupied patches by decreasingrates of extinction (e) .Hence, species may be preserved by protecting large fragments ofhabitat that reduce extinction risk, or by ensuring that individuals candisperse to and from patches Larger fragments -done with animals when we build roads or border walls, make overpass structure , wildlife corridor over or under-->simultaneously dec e but increase c , fish ladders so salmon return to birth place

Monitoring Moose in Michigan

CHECK FOR INTRO?

According to the metapopulation model, what must happen for a metapopulation to persist?

Colonization of unoccupied patches must equal the number of subpopulations that have gone extinct.

moreCyclic population fluctuations

Cyclic populations can occur among related species and across large geographic areas (e.g., the synchronous cycles of the capercaillie, black, and hazel grouses in Finland). all 6-7 yr cycle same fluctuations high/low of the separated 3 ground grouse species following same fluctuations over large geo area, mostly from same enviro surveys in 11 provinces to determine the abundance of three species of grouse: capercaillie (Tetrao urogallus), black grouse (Tetrao tetrix), and hazel grouse (Bonasa bonasia). After monitoring the birds for 20 years and graphing the data, as shown in Figure 12.9, they found that all three species of grouse experienced natural population cycles every 6 to 7 years. Moreover, these three species appear to exhibit high and low populations at the same time and across all the Finland provinces. had simultaneous high and low populations across all the Finland provinces. -This suggests that the drivers of natural population cycles can happen over large areas. we will examine the inherent cycling behavior of populations that can be caused by fluctuating resources. In doing so, we will apply a modified version of the logistic growth equation. (lokta?)

Cycles in laboratory populations

Delayed density dependence may occur because the organism can store energy & nutrient reserves (water flea Daphnia galeata) larvae=no problem staying around k, here adults limited and died off while adult (past larvae) made it In a second experiment, he limited the food given to the adults. This limited reproductive output; eliminated the time delay, and caused the adult population to reach K and remain there., adults died off?

Cycles in laboratory populations Delayed density dependence may occurbecause the organism can store ? or because there is a time delay in development from one life stage to another

Delayed density dependence may occurbecause the organism can store energy andnutrient reserves. Example:When populations are low and food is abundant, the water flea Daphnia galeata stores surplus energy as lipid droplets. (our use for fuel) fleas store lipid droplet food When resources are less abundant, adults use thisstored energy to reproduce. Eventually, lipid reserves are used up and thepopulations decline to low numbers. In contrast, Bosmina longirostris does not store energyand does not exhibit oscillations in population size., not really delay due to reserves, just knows amt of food it haves and no delay in reaching K Delayed density dependence can occur when there is a time delay in development from one life stage to another n a study of the sheep blowfly, A. J. Nicholsonfed larvae a fixed amount of food but fed theadults unlimited food. The adult population increased to more than4,000 individuals. As this occurred, larvae hadless per capita food and eventually all larvae died.A few surviving larvae restarted the population (eventually adult stage collapses following delayed dependence of not having food only given to blowfly, as larvae eventually come to be adult they collapse) In a second experiment, he limited the food givento the adults. This limited reproductive output; eliminated the time delay, and caused the adultpopulation to reach K and remain there-->larvae would eventually reach adults and carrying capacity at this pt

Classify each example as a case of demographic stochasticity or environmental stochasticity.

Demographic stochasticity In an isolated population of ten Florida panthers, all four offspring born one year are female. The first two rat snakes accidentally released on an island are male, so no young are born. Environmental stochasticity Lightning strikes the tree in which an osprey is nesting, killing the chicks. After a fire burns a forest patch, the additional sunlight and nutrients available in the burned patch allow more white pine seeds to sprout than in the unburned forest. Stochastic events are unpredictable and affect individuals or populations randomly. Stochasticity can involve random variations in population demographics, or can be caused by random events in the environment. Demographic stochasticity may affect the sex or age ratio of a small population. It can also affect the birth or death rate of a population. Demographic stochasticity is more likely to affect small populations than large ones. The demographics of a small population of Florida panthers could shift by chance if only males are born one year. Environmental stochasticity occurs because of chance variations in the abiotic conditions of a habitat. A forest fire only improves nutrient and sunlight availability in the part of the forest in the fire's path. Seeds sprout in the burned area because the conditions there promote germination. The seeds are no different genetically from the seeds in the unburned forest. Similarly, an osprey cannot predict which tree lightning will hit. The birth rate for the osprey population drops if the tree with the osprey nest gets hit by lightning before the young leave the nest. both methods of stochasticy affect populations

You are studying an herbaceous perennial plant that lives in a grassland habitat. The population size of this herbaceous perennial remained stable at its carrying capacity for roughly six consecutive years while precipitation and soil nitrogen were abundant. In the seventh year, the grassland experienced a severe drought, whereby precipitation and soil nitrogen significantly limited the growth of this herbaceous perennial. What is MOST likely to occur to this herbaceous perennial population?

Due to reduced precipitation and soil nitrogen, this herbaceous perennial population will overshoot its carrying capacity and experience a die-off. will prob produce norm Amt

Metapopulations in nature

Example:Researchers have monitored populations ofthe Glanville fritillary butterfly on the ÅlandIslands of Finland. Only 12 to 39 habitats out of 1,600 suitablemeadows were occupied in any year Over a 9-year period, ~100 patchesexperienced extinction and ~100 patchesexperienced colonization; the metapopulationpersisted because extinctions were offset bycolonization When the researchers introduced butterfliesto 10 meadows on an island with 20 totalmeadows, they observed similar dynamics.

Delayed Density Dependence in the Flixweed

Flixweed (Descurainia sophia) is a weed that is native of Europe but has been introduced into North America. Studies of this weed show that the number of plants per square meter of soil fluctuates in a cyclical manner over time. The population grows according to a delayed density dependence model, where where pops have cyclical fluctuations based on some time delay From plant surveys, we know that there were 10 plants per square meter in year 1 and 20 plants per square meter in year 2. Based on these data, we can calculate the expected change in population size in year 3: Rounded off to the nearest whole number, the flixweed will add 20 individuals to the population in year 3. Given that the population in year 2 is 20 individuals, adding 20 more individuals in year 3 will produce a total population size of 40 individuals. using regular logistic model rate dn/dt=rN2(1-N1/K) 1.1 , and τ = 1 .-->1.1 product=damped oscillation

Habitat fragmentation

Habitat fragmentation: the processof breaking up large habitats into anumber of smaller habitats. Often occurs as a result of humanactivities (e.g., clearing forests, roadconstruction, draining wetlands). -we drained wetlands in Florida for suitable habitat Some habitat fragments experience extinctions, whereas others arecolonized by dispersers. dispersers to dif fragments The basic metapopulation model assumes that all habitat patches areequal in quality and that the matrix between patches is inhospitable dif than source-sink model Sources are high-quality patches that produce a large number of individuals that disperse to other patches. Sinks are low-quality patches that produce few individuals and rely on dispersers to keep the sink population from going extinct. Habitat fragmentation4Sources are high-quality patches that produce a large number ofindividuals that disperse to other patches Sinks are low-quality patches that produce few individuals and relyon dispersers to keep the sink population from going extinct.If subpopulations rarely exchange individuals, fluctuations inabundance will be independent among subpopulations If subpopulations frequently exchange individuals, thesubpopulations will act as one large population. If subpopulations rarely exchange individuals, fluctuations in abundance will be independent among subpopulations. suburban people with jobs connected to city, even With intermediate patch connectivity, abundance in onesubpopulation can influence the abundance of other subpopulations.

Patch size and isolation

Habitat patches are rarely equal in quality; some patches are larger orcontain a higher density of resources Example:Suitable habitat fragments for the Californiaspotted owl vary greatly in size and distancefrom other patches Small patches are likely to experience higher rates of extinction andare less likely to be occupied OR RECONOLIZED than large patches. 6 IS SUPER SMALL AND CUTOFF FROM LARGER-->EXTINCTION Dispersal success is inversely related to the distance of dispersal ;hence, more distant patches will have a lower probability of beingoccupied than closer patches SIZE AND DISTANCE Unoccupied patches that are close to occupied patches are more likely to be colonized. Rescue effect: when dispersers supplement a decliningsubpopulation and thereby prevent it from going extinct IF WE HAVE ISLADN AND FUMIGATE for all insects but large island off shore, can be recolonized, .Less isolated patches are more likely to be rescued and are also morelikely to be colonize Researchers surveyed common shrews on islandsoff the coast of Finland. Islands varied in size from 0.1 to 1,000 ha and inisolation from 0.1 to 2 km from other islands. They found that shrews were less likely tooccupy smaller and more isolated islands.

