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Community Ecology- Chapter 4 and 5
Terms in this set (60)
Biological Diversity (1)
The variety of Earth's species and the vast and different amounts of genes they contain, the varying ecosystems in which they live, and the ecosystem processes and nutrient cycling that sustain all life (page 78).
Biodiversity has several different forms, in functional, ecological, genetic, and species diversity. It is considered a renewable resource, and is vital to all life on Earth. It provides us with food, energy, medicines, plant material, and clean water and air. Biodiversity in this way also makes itself a part of the Earth's natural capital, as these processes are used to drive the human economy.
Species Diversity (1)
-The number and abundance of species present on Earth. There are an estimated 4-100 million different species of organisms on Earth, and only 1.8 million have been identified (page 79). The two characteristics of species diversity are species richness and species evenness (89)
-Though this is the most obvious form of biodiversity, it is not the only component. It is vital that there is a large amount of different types of species in the ecosystem however. Because there is a variety of organisms living in an environment at a given time, each with its own needs and niche, more organisms are able to coexist in symbiotic relationships. Without a large degree of diversity in species, there would be fierce competition between all organisms on Earth who would all go after the same resources, and there would simply not be enough resources to go around.
The process where all of Earth's life changes over time through changes within the genes of it's organisms's populations (page 80). This evolution is also known as a change in the genetic characteristics of a given population of an organism from one generation to another, and was first observed by Charles Darwin and David Wallace. This idea holds that all organisms change over time in reaction to environmental factors which select for the most favorable traits to reproduce with the greatest frequency, thus passing along their genetic traits to the next generation and over millions of years evolving a species.
The idea of evolution is very important to ecology. This theory is the basis for the creation of the six kingdoms of life and the 'tree of life' which organizes these organisms according to how recent their mutation was that separated them from the earlier kingdoms. Without evolution, all organisms would still be in the same state that they were in billions of years ago, most likely as a single celled amoeba, and would not change at all over time. it is this theory of evolution that is the basis for all species life on Earth. Evolution acts over generations of a population, while natural selection acts on individuals. Natural selection, and therefore evolution, is limited by the fact that it can only pass on traits that are already present within the genetics of a population or through mutations, and by the reproductive capacity of the population itself.
Natural Selection (1)
-A process which occurs when certain individuals within a population that possess favorable traits for their particular environment are more likely to survive and produce more offspring than their counterparts without this favorable trait. They therefore pass on the favorable trait, and over many years the trait should become a dominant part of the species. Natural selection is seen as the vehicle that drives the process of evolution (page 80)
-Natural selection is a vital part of evolution and of ecology as a whole. Without natural selection, there would be no force or way for organisms to adapt, because if the environment did not necessarily 'pick' the favorable traited organisms to survive longer and produce more offspring, over time their traits would not become the majority within the population. This theory allows for organisms with advantageous traits to pass on these traits to a wide berth of offspring, and therefore make the species itself better adapted to its environment. Natural selection acts on individuals, while evolution acts over generations in populations. Natural selection is limited by the fact that it can only pass on traits that are already present within the genetics of a population or through mutations, and by the reproductive capacity of the population itself.
Fossil Record (1)
-The cumulative amount of fossils, the mineralized replicas of skeletons, bones, leaves, bones, teeth, shells,and leaves of items found in rocks, that are found within the Earth. Though there are many fossils on Earth, because many of them have decomposed and many organisms left no fossils, the fossil record is not a complete picture of past life on Earth. (page 81)
-This is vital because the fossil record is one of the best methods, used by paleontologists, for humans to learn about the past organisms that once lived on the Earth. Unfortunately, due to decay, it represents only about 1% of all species that lived on Earth.
-Random changes in the structure and/or number of DNA molecules within a cell of an organism that can be inherited by offspring. (page 82). These mutations are the result of random changes in DNA through errors in mitosis or meosis. Mutations can also occur through exposure to mutagens such as x rays and radioactivity.
