APES Unit 6 Quiz
Terms in this set (40)
Hurricanes, ice storm, tsunamis, tornadoes, volcanic eruptions, and forest fires can all be classified as a disturbance.
A disturbance is an event caused by physical, chemical, or biological agents, resulting in changes in population size or community composition
Although the population of a particular producer species might be diminished or even eliminated, the net primary productivity of all the producers in the ecosystem might remain the same. When this is the case, we say that the productivity of the system is resistant.
Resistance is a measure of how much a disturbance can affect flows of energy and matter in an ecosystem
When the flows of energy and matter of an ecosystem are affected by a disturbance, environmental scientists often ask how quickly and how completely the ecosystem can recover its original condition.
Resilience is the rate at which an ecosystem returns to its original state after a disturbance.
A highly resilient ecosystem returns to its original state relatively rapidly; a less resilient ecosystem does so more slowly
Growing interest in restoring damaged ecosystems has led to the creation of a new scientific discipline called restoration ecology.
Restoration ecology is the study and implementation of restoring damaged ecosystems.
Restoration ecologists are currently working on two high-profile ecosystem restoration projects, in the Florida Everglades and in the Chesapeake Bay, to restore water flows and nutrient inputs that are closer to historic levels so that the functions of these ecosystems can be restored
Scientists can measure all of the ecosystem processes.
Scientists commonly conduct such studies in a watershed.
A watershed is all land in a given landscape that drained into a particular stream, river, lake, or wetland
Intermediate Disturbance Hypothesis
Some level of ecosystem disturbance is natural, and may even be necessary to maintain species diversity.
Intermediate disturbance hypothesis is the hypothesis that ecosystems experiencing intermediate levels of disturbance are more diverse than those with high or low disturbance levels
Virtually every community experiences ecological succession.
Ecological succession the predictable replacement of one group of species by another group of species over time.
Depending on the community type, ecological succession can occur over time spans varying from decades to centuries
Some terrestrial communities begin with bare rock and no soil.
A community may begin forming on newly exposed rock left behind after a glacial retreat, newly cooled lava after a volcanic eruption, or an abandoned parking lot.
Primary succession ecological succession occurring on surfaces that are initially devoid of soil.
The bare rock can be colonized by organisms such as algae, lichens, and mosses --- organisms that can survive with little or no soil
Secondary succession the succession of plant life that occurs in areas that have been disturbed but have not lost their soil.
Secondary succession follows an event, such a forest fire or hurricane, that removes vegetation but leaves the soil mostly intact.
Secondary succession also occurs on abandoned agricultural fields.
It usually begins with rapid colonization by plants that can easily disperse to the disturbed area
Pioneer species a species that can colonize new areas rapidly and grow well in full sunshine.
As the pioneer trees increase in number and grow larger, however, they cause an increased amount of shade on the ground.
Because pioneer trees need full sunshine to grow, new seedlings of trees cannot persist
Theory of island biogeography
Theory of island biogeography a theory that demonstrates the dual importance of habitat size and distance in determining species richness
1. dispersing species are more likely to find larger habitat
2. at any given latitude, larger habitats can support more species (less prone to extinction)
3. larger habitats often contain a wider range of environmental conditions, which in turn provide more niches that support a larger number of species
Earth's biodiversity is the product of evolution, which can be defined as a change in the genetic composition of a population over time
Evolution below the species level, such as the evolution of different varieties of apples or potatoes, is called microevolution.
Evolution below the species level
When genetic changes give rise to new species, or to new genera, families, classes, or phyla --larger categories of organisms into which species are organized-- we call the process macroevolution.
Evolution that gives rise to new species, genera, families, classes, or phyla.
Among these levels of macroevolution, the term speciation is restricted to the evolution of new species
Genes are physical locations on chromosomes within each cell of an organism.
A given gene has DNA that codes for a particular trait, such as body size, but the DNA can take different forms known as alleles.
An organism's genes determine the range of possible traits (physical or behavioral characteristics) that it can pass down to its offspring
The complete set of genes in an individual is called its genotype.