You are examining the population dynamics of a butterfly metapopulation consisting of four highly suitable habitat patches of varying size and quality within a matrix of less suitable habitat. Within each patch, you record the number of individuals present when you began your study, as well as the average number of individuals that die and are born each year over the course of a decade. Finally, you estimate the maximum number of individuals that the patch can sustain given the resource availability and consumption rates of the individuals within each patch. With these data, you make the following table:

If the birth and death rates of each patch remain fairly consistent for the future, which patch in this metapopulation is most likely to become the first source population? 4 Births and deaths are balanced in this population, which is already at its maximum supportable size, so the patch 4 subpopulation will be neither a source subpopulation nor a sink subpopulation. N should not be max N 1

You have recently been hired to study the age structure of a small population of a newly discovered monkey species in South America. This monkey species is unique in that the gestation period is 2 years. The number of offspring that a female will produce is directly influenced by the amount of calories she ate in the year before she got pregnant. During the past 4 years, you have recorded the following age structure data for this monkey population by sampling the population each spring:

In which year did reproductively mature females consume an unusually high number of calories? 2016 If the females ate an unusually high number of calories in 2016 and became pregnant in 2017, age class 0 should have been the largest class in 2019, but age class 0 was the second-largest class in 2019. year w largest class: go three years back b4 age class zero for abundant food but age class 0 was the largest class in 2019. highest age class is age 1 in 2017(born in 2016) 2014 confused

In a metapopulation, what is the relationship between the amount of dispersal among subpopulations and the synchrony of fluctuations among subpopulations?

Increased dispersal among subpopulations causes the subpopulations to fluctuate at the same rate.

Why might the Isle Royale wolf population be more prone to extinction than other wolf populations?

Isle Royale is only large enough to support a small population of wolves, even at the best of times. and Ice rarely forms a travel corridor between Isle Royale and the mainland, which isolates the island wolves. At least one your choices is not a factor that increases the chances of extinction for the Isle Royale wolves. At its closest, Isle Royale is more than 20 km from the mainland, making it impossible for many animals to travel between the two in summer. Wolves on the island prey on moose, snowshoe hare, and beaver. Moose and beaver prefer to eat the new growth of trees, such as aspen and birch, that colonize recently burned areas. Small, isolated populations face a higher risk of extinction than larger populations. In part, this is because isolated populations do not receive many immigrants to boost depleted numbers. The wolf populations on Isle Royale offer an opportunity to observe drivers of population fluctuations in small, isolated populations. Chance events, such as lack of food or random losses of females, have a greater impact on small populations than on large ones. The Isle Royale wolf population only reached 50 individuals when under favorable prey conditions. For wolves, 50 represents a small population size. A population so small can lose most of its members if a small number of individuals die. Mortality without replacement makes populations more vulnerable to extinction under further stochastic losses. Isolation also increases the extinction risk of populations. Sometimes immigrants can save populations from extinction through the rescue effect. The rescue effect is when dispersing animals supplement numbers of declining populations. When isolated populations experience a crash, population numbers rarely recover due to immigration. At Isle Royale, it is difficult for wolves to swim the distance between the mainland and the island. Instead, most animals cross the ice in winter. However, ice rarely forms a bridge to the island that is strong enough or lasts long enough for wolves to immigrate. The distance between the mainland and the island is too far for most terrestrial animals to swim. Immigrant wolves crossed to the island on ice. Canine parvovirus was likely brought to the island by a visitor's dog. It is lethal to wolves and killed all but 14 of the 50 wolves that were present on the island. Fires on Isle Royale would likely increase the amount of food available for the moose. An increase in food for the moose population would likely lead to an increase in numbers of moose, followed by an increase in numbers of wolves. Fires on Isle Royale are infrequent, and they therefore have little impact on population sizes of moose or wolves.

A scientist in Greenland is studying a population of lemmings, a small rodent that inhabits regions of the Arctic Circle. Growth of the lemming population follows a delayed density dependence model, where the regional carrying capacity is 76, the intrinsic growth rate is 0.92, and the delay time is 4 years. In 2016, the population consisted of 24 individuals, and in 2020, the population consisted of 36 individuals. Given this information, What will the approximate population size be in 2024? (Round to the nearest whole number.)

K=76, r = 0.92, tau=4 .92(36)(1-24/76), each 4 years?=22.664016 added, so 36+23=59 Try calculating the expected change in population size for every four-year increment by applying the following equation, where N1 = population size in 2016 and N2 = population size in 2020:

What is true about habitat patches for any given species?

Patches vary in size and quality.

Delayed density dependence

Population cycles can be modeled by starting with the logistic growthmodel We can incorporate a delay between a change in environmentalconditions and the time the population reproduces. Delayed density dependence: when density dependence occurs based on a population density at some time in the past. -rate of growth is still slowing? rate slowing based on some sort of constrained but based on pop at pt in past, pop operating as if at carrying K in the past In population ecology delayed density dependence describes a situation where population growth is controlled by negative feedback operating with a time lag Moose breed in the fall; if carrying capacity is high, many parents will breed.However, reduced resources in the spring may not support all of the offspring To incorporate a time delay (τ) into the logistic growth model As the time delay increases, density dependence (the slowing of growth from comp or constrained resources does not occur at the time it would without any time delays, growth not constrained before overshooting) is delayed and thepopulation is more prone to both overshooting and undershooting K The amount of cycling in a population depends on the product of rand τ. When rτ < 0.37, the populationapproaches carrying capacitywithout oscillations-->pop self-regulating, stopping when knowing constrained by food, paramecium, no cycling just level off rN(1-(n^t-tau)/K) When 0.37 < rτ < 1.57, the populationexhibits damped oscillations formula with tau makes density dependent part of eqn based on population sizes at tau time units in past -pop slows growth when size at tau time units in past approaches K Damped oscillations: a pattern ofpopulation growth in which thepopulation initially oscillates but themagnitude of the oscillations declinesover time smaller overshoot and die off further in future, decrease these mags around K over/die-off mag stay same in stable lim cycle, same overshoot die off mag in periodic fashion with rtau>1.57=large oscillation over time Stable limit cycle: a pattern ofpopulation growth in which thepopulation continues to exhibit largeoscillations over time.

Cyclic population fluctuations

Population cycles: regular oscillation of a population over a longer period of time. Some populations can exhibit highly regular fluctuations in size. gyrfalcons regular fluctuations experience large fluctuations over time, including overshoots and die-offs. But regular patterns known as population cycles can be seen in some populations studied over many decades. Example: In the eighteenth century, gyrfalcons were captured and exported from Iceland for European nobility. Falconry was a popular pastime among European nobility during the seventeenth and eighteenth centuries he Danish royalty would then present the falcons as diplomatic gifts to the royal courts of Europe. The governor of Iceland wrote the export permits, which provide a detailed historical record of gyrfalcon exports over several decades falcon royal court gift, tracked pop cycles with historical record of gyrfalcon exports over several decades in 1700s number of gyrfalcons exported from Iceland between 1731 and 1793 reveals 10-year cycles of abundance, which reflects natural fluctuations in the abundance of the gyrfalcons in natur exports reflect natural abundance flucs in nature, more exports higher pop Export records documented the number of falcons exported each year. Until 1770, gyrfalcons were intensely sought and records indicate a 10-year cycle in falcon abundance. -After 1770, falconry became less popular, so exports declined to very low levels regardless of the bird's abundance in nature. -In Chapter 11, we saw that populations experiencing density dependence grow quite rapidly at first, but then the growth rate slows as the population reaches its carrying capacity. However, populations in nature rarely follow a smooth approach to their carrying capacity In many cases, they grow beyond their carrying capacity, a phenomenon referred to as an . An overshoot can occur when the carrying capacity of a habitat decreases from one year to the next. -overshoot from enviro resources -, if one year has abundant rainfall and the next year has a drought, the habitat will produce less plant mass in the second year. As a result, the carrying capacity for herbivores that rely on the plants for food will be reduced -. A population that overshoots its carrying capacity is living at a density that cannot be supported by the habitat. Such populations experience a , which is a substantial decline in population density that typically goes well below the carrying capacity. -The population begins small but grows at such a rapid rate that it exceeds the carrying capacity. Following the overshoot, the population experiences a rapid die-off to a point that is below the carrying capacity. -Isle Royale. Over time, the moose exceeded their carrying capacity and the population underwent massive die-offs from starvation. -In 1911, the U.S. government introduced 25 reindeer to St. Paul Island, Alaska, to provide a source of meat for the local population. The island contained no predators of reindeer, and the reindeer population quickly began to reproduce -this rate of growth followed a J-shaped growth curve that indicates exponential growth. As the population grew in the early years, the lichens they consumed in the winter remained abundant. -Following a peak in 1938, the reindeer population began to experience a massive die-off, probably from a combination of scarce food during the winter and unusually cold winters. -n 1940 and 1941, the government culled several hundred reindeer in an attempt to reduce the size of the herd to get it closer to the island's now much-reduced carrying capacity. Despite this effort, the population continued to decline and, by 1950, only 8 individuals remained.

Cyclic behavior of populations Populations behave like the pendulum; the momentum of population increases, and decreases ?. based on growth rates increase or decrease Populations are stable at their carrying capacity. Whenever the size of the population decreases due to ?