-Mutations are vital because they are one of the main causes of genetic diversity within organisms that allows for natural selection to occur. Without mutations, there would be no new traits present within organisms, and there would not be any natural selection because no new traits would be inherited by offspring. These inheritable mutations also allow for a species to survive in changing conditions, as there is a chance that when the environment changes, a particular organism or subgroup of organisms within a species will have the traits necessary to survive and continue the species.
-Any heritable trait that enables an individual organism to survive and reproduce better than other individuals under the same environmental conditions within the same time period (Page 82). These traits are usually mutations, and are passed onto an organism's offspring so long as the trait is heritable.
-Adaptations are an important part of natural selection. If these adaptations are heritable to the offspring they will pass on to a larger number of organisms than will the matching allele, and therefore will, over successive generations, become prominent among a population of organisms. Adaptations allow organisms with the trait to survive in harsh environmental conditions and carry on the species when other organisms without the trait do not survive.
Differential Reproduction (3)
-A type of reproduction which enables individuals with a particularly advantageous trait to leave more offspring than the other members of a population who do not have the trait leave (page 82).
-Differential reproduction does not act on traits that allow an organisms to reproduce for the same amount of time as other organisms, but is not advantageous. For example, if there is a species of bunny who will reproduce until it is 5 years old, and a trait that allows these bunnies to live three years longer than other bunnies by avoiding a disease it gets at the age of 6, this trait will not be passed on through differential reproduction, because it does not affect the amount of offspring an organism will have in its lifetime. Though it will be passed on to this organism's offspring, this trait will not serve as an adaptation through natural selection.
Geographic Isolation (2)
The first stage of speciation, the process where two species arise where there was formerly only one species. This first phase occurs when different groups of the same population of species are separated from one another for a very long period of time by physical location. This can be when one group of an organism leaves a land mass to search for food and does not return, or after the breaking apart of land masses (page 86)
This is important because the geographic barrier provides the catalyst in the form of changing environmental conditions that allows for natural selection to slowly work upon two sets of the same organism in order to produce wildly different sets of organisms where before there was only one population. It is believed that all life on Earth may have evolved in this way from one original organism.
Reproductive Isolation (2)
The second phase of speciation, where after the two groups of the same population of organism are separated by a physical barrier, natural selection and mutations take their coarse independently in each geographic population. Over time, due to the difference in environmental factors in each location, the species will generally evolve to a point where they are no longer the same species of organism. (page 86).
Humans today are leading to an increase in this speciation , as we have genetically engineered organisms through the shuffling of their genetic materials in order to create organisms with more favorable traits, as seen in genetically modified foods. Reproductive isolation is also important because it is a process which creates a greater amount of genetic and species diversity within the ecosphere, which is a valuable form of natural capital.
The process by which an entire species ceases to exist on the Earth (page 87).
This is important because when species cease to exist they take away biodiversity from the planet, causing a lack of natural capital. It is also detrimental to an organism's respective ecosystem, as it's niche is no longer filled, causing a detrimental effect upon the other organisms that relied upon the services it provided. Humans play a large (and often negative) role in extinction, as we often cause extinction of organisms by wiping out their habitats or hunting them.
Endemic Species (3)
Species that are found only in one area of the world, and are therefore especially vulnerable to becoming extinct. They usually exist on islands and in other small areas such as the tropical rain forest, where those specialized environmental conditions are the only place in the world that allow their survival (87).
Endemic species are important because they are extremely susceptible to extinction, because if the one area that they are accustomed to living in is destroyed, they no longer have a home and have no way to adapt to another environment. An example of this is the Golden Toad of Costa Rica, which went extinct in 1989 due to climate change causing a lack of moisture to it's forest home.
Background Extinction Rate (1)
The low rate which most species have become extinct on Earth, which is a natural process for the Earth and not very detrimental. Based on fossil records, the average background extinction rate for organisms was between one to five species for each million species on Earth per year to go extinct (88)
Mass Extinction (1)
The significant rise in the extinction rates above the background level. In large, widespread events which often span the globe, many groups of species are wiped off in a geological period lasting up to five million years. According to fossil records, the Earth has experience five mass extinctions during the past 500 million years. (page 89)
Mass extinctions are important ecause they provide an opportunity for new species to evolve to fill the void left by now extinct species. Because specialization and extinction are currently in balance (as evidenced by the millions of species of organisms currently populating the Earth), this means that a mass extinction is not likely to occur naturally at this moment, barring a widespread catastrophic disaster or a man made disaster.
