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Ecology
Population and Community Ecology (Chapters 53+54: AP/ECE BIO)
| Term | Definition |
|---|---|
| Population Ecology | The study of factors affecting the size of a population and how it changes over time |
| Population | A group of individuals of a single species living in the same general area. Described by their boundaries and size (# of individuals). |
| Natural Boundaries | Lake or Island |
| Arbitrary Boundaries | Investigator (A County) |
| Density | The number of individuals per unit area or volume, an example of a dynamic property |
| Dispersion | The pattern of spacing among individuals within the boundaries of the population |
| Dynamic Property | Increases and decreases as individuals are added or removed |
| Immigration | The influx of new individuals from other areas. Births increase population size |
| Emigration | The movement of individuals out of a population. Deaths decrease population size |
| Clumped | Individuals aggregate in patches. They might aggregate in areas of high resource availability or favorable physical conditions |
| What also influences clumped dispersion? | Mating behavior, group predation, defense against predators |
| Uniform Dispersion | Individuals are evenly spaced |
| What can plants do? | Secrete chemicals that inhibit germination and growth of competing individuals |
| Random Dispersion | Also known as unpredictable spacing. The position of each individual is independent of other individuals. It occurs in thee absence of strong attractions or repulsions |
| Biotic (living) and Abiotic (nonliving) factors influence... | Birth, death, and migration rates of populations |
| Demography | Study of vital statistics of a population and how they change over time |
| Life Table | Age-specific summary of the survival and reproductive rates within a population |
| Cohort | A group of individuals o f the same age from birth to death |
| Survivorship Curves | A plot of the proportion or the numbers in a cohort still alive at each age, shows the pattern of survivorship for a population |
| Type I Curve | Low death rates during early and middle life and a sharp increase in death rates later in life (found in large mammals that produce few offspring but provide them with good care) |
| Type II Curve | Constant death rates over the lifespan (found in some rodents, invertebrates, lizards, and annual plants) |
| Type III Curve | High death rates for the young; death rates steeply declines for survivors of early period die-off (found in organisms that produce very large #s of offspring but provide little to no care (found in long-living plants, many fishes, marine invertebrates) |
| In nature... | Unlimited growth is unsustainable because resources are depleted as the population gets larger |
| Studying population growth under ideal conditions reveals... | Populations can grow exponentially |
| Exponential growth occurs under... | Ideal conditions (all individuals have access to abundant food and reproduce at physiological capacity). In these conditions population can increase under a constant proportion |
| The exponential growth model assumes... | Resources will remain abundant as population size increases |
| In nature... | Each individual has access to fewer resources as population size increases |
| Carrying Capacity (K) | Realistic models of population growth incorporate this, this is the maximum population size that a particular environment can sustain |
| Life history traits | Products of natural selection. They comprise the traits that affect an organism's schedule of reproduction and survival. These traits are evolutionary outcomes reflected in the development, physiology, and behavior of an organism |
| An organism's life history entails... | The age at first reproduction (maturity), how often the organism reproduces, how many offspring are produced per reproductive episode |
| Semelparity | Refers to the case where individuals undergo a "one-shot" pattern of big-band reproduction |
| Iteroparity | Refers to the case where individuals undergo repeated reproductive events throughout their lifetime |
| Species that produce one of few offspring... | May provision them better than those who produce many offspring |
| Trade-Offs | Occur because organisms do not have access to unlimited resources |
| The use of resources for one function (e.g. reproduction)... | Can reduce the number of resources available |
| In some species... | Parents produce relatively few offspring and invest more energy in each offspring to increase the probability of survival for each |
| Variations in life history traits... | Are related to the logistic growth model |
| Logistic Growth | A population's per capita growth rate gets smaller and smaller as population size approaches a maximum imposed by limited resources in the environment (carrying Capacity). This growth produces an S-Shaped curve. |
| Exponential Growth | A population's per capita growth rate stays the same regardless of population size, making the population grow faster and faster as it gets larger |
| K-Selection | Refers to selection for life history traits that are advantageous where density is high (near K), resources are low, and competition is strong |