Populations have an inherent periodicity and tend to fluctuate up and down, although the time required to complete a cycle differs among species. Populations behave like a swinging pendulum, which is stable when hanging straight up and down. Gravity will force the pendulum back to the center, but momentum causes it to overshoot the center. stable at K, reduction occurs first and overshoot will follow when gravity being back to center -However, since this movement back to the center has momentum, the pendulum overshoots the stable center position and swings to the other sides stable center- cary capac, overshoot when moving to this grow too fast -Gravity then pulls it back toward the center, where momentum once again causes it to overshoot the stable center position. Populations are stable at their carrying capacity; when reductions in population sizes occur, the population responds by growing—often overshooting carrying capacity. Overshoots can occur when there is a DELAY between the initiation of breeding and the time that offspring are added to the population. (GESTATION=DELAY, BREEDING TO ADDING OFFSRPING, DON'T ANTICIPATE CHANGE) pregnant during natural disaster, makes conditions when added to population unknown alge not working about delay momentum causes populations to oscillate predation, disease, or a density-independent event,, respond pop by growing Populations that overshoot their carrying capacity subsequently experience a die-off that causes the population to swing back toward its carrying capacity, undershoot w die off

Overshoots and die-offs

Populations in nature rarely follow a smooth approach to their carrying capacity. -level off, usually exceed K not smooth populations experiencing density dependence grow quite rapidly at first, but then the growth rate slows as the population reaches its carrying capacity. overshoot increase mate, food, space competition, some may starve, needs not being met won't mate as much -animals don't recognize they will overshoot K when mating and stuff, only once they don't have enough of a resource to see decrease , don't know things get better though after die off -however, we can detect fluctuations over time by examining a population's age structure. -When a certain age group contains an unusually high or low number of individuals, it suggests that the population experienced unusually high birth or death rates in the past. -This suggests that in 1944, the whitefish population experienced a very high rate of reproduction Overshoot: when a population grows beyond its carrying capacity; often occurs when the carrying capacity of a habitat decreases from one year to next (e.g., because less resources are produced). in the subsequent year For example, if one year has abundant rainfall and the next year has a drought, the habitat will produce less plant mass in the second year. As a result, the carrying capacity for herbivores.K for herbivore reduced next year living at a density that cannot be supported by the habitat. Such populations experience a die-off, Over time, the moose exceeded their carrying capacity and the population underwent massive die-offs from starvation. You can see these data in Figure 12.6. As the moose experienced a large increase in population size in the 1980s and 1990s, Die-off: a substantial decline in density that typically goes well below the carrying capacity. Die-offs often occur when a population overshoots its carrying capacity. -ST PAUL island reindeer started feeding on lichen off trees, no predators on island led to overshoot, govt must manage reindeer for less oscillations, deer managed around here too, Adirondacks have more top predators checking deer , with continued growth of the reindeer population, the lichens became rare, which suggests that the reindeer had far exceeded the carrying capacity of the island., As you can see in Figure 12.7, this rate of growth followed a J-shaped growth curve that indicates exponential growth In 1940 and 1941, the government culled several hundred reindeer in an attempt to reduce the size of the herd to get it closer to the island's now much-reduced carrying capacity St. Paul Tribal Government, which maintains the population at just a few hundred animals. In 2017, the population was estimated to be 400 reindeer. The reindeer, maintained at a sustainable population size, can now continue to provide valuable and affordable meat to the local residents. -The age structure of a forest is also readily analyzed. As you may know, the age of a tree can be determined by counting the number of rings in its trunk; -under most circumstances, one ring is added each year. To examine how fluctuations affect the age structure of forest populations, researchers work at sites that have not been logged, because logging alters the age structure of the current tree population -Researchers drilled into the trunks of trees to remove a sample of wood that contained tree rings. Using these samples, they determined the age of each tree and, therefore, the time when each tree started its life. drilling trunks -A fire and drought in the mid-1600s killed many of the oaks trees, thereby creating openings in much of the forest. Following the fire, oak seedlings reestablished themselves in the forest, but there was also an increase in the number of new white pines ( -, however, they cast so much shade that new white pine seedlings had a hard time surviving, leading to a decline in their survival during the late 1700s. -American beech trees (Fagus grandifolia) and eastern hemlock trees (Tsuga canadensis) are very tolerant of high-shade environments; new individuals of these species began to grow as the white pines came to dominate and shade the forest -These two species continued to recruit new individuals over time, which caused beech and hemlock to have a population age structure that was more evenly distributed than that of white pine.

Populations of collared lizards fluctuate over time as they approach and overshoot the carrying capacities of their habitats. In a metapopulation of collared lizards, how does decreasing the distance between habitat patches affect the synchrony of fluctuations among lizard subpopulations?

Populations naturally fluctuate over time as organisms reproduce and overshoot the carrying capacity of their habitats. In a metapopulation composed of distinct subpopulations, the synchrony of fluctuations between patches depends on how easily individuals can move from one patch to another. In a metapopulation of collared lizards, lizards can disperse easily from one patch to another when patches are near one another. Because of this dispersal, the metapopulation functions as a single unit. Subpopulations decline or recover in unison as lizards move from one subpopulation to another. In a metapopulation where patches are far apart, individual lizards cannot move easily from one patch to the next. Dispersal is infrequent, so each subpopulation fluctuates independently. Different patches may approach their carrying capacities at different rates according to local conditions. Declining subpopulations cannot be restored easily by immigrating lizards from other patches. The odds of any single population going extinct do not increase when patches are close together. Any patch may experience extinction due to local conditions or random chance. However, individuals from a nearby subpopulation can disperse to declining habitats and rescue the population from extinction. A declining subpopulation that is isolated from other patches cannot be easily rescued.

Patchy habitats

Preferred habitat often occurs as patches of suitable habitatsurrounded by a matrix of unsuitable habitat -fish in each little wetland pond, fish could not get from top to bottom lake, if flooding they may get to dif wetland lakes Example:Each wetland in a landscape cancontain many different species ofaquatic organisms. Terrestrial habitat betweenwetlands is inhospitable to theseorganisms. Many individuals are still able todisperse between wetlands,depending on how fast and far anindividual can move Preferred habitat =not always continuous

In models of delayed density dependence, why do intrinsic growth rate and amount of time delay determine the magnitude of population cycling?

R AND DELAY FOR CYCLING The higher a population's maximum growth rate and the longer a population takes to respond to its environment, the more the population will overshoot and undershoot the carrying capacity. Delayed density dependence models predict that populations may cycle as they periodically overshoot the carrying capacity and then undershoot the carrying capacity, or otherwise undergo a die-off. The magnitude of these oscillations depends on the intrinsic rate of population growth and the length of the time delay in the population's response to the environment. For example, the higher the population's growth rate under ideal conditions and the longer the time delay, the more the population will grow rapidly. This creates the potential of the population becoming too large for its environment. AND HAVING GREATER TIME DELAY TO RESPOND, Therefore, the intrinsic growth rate and the amount of time delay interact to affect the magnitude of population oscillations. DELAYED DENS DEP FOR VARIATION IN K OVER TIME, GROW ACCORDING TO GREATER PAST K Carrying capacity is not fixed, but instead can fluctuate in response to changes in population density, resource availability, and other factors. A delayed density dependence model takes into account the variation in carrying capacity over time and the amount of time of delays in population adjustment to these changes. When a population grows rapidly according to its past lower population density and greater carrying capacity, rather than its current state, the population tends to grow beyond the limits of the environment. Although a longer time delay does increase the magnitude of population oscillations, a population's intrinsic growth rate does not negatively correlate with the carrying capacity. A longer delayed response to the environment may more likely lead to overshooting the carrying capacity, but intrinsic growth rate and carrying capacity do not positively correlate either. The product of the intrinsic population growth rate and the time delay length determine how strongly a population cycles, but the two variables are not negatively correlated with each other. (R*T)=STRENGTH CYCLE

MISSING RAY SLIDE

RAY POP INCREASE IN SMALL SHARKS, OUTSIDE SHARKS DECREASE , BUT FIN TOOTH SHARK DASH=ORIGINAL POP SIZE colored circle=current population size outer ring large sharks decrease-->overfishing of top predators, middle predators able to flourish, smaller sharks/rays-->mid level predator feed clam/scallops and their pop shrink *we're all connected

The basic metapopulation model explains how to find the proportion of occupied patches, 𝑝, in a fragmented habitat. In this model, 𝑝 is 1 minus the probability of extinction, 𝑒, divided by the probability of colonization, 𝑐. The basic metapopulation model also allows for the calculation of extinction rates and colonization rates. Select the graph that correctly plots the relationships between the proportion of occupied patches and the rates of extinction and colonization.

Rate of colonization down as Rate of extinction goes up cross when occupied patches = 0.5 In this dataset, as the proportion of occupied patches, 𝑝, increases, the rate of extinction also increases. The rate of extinction has a positive linear relationship with 𝑝 with a slope of 0.025. In this dataset, as 𝑝 increases, the rate of colonization increases until 𝑝 equals 0.5, then the rate decreases. The rate of colonization has a negative parabolic relationship with 𝑝. The parabola opens downward with an apex at (0.5,0.125). The rate of extinction and the rate of colonization come into equilibrium at the coordinates (0.5,0.125). This is the point where the line for the rate of extinction intersects the curve for the rate of colonization. When 𝑝 is 0.5, both the rate of extinction and the rate of colonization equal 0.125.