Species Richness (2)
-The number of different species that a community contains. This is a characteristic that determines the species diversity of an ecosystem. (89).
-Communities with a large species richness, such as those in the Tropical Rain Forest, generally have a low amount of species evenness, or abundance of organisms. For example, Terry Erwin found a great number of beetle species within a single tree in the Panama (1700 species!), but only a few organisms within each species. Species richness is generally highest in the tropics and declines as one moves from the equators to the poles. The areas with the highest species richness are the Tropical Rain forests, coral reefs, ocean bottom zone, and tropical lakes. It is hypothesized that higher species richness allows for higher plant productivity ad increases ecosystem stability, but more research is needed to confirm these claims.
Ecological Niche (1)
The distinct role that a species plays within it's ecosystem. This includes everything that affects the survival and reproduction of a species, including the amount of food and water it needs, the amount of space it needs, the type of food it needs, the optimum climate and temperature range it needs, and the amount of space it takes up. The niche is a pattern of living, whereas a habitat is the physical location where an organism lives (page 91)
A niche is a vital part of ecology. Because each organism has its own niche within its ecosystem, a large variety of different organisms are able to exist together within one ecosystem. Organisms with more specialized niches are able to survive in a lower range of conditions, and are therefore more susceptible to extinction than organisms with a wider range of niches.
Generalist Species (1)
Organisms with broad niches that can live in many different areas, eat a variety of different foods, and also tolerate a wide range of environmental conditions (page 92). Generalists are more advantageous than specialists in environments where there is rapid change.
Examples of generalist species are flies, cockroaches, raccoons, deer, and even humans, as they can live in a wide variety of environments and survive on a variety of foods.
Specialist Species (1)
A species that occupies a narrow niche, and is therefore able to only live in one type of habitat, tolerate a narrow range of climate conditions, and eat one or a few types of food available in certain places. These species are more prone to extinction during a change in environment. (page 92). Specialists are more advantageous than generalists in environments which do not rapidly change.
Examples of specialist species include the tiger salamander, (who can only breed in fishless ponds), the Giant Panda in China, and shorebirds.
Native Species (1)
One of the five classification of niches for species. These species live and thrive normally in a particular ecosystem. (page 92)
An example of a native species would be the Field Sparrow, which is a native bird of Ohio.
Non-Native Species (1)
One of the five niches of species classification. Species that migrate into or are otherwise introduced into another ecosystem. They are also called invasive, alien, or exotic species.(page 93)
Examples of these species are domesticated crops and animals such as chicken, cattle, and fish. These are beneficial non-native species. Other species, such as the freakin' Gypsy Moth, can become pests, and humans will go out of their way to eliminate the species, usually futilely. These organisms can spread rapidly if they find a niche more favorable than their own, where they do not face predators or diseases.
Indicator Species (1)
One of the five niches of species classification. Species that provide early warnings of damage to a community or an ecosystem. These species serve as 'biological smoke alarms (really book? Even I know that is a very lame analogy) for when an ecosystem is no longer healthy. (page 93).
Examples of indicator species include the trout, which when they are absent, indicate a low level of water quality, because trout need water that is very clean with high levels of dissolved oxygen. Other examples include birds, butterflies, and amphibians.
Keystone Species (1)
One of the five niches of species classification. Species that have a large effect on the types and abundance of other species within an ecosystem (page 95). These species can have a great effect on their environment despite relatively low numbers of organisms (which can make them more vulnerable to extinction).Elimination of a keystone species can drastically alter a community.
