What does the term rescue effect mean in reference to populations that are fragmented?
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The experimental fragmentation of landscapes of a natural ecosystem resulted in declines in the abundance and distribution of most species in the multispecies animal community inhabiting the landscapes and the extinction of many species. These declines caused the deterioration of the positive interspecific relation between local population abundance and distributional extent in this community. However, when patches were connected by habitat corridors, an immigration "rescue effect" arrested declines in both abundance and distribution and maintained the observed positive relation between them. These results demonstrate the importance of metapopulation dynamics and landscape connectivity for the persistence of populations in fragmented landscapes.
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Losing any plant can drastically affect the local environment.  Loss of the phlox (which grows on sandy soil) is bound to have serious erosion consequenses as the roots of the phlox bind the soil together.  Insects will lose a source of nectar and so the food chain will suffer further up.  \nYou may find the site belwo of interest...;
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They can kill off plants or animals that other animals compete with causing an overpopulation of that species. Or they can introduce a new species into a previously stable ecosystem. The new species may have no competition in the new environment and may overpopulate or it may eat another species and wipe it out.
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The US wildlife service has chosen to reintroduce the wolf back into Yellowstone and other Northern Rockies area.  It has been very successful.  I think that helping to manage what man has destroyed is a good idea.  Look at the overgrown deer population in many parts of the country - a danger to people, a nuisance with no natural enemies, and often starving.    \n\nScotland is doing the same thing.\n\nI don't think that a genetic defect or inbreeding has much to do with it.  Ultimately the lack of population would be man's fault as we encroach and destroy.  It's a red herring.
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Over the last several decades a significant decline in frog populations all over the world have been noticed, they are just not moving to diffrent locations.  Right now thousands of species are considered endangered or extinct.\n\nFrogs have been on this planet for more the three hundred millions years.  They were around at the time of the dinosaurs and out lived them.  They belong to the class amphibia, meaning double life.  This name fits them because they spend part of their life in the water and part of their life on land.  Unlike reptiles amphibians as a whole rely on water a lot more and can never move far from it.  Today there are almost 5900 species of known amphibians, which 4800 are frog species.  Frogs and toads (which are a type of frog) belong to the order anura.  Of this order there are 29 different families.  Many biologists question why frogs are in a state of decline, an answer with more the one apparent culprit.  It seems to be a combination of problems such as habit destruction, cattle grazing, agriculture, pollution, climate change, UV radiation, pesticides, invasive species, and even road traffic.\n\nHumans have caused much destruction to the natural environment.  We reduce the number of habitats suitable for many species to thrive in, causing them to migrate elsewhere, adapt to us, or die off.  Frogs are very fragile creatures that adapt slowly to major change.  They always must maintain wet, moist skin and due to their dependency on water they are unable to migrate long distances to find suitable habitat.  If we destroy the only pond in an area where will the frogs go?  We forget that they are small animals and a distance of a mile might be too much for them.  \n\nForest fragmentation of a few hundred feet is enough to wipe out an entire population of frogs.  Something as simple as a road can devastate a species’ numbers.  If a road blocks them from their mating ground it can be an impossible task to cross it.  Many times on a warm sunny day the road will get very hot, and the frog’s skin will dry out while crossing it, resulting in its death.    Along with forest fragmentation comes the edge effect.  With the edge effect a once cool shaded area can change dramatically.  The edge effect causes greater changes in temperature and moisture that can be unsuitable for many frog species.   Microhabitats can dry out and temperatures inside the forest fragment can become increasing cold due wind patterns.  Along the edge different vegetation can take over resulting in invasive species of both plant and animal.  In Brazil an Amazonian frog species has shown great decline and forest fragmentation seems to play a key role.  Adult survival was not effected by fragmentation but mean clutch size was reduced by 17%.  By experiments it has been shown that the fragmentation of the forest causes increase predation, increase in interspecific competition, and slower growth rate resulting in delayed reproduction.  \n\nNot just forest fragmentation causes frog decline but also other human alterations to habitats is causing declines worldwide.  Wetlands are the homes of many species of frogs and humans over the years have in some way changed the landscape.  The wetting and drying of the wetlands has great influence on many organisms and frogs are no different.  The Murray-Darling Basin of Australia has been modified for irrigation flow and has reduced the overbank flooding into flood plain wetlands.  This degradation of the wetlands has caused all frog species in the area to decline by an average of 23%.\n\nAgriculture is also another way in which humans alter the habitat.  Both rangeland and cropland reduces the population size of frogs.  Cattle grazing greatly alters the habitat.  First off the habitat many times must be made suited for grazing.  This means frog habitat can be destroyed causing a direct effect or the cattle can interfere with frog migration, causing an indirect effect.  By the grazing of livestock migrat