| R-Selection | Refers to the selection for life history traits that maximize reproductive success when density is low and there is little competition for resources |
| Assuming immigration and emigration offset each other... | A population will grow when the birth rate exceeds the death rate and will decline when the death rates exceeds the birth rate |
| A birth rate or death rate... | Does not change with population density it is density-independent |
| If a death rate increases of a birth rate decreases with increasing density... | It is density-dependent |
| Density-Independent factors CANNOT | Regulate population size |
| Density-Dependent birth and death rates are an example of... | Negative feedback that regulates population growth |
| Competition For Resources | In crowded populations, increasing population density intensifies this and reduces birth rates |
| Diseases | Can regulate population density if its transmission rate increases as the population becomes more crowded |
| Territoriality | Can limit population density when space becomes the resource for which individuals compete (ex. cheetahs use chemical markers in urine to warn other cheetahs of their specific boundaries) |
| Population Dynamics | Focuses on the complex interactions between the size, composition, and distribution of populations, and how they change over time` |
| When a population becomes crowded and resource competition increases... | Emigration often increases |
| Metapopulations | Groups of local populations linked by immigration and emigration |
| Local populations in a metapopulation... | Occupy discrete patches of suitable habitat surrounded by unsuitable habitats |
| In the last few centuries... | The human population has grown at an unprecedented rate |
| Can populations grow indefinitely? | NO (Humans are NOT exceptions) |
| The global population is now... | Greater than 7.6 billion people, and is increasing by 80 million per day (predicted to reach 9.8 billion by 2050) |
| Regional Patterns Of Population Change Are...(they both maintain stability) | Zero population growth = high birth rate - high death rate; Zero population growth = low birth rate - low death rate |
| Demographic Transition Is... | The move from the first state to the second state |
| Age Structure | This is important for affecting population growth. It is the relative age number of individuals of each age in a population |
| Within a community... | Members of different species participate in several ecological interactions |
| Community Structure | Affected by the number composition and relative abundance of different species within a community |
| Interspecific Interactions | Are any interactions that occur between individuals of different species (includes competition, predation, herbivory, parasitism, mutualism, and commensalism) |
| Interspecific Interactions have three broad categories that are... | Positive, negative, or have no effect (are neutral) on the survival and reproduction of individuals involved. |
| Competition (-/-) | Occurs when individuals of different species use a resource that limits the survival (exemplified in the relationship between garden weeds and garden plants when searching for soil nutrients and war). |
| Species that do not compete for resources... | That are not short in supply |
| Competitive Exclusion | Local elimination of the inferior competitor--can result when two species use the same limited resources (exemplified when Paramecium Aurelia and Paramecium caudatum is driven to extinction |
| G.F. Gause concluded that... | Two species competing for the same limiting resources cannot co-exist permanently in the same place |
| An organism's ecological niche is... | The specific set of biotic and abiotic environmental resources it uses (e.g. the niche of a tropical tree lizard includes the temperature range it tolerates, the size of branches it perches on, the time it's active, and the size/kind of insects it eats) |
| The niche concept can be used to... | Restate the principle of competitive exclusion |
| Two species cannot co-exist permanently in a community if... | Their niches are identical |
| Ecologically similar species can co-exist... | If one or more significant differences in their niches arise |
| Resource Partitioning | The differentiation of niches that enables similar species to co-exist in a community |
| A species' fundamental niche... | Is the niche potentially occupied by that species |
| As a result of competition... | A species' fundamental niche may differ from its realized niche (species can partition their niches in time and space) |
| Character Displacement | The tendency for characteristics to diverge more in sympatric than in allopatric populations (e.g. beak depth is similar between allopatric populations of 2 species of Galapagos finches, but has diverged considerably in sympatric populations |
| Exploitation (+/-) | Refers to any positive-negative interaction in which individuals of one species benefits at the expense of the other (includes predation, herbivory, and parasitism) |
| Predation (+/-) | Refers to an interaction in which an individual or one species--the predator--kills and eats an individual of another species--the prey |