Important roles of keystone species include pollination, and performing the role of the top predator. Examples of pollinators include butterflies and bees. Examples of the top predator species include alligators, wolves, leopards, and sharks. The loss of keystone species can lead to population crashes and the extinction of other species within the community.The difference between a foundation and a keystone species is that foundation species help to create habitats and ecosystems, whereas keystone species play a foundation role, but also an active role in maintaining its ecosystem for its own purposes.
Foundation Species (1)
One of the five niches of species classification. A species which plays a major role in shaping communities by creating and enhancing their habitats to benefit other species (page 95).
An example of a foundation species is the elephant, which will uproot trees which create forest openings in the grasslands of Africa, which promotes grass growth for other small species, such as antelope, to eat. Beavers are also foundation species, as the dams they build as their homes create pond ecosystems for other organisms to live in. The difference between a foundation and a keystone species is that foundation species help to create habitats and ecosystems, whereas keystone species play a foundation role, but also an active role in maintaining its ecosystem for its own purposes.
Interspecific Competition (1)
One of the five basic types of interactions between species that share limited resources. This occurs when members of two species interact and are in competition to gain access to the same limited resource (food, light, etc).(Page 101). An example of this is between the grubs and squirrels that live within a deciduous forest, which are both in competition to eat acorns.
One of the five basic types of interactions between species that share limited resources. This occurs when a member of one species feeds on a member of the other species. The predator is the organism feeding, and the prey is the organism that is being used as food.(page 101).
Omnivores, herbivores, and carnivores are considered predators, but detritus feeders and decomposers are not, because the organisms they feed off of are not living. One example of a predator prey relationship is the grizzly bear and the army cutworm moth, where the grizzly bear will serve as the predator and consume over 40,000 moths a day as prey before winter to store fat! Another example is the sea urchin, that moves along the ocean bottom as a predator to capture its prey, the plants it feeds on. Carnivores use several tactics for finding prey, such as pursuit, ambush, camouflage, and even chemical warfare. Prey species have adapted as well to avoid predation by travelling fast, having highly developed senses to alert themselves of predators, having protective shells or thick bark, and even thorns. Some prey use chemical warfare themselves to discourage predators using chemicals that are irritating, foul smelling, or bad tasting. This is a very important relationship because predators drive the evolution of prey species by providing a pressure for natural selection .
One of the five basic types of interactions between species that share limited resources. This occurs when one organisms feeds on the body of another organism, living on or in its host. The parasite is the organism stealing the energy, and the host is the organism getting sucked of its energy. (page 101).
A parasite is different than a predator because it is smaller, and generally does not immediately kill the host (if it kills the host at all, which is rare). It instead only takes nourishment from the host, which can weaken the host over time. An example of a parasite is a tapeworm, which live inside of the host, such as a human. Another example is a mosquito, which attaches itself to the outside of its host, often again a human. Some parasites move hosts rather quickly, while other parasites remain on one host for an extended period of time. Parasites promote biodiversity by increasing species richness and keeping host populations under control. Coevolution can also result from parasite-host relationships.
One of the five basic types of interactions between species that share limited resources. This occurs in an interaction that benefits both species by providing each with a limited resource that they require for survival. (page 101)
Mutualistic relationships often provide nutrition and protection to each organism. An example of mutualism is gut inhabitant mutualism, where a large amount of bacteria within animal digestive systems help digest food and in turn receive a habitat and food. Each species benefits by unintentionally exploiting the other as a result of traits it developed via natural selection. Other examples of mutualism include clownfish species who live in anenome's for protection and detritus food, and the anenome in turn recieves protection from some predators. Another example are the oxpeckers that ride on the back of rhinoceroses, that eat parasites and bugs off of them. The birds receive a free meal, and the rhinocerous is then free of pests and is alerted to predators by the birds high pitched call.
One of the five basic types of interactions between species that share limited resources. An interaction that benefits one species but has no effect on the other species. (page 101).
An example of this is silverfish insects who move along with army ants to share food with the ants after raids. Since the silverfish insect benefits and the ant is not harmed or benefited, this is commensalism. Another example is epiphytes, which grow up the base of some trees in tropical forests to receive more light and water. The epiphytes are benefited by gaining more resources, and the tree is neither harmed nor helped by this interaction.
