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87 Cards in this Set
- Front
- Back
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population
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a group of individuals all of the same species living in the same area.
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community
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a group of populations living in the same area
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ecosystem
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the interrelationships between the organisms in a community and their physical
environment |
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biosphere
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all the regions of the earth that contain living things.
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habitat
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the type of place where it usually lives
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niche
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all the biotic (living) and abiotic (nonliving) resources in the environment
used by an organism. |
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size of a population,
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symbolically represented by N, is the total number of individuals in the population
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density of a population
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total number of individuals per area or volume occupied
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Dispersion
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how individuals in a population are distributed
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Age structure
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description of the abundance of individuals of each age
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Type I Survivorship
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describe species in which most individuals survive to middle age. After that age, mortality is
high. Humans. |
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Type II Survivorship
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describe organisms in which the length of survivorship is random, that is, the likelihood of
death is the same at any age. Many rodents and certain invertebrates (such as Hydra) are examples. |
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Type III Survivorship
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describe species in which most individuals die young, with only a relative few surviving to
reproductive age and beyond. Type III survivorship is typical of oysters and other species that produce freeswimming larvae that make up a component of marine plankton. Only those few larvae that survive being eaten become adults. |
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biotic potential
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maximum growth rate of a population under ideal conditions, with unlimited resources
and without any growth restrictions. |
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Contributing factors to biotic potential
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• Age at reproductive maturity
• Clutch size (number of offspring produced at each reproductive event) • Frequency of reproduction • Reproductive lifetime • Survivorship of offspring to reproductive maturity |
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carrying capacity
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maximum number of individuals of a population that can be sustained by a particular
habitat |
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Limiting factors of biotic potential
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• Density-dependent factors are those agents whose limiting effect becomes more intense as the population density
increases. Examples include parasites and disease (transmission rates increase with population density), competition for resources (food, space, sunlight for photosynthesis), and the toxic effect of waste products. Also, predation is frequently density-dependent. In some animals, reproductive behavior may be abandoned when populations attain high densities. In such cases, stress may be a density-dependent limiting factor. • Density-independent factors occur independently of the density of the population. Natural disasters (fires, earthquakes, volcanic eruptions) and extremes of climate (storms, frosts) are common examples. |
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reproductive rate (or growth rate) equation
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r = (births - deaths)/N
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intrinsic rate of growth
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When the reproductive rate, r, is maximum (the biotic potential)
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Exponential growth
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whenever the reproductive rate is greater than zero. On a graph where population
size is plotted against time, a plot of exponential growth rises quickly, forming a J-shaped curve |
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Logistic growth
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when limiting factors restrict the size of the population to the carrying capacity of the
habitat. In logistic growth, when the size of the population increases, its reproductive rate decreases until, at carrying capacity (that is, when N = K), the reproductive rate is zero and the population size stabilizes. A plot of logistic growth forms an S-shaped, or sigmoid, curve |
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Population cycles
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fluctuations in population size in response to varying effects of limiting factors. For example,
since many limiting factors are density-dependent, they will have a greater effect when the population size is large as compared to when the population is small. |
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r-selected species
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exhibits rapid growth (J-shaped curve). This type of reproductive strategy is characterized
by opportunistic species, such as grasses and many insects, that quickly invade a habitat, quickly reproduce, and then die. They produce many offspring that are small, mature quickly, and require little, if any, parental care. |
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K-selected species
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one whose population size remains relatively constant (at the carrying capacity, K). Species
of this type, such as humans, produce a small number of relatively large offspring that require extensive parental care until they mature. Reproduction occurs repeatedly during their lifetimes |
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About a thousand years ago, the human population began exponential growth. Why?