Genotypes help to determine the traits of individuals and the two processes that can create genetic diversity in a population: mutation and recombination. An individual's genotype serves as the blueprint for the complete set of traits that organism may potentially possess
An individual's phenotype is the actual set of traits expressed in that individual
Include individual's anatomy, physiology, and behavior
Ex. color of your eyes
DNA is copied millions of times during an organism's lifetime as cells grow and divide.
An occasional mistake in the copying process produces a random change in the genetic code, which is known as a mutation
Genetic diversity can also be created through recombination.
In plants and animals, genetic recombination occurs as chromosomes are duplicated during reproductive cell division and a piece of one chromosome breaks off and attaches to another chromosome
Evolution by artificial selection
When humans determine which individuals to breed, typically with a preconceived set of traits in mind, we call the process evolution by artificial selection.
Artificial selection has produced numerous breeds of horses, cattle, sheep, pigs, and chickens with traits that humans find useful or aesthetically pleasing
Evolution by natural selection
In evolution by natural selection, the environment determines which individuals survive and reproduce.
Members of a population naturally vary in their traits, and certain combinations of those traits make individuals better able to survive and reproduce. As a result, the genes that produce those traits are more common in the next generation
Rather, natural selection favors any combination of traits that improves an individual's fitness -- its ability to survive and reproduce, as we saw in the case of the smallest amphipods surviving predation by fish.
Traits that improve an individual's fitness are called adaptations
Gene flow is the process by which individuals move from one population to another and thereby alter the genetic composition of both populations
Genetic drift is a change in the genetic composition of a population over time as a result of random mating.
Genetic drift is non adaptive, random process.
It can have a particularly important role in altering the genetic composition of small populations
A drastic reduction in the size of a population that reduces genetic variation -known as a bottleneck effect- is another random process that can change a population's genetic composition
Once a species has been forced through a bottleneck, the resulting low genetic diversity causes it to decline to extinction which occurs when the last member of a species dies
Colonizing individuals, or founders, will give rise to an island population that has a genetic composition very different from that of the original mainland population.
A change in the genetic composition of a population as a result of descending from a small number of colonizing individuals is known as the founder effect.
Random process that is not based on differences in fitness
One common way in which evolution creates new species is through geographic isolation.
Geographic isolation is the physical separation of a group of individuals from others of the same species
The process of speciation that occurs with geographic isolation is known as allopatric speciation.
Allopatric speciation The process of speciation that occurs with geographic isolation
Reproductive isolation The result of two populations within a species evolving separately to the point that they can no longer interbreed and produce viable offspring.
At this point, the two populations will have become distinct species
Sympatric speciation The evolution of one species into two, without geographic isolation.
It usually happens through a process known as polyploidy
Genetically modified organism (GMO)
Genetically modified organism (GMO) An organism produced by copying genes from a species with a desirable trait and inserting them into another species.
Inserting genes into an organism is a much faster way to produce desired traits than traditional plant and animal breeding, which can only select from the naturally available variation in a population
Range of Tolerance
All species have a range of tolerance, or limits to the abiotic conditions they can tolerate, such as extremes of temperature, humidity, salinity, and pH.
The suite of abiotic conditions under which a species can survive, grow, and reproduce is the fundamental niche of the species.
The fundamental niche establishes the abiotic limits for the persistence of a species
Biotic factors further narrow the fundamental niche that a species actually uses.
The range of abiotic and biotic conditions under which a species actually lives is called its realized niche
Once we determine what contributes to the realized niche of a species, we have a better understanding of the distribution of the species, or the areas of the world in which the species lives
When we examine the realized niches of species in nature, we see that some species, known as niche generalists, can live under a very wide range of abiotic or biotic conditions.
Niche generalists should fare better under changing conditions because they have a number of alternative habitats and food sources available
Niche specialists are specialized to live under a very narrow range of conditions or feed on a small group of species
The fossil record has revealed five periods of global mass extinction, in which large numbers of species went extinct over relatively short periods of time
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