Competitive Exclusion Principle (1)
The concept that states that no two species can occupy the exact same niche and survive indefinitely. (page 102). While many organisms do have an overlap of their niches, this overlap cannot be complete, otherwise there will not be enough resources and competition will become too fierce for both populations to survive in that ecosystem.
When two species are in competition for the same resources, one species will take over, and the other species is forced to migrate, change its feeding habits via natural selection to alter its niche, drastically reduce its population, or suffer extinction. Humans have been dominating the resources of many organisms and may be forcing them into extinction.
A protective device used by some prey species. This allows them to gain protection by looking and acting like a species that is poisonous to a predator (page 103).
An example of mimicry is the nonpoisonous viceroy butterfly, which uses mimicry to look like a Monarch butterfly, which predators avoid because they know it is poisonous.
When populations of two different species interact over a long period of time and cause changes in the gene pool of each other, inevitably causing both sides to become more competitive (page 104).
An example of coevolution is between bats and moths. Bats evolved to eat moths by hunting at night and using echolocation to detect its prey. Moths evolved ears sensitive to sound frequencies used by bats to find them as a defense against the bat predator. Bats developed a countermeasure against this by changing the frequency of their sound pulses so that the moths can no longer detect them. In turn, some moths are now able to jam the bats echolocation systems using their own method of high pitched clicks. In this way both species of animals were shaped by the other. Coevolution promotes biodiversity by increasing species diversity, and encourages long term sustainability of the environment.
Resource Partitioning (1)
An occurrence where species competing for a shared, scarce resource adapt their behavior so that they can both use the given resource but at different times, in different ways, or in different places. This allows several organisms who need the same resource to thrive in a community without too much competition between species (page 107)
An example of resource partitioning is in insect eating bird species, where several different species of bird will all eat the insect population from a certain species of tree, but each bird will only eat from a certain area of the tree unique to their species. This allows all bird species to eat an insect population from a given tree without causing over competition or a food scarcity.
Population Dynamics (1)
The study of how the distribution numbers, age structure, and density of populations change in response to any changes in the environmental conditions (page 108). These conditions include temperature, presence of disease or chemicals, resource availability, and the populations of other competing species.
Population dynamics are important in understanding the biological importance of a species of organism within their respective ecosystem, such as in finding that the sea otter is a keystone species within its ecosystem. Population dynamics can also show humans how their treatment of the environment through pollution or habitat destruction has altered the population of a given organism.
Age Structure Diagram (1)
-A diagram that depicts the proportions of individuals at various ages within a population of a species (page 109). These diagrams separate individuals into pre-reproductive age, reproductive age, and post-reproductive age, (which is a listing of too young to mate, mating age, and too old to mate, respectively).
This diagram can show how likely a population is to grow, shrink, or remain stable. A population with mostly post-reproductive age organisms will likely begin to shrink, a population with organisms in their reproductive or pre-reproductive stage will likely grow, and a population with an equal population dispersion among the three classes will remain stable. This age structure diagram does not take into account possible emigration or immigration, however, so is not completely accurate.
Biotic Potential (1)
The capacity of a species population to grow under ideal conditions (page 109). Species with a high biotic potential will produce more offspring in ideal conditions, and species with a low biotic potential will produce less offspring in ideal conditions.
Large individuals such as elephants or humans, have relatively low biotic potentials due to the long time it takes them to produce a child and the small carrying rate of children (generally one at a time). Smaller individuals, such as bacteria, have a very high biotic potential because they reproduce so rapidly.
Intrinsic Rate of Increase (1)
Abbreviated as (r). This is the rate a population's species would grow at if it had completely unlimited resources. Organisms with a high intrinsic rate generally reproduce early in life, have shorter generation times, can reproduce multiple times, and have many offspring each reproductive cycle (page 109).
The higher the intrinsic rate of increase, the higher the biotic potential is for an organism, meaning that they will produce more offspring under ideal conditions. The intrinsic rate of increase is a numerical value which quantifies the biotic potential of an organism. No population can grow at this rate indefinitely due to a scarcity of resources and competition between other species and within an organism's own species for these resources.