Extinctions in small populations

Small populations are more vulnerable to extinction than larger populations Example:Researchers conducted a survey of birds on theChannel Islands off the coast of California.Over 80 years, they studied the number ofbreeding pairs of different species and rates ofextinction. Extinction probability was INVERSELY correlated with population size -CHANCE EVENTS STILL RISKIER FOR SMALLER POPS Extinction due to growth rates3Although data suggest that small populations are more likely to goextinct, growth models suggest that small populations should havemore rapid growth and be resistant to extinction.

The metapopulation of California spotted owls is divided among several patches of suitable forest habitat. The forest patches differ in size, the number of owls they can support, the quality of the habitat, and their degree of isolation from other patches. Which combination of habitat characteristics would lead to the highest probability of extinction due to stochastic events for the owl population living on the patch?

Small, isolated populations have the highest probability of extinction due to stochastic events. In the example of California spotted owls, a forest patch so small that it can only support six owls cannot provide protection from random events, no matter how good the forest quality. A single stochastic event, such as an earthquake, fire, or mudslide, could kill all six owls or destroy their nest trees. The existing population would go extinct, even if owls from the other populations later disperse to the empty patch. Smaller populations are also more at risk of extinction due to stochastic events that affect demography than are large populations. If two females die in a population consisting of two females and four males, the population becomes effectively extinct. However, losing two females from a population of 500 would have little effect on the population's sex ratio or its chances of survival. The risk of extinction from chance events is also higher for isolated populations than for populations that are part of a metapopulation. If individuals from one patch can easily move to other patches, the populations of all the patches are part of a metapopulation. As individuals in a patch die, individuals from other patches may disperse into the available territory. A chance event could lead to the extinction of an owl population in a small patch if the patch is isolated. More connections between patches decrease the risk of extinction in all the patches. Poor‑quality patches that can support large populations, or that are well-connected to good-quality patches, can support populations better than small and isolated good-quality patches. a good‑quality patch large enough for six owls that is reachable from two slightly larger, good‑quality, somewhat distant patches--Small, isolated populations STOCHAS EVENT LIKE NAT DISASTER, not even well-connected to good-quality patches,

e basic model of metapopulation dynamics does not consider variations found in nature that make, habitat patches rarely equal in quality.

Some patches contain more resources because they are larger or because they contain a higher density of needed resources basic model of metapopulation dynamics does not consider variations found in nature as shown in Figure 12.19, these fragments are of very different sizes, and the estimates of how many spotted owls could be supported in each fragment range from 6 to 266. Moreover, not all patches are equally distant from all other patches Some patches contain more resources because they are LARGER or MORE DENSE because they contain a higher density of needed resources When each patch in a metapopulation supports a different number of individuals, we expect the small patches to experience higher rates of extinction. As a result, small patches are less likely to be occupied than large patches. At the same time, we might also predict that more distant patches will have a lower probability of being occupied than closer patches successful dispersal is a function of the distance an individual has to travel. Therefore, unoccupied patches that are close to occupied patches have a better chance of being colonized when uneq in indivs, , we expect the small patches to experience higher rates of extinction. As a result, small patches are less likely to be occupied than large patches. At the same time, we might also predict that more distant patches will have a lower probability of being occupied than closer patches We make this prediction because successful dispersal is a function of the distance an individual has to travel. Therefore, unoccupied patches that are close to occupied patches have a better chance of being colonized

This figure illustrates a large number of patches that could be occupied by the skipper butterfly in Britain, as well as their size and distance from other patches. Which statement is the BEST explanation for the fact that the patch indicated by the red arrow is occupied while other, similar patches remain unoccupied?

The patch is larger than almost any other patch, which makes it easier for dispersing butterflies to find. The patch indicated by the red arrow is fairly large, but there are a number of occupied and unoccupied patches that are similar-sized or larger, so size is not the reason the patch indicated by the red arrow is occupied while most other isolated patches are unoccupied. is it bigger than all around it nah among other large patch, not valid wind facilitated dispersal of a small butterfly group much further than disperse

The basic model of metapopulation dynamics describes subpopulation extinction and habitat colonization. How does the rescue effect influence metapopulation dynamics?

The rescue effect reduces the probability of extinction and does not influence the probability of colonization. reduced e but no effect on entire new patch colonized Metapopulations consist of subpopulations that each occupy a distinct habitat, or patch. EACH patch has some probability of going EXTINCT in a given amount of time. Metapopulations persist even when subpopulations go extinct because of the balance between patch extinction and patch colonization. The rescue effect refers to the dispersal of individuals FROM a SOURCE habitat patch TO a DECLINING subpopulation. By moving into a new patch, the dispersing individuals reduce the probability that the subpopulation will go extinct. In metapopulation dynamics, the probability of colonization is not a function of the rescue effect.

Why may human intervention be necessary in order for the small population of wolves on Isle Royale to survive?

The rescue effect will not occur with the decrease in ice bridge formation between the mainland and the isle. smaller need influx , rescue effect, is less and less likely to happen because ice bridges are forming less frequently between Isle Royale and the mainland due to global warming, Humans may eventually need to intervene by introducing additional wolves to the island to supplement the population. this change will not necessarily result in the extinction of the wolf. Instead, wolf and moose populations vary over time relative to one another. When the moose population decreases, the wolf population eventually decreases as well. This pattern means that the wolf population is unlikely to grow far beyond what the moose population can sustain Smaller populations are more susceptible to random environmental and demographic effects and need a fairly frequent influx of individuals from other subpopulations. For example, the population of wolves on Isle Royale is dwindling and in need of such an influx to prevent its extinction. This process, called the rescue effect, is less and less likely to happen because ice bridges are forming less frequently between Isle Royale and the mainland due to global warming. Humans may eventually need to intervene by introducing additional wolves to the island to supplement the population. Although it is possible that the moose population could suffer a die‑off, this change will not necessarily result in the extinction of the wolf. Instead, wolf and moose populations vary over time relative to one another. When the moose population decreases, the wolf population eventually decreases as well. This pattern means that the wolf population is unlikely to grow far beyond what the moose population can sustain. Short‑term changes in birth rate do little to affect a wolf population because of the large body size and long life span of the wolf. These traits mean that, at any given time, the population contains a proportionate number of individuals in every age group in reality, The wolves are less susceptible to fluctuations in birth rate because they are large, long‑lived animals.

Scientists collected data on the wolf and moose populations on Isle Royale for several decades. Wolves are the only predator of the moose on Isle Royale, and moose are the wolves' main prey. Use the information in the graph to place the descriptions of the marked events in the sequence in which they occurred

The sizes of predator and prey populations tend to affect each other. If the prey population expands, it can support more predators. As the number of predators increases, the predators eat more prey, reducing the prey population size. Scientists have studied predator‑prey dynamics on Isle Royale, which is a large island in Lake Superior, for decades because the resident wolves were the only predator of the moose on the island and the moose were the only large prey species for the wolves. Scientists estimate that the carrying capacities for the two populations on Isle Royale are about 20 wolves and fewer than 1000 moose. Carrying capacity equals the number of individuals of a species the environment can sustainably support. If a population expands beyond its carrying capacity, individuals have to compete with each other for a limited resource, such as food, territories, or den sites. The wolves on Isle Royale began to overshoot their carrying capacity in about 1974. Moose numbers increased prior to 1974, and few wolves died for lack of food. Between 1974 and 1980, the wolf population became unsustainably large and crashed from about 50 individuals in 1980 to a minimum of about 10 individuals two years later. A combination of factors caused the crash in the wolf population. One important factor was the lack of moose to feed all the wolves. The moose population experienced a similar situation between 1995 and 1998. The wolf population, which was probably beginning to suffer from inbreeding depression, remained very small until a new wolf joined the population in 1997. With fewer predators, more moose survived each year until their population got so large that hardly any of them found enough food to survive. In 1996, a lack of food coupled with other environmental factors caused the moose population to crash. 1969 The wolf population increased above its carrying capacity when food was plentiful. The wolf population crashed after overshooting its carrying capacity. The moose population responded to a drop in the number of wolves by increasing rapidly. The moose population overshot its carrying capacity and crashed.

What is NOT a reason a single age group may be more abundant than younger age groups in a population's age structure?