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Extinction. \n  \n\nExtinction is a hot topic, of central interest to conservation, environmentalism and also to academic ecology. Ecologists are increasingly realizing that extinction has shaped the communities and ecosystems we see today, and that it operates on a range of timescales and spatial scales. \n\nExtinction doesn't just involve the complete loss of species, vanishing from the Earth. Extinction of local populations is often of key importance in shaping communities, even though other populations of the same species may exist in the same general area. \n  \n\nLocal extinction of populations. \n\nIn any area of forest, or patch of swamp, or coral reef, populations of animals and plants will be coming and going. If you were to compile lists of (say) all the bird species nesting in an fairly small isolated area of forest in Connecticut in one year then come back 20 years later, although most of the species in the list would be the same, the chances are that some of them would be absent (but quite likely replaced by other species). The ones that have come and gone would likely be the ones that had relatively few nesting pairs there anyway. \n\nWhy would they have gone extinct? Well, most often it would simply be that the population had a run of bad luck. Maybe there were 3 pairs nesting, and just by chance there for several years in a row there were late frosts that killed all the insects so the parents had nothing to feed their young, so the nestlings all died. Small populations are at the mercy of such 'bad luck', known as stochasticity. Even an initially abundant population (of say 150 nesting pairs) might still suffer a series of bad luck events (an exceptionally cold winter knocking back the population, followed by the late spring frosts) that can take it down from abundance to nothing at all in a few generations. \n\nAnother problem in a small population might be inbreeding. In species that normally have quite large populations and lots of exchange of genes, a range of harmful recessive genes can be present in the population without often showing themselves. Only when the population shrinks due to bad luck is there a significant chance of close relatives mating (e.g. if there are only 2 nesting pairs in the forest each year, the young are bound to end up mating with close relatives). When close relatives mate, they each have a good chance of carrying some recessive lethal genes in common; the result may be high mortality among the offspring. Experiments with repeated brother-sister crossings in domesticated animals (for several generations in a row) show that within 3 or 4 generations the young almost never survive to maturity because they have so many things wrong with them. This inbreeding effect is thought likely to hammer many isolated populations as their numbers get low, adding to the bad luck, although there are no well-documented cases of it occurring in wild populations. An apparent example of inbreeding effects appears to be the cheetah (see below), which has very low genetic variability apparently due to its numbers crashing to only 4 or 5 individuals at some unknown time in the last 10,000 years, then expanding rapidly again. Cheetahs have low fertility rates (e.g. very low viable sperm counts), and their cubs have high death rates that seem to be the result of its recent history of inbreeding. In this case, the population remained viable and recovered despite the inbreeding effects, but one can imagine that the problems might equally well kill off less lucky populations/species that reach very low numbers. \n\nObservations suggesting the importance of inbreeding in causing near-extinction:\n\n1) Gray Wolves of Isle Royale, Canada. The population was established by 1 breeding pair of wolves around 1949. By 1980 the population had grown to approximately 50 individuals, but by 1990 it had dropped to 14. Few pups were sighted by investigators who also noted that females were not breeding. Furth
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Extinction is applied only after a species hasn't been recorded for a specified period of time (commonly 50 years) and only after an adequate search has been carried out. It has a very specific meaning. Essentially when a species is declared extinct it means that there is very good reason to believe it is extinct.\n\nPresumed extinct is used fairly regularly. It means that there is reasonable grounds to assume extinction, but either the requiredtime period hasn;t elapsed or for one reason or another exhaustive searches can't be carried out.  Presumed extinct is usually applied either to species that were never well known, so it's impossible to know where to focus a search, or to species that inhabited rugged regions or war zones so that thorough searches are impossible.
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All it has to do is not have a massive penalty, it can be totally useless provided that the population is not very strongly stressed or it uses little extra energy.  If it's a liability it will tend to be selected against but something that's useless doesn't necessarilly put the organism in much more risk.
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Typically called an 'edge effect'.\nAny disturbance in an ecosystem will create  fragmentation of a habitat.... depending on what species' habitat you're talking about.  For example, the pine martin requires large areas of mature coniferous cover.  Putting a clearcut in the middle of a large area of mature coniferous cover will fragment the martin habitat.  The boundary of the mature forest at the clearcut, though, will provide habitat for 'edge species' which require characteristics of both habitat types (mature coniferous and clearcut).  Some species include deer and moose and bears who value the browse and berries in the clearcut, AND the cover of the forest.  Raptors like hawks use the edge as it increases their kill rate: it's easier to see and kill their prey.\nSome species need the variation in habitat on the edges of lakes, too.  Waterfowl need the water for food, and the shore for nesting.  Some fish depend on the insect life that exist only on the edge of their lake.