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1. Increases in food supply. By domesticating animals and plants, humans were able to change from a hunter/gatherer
lifestyle to one of agriculture. In the last hundred years, food output from agriculture was increased as a result of technological advances made during the industrial and scientific revolutions. 2. Reduction in disease. Advances in medicine, such as the discoveries of antibiotics, vaccines, and proper hygiene, reduced the death rate and increased the birth rate. 3. Reduction in human wastes. By developing water purification and sewage systems, health hazards from human wastes were reduced. 4. Expansion of habitat. Better housing, warmer clothing, easy access to energy (for heating, cooling, and cooking, for example) allowed humans to occupy environments that were previously unsuitable. |
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interspecific competition
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competition between different species
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competitive exclusion principle (Gause’s principle)
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When two species compete for exactly the same
resources (or occupy the same niche), one is likely to be more successful. As a result, one species outcompetes the other, and eventually, the second species is eliminated. The competitive exclusion principle, formulated by G. F. Gause, states that no two species can sustain coexistence if they occupy the same niche. |
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Resource partitioning
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Some species coexist in spite of apparent competition for the same resources. Close study,
however, reveals that they occupy slightly different niches. By pursuing slightly different resources or securing their resources in slightly different ways, individuals minimize competition and maximize success. Dividing up the resources in this manner is called resource partitioning. |
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Character displacement (niche shift)
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As a result of resource partitioning, certain characteristics may enable
individuals to obtain resources in their partitions more successfully. Selection for these characteristics reduces competition with individuals in other partitions and leads to a divergence of features, or character displacement. |
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Realized niche
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part of their existence where niche overlap is absent, that is, where they do not compete for
the same resources. |
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fundamental niche
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The niche that an organism occupies in the absence of competing species
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Predation is another form of community interaction.
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any animal that totally or partly
consumes a plant or another animal |
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true predator
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kills and eats another animal
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parasite
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spends most (or all) of its life living on another organism (the host), obtaining nourishment from the
host by feeding on its tissues. Although the host may be weakened by the parasite, the host does not usually die until the parasite has completed at least one life cycle, though usually many more. |
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parasitoid
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an insect that lays its eggs on a host (usually an insect or spider). After the eggs hatch, the larvae
obtain nourishment by consuming the tissues of the host. The host eventually dies, but not until the larvae complete their development and begin pupation. |
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herbivore
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an animal that eats plants. Some herbivores, especially seed eaters (granivores), act like predators
in that they totally consume the organism. Others animals, such as those that eat grasses (grazers) or leaves of other plants (browsers), may eat only part of the plant but may weaken it in the process. |
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Symbiosis
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two species that live together in close contact during a portion (or all) of their lives
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Mutualism
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a relationship in which both species benefit (+,+)
• Certain acacia trees provide food and housing for ants. In exchange, the resident ants kill any insects or fungi found on the tree. In addition, the ants crop any neighboring vegetation that makes contact with the tree, thereby providing growing space and sunlight for the acacia. • Lichens, symbiotic associations of fungi and algae, are often cited as examples of mutualism. The algae supply sugars produced from photosynthesis, and the fungi provide minerals, water, a place to attach, and protection from herbivores and ultraviolet radiation. In some cases, however, fungal hyphae invade and kill some of their symbiotic algae cells. For this and other reasons, some researchers consider the lichen symbiosis closer to parasitism. |
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commensalism
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one species benefits, while the second species is neither helped nor harmed (+,0)
• Many birds build their nests in trees. Generally, the tree is neither helped nor harmed by the presence of the nests. • Egrets gather around cattle. The birds benefit because they eat the insects aroused by the grazing cattle. The cattle, however, are neither helped nor harmed. |
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parasitism
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the parasite benefits from the living arrangement, while the host is harmed (+,–)
• Tapeworms live in the digestive tract of animals, stealing nutrients from their hosts. |
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coevolution
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evolution of one species in response to new adaptations that appear in another species
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Secondary compounds
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toxic chemicals produced in plants that discourage would-be herbivores
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Camouflage (or cryptic coloration)
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any color, pattern, shape, or behavior that enables an animal to blend in
with its surroundings. Both prey and predator benefit from camouflage. |
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Aposematic coloration (or warning coloration)
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conspicuous pattern or coloration of animals that warns
predators that they sting, bite, taste bad, or are otherwise to be avoided. |
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Müllerian mimicry
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when several animals, all with some special defense mechanism, share the same
coloration. Müllerian mimicry is an effective strategy because a single pattern, shared among several animals, is more easily learned by a predator than would be a different pattern for every animal. Thus, bees, yellow jackets, and wasps all have yellow and black body markings. |
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Batesian mimicry
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when an animal without any special defense mechanism mimics the coloration of an
animal that does possess a defense. For example, some defenseless flies have yellow and black markings but are avoided by predators because they resemble the warning coloration of bees. |
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Pollination of many kinds of flowers
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a result of the coevolution of finely-tuned traits between the flowers
and their pollinators. • Pollen from flowers of the Yucca plant is collected by yucca moths. Pollination is accomplished when the moths roll the pollen into a ball, carry it to another Yucca plant, and deposit it on the stigma of a flower. The moth also deposits its eggs into some of the flower’s ovules, but only about a third of the flower’s seeds are eaten by the moth larvae after hatching from the eggs. There are no other pollinators for Yucca and no other hosts for yucca moth egg-laying. • Red, tubular flowers with no odor have coevolved with hummingbirds who are attracted to red and have long beaks and little sense of smell. The flowers provide a copious amount of nectar in exchange for the transfer of their pollen to other flowers. |
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Ecological succession
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change in the composition of species over time.