They were born following a die-off, so reproduction was high. Predators were less abundant during the year they were born. They inherited an adaptation that made them survive better than subsequent generations.-->not reason

Extinction due to growth rates

This contradiction can be resolved by incorporating random variationof growth rates into growth models .Deterministic model: a model that is designed to predict a resultwithout accounting for random variation in population growth rate. Stochastic model: a model that incorporates random variation inpopulation growth rate; assumes that variation in birth and deathrates is due to random chance. Demographic stochasticity: variation in birth rates and death ratesdue to random differences among individuals Environmental stochasticity: variation in birth rates and death ratesdue to random changes in the environmental conditions (e.g.,changes in the weather A population that randomly experiences a string of years with lowbirth rates or high death rates is morelikely to go extinct With time, there is an increased chanceof having a string of bad years. Smaller populations are at more risk ofextinction if they experience a string ofbad years Although data suggest that small populations are more likely to go extinct, growth models suggest that small populations should have more rapid growth and be resistant to extinction. This contradiction can be resolved by incorporating random variation of growth rates into growth models. Deterministic model: a model that is designed to predict a result without accounting for random variation in population growth rate. Stochastic model: a model that incorporates random variation in population growth rate; assumes that variation in birth and death rates is due to random chance. STOCHSTIC=REALISTIC stuff in enviro and demography may be random Demographic stochasticity: variation in birth rates and death rates due to random differences among individuals.-->not all want kids Environmental stochasticity: variation in birth rates and death rates due to random changes in the environmental conditions (e.g., changes in the weather). A population that randomly experiences a string of years with low birth rates or high death rates is more likely to go extinct. With time, there is an increased chance of having a string of bad years. Smaller populations are at more risk of extinction if they experience a string of bad years. further in time=higher prob of random things leading to extinction

Which event would decrease the severity of a die-off for a population above its carrying capacity?

a decrease in the number of reproductive females would decresase die-off, how an environmental disturbance that decreases resource abundance an increase in the abundance of a predator More predators would cause more deaths in the population and increase the severity of the die-off. a decrease in the population's carrying capacity This means the environment would support even fewer individuals, which would increase the severity of the die-off What is NOT an event that would eventually cause a population above its carrying capacity to undergo a die-off?-->would not die off from lacking repro indivs , why?

Given the information on this graph of the number of reindeer on St. Paul Island, which estimate of the carrying capacity for this population is MOST likely correct?

about 2,000 individuals The population size at its maximum in the graph likely represents an overshoot, as it is followed by a die-off, so the carrying capacity is less than 2,000 individuals lower than 2,000 individuals

The ? ? model describes a scenario in which there are patches of suitable habitat embedded within a matrix of unsuitable habitat. All suitable patches are assumed to be of equal quality. Some suitable patches are occupied while others are not,

basic metapopulation Some suitable patches are occupied while others are not, although the unoccupied patches can be colonized by dispersers from occupied patches. The basic metapopulation models emphasize how colonization and extinction events can affect the proportion of total suitable habitats that are occupied. unoccupied patches can be colonized by dispersers from occupied patches WITHIN MATRIX EQUAL QUAL PATCH

what leads to pop increase adn decrease from an initial size

births/immigraiton increase pop death and emigration out -massive bison hunting deaths, decrease in deaths for bison later from domestication and increased population size, polar bear starving passenger pigeon hunting by people ray decrease death from top level predator being gone

Isle Royale, which is part of the state of Michigan and located off the northern shore of Lake Superior, has long served as a natural laboratory for ecologists. In the early 1900s, the island was colonized by moose from the mainland. This unlikely feat probably occurred during winter when the lake was frozen and the moose could travel the 40 km from the shores of the province

but in 1934, when the population finally exceeded the island's carrying capacity, the moose suffered starvation and many died. In 1936, the island experienced extensive forest fires that stimulated new plant growth and, as a result, the moose population began to increase By the late 1940s, the moose once again exceeded the carrying capacity of the island and they experienced another decline due to starvation. but sometime in the late 1940s, gray wolves (Canis lupus) arrived on Isle Royale by crossing the ice during the winter. Beginning in 1958, ecologist David Mech and his colleagues started estimating the number of moose and the number of wolves on the island. wolves disrupting cycle in 1981, a lethal virus (canine parvovirus) arrived on the island, probably carried to the island by a visitor's domestic dog. The virus caused the wolf population to experience a major decline, dropping from approximately 50 to 14 animals With fewer wolves on the island, the moose population rebounded and it continued to grow. In 1996, the moose once again exceeded their carrying capacity and experienced widespread starvatio he reduced number of plants to eat, combined with an abundant wolf population, caused the moose population to decline further to just 500 individuals by 2008. The lower moose population, in turn, led to a smaller wolf population that experienced inbreeding depression. By 2016, only two wolves remained. wolf predator, pop effects following moose global warming has made it less common for ice to form between the mainland and the island, so the wolves are less likely to naturally recolonize. National Park Service, which manages the island, announced in 2016 that it would introduce 20 to 30 wolves to the island over a period of 3 years. By late 2019, the 13 introduced wolves were still alive, bringing the total number of wolves on the island to 15. Researchers were also encouraged when they found that nearly half of the wolves' diet was comprised of moose.

You are examining the metapopulation dynamics of a series of polar bear subpopulations on various ice-covered islands in northern Canada to determine the impact of melting ice on the future of the polar bear. You discover that from 2000 to 2010, polar bears occupied only 2 percent of available islands and that the probability of a polar bear subpopulation colonizing an unoccupied island from 2000 to 2010 was 28 percent. However, from 1990 to 2000, 10 percent of available islands were occupied by polar bears and the probability that an unoccupied island would be colonized by a polar bear subpopulation was 18 percent. If we assume that the extinction and colonization rates were in equilibrium during each respective decade, approximately how much of an increase was there in the probability that a given polar bear subpopulation on an ice-covered island would go extinct?

c=.28 and p = .02, finding .02(.28)=1-e. =1-0056=.9944 increase in e probability that a given polar bear subpopulation on an ice-covered island would go extinct? c=.18 p=.10 1-(.1*.18)(.018)=.982

This figure illustrates a large number of patches that could be occupied by the skipper butterfly in Britain, as well as their size and distance from other patches. The patches in the circled area on the graph are expected to have low _____ rates, and the ones in the group labelled "B" probably have high _____ rates.

colonization; extinction

Scientists studying a population of an unidentified tropical fish species finds that the population has an intrinsic rate of growth of 0.88 and an rτ value of 1.76. The population size cycle is mostly likely described by _____.

damped oscillations

What is it called when the magnitude of the fluctuations of a population's size around its carrying capacity decreases over time?

damped oscillations decrease around K capacity fluctuations of a population's size, dif patterns approaching K

missing slides

dashed=originl pop size, colored=current population larger sharks on outside decreasing from fishing, top predators are gone due to fishing, now middle layer predators can flourish when top gone, adn their population expand -feed on clams and scallops so their pop shrink -mapping out effects of humans targeting top level sharks constraints on growth.survival orgs: principal of limiting factors from herbivory, predation, competition (3 biological), also physical limiting sunlight temp, moisture, nutrients (can also constrain how much pop can grow)-->usually not moisture problem here

If you were trying to save an endangered species that lived in a metapopulation, how might you try to to increase the proportion of occupied patches?

decrease patch isolation

When density dependence occurs based on a population density at some time in the past, it is called? Population cycles are simply Regular oscillation of population size over a long period of time. Danish royalty imported gyrfalcons from Danish territories in Iceland, where the falcons were trapped and then transported to Copenhagen. The Danish royalty would then present the falcons as diplomatic gifts to the royal courts of Europe

delayed density dependence.-->When density dependence (slower/limited growth) occurs based on a population density at some time in the past, overshoot based on past conditions, may currently be lower capacity K For example, large herbivores such as moose often breed in the fall but do not give birth until the following spring. If food is abundant in the fall, the carrying capacity is high, but by the time the offspring are born in the spring, the carrying capacity of the habitat may be much lower. The offspring will still be born, but the population will now exceed the carrying capacity of the habitat AMT of REPRODUCTION was based on the earlier environmental conditions The lack of prey will cause the carrying capacity of the predator to decline just as the predator population is increasing -When predators experience an increase of prey, their carrying capacity increases. However, it may take weeks or months for the predatorsDELAY TO CONVERT abundant prey into an increased number of offspring and, by this time, the prey may no longer be abundant. cause the carrying capacity of the predator to decline just as the predator population is increasin DELAYED DENS DEP, POP INCREASING DUE TO PAST CONDITIONS WHILE K DECREASING FOR THAT SPECIES the population experiences a time delay in density dependence. by time more growth using past predators for offspring, less prey in enviro

You are studying the population dynamics of an elephant herd containing 23 individuals on a game reservation. In the past 3 years, the population has gone from 18 to 20 to its current size, a promising trend. Although the intrinsic rate of increase of this population is 0.8, the fate of the population is unclear because elephants have a 2-year gestation period. Based on this information, this population will likely _____.

delayed, tau=2, r =.8, 1.6 The amount of cycling in a population experiencing delayed density dependence depends on the product of r and τ. When the product is a high value (rτ>1.57) the population will oscillate over time as a stable limit cycle have a stable limit cycle

You have been conducting research into the birth and death rates of an isolated population of arctic fox. You find that birth and death rates seem to change randomly among individuals, despite environmental conditions that are becoming worse at a predictable rate. What would be the BEST type of model to use to predict the growth rate of this population?

demographically stochastic

The models that we have studied up to this point have assumed a single birth rate and death rate for each individual in the population. When a model is designed to predict a result (like extinction, where pop is going) without accounting for random variation in the population growth rate, we say it is a ?. Although deterministic models are simpler to work with, not every individual in the real world has the same birth rate or the same probability of dying.

deterministic model-->assumed a single birth rate and death rate for each individual in the population.-->Rather, because we see random variation among individuals in a population in birth and prob death, the growth rate is not constant; it can vary over time. Models that incorporate random variation in population growth rate are known as stochastic models.