| Predators have... | Acute sense and adaptations like claws, fangs, or poison to fin, identity, catch, and subdue their prey. They pursue their prey in a fast and agile manner; those that lie in ambush are generally disguised in their environment |
| Prey Species | May have behavioral defenses (including hiding, fleeing, and forming herds of schools) |
| Animals also have a variety of... | Morphological and Physiological defense adaptations. Some species are protected by mechanical or chemical defenses. Some animals synthesize toxins and other accumulate them from the plants they eat |
| Animals with chemical defenses... | Often exhibit bright warning colorations (yellow, red, orange) called aposematic coloration . Predators avoid brightly colored prey |
| Cryptic Coloration | Also known is camouflage, makes prey difficult to see at night |
| Some species are protected by... | Their resemblance to other species |
| Batesian Mimicry | A palatable or harmless species mimics an unpalatable or harmful model |
| Harmless individuals that resemble members of a harmful species are... | Avoided by predators that have learned not to eat the harmful ones |
| Mullerian Mimicry | When one or more unpalatable species resemble and mimic each other's warning signals |
| Predators can learn to avoid unpalatable prey faster... | When they encounter more of them with a similar appearance |
| Herbivory (+/-) | Refers to an interaction in which an herbivore eats parts of a plant or algae |
| Herbivores... | Harm, they do not usually kill the plants and algae that they feed on |
| Large mammals... | The most familiar herbivores, but most herbivores are invertebrates |
| Herbivores have many specialized adaptations including... | Chemical sensors which help distinguishing toxicity or nutritional value of plants, specialized teeth or digestive systems for processing vegetation |
| Plants often have... | Mechanical defenses (like spines or thorns) or chemical defenses (toxins) |
| Non-Toxic chemical defenses... | May cause abnormal development of herbivores or be distasteful to them |
| Parasitism (+/-) | One organism, the parasite, derives nourishment from another organism, its host is harmed in the process |
| Endoparasites | Parasites that live within the body of their host |
| Ectoparasites | Parasites that live on the external surface of a host |
| Parasites can significantly affect... | Survival, reproduction, and density |
| Mutualism (+/+) | Is a common interspecific interaction that benefits individuals or both species |
| In some mutualisms... | Each species depends on the other for their survival and reproduction; in others, both species can survive alone |
| Commensalism (+/0) | Is an interaction in which individuals or one species benefit while members of other species is neither harmed nor helped (e.g. shade-tolerant wildflowers depend on the shade provided by forest trees, but the trees aren't affected by the wildflowers) |
| Ecological communities are characterized by... | General attributes like diversity and feeding relationships between species. In some cases, a few species in a community exert strong control on that community's structure |
| The species diversity of a community (the variety of organisms it includes)... | Has 2 components: species richness (the number of different species in the community) AND relative abundance (the proportion each species represents of all individuals in the community) |
| Higher diversity plant communities are generally... | More productive (producing biomass-total mass of all organisms per year), more stable yearly in their productivity, better able to withstand & recover from environmental stress |
| Higher diversity communities are often... | More resistant to introduced species (organisms that humans have moved outside their native range. An introduced tunicate was 4X likely to survive in lower-diversity communities. |
| The feeding relationships between organisms in a community... | Is the key factor affecting community Structure and dynamics |
| Energy is transferred from... | Autotrophs (primary producers) through herbivores (primary consumers) to carnivores (secondary and higher consumers) |
| The final link of trophic structure... | Decomposers. Referred to as a food chain |
| Trophic Level | The position an organism occupies in a food chain |
| Food Web | A group of food chains linked together forming complex trophic interactions. Arrows like species in the food Web according to who eats whom |
| Energetic Hypothesis | Suggests that length is limited by inefficient energy transfer |
| Only about __ of the energy stored in organic matter at each trophic level is converted to organic matter at the next trophic level | 10% (e.g. a producer level consisting 100 kg of plant material can support about 10 kg of herbivore biomass and 1 kg of carnivore biomass) |
| Another factor limiting food chain length... | Carnivores tend to be larger at higher trophic levels |
| Large carnivores... | Cannot obtain enough food from their small prey in a given time to meet metabolic needs |
| Foundation species... | Have strong effects due to their large size or high abundance. They often have community-wide effects because they provide habitat or food. May be competitively dominant by exploiting key resources (space, water, nutrients, light) |