Limiting Factors (1)
A resource in an ecosystem that is only given in a fixed amount and but is needed by every organism within a species. Limiting factors are therefore scarce, and due to this scarcity they prevent the exponential population growth of organisms, as not every organism can attain all of the limiting factors they need to survive and reproduce if the population is growing too quickly and has used the resources up before they are replenished (page 109).
Examples of limiting factors include light, water, space, nutrients, and a hiding mechanism to avoid exposure to predators.
Environmental Resistance (1)
The combination of all of the factors together that act to limit the growth of a population of organisms (page 110). Basically, this is everything in nature that is working to control the population, like the buzzkill of nature trying to end the population party early.
Environmental resistance is the sum of all of the limiting factors in the environment, so an example of the environmental resistance for plants within a temperate forest would be the amount of light, the amount of water, the amount of soil nutrients, the amount of space available, and the amount of protection they could receive from herbivores. This value is used with the biotic potential in order to determine the carrying capacity of a population.
Carrying Capacity (1)
Abbreviated as (K). This is the maximum population of a given species that a particular habitat can hold indefinitely without being degraded. This can be thought of as the 'Max Setting' on the population of organisms, like the most people you can invite to a house party before you completely run out of party food and people begin to raid your fridge (page 110).
As a population gets closer to its carrying capacity, its growth rate will inevitably slow down because it encounters a severe scarcity of limiting factors. The lesser amount of the limiting factors there are within an organisms environment, the lower the carrying capacity will be.
Exponential Growth Model (1)
The descriptive model that depicts the population growth of an organism which begins slowly and increases at an increasing rate, creating a 'J-shaped' curve (page 110). Basically, the more of the organisms there are, the more they will get their freak on, and the more little baby organisms they will produce.
This population model generally occurs in populations with very few or no limitations upon their population growth, allowing their population to skyrocket.
Logistic Growth Model (1)
The descriptive model that depicts the population growth of an organism which involves very rapid initial population growth followed by a steady decrease in population growth until the population hits a point where it 'levels off' (page 110). This means that a population gets really high really fast, and then has to get rid of some of its population like a little child that eats too much food too fast and ends up vomiting.
The slowdown in population growth indicates that the scarce amount of limiting factors is not enough to support the growing population, and therefore many organisms were not able to access these resources and died. Populations will fluctuate slightly, but remain generally around the leveling off point until there are changes to the environmental conditions. This growth model creates a s-shaped and then flattish curved graph.
Population Crash (1)
The massive death of a large amount of a population which occurs when a population is switching from exponential growth to logistic growth due to an increase in population that is over the amount of resources necessary to support it. The reproductive time lag, which is the time needed for a birth rate to fall and death rate to rise in order to account for the lack of resources, generally causes this population crash. This most often occurs when a population is input into a new environment which lacks limiting factors their old environment contained, allowing unchecked growth.There becomes a scarcity of resources quite suddenly due to reproductive lag, which causes a massive amount of the population to die at once before it restores to its carrying capacity population (page 111).
This massive die-off of species eventually leads to a resurgence of species over time at a more reasonable capacity assuming there is no massive emigration and no change in environmental conditions, as well as no extinction of the organism completely.
r-selected species (1)
Species that have a capacity for a high rate of population increase (112). These species have a large amount of offspring that they do not care for for long periods of time. They generally also have high losses of offspring, but they compensate for this by producing a large number of offspring. These are basically the horrible alcoholic mothers of the animal world, who just send their kids off and hope for the best.