In _____ models, every individual in the population has the same birth and death rates.

deterministic, no demographic or enviro stochastic

group of small populations that is interconnected by occasional dispersal have a unique dynamic in that ? can form new subpopulations.

dispersers connect fragments AND can form new subpopulations.,, This balance of extinctions and colonizations allows the metapopulation to persist over time.

You are studying a metapopulation of frogs living in a fragmented habitat consisting of numerous separate wetlands. In this metapopulation, the probability that any frog subpopulation will go extinct within one decade is 0.15. Further, the probability that any unoccupied patch could be colonized within the decade is 0.23. If the probability of extinction and colonization are in equilibrium, what is the probability that any patch in the metapopulation will be occupied within the next decade? ANY FUTURE TIME IF IN EQUILBI PROBS FOR DECADE

e=.15, c=.23 p=1-.15/.23=.35 0.35 Using these variables, the proportion of occupied patches when at equilibrium, as indicated by p^ equilibrium conditions for patch occupation

Changes in the weather or natural disasters can cause _____ stochasticity, while differences in individuals' fertility rates can cause _____ stochasticity.

environmental; demographic

When the product of a population's intrinsic growth rate and time delay (i.e., τ) is greater than 1.57, the population will _____.

exhibit a stable limit cycle

goals and Population fluctuations production decrease with COMPETITION

fallen try= bad ice , lake royal -michigan, shore off Lake Superior , ice bridge uses trees pointing outwards towards shore, if tree falls on lake go back -coloinzed by meese in 1900, ON LAKE ROYALE looked at natural population fluctuations -->then wolves came WHEN ANOTHER GOOD FREEZE WOLVES CAME OVER, MOOSE NATURAL POP FLUCTUATIONS (G/DECLINE) UNTIL MOOSE, NOW FLUC TOGETHER -deer quality high when deer production/population/number deer low-->all resources you want -hit point w max deer production, still decent deer quality but population lil lower -deer quality and production terrible during overpopulation-->too much competition Populations fluctuate naturally over time. Density dependence with time delays can cause populations to be inherently cyclic.-->overshoot capacity, die off go back below Chance events can cause small populations to go extinct. Hawaii METApopulations are composed of SUBpopulations that can experience INDEPENDENT population dynamics ACROSS SPACE. -island colonized by moose, solid freeze and wolves came, wolves and moose fluctuate in synchrony LAKE ROYALE=MICHIGAN COAST , OFF Lake Superior COAST,ICE BRIDGE XMAS TREES PPOINT TO MAINE SHORE, FALLING TTREE ON LAKE=DON'T DRIVE ON ICE All populations experience fluctuations due to factors such as availability of resources, predation, competition, disease, parasites, and climate. no fluctuation factors are stable RPCDP competition changes and all other factors like disease all fluctuate Fluctuations include RANDOM and CYCLIC changes through time. Some populations tend to remain relatively stable over long periods. (deer on the Isle of Rum in Scotland) Example: Over 30 years, the population of red deer on the Isle of Rum in Scotland has remained relatively stable.

The basic metapopulation model explains how to find the proportion of occupied patches, 𝑝, in a fragmented habitat. In this model, 𝑝 is 1 minus the probability of extinction, 𝑒, divided by the probability of colonization, 𝑐. Based on the equation for calculating 𝑝, select the set of changes that would increase the proportion of occupied patches.

increasing the probability of colonization or increasing the probability of extinction When natural or human activities break a habitat into fragments, the subpopulations in those fragments make up a metapopulation. The value of 𝑝 increases as the quotient of 𝑒 divided by 𝑐 decreases. Thus, to increase 𝑝, either 𝑒 must decrease or 𝑐 must increase. Ways to decrease the chance of extinctions include lowering the number of predators or eradicating parasites that threaten subpopulations. A way to increase the chance of colonizations would be to introduce more corridors between patches to promote movement.

A population that overshoots its carrying capacity _____.

is living at a higher density than the habitat can support

The landscape metapopulation model is even more realistic than the source-sink model because?

it incorporates differences in the quality of the suitable patches ADN the quality of the surrounding matrix. MATRIX QUALITTY matrix can vary in quality for dispersing organisms like high-quality matrix of open forest that allow for dispersal for a regional population of collared lizards to persist and grow requires both high-quality glade habitats and a high-quality matrix of open forest that allow for dispersal consider the challenge that metamorphosing frogs encounter when they move from their natal pond. They face risks of both predation and desiccation. IN FOREST MATRIX DRY UP Moving through a grassy field poses a much higher risk of predation and desiccation than moving through a humid forest. Although neither field nor forest is a suitable habitat for the frog to reproduce, the forest represents a higher-quality matrix for dispersal between ponds. the forest represents a higher-quality matrix for dispersal between ponds FOREST=LESS DESSIC AND OPEN SPACE The landscape model, which is illustrated in Figure 12.17, represents the most realistic, yet also the most complex, spatial structure of populations. Between these two extremes is the scenario in which individuals occasionally move between habitat patches, such as when juvenile animals disperse away from their family to find a mate. fluctuations in abundance in one subpopulation can influence the abundance of other subpopulations., if subpopulations are highly connected by individuals frequently moving among habitat patches EVEN IN scenario in which individuals occasionally move between habitat patches,

Delayed density dependence can be modeled with a modified form of the logistic growth model equation, which we introduced in Chapter 11. This model incorporates density dependence, which causes population growth rates to slow as the population increases in size

logistic; derive of N=rN(1-N/K) Where d N d t is the rate of change in the population size dependent population cycles is to incorporate a delay between a change in carrying capacity and the time the population reproduces. To incorporate a time delay, we begin by clarifying that N t is the current size of the population at time t and then defining the magnitude of the time delay as τ ,For example, in the case of the moose, the time delay from when breeding occurs to when the offspring are born is about 6 months now we do: deriv=rN(1-Nt-tau/K) In words, this equation tells us that the population SLOWS its growth when the population's SIZE, at τ time UNITS IN the PAST, approaches the carrying capacity. PAST K FROM CERTAIN TIME based on magnitude of past pop from car capacity to tell us about growth, modified growth based on past densities

more Population fluctuations

more Population fluctuations In contrast, some populations exhibit much WIDER fluctuations.PROBS BC SMALLER , REPRO FASTER respond faster to bad conditions the algae population fluctuated widely from nearly 0 cells per cubic centimeter in June to more than 7,000 cells per cubic centimeter in September. These wide fluctuations occurred across time scales of days, weeks, and months. ALGAE REPROD AND DIE FASTER, RESPOND TO CONDITIONS Example: Over a single year, the algae population in Lake Erie exhibits wide fluctuations from 0-7,000 cells per m3. ALGAE IN ERIE , SOME ENITRELY DIE IN ONE PART YR -->PROBS BC SMALLER , REPRO FASTER The populations of green algae and diatoms that compose the phytoplankton varied by several orders of magnitude on a scale of days, weeks, and months. Small organisms (e.g., algae) tend to reproduce much faster than larger organisms (e.g., red deer), so their populations often respond faster to favorable and unfavorable conditions. Larger organisms have a lower surface-area-to-volume ratio, which allows them to maintain homeostasis in the face of unfavorable environmental changes. LARGE DIE OFF IN ALGAE AT SPRING END(in June) from early spring chemical, PROBB FERTILIZER IN EARLY SPRING, FERTILIZIER WENT INTO ERIE, ALGAE GET NUTRIENTS NAD SHOT UP, AND CONSUMED IT ALL AND DIED OFF AFTER CONSUMING NUTRIENTS

Patch size and isolation

n Britain, skipper butterflies prefer to livein grasslands grazed by rabbits. Grassland patches varied from 0.01 to 10ha in area. Distances between patches ranged from0.02 to 100 km. The largest and least isolated patches were most likely to be occupied; the smallestand most isolated patches were least likelyto be occupied medium to large and clsoe-e->left of line good chance occupation

The source-sink metapopulation model builds on the basic metapopulation model and adds the reality that different patches of suitable habitat are ?

not of equal quality.m Source sink w low and high qual model that occupants of high-quality habitats are a source of dispersers. Such populations are referred to as source subpopulations. At the same time, there can be low-quality habitats that rarely produce enough offspring to produce any dispersers. These habitats depend on outside dispersers to maintain the subpopulation. These subpopulations are known as sink subpopulations. NEED dispersers TO MAINTAIN

patch size and isolation are important not only to the metapopulation of one species but also to the total ? that live on habitat islands.