Succession occurs in some regions when climates change over thousands of years. Over shorter periods of time, succession occurs because species that make up communities alter the habitat by their presence. In both cases, the physical and biological conditions which made the habitat initially attractive to the resident species may no longer exist, and the habitat may be more favorable to new species. |
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climax community
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a final successional stage of constant species composition. The climax community persists relatively unchanged until destroyed by
some catastrophic event, such as a fire. |
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Some of the changes induced by resident species are
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1. Substrate texture may change from solid rock, to sand, to fertile soil, as rock erodes and the decomposition of
plants and animals occurs. 2. Soil pH may decrease due to the decomposition of certain organic matter, such as acidic leaves. 3. Soil water potential, or the ability of the soil to retain water, changes as the soil texture changes. 4. Light availability may change from full sunlight to partly shady, to near darkness as trees become established. 5. Crowding, which increases with population growth, may be unsuitable to certain species. |
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pioneer species
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The plants and animals that are first to colonize a newly exposed habitat.
They are typically opportunistic, r-selected species that have good dispersal capabilities, are fast growing, and produce many progeny rapidly. Many pioneer species can tolerate harsh conditions such as intense sunlight, shifting sand, rocky substrate, arid climates, or nutrient-deficient soil. For example, nutrient-deficient soils of some early successional stages harbor nitrogen-fixing bacteria or support the growth of plants whose roots support mutualistic relationships with these bacteria. |
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Primary succession
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occurs on substrates that never previously supported living things. For example, primary
succession occurs on volcanic islands, on lava flows, and on rock left behind by retreating glaciers. Two examples follow: • Succession on rock or lava usually begins with the establishment of lichens. Hyphae of the fungal component of the lichen attach to rocks, the fungal mycelia hold moisture that would otherwise drain away, and the lichen secretes acids which help erode rock into soil. As soil accumulates, bacteria, protists, mosses, and fungi appear, followed by insects and other arthropods. Since the new soil is typically nutrient deficient, various nitrogenfixing bacteria appear early. Grasses, herbs, weeds, and other r-selected species are established next. Depending upon local climatic conditions, r-selected species are eventually replaced by K-selected species such as perennial shrubs and trees. • Succession on sand dunes begins with the appearance of grasses adapted to taking root in shifting sands. These grasses stabilize the sand after about six years. The subsequent stages of this succession can be seen on the dunes of Lake Michigan. The stabilized sand allows the rooting of shrubs, followed by the establishment of cottonwoods. Pines and black oaks follow over the next fifty to one hundred years. Finally, the beech-maple climax community becomes established. The entire process may require a thousand years. |
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Secondary succession
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begins in habitats where communities were entirely or partially destroyed by some kind of
damaging event. For example, secondary succession begins in habitats damaged by fire, floods, insect devastations, overgrazing, and forest clear-cutting and in disturbed areas such as abandoned agricultural fields, vacant lots, roadsides, and construction sites. Because these habitats previously supported life, secondary succession, unlike primary succession, begins on substrates that already bear soil. In addition, the soil contains a native seed bank. Two examples of secondary succession follow: • Succession on abandoned cropland (called old-field succession) typically begins with the germination of r-selected species from seeds already in the soil (such as grasses and weeds). The trees that ultimately follow are region specific. In some regions of the eastern United States, pines take root next, followed by various hardwoods such as oak, hickory, and dogwood. 243 |
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trophic levels
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plants and animals are organized into groups called trophic levels that reflect their main energy source
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Primary producers
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autotrophs that convert sun energy into chemical energy. They include plants, photosynthetic
protists, cyanobacteria, and chemosynthetic bacteria. |
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Primary consumers
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herbivores, eat the primary producers
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Secondary consumers
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primary carnivores, eat the primary consumers
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Tertiary consumers
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secondary carnivores, eat the secondary consumers
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Detritivores
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consumers that obtain their energy by consuming dead plants and animals (detritus).