These species are examples with a high biotic potential and high intrinsic rate of increase. These organisms could be bacteria, rodents, frogs, turtles, and most insects. They generally reproduce and disperse rapidly in favorable conditions, and increase their population when environmental conditions change through instances such as through fires or volcanic eruptions. This makes them opportunists. These populations go through irregular boom and bust cycles.
k-selected species (1)
Species that tend to reproduce later in life and have a small number of offspring with long life spans. They are also known as competitor species (page 112). The offspring generally develop inside of their mothers (womb), are large, mature slowly, and are protected by one or both parents until the age of maturity (or even remain in a lifelong pack). This creates a few individuals that are strong and will reproduce a few young. These species are the doting helicopter mothers of the animal kingdom, who are almost TOO involved in the lives of their kids (is that where the expression 'Tiger Mom' comes from? Because tigers would be k-selected species...)
These species succeed when their population is close to the carrying capacity. Examples of k-selected species include elephants, whales, humans, cacti, tropical rainforest trees, and dolphins. These species are the most prone to extinction due to their low biotic potential.
Demographic Bottleneck (3)
This an a factor which effects the genetic diversity of a population that plays a role in the genetic diversity and overall survival of an isolated population of organisms. It occurs when a few individuals within a population are the lone survivors of a huge catastrophe (like a tornado or volcanic eruption), and therefore serve as the only source of genetic material for the future population in that area (page 113).
This lack of genetic diversity may cause these populations to have very little diversity of traits when they rebuild the population, and could lead to an increase of genetic mutations that are harmful due to inevitable inbreeding as the population grows. An example would be Noah and his family as the lone survivors on Earth after the flood that devastated all of Earth in The Bible. Since Earth had only, like, 6 people total that eventually created 6 billion, I would not be surprised if mankind lost some pretty cool traits along the way.
Island Biogeograhy (3)
The Theory of Island Biogeography states that the species richness (the number of different species) that are found on an island is determined by both the rate at which new species immigrate to the island and the rate at which species become extinct on an island (page 90). According to the model, eventually the rate of immigration and the rate of extinction will even out andn form a balance point, which will determine the islands average species richness over time.
According to this, the two factors that affect the biogeography are its size and its distance from the nearest mainland. The larger the island, the more different species it will be able to support with its limiting factors, leading to lower extinction rates and higher species richness. Also, the larger the island, the more organisms will come to it because it is a bigger target. The closer an island is to a mainland, the more organisms will make a successful journey to the island, leading to a higher immigration rate and a higher species richness. This is used to evaluate the habitat islands today and help scientists to preserve island ecosystems and preserve wildlife there.
Population Density (1)
The number of individuals in a population found in a particular area or volume of space (page 113). As a population density increases, density dependent population controls, limiting factors which have greater effects once population density increases, become problematic and decrease population growth. These controls include disease, parasitism, predation, and competition. Higher population density helps sexual reproducers find mates and get jiggy with it, but leads to increased mating competition as well, leading to bruised egos. High population density also leads to more competition for food and space overall, as well as could lead to an increased vulnerability by traveling in a large group. Also, more organisms traveling close together could lead to an increased risk of the spread of disease.
A population density is higher in small areas that contain a lot of organisms. For example, a million bacteria living on a ten inch square of dirt have a higher population density that the one worm that lives on that one inch square of dirt.
The gradual change in species composition in a given area over time (page 115). Succession describes how certain populations of organisms rise over time, and others decline or even go extinct in an area.
Succession is important because it allows ecosystem to change in response to changes within the environment, so that an ecosystem is sustainable. It can also increase the biodiversity of an area by having a gradual change for the increase in population of novel species in an area.
Primary Succession (2)
A type of succession where there is a gradual establishment of life in areas where there previously was none, and where there is no soil or bottom sediment to begin with (page 115)
Examples of primary succession would be the slow development of plant life where a glacier has retreated, or the development of life after a volcanic eruption has stripped an area to rock.
Secondary Succession (2)
A type of succession where a series of communities with different species develop in places that contain soil and sediment (page 116)
In this process, an ecosystem may have been damaged, but there is still soil and nutrients present to develop.
Examples of secondary succession would be the turning of abandoned farmland or a cut down forest into a forest ecosystem. New vegetation can germinate in the soil in these places and produce plant life, thus working much faster than primary succession to develop an area.