number of species, spp richness

You have been conducting research into the birth and death rates of an isolated population of arctic fox. You find that random changes in environmental conditions cause birth and death rates to vary from year to year. However, some individuals have CONSISTENTLY higher birth rates and lower death rates than others regardless of the environmental conditions (but these differences that remain consistent year-to-year) What would be the BEST type of model to use to predict the growth rate of this population?

one that is both demographically and environmentally stochastic Demographic stochasticity is caused by unpredictable changes in individual birth and death rates, not differences that remain consistent year-to-year. so just use environmentally stochastic

Which type of unoccupied patch would be more likely colonized?

one that is closer to an occupied patch

Population models that incorporate delayed density dependence help us understand how time delays cause populations to ?

oscillate in regular cycles. the models do not identify specific mechanisms by which time delays occur, n some cases, delayed density dependence occurs because the organism can store energy and nutrient reserves. The water flea Daphnia galeata, for example, is a tiny zooplankton species that lives in lakes low pop lots food, ndividuals can store surplus energy in the form of lipid droplets. As the population grows over time to the carrying capacity and food becomes scarce, adults with stored energy can continue to reproduce grows over time to the carrying capacity and food becomes scarce, adults with stored energy can continue to reproduce. Daphnia mothers can also transfer some of these lipid droplets to their eggs, which allows their offspring to grow well even if the carrying capacity of the lake has been exceeded. water fly lipid energy transfer to eggs from Daphnia mothers Eventually, the stored energy is used up and the Daphnia population crashes to low numbers. When the population is low, the food can once again become abundan stored past energy buffering food reduction Daphnia galeata water fleas can store high amounts of energy, which allows them to survive and reproduce even after reaching carrying capacity. When energy reserves run out, the population crashes to very low numbers and then rebounds and continues to oscillate oscillation continues after crashing We can contrast the story of the water flea Daphnia with the story of another species of water flea, Bosmina longirostris. Bosmina do not store as many lipid droplets as Daphnia, so when their population approaches the lake's carrying capacity, they have little energy to buffer the reduction in food As a result, Bosmina populations do not exhibit large oscillations. Instead, as illustrated in Figure 12.11b, they grow to their carrying capacity and remain there. not enough en to grow past reproduce beyond the carrying capacity Daphnia galeata water fleas can store high amounts of energy, which allows them to survive and reproduce even after reaching carrying capacity contin oscillations between carrying die-off and overshoot

A population that has an intrinsic rate of growth of 0.42 and a reproductive time delay of 2 years will most likely _____.

oscillate initially, but the magnitude of the oscillations will decline over time

What was NOT involved in the decline of the black-footed ferret's population in the American West?

overharvesting for fur

12.4 Metapopulations are composed of subpopulations that experience independent population dynamics

population dynamics over time, but population dynamics also occur over space. Whether on land or in water, species that have a particular geographic range are commonly subdivided into smaller subpopulations, time space population, and into smaller sub pop This happens because preferred habitat is not continuous, but occurs as patches of suitable habitat that are surrounded by a matrix of unsuitable habitat As you may recall from our description of the collared lizards in Chapter 10, the animals did not live in the entire forest, but rather in glades, for optimal temp and food As illustrated by the lizards, it is not always easy to move from one patch of habitat to another As a result, the larger population is broken up into smaller groups of conspecifics that live in isolated patches called subpopulations. based on how much can dispersing to other habitat patches. When individuals frequently disperse among subpopulations, the whole population functions as a single structure and they all increase and decrease in abundance synchronously. When dispersal is infrequent, however, the abundance of individuals in each subpopulation can fluctuate independently of one anothe The collection of subpopulations that live in isolated patches and are linked by dispersal is called a metapopulation. populations are broken up into metapopulations and review the three types of metapopulation models.

constraints on growth and survival orgs

principle of limiting factors, pops limited by predation, herbivory and competition-->we have biol limiting factors, also PHYSICAL limiting factors, that also constrain growth-->sun, temp, moisture, nutrients., not having right conditions like too icy for plants to grow, moisture not limiting in New York for example

The basic metapopulation model explains how to find the proportion of occupied patches, 𝑝, in a fragmented habitat. In this model, 𝑝 is 1 minus the probability of extinction, 𝑒, divided by the probability of colonization, 𝑐. The basic metapopulation model also allows for the calculation of extinction rates and colonization rates. Use the data in the table to calculate the missing rates of extinction and rates of colonization. Round your answer to three decimal places.

rate of extinction when 𝑝=0.2: Proportion of occupied patches 𝑝 is 0.2 Probability of extinction e is 0.25 so e x p gives Rate of extinction-0.05 Rate of colonization where c = probability colonization (𝑐×𝑝)×(1−𝑝)= 0.50 * 0.2, = (0.1)*(1-0.2)=0.08 rate of colonization when 𝑝=0.2: 0.08

density-dependent population models we have examined show that small populations have more rapid growth rates than do large populations. This suggests that a small population should quickly ? and become a larger population. By this reasoning, small populations should be resistant to extinction

rebound smaller due to higher growth The models that we have studied up to this point have assumed a single birth rate and death rate for each individual in the population

sumlxbx for ? sumlxbx/lxbx

reproduction rate generation time intrinsic growth rate lambda

subpopulations on the brink of extinction can be supplemented by the arrival of dispersers from other subpopulations. The phenomenon of dispersers supplementing a declining subpopulation that is headed toward extinction is called the?

rescue effect The rescue effect should result in a higher probability that less isolated patches will be occupied. but effect not itself that less isolated ones saved more subpopulations on the brink of extinction can be supplemented by the arrival of dispersers from other subpopulations. The phenomenon of dispersers supplementing a declining subpopulation that is headed toward extinction is called the rescue effect Rescue effect should result in a higher probability that less isolated patches will be occupied.

German plants

researchers placed the populations into one of six population size categories and averaged the extinction rates across the eight species for dif pop size cats,, they found that the probability of extinction was higher for smaller population sizes and lower for larger populations. researchers in Germany examined the persistence of 359 populations of plants that spanned eight different species . They subsequently placed the populations into six size categories and averaged extinction rates across the eight species They found that populations with the lowest number of individuals experienced the highest probability of extinction over a 10-year period

In our models of population growth, we have seen that when populations are large, density-dependent factors cause ? growth, and when populations are small, density-dependent factors cause faster growth.

slower growth if dens dependent, how to explain extinction . In this section, we will explore the relationship between population size and the probability of extinction. We will then examine the underlying

?populations are more vulnerable to extinction than are larger populations. To study this phenomenon in birds, biologists conducted surveys of bird populations on the Channe, measured with

small pops Similar patterns have been observed for many other groups of animals, including mammals, reptiles, and amphibians. To study this phenomenon in birds, biologists conducted surveys of bird populations on the Channel Islands, which are located off the coast of California. The islands range widely in size, from 2.6 to 249 km 2 . A breeding pairs of different species and the extinction rates of populations on particular islands . Bird populations of the Channel Islands off the coast of California were measured in terms of the number of breeding pairs. Islands with larger population sizes had a reduced probability of going extinct o the smallest populations experienced the highest probability of extinction and the largest populations experienced the lowest probability of extinction

You are conducting a research project examining the spatial structure and movement of an endangered forest-dwelling bird species across the fragmented landscape where it is endemic. During your study, you collect data on the type and amount of resources available for the bird in all forest patches throughout its geographical range. In each of these forest patches, you also carefully document the immigration and emigration of individuals, colonization of new patches, and extinction events. If these are the only data that you collect, you are using the _____ model.

source-sink metapopulation

Rather, because we see random variation among individuals in a population, the growth rate is not constant; it can vary over time. Models that incorporate random variation in population growth rate are known as ? models. dif model based on source of dif birth.death variation in birth rates and death rates is due to differences among individuals and not due to changes in the environment, we call it.

stochastic Stochastic include random birth death variation demographic stochasticity-->birth rates and death rates is due to differences among individuals and not due to changes in the environment, In contrast, when random variation in birth rates and death rates is due to changes in the environmental conditions, we call it environmental stochasticit ( weather, small growth r changeS) and natural disasters, which can cause large changes in the growth rate of a population. Examples of environmental stochasticity include changes in the weather, which can cause small changes in the growth rate of a population, and natural disasters, When we use stochastic models, there is an average growth rate with some variation around that average. The ACTUAL growth rate experienced by the modeled population can take any of the values within the range AROUND THE AVERAGE ESTIMTION of this variation. determinisitc=one growth rate assuming eq birth for all if a population experiences a string of years with above-average growth rates, it will have faster growth model stochastic population growth by modifying the exponential growth model discussed in Chapter 11. For example, we can set the birth rate and death rate to 0.5, which are reasonable values for adult mortality We can let the values for average birth and death rates vary at random. When a population randomly experiences years of low birth rates or high death rates, it is more likely to go extinct LOW B HIGH D=EXTINCT String yrs low birth and death=extinction A string of bad years can drive the population extinct faster in small populations than in large populations. STRING SMALL BAD YRS=RISKY Moreover, at a given population size, as time passes, there is an increased chance that a population will have a string of bad growth years and go extinct MAPPING POP AND PROB EXTINCTION OVER DIF TIMES CHANGING BY 10 FACTOR For example, in a population with 10 individuals, the average probability of extinction within 10 years is 0.16, the average probability of extinction within 100 years is 0.82, and extinction becomes virtually certain (0.98) within 1,000 years. within 1,000 years. In contrast, a population with an initial size of 1,000 has an average probability of extinction of only 0.18 within 1,000 years. about same as pop of 10 within 10 yrs