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decomposers
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smallest
detritivores, called decomposers, include fungi and bacteria. |
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Ecological pyramids
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used to show the relationship between trophic levels
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Ecological efficiency
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the proportion of energy represented at one trophic level that is transferred to the next
level. The relative sizes of tiers in an energy pyramid (or pyramid of productivity) indicate the ecological efficiency of the ecosystem. On average, the efficiency is only about 10 percent, that is, about 10 percent of the productivity of one trophic level is transferred to the next level. The remaining 90 percent is consumed by the individual metabolic activities of each plant or animal, or is transferred to detritivores when they die. Because ecological efficiency is so low, nearly all domestic animals used for food or work are herbivores. If a carnivore were raised for food or work, the energy required to raise and sustain it would far exceed its value in food or work. The meat consumed by the carnivore would yield a greater return by merely using it directly for human food. |
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Biogeochemical cycles
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describe the flow of essential elements from the environment to living things and back to the
environment |
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Hydrologic cycle (water cycle).
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• Reservoirs: oceans, air (as water vapor), groundwater, glaciers. (Evaporation, wind, and precipitation move
water from oceans to land.) • Assimilation: plants absorb water from the soil; animals drink water or eat other organisms (which are mostly water). • Release: plants transpire; animals and plants decompose. |
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Carbon cycle
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• Reservoirs: atmosphere (as CO2), fossil fuels (coal, oil), peat, durable organic material (cellose, for example).
• Assimilation: plants use CO2 in photosynthesis; animals consume plants or other animals. • Release: plants and animals release CO2 through respiration and decomposition; CO2 is released when organic material (such as wood and fossil fuels) is burned. |
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Nitrogen cycle.
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• Reservoirs: atmosphere (N2); soil (NH4
+ or ammonium, NH3 or ammonia, NO2 – or nitrite, NO3 – or nitrate). • Assimilation: plants absorb nitrogen either as NO3 – or as NH4 +; animals obtain nitrogen by eating plants or other animals. The stages in the assimilation of nitrogen are as follows: Nitrogen fixation: N2 to NH4 + by nitrogen-fixing prokaryotes (in soil and root nodules); N2 to NO3 – by lightning and UV radiation. Nitrification: NH4 + to NO2 – and NO2 – to NO3 – by various nitrifying bacteria. NH4 + or NO3 – to organic compounds by plant metabolism. • Release: denitrifying bacteria convert NO3 – back to N2 (denitrification); detrivorous bacteria convert organic compounds back to NH4 + (ammonification); animals excrete NH4 + (or NH3), urea, or uric acid. |
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Phosphorus cycle
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• Reservoirs: rocks and ocean sediments. (Erosion transfers phosphorus to water and soil; sediments and rocks
that accumulate on ocean floors return to the surface as a result of uplifting by geological processes.) • Assimilation: plants absorb inorganic PO4 3– (phosphate) from soils; animals obtain organic phosphorus when they eat plants or other animals. • Release: plants and animals release phosphorus when they decompose; animals excrete phosphorus in their waste products. 245 |
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biomes
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The biosphere is divided into regions called biomes that exhibit common environmental characteristics
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Tropical rain forests
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characterized by high temperature and heavy rainfall. The vegetation consists predominately
of tall trees that branch only at their tops, forming a spreading canopy that allows little light to reach the forest floor. Epiphytes (plants that live commensally on other plants) and vines commonly grow on the trees, but due to lack of light, little grows on the forest floor. |
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Savannas
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grasslands with scattered trees. Because savannas are tropical, they are subject to high temperatures.
However, they receive considerably less water than rain forests. |
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Temperate grasslands
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receive less water and are subject to lower temperatures than are savannas. The North
American prairie is an example. |
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Temperate deciduous forests
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regions that have warm summers, cold winters, and moderate precipitation.