| One of way to discover the impact of foundation species is... | Removing it from the community |
| Keystone Species | Exert strong control on a community by their pivotal ecological roles. They are usually not abundant in a community (e.g. a sea star affects its community by feeding on and limiting the abundance of a dominant species like a mussel) |
| Ecosystem Engineers | Create or dramatically alter their physical environment (e.g. beavers build dams that can transform landscapes on a very large scale) |
| Some foundation species like trees... | Are considered ecosystem engineers because their presence creates habitats for other species |
| Adjacent trophic levels can affect one another in 2 general ways... | Organisms can be controlled by what they eat ("bottom-up" control), Organisms can be controlled by what eats them ("top-down" control) (e.g. Grasshoppers dying causing the animals that eats them to die off and then so on--bottom up phenomenon) |
| In bottom-up control... | The abundance of organisms at each trophic level is limited by nutrient supply or food availability at lower trophic levels. Here, the biomass or abundance of organisms at lower trophic levels would have to be altered to change community Structure. |
| In top-down control... | The abundance of organisms at each trophic level is controlled by the abundance of consumers at higher trophic levels |
| The effects of removing top-level carnivores... | More down the trophic structure as alternating +/- effects |
| Decades ago, most ecologists favored the view that biological communities are at... | Equilibrium, unless seriously disturbed by human activities |
| This view focused on... | Competition as a key factor determining composition and stability of communities |
| Disturbance... | Keeps many communities from reaching equilibrium |
| What is Disturbance? | An event that changes a community by removing organisms from it or altering resource availability. |
| Non-Equilibrium Model | Describes communities as constantly changing after disturbance |
| The types of disturbances and their frequency/severity... | Vary among communities |
| Significant sources of disturbances in many communities | Storms, fire, and seasonal flooding |
| A high level of disturbance... | Is the result of frequent and intense disturbance |
| Low levels of disturbance... | Can result from low frequency or low intensity of disturbance |
| Intermediate Disturbance Hypothesis | States that moderate levels of disturbance foster greater diversity than do high or low levels of disturbance |
| What levels of disturbance excludes many slow-growing species? | High Levels |
| What levels of disturbance allows competitively dominant species to exclude the less dominant ones? | Low Levels |
| Ecological Succession | Refers to the pattern of colonization and species replacement that occurs in a community following a severe disturbance |
| Primary Succession | When ecological succession begins in a virtually lifeless area, such as a new volcanic island |
| During primary succession... | Prokaryotes and Protists are the only life forms initially presents |
| What organic matter accumulates as early colonizers decompose? | Lichens and mosses arrive first, soil gradually develops in conjunction with rocks and weather |
| What establishes after soil develops? | The plant community |
| Early-Arriving species and Later-Arriving Species may be linked... | Through priority effects (the influence early-arriving species have on the community structure of an ecosystem) |
| Secondary succession... | Involves the recolonization of an area after a major disturbance has moved most but not all of the organisms (e.g. abandoned agricultural land may return to its original state through secondary succession |
| Humans... | Have the greatest impact on biological communities worldwide |
| Both terrestrial and marine ecosystems... | Are subject to human disturbance |
| What usually reduces species diversity? | Human Disturbance |
| Robert MacArthur and E.O. Wilson... | Developed the island equilibrium model, a method for predicting species diversity on islands |
| In the island equilibrium model... | Species richness on islands represents a balance between immigration of new species and extinction of established species |
| As the # of species on an island increases... | Immigration decreases and extinction increases |
| Pioneer Species | The species that first inhabit a particular region |
| The Equatorial Gradient depends on these two factors: | Evolutionary History + Climate |
| Evapotranspiration is determined by... | Solar Radiation |
| What is a Zoonotic Pathogen? | A pathogen that is transferred from another species to humans |
| Pathogen | A disease-causing microorganism |
| Ecological Footprint | A metric that measures how much of the natural world is required to support human activities and economies |
| Allopatric | Groups from an ancestral population evolve into separate species due to a period of geographical separation |
| Sympatric | Groups from the same ancestral population evolve into separate species without any geographical separation |
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