When considering the metapopulation concept, what is meant by the matrix?

the area between habitat patches that is less suitable for the species

The effect of patch size and patch isolation on patch colonization has been tested by studying populations of ?

the common shrew As shown in Figure 12.20, the researchers found that shrews were much less likely to occupy islands that were smaller and more isolated In Britain, for example, skipper butterflies (Hesperia comma) prefer to live in calcareous grasslands that are heavily grazed by rabbits. The grassland patches varied from about 0.01 to 10 ha in area, and the distances between patches ranged from 0.02 to 100 km. The islands vary in size from about 0.1 to 1,000 ha, and they vary in isolation from less than 0.1 to more than 2 km from other islands or from the shore of the lake he researchers found that the largest and least isolated patches were more likely to be occupied, whereas the smallest and most isolated patches were not occupie In Britain, for example, skipper butterflies (Hesperia comma) prefer to live in calcareous grasslands that are heavily grazed by rabbits. The grassland patches varied from about 0.01 to 10 ha in area, and the distances between patches ranged from 0.02 to 100 km. As shown in Figure 12.21, the researchers found that the largest and least isolated patches were more likely to be occupied, whereas the smallest and most isolated patches were not occupied. All populations have some chance of going extinct given enough time but the smallest populations face a much higher risk of extinction due to demographic and environmental stochasticity. Population dynamics over time can be offset by population dynamics over space, as observed in metapopulations in which habitat fragments can experience extinctions and colonizations that allow the entire metapopulation to persist over time.

Principle of Limiting Factors

the concept that external factors limit the growth and/or survival of organisms Limiting factors are the factors that are not present in abundance. These are the environmental conditions or resources that limit the growth or distribution of an ecosystem. These can be either physical or biological factors which are identified by the increase or decrease in growth or distribution of a population.

The size of subpopulations and the distance between habitat patches influence ?

the probability of colonization.

Whether a population cycles above and below the carrying capacity depends on both the magnitude of the? ( τ ) and the ? (r)

time delay and magnitude of the intrinsic growth rate As the time delays increase, density dependence is further delayed, making the population more prone to overshooting and undershooting the carrying capacity. DELAY INCREASE DENS DEP , PRONE TO OVERSHOOT IF GREATER DELAY BC CONDS MAYBE DIF? AND IF HIGH R In addition, having a high intrinsic rate of growth allows a population to grow more rapidly in a given amount of time, making it more likely that the population will overshoot the carrying capacity high r mena s making it more likely that the population will overshoot the carrying capacity.

Fluctuations over ? are quite common in nature, and some of these fluctuations exhibit cyclic patterns that are due to ? In our models of population growth, we have seen that when populations are large, density-dependent factors cause ? growth, and when populations are small, density-dependent factors cause ? growth

time, delayed density dependence In our models of population growth, we have seen that when populations are large, density-dependent factors cause SLOWER growth, and when populations are small, density-dependent factors cause FASTER growth All populations have some chance of going extinct given enough time, but the smallest populations face a much higher risk of extinction due to demographic and environmental stochasticity. BOTH stochasticity FACTORS Population dynamics over time can be offset by population dynamics over space, as observed in metapopulations in which habitat fragments can experience extinctions and colonizations that allow the entire metapopulation to persist over time

Metapopulations can naturally occur when a habitat is naturally patchy. A good example of a patchy habitat is the ? that are dotted

wetlands, THE FRAGMENTED NATURE OF HABITATS Metapopulations can naturally occur when a habitat is naturally patchy. A good example of a patchy habitat is the wetlands that are dotted across the landscape of many parts of North America (Figure 12.15). errestrial habitat located between these wetlands is generally inhospitable to these organisms, yet individuals of many species are able to disperse across these intervening regions to arrive at another wetland. As you might guess, the amount of movement among wetlands depends on the distance between neighboring wetlands and how far and fast an individual can move. DISTANCE AND SPPED=DISPERSAL Metapopulations also occur as a result of human activities such as clearing forests; draining large wetlands; and constructing roads, housing developments, and commercial properties large habitats into a number of smaller habitats (Figure 12.16). Because the small habitats represent only fragments of the original habitat, this process is called habitat fragmentation. Small habitats typically support small populations, which, as we have seen, are more prone to extinction. However, a group of small populations that is interconnected by occasional dispersal have a unique dynamic in that dispersers can form new subpopulations.

What is NOT true about a metapopulation?

what is true : The metapopulation is made up of a number of subpopulations. and In a metapopulation, individuals are able to move between subpopulations. and In a metapopulation, the habitat between subpopulations is not as favorable as the habitat of the subpopulations. false: The metapopulation as a whole does not experience population growth or decline.

The rescue effect

when dispersers supplement a declining subpopulation and thereby prevent it from going extinct refers to the dispersal between source and sink populations.

Age structure fluctuations age structure in whitefish Erie and tree rings can see higher/lower growth of certain class way into future

whitefish: A classic example of age structure as an indication of population fluctuations comes from data of the commercial harvest of whitefish (Coregonus clupeaformis) in Lake Erie from 1945 to 1951. Biologists determined the age of each fish by examining the scales of the harvested fish, found whitefish ages in 1947, there was a particularly large number of 3-year-old whitefish. This suggests that in 1944, the whitefish population experienced a very high rate of reproduction high birth 3 yr earlier, largest age group as they got older when 2 they out survived and kept massive size far into the future This cohort continued to dominate the population's age structure in subsequent years, with high numbers of 4-year-old fish in 1948 and 5-year-old fish in 1949. Even in 1950, the 6-year-old age class contained more individual still highest age class around 1947 though The whitefish population in Lake Erie experienced an unusually high amount of reproduction in 1944. However, young fish are not captured by fishing nets until they are 2 years old, so the large 1944 cohort was not detected until 1946. When an age group contains a high or low number of individuals, the population likely experienced high birth or death rates in the past. With larger animals that live for several years and have longer generation times, a population at a given time includes individuals born over a long period, which tends to even out the effects of short-term fluctuations in birth rate. pop any time are indivs over long period Example: From 1946-1951, researchers determined the age of harvested whitefish by examining their scales. In 1947, there was a large number of 3-year- old fish. This cohort continued to dominate the population's age structure in subsequent years. Long-term fluctuations in age structure can be determined for a forest by examining tree rings. Example: In a Pennsylvanian forest, researchers removed samples of wood from tree trunks to count growth rings. -cover tree to prevent infection, no open tree wound, inject sterile caulk to not breed mold?, take small core out of tree not chopping down In the 1500s, the forest was largely composed of several species of oak trees. Fire and drought in the mid-1600s led to an increase in white pine trees. oak-->white pine , American beech and eastern hemlock white pine shaded themselves out, beech and hemlock grew and those two now dominate -oaks not extend much past 1500s, didn't add indiv in pop past 1650 American beech trees (Fagus grandifolia) and eastern hemlock trees (Tsuga canadensis) are very tolerant of high-shade environments; new individuals of these species began to grow as the white pines came to dominate and shade the forest. These two species continued to recruit new individuals over time, which caused beech and hemlock to have a population age structure that was more evenly distributed than that of white pine. Following the fire, oak seedlings reestablished themselves in the forest, but there was also an increase in the number of new white pines (Pinus strobis), which grow well under high-sunlight conditions white pines grew large, however, they cast so much shade that new white pine seedlings had a hard time surviving, white pine pop constrained to s a result, most white pine trees in the modern forest dated from the late 1600s and early 1700s As the white pines grew, they shaded out conspecifics and allowed American beech and eastern hemlock trees to grow. POPULATIONS OF RAYS rays increase in small shark, outside shark decrease , fin tooth shark dashed=originl pop size, colored=current population larger sharks on outside decreasing from fishing, top predators are gone due to fishing, now middle layer predators can flourish when top gone, adn their population expand -feed on clams and scallops so their pop shrink -mapping out effects of humans targeting top level sharks -Small organisms such as algae can reproduce in a matter of hours, which means that their populations respond very quickly to both favorable and unfavorable environmental conditions. -heir small bodies and the associated high surface-area-to-volume ratio cause them to be much more affected by environmental changes, including abiotic conditions such as temperature As a result, their rates of survival and reproduction can change quickly for smaller orgs With larger animals that live for several years and have longer generation times, a population at a given time includes individuals born over a long period, which tends to even out the effects of short-term fluctuations in birth rate. life hist bigger animals make them less changed by weird birth fluctuations