Pioneer Species (1)
A species within succession that is the first population to arrive, and is often later replaced by other species as the ecological conditions of the area grow and change (page 115). These species attach themselves to weathered rocks to receive the little amount of nutrients they need, and over a long period of time will expel soil which can be used to grow future plants.
An example of pioneer species would be lichens and mosses, which are the first to colonize a bare area in primary succession, but once the area develops their population severely declines as the shrus and herbs that grow due to the fertile soil they have expelled shade them out of existence.
Climax Community (1)
A stable community dominated by long-living plant species that over time will propagate itself. In ideal conditions, this ecosystem will last indefinitely and remains in a state of balance (118). This is seen as the hypothetical 'end of succession', though in life that is not the case.
Most ecologists now accept that these areas are in constant flux due to the constant struggle of organisms to obtain enough light, water, and food.
The ability of a living system to survive moderate disturbances (page 119). If an area is able to survive when disturbances, such as a lack of water to an area or a species extinction, occurs, then it is said to be very persistent.
An example of a persistent ecosystem is the Tropical Rain Forest, which has a high species diversity allowing one species to thrive when others fail in changing environmental conditions. This in turn gives it a very high persistence. Persistence and resilience are inversely related.
The ability of a living system to be restored through secondary succession after a disturbance (119). An ecosystem with a high resilience would be able to rebuild itself fairly easily and develop quickly after a natural disturbance such as a fire or flood.
An example of an ecosystem with a high resilience is grassland. Because grasses store most of their nutrients in their roots held underground, the entire grassland ecosystem can be destroyed but the roots and nutrients remain in tact. This allows the ecosystem to rebuild itself following fires or floods relatively easily.
Tipping Point (3)
The point at which any additional stress to an ecosystem can cause the system to change in an abrupt and irreversible way that usually involves its collapse (page 119). This generally results from chronic pollution or intervention to an area, such as releasing CO2 or cutting down trees for a long amount of time.
An example of an ecosystem reaching a tipping point would be a Tropical Rain Forest, which after years and years of logging will eventually reach its tipping point and no longer be able to sustain the remaining trees which grow there, and would become a grassland.
An interaction between two organisms living within an ecosystem. These relationships can be advantageous to both, harmful to one and advantageous to another, or advantageous to one and unaffected to the other.
An example of symbiosis would be the relationship seen between the digestive bacteria and humans. The bacteria live in a digestive system and receive the benefit of food and shelter, while humans receive the benefit of having much of their food digested, which they could not otherwise eat.
Range of Tolerance (1)
The varying range of conditions that a species can tolerate without a population decline to extinction. Because of individual adaptations and mutations within organisms, as well as the genetic variation of all sexual reproducing organisms, the range of tolerance can be large for many organisms.
An example of a range of tolerance would be a forest in Ohio that is able to tolerate up to two weeks of no sunlight due to rainy conditions, and up to two weeks of assaulting high intensity light. If these conditions were to persist for much longer, a very large chunk of the population would die and the population could become extinct.
Adaptive Radiation (3)
The diversification of a group of organisms into different forms in order to fulfill adaptive niches.
An example of this would be the finches studied by Darwin who have adapted different sized beaks but retained their form of 'finches' in order to be better suited to feed in their individual environment.
Convergent Evolution (3)
The evolution of a species where different species seperately involve similar traits in order to better adapt to their environmental conditions. This trait is similar in form to achieve a specific function, but was not present in the last common ancestor of the two organisms. This provides evidence that evolution is caused by natural selection in order to fulfill a function in the most advantageous way for organisms.
An example of convergent evolution would be koalas having adapted fingerprints very similar to humans. Though both have the same form, these fingerprints were not seen in the last common ancestor of the koala and the human.
The formation of a new species through the process of evolution. This entails a population being moved through some means and then new traits being selected for that are more advantageous to the new environment through natural selection. This would then make a new species that would be unable to breed with the original species.
An example of speciation would be the creation of new species of the Galapogas Finches studied by Darwin. Though they originated from one common Finche-y ancestor, over time different environments caused different sets of their traits to be selected for, so that they developed different species of the Galapogas Finch unable to breed with one another.
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