Deciduous trees shed their leaves during the winter, an adaptation to poor growing conditions (short days and cold temperatures). |
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Deserts
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hot and dry. Growth of annual plants is limited to short periods following rains. Other plants have
adapted to the hostile conditions with leathery leaves, deciduous leaves, or leaves reduced to spines (cacti). Many animals have thick skins, conserve water by producing no urine or very concentrated urine, and restrict their activity to nights. |
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Taigas
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characterized by coniferous forests (pines, firs, and other trees with needles for leaves). Winters are
cold, and precipitation is in the form of snow. |
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Tundras
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subject to winters so cold that the ground freezes. During the summer, the upper topsoil thaws, but
the deeper soil, the permafrost, remains permanently frozen. During the summer, the melted topsoil supports a grassland type community consisting of grasses, sedges, and other vegetation tolerant of soggy soils. |
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Fresh water biomes
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include ponds, lakes, streams, and rivers.
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Marine biomes
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estuaries (where oceans meet rivers), intertidal zones (where oceans meet land), continental
shelves (the relatively shallow oceans that border continents), coral reefs (masses of corals that reach the ocean surface), and the pelagic ocean (the deep oceans). |
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Global climate change
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The burning of fossil fuels and forests increases CO2 in the atmosphere. Increases in CO2
cause more heat to be trapped in the earth’s atmosphere. As a result, global temperatures are rising. Warmer temperatures could raise sea levels (by melting more ice) and decrease agriculture output (by affecting weather patterns). |
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Ozone depletion
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The ozone layer forms in the upper atmosphere when UV radiation reacts with oxygen (O2)
to form ozone (O3). The ozone absorbs UV radiation and thus prevents it from reaching the surface of the earth where it would damage the DNA of plants and animals. Various air pollutants, such as chlorofluorocarbons (CFCs), enter the upper atmosphere and break down ozone molecules. CFCs have been used as refrigerants, as propellants in aerosol sprays, and in the manufacture of plastic foams. When ozone breaks down, the ozone layer thins, allowing UV radiation to penetrate and reach the surface of the earth. Areas of major ozone thinning, called ozone holes, appear regularly over Antarctica, the Arctic, and northern Eurasia. |
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Acid rain
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The burning of fossil fuels (such as coal) and other industrial processes release into the air pollutants
that contain sulfur dioxide and nitrogen dioxide. When these substances react with water vapor, they produce sulfuric acid and nitric acid. When these acids return to the surface of the earth (with rain or snow), they kill plants and animals in lakes and rivers and on land. |
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Desertification
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Overgrazing of grasslands that border deserts transform the grasslands into deserts. As a result,
agricultural output decreases, or habitats available to native species are lost. |
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Deforestation
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Clear-cutting of forests causes erosion, flooding, and changes in weather patterns. The slash-andburn
method of clearing tropical rain forests for agriculture increases atmospheric CO2, which contributes to the greenhouse effect. Because most of the nutrients in a tropical rain forest are stored in the vegetation, burning the forest destroys the nutrients. As a result, the soil of some rain forests can support agriculture for only one or two years. |
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Pollution.
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Air pollution, water pollution, and land pollution contaminate the materials essential to life. Many
pollutants do not readily degrade and remain in the environment for decades. Some toxins, such as the pesticide DDT, concentrate in plants and animals |
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biological magnification
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As one organism eats another, the toxin becomes more and more concentrated,
a process called biological magnification |
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algal blooms
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A lake, for example, can
be polluted with runoff fertilizer or sewage. Abundant nutrients, especially phosphates, stimulate algal blooms, or massive growths of algae and other phytoplankton. The phytoplankton reduce oxygen supplies at night when they respire. In addition, when the algae eventually die, their bodies are consumed by detrivorous bacteria, whose growth further depletes the oxygen. The result is massive oxygen starvation for many animals, including fish and invertebrates. In the end, the lake fills with carcasses of dead animals and plants. |
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eutrophication
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The process of nutrient enrichment
in lakes and the subsequent increase in biomass is called eutrophication. When the process occurs naturally, growth rates are slow and balanced. But with the influence of humans, the accelerated process often leads to the death of fish and the growth of anaerobic bacteria that produce foul-smelling gases. |
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Reduction in species diversity
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As a result of human activities, especially the destruction of tropical rain forests
and other habitats, plants and animals are apparently becoming extinct at a faster rate than the planet has ever previously experienced. If they were to survive, many of the disappearing plants could become useful to humans as medicines, foods, or industrial products. |