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How can we save humans from extinction.
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I would say C. The animals that died were weaker than the animals that survived. Their deaths might have occured because they did not possess the genes that enabled them to survive. The wildebeests that survived had adaptations that allowed them to better adapt to the environment.\n\nHowever, it could also be B. Perhaps the animals that died were just old and died of natural causes.\n\nIn my opinion, this question is poorly worded.
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THE NICHE CONCEPT & ETHNIC DIVERSITY\n\n\nIntro\n\nOne of the striking facts about contemporary society, and indeed of much of recorded history, is the division of the human species into distinct ethnic groups, whose interrelations are sometimes antagonistic and sometimes mutualistic\n\nWhile there are many interesting ways social scientists analyze this phenomenon, ecological theory may provide some additional insights\n\nThis lecture approaches this topic as follows:\n\n1. What is ecological niche theory? (brief summary)\n2. How can we apply this theory to human ethnic diversity?\n3. Discussion of Swat case (Barth reading)\n\nCharacter displacement refers to the phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co-occur but are minimized or lost where the species’ distributions do not overlap. This pattern results from evolutionary change driven by competition among species for a limited resource (e.g. food). The rationale for character displacement stems from the competitive exclusion principle, also called Gause's Law, which contends that to coexist in a stable environment two competing species must differ in their respective ecological niche; without differentiation, one species will eliminate or exclude the other through competition.
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It would certainly matter if it were a different animal- I could do that without it significantly hurting my career, but I would lose a lot of time doing the things I love- the bald eagle would be a tough call, since it's so emotionally evocative.  To save gorillas, certainly- Algae, without a second thought-spotted owl, no way.  For me it would depend on the importance of the animal to the overall ecosystem, to the survival of humans as a species, and my own emotional response to the animal.  I doubt losing the bald eagle would have a terribly significant effect on the ecosystem compared to, for example, the rabbit.  Losing gorillas would likely have almost no effect on the ecosystem in general, but they are so much like us, and have such a close link and intelligence, that I would hate to lose them.  The trauma done to the ecosystem with a loss of algae would be unimaginable-Human probably wouldn't survive it.  Spotted owl?  There are very few of them, the niche is already taken by others which would move in to replace them, they have no discernible effect on human life, and I have no emotional attachment to them.  This may all seem cold, but it's how humans are-It's why we use pictures of cute baby seals, instead of salamanders, to elicit donations.
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We have catalogued an estimated less than half the species out there- And once catalogued, we don't have an active system to determine populations of most species.  Thus, we are in the dark about what species are there, how many there are in the population, etc.  GIven that, we have only vague guesses about the number of species lost.  In a similar vein, we assume new species are being born each year, or at least each decade, but since we don't know what species were there before, we certainly can't tell if a species is newly evolved, or is just one we have never seen before.
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B - Habitat degradation would be the closest I would say. \n\nBut, environmental degradation would be a better answer:\nIt is related to the deterioration of the environment both in terms of quantity and extinction of some wildlife species and quality like air, water or land pollution.
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1- large amount of offspring in shorter time than K selected species.\n2- Early reproduction \n3- low biomass\n3- short lifespan\n\nBacteria, mice, insects... they're all r-selected.
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There is this really great book called EXTINCTION by the Ehrlichs(?)...which starts out with a beautiful analogy about the environment. It starts off with this guy who removes rivets (screws) from an airplane wing so that he could sell them for profit. Each rivet/screw represents a unique species that plays an important role in our ecosystem. The loss of each one has an adverse effect on the whole structure. It is true that such effects may or may not have an immediate recognizable effect on us but that does not mean that it is not happening. Also, we humans, have proven that we are really self centered that we do not recognize the damage that we are doing unless it hits us in the face. There are countless examples of chain reactions in the ecosystem due to a loss of an integral species. For example, (although I am no longer certain about the details) due to the misuse of a pesticide by farmers in rural Peru, an outbreak of more resistant  pests evolved. The farmers in reaction started to use more pesticides which affected the other species that naturally feed on and control these pests. The situation got so bad that it escalated to such an extent that cats which controlled the rat population died out because they got the higher dose of the poisonous pesticide in their system. Finally, (believe it or not) they had to fly cats to the area and dropped them from helicopters...thus it did rain cats that day in Peru.