Chapter 5
Interspecific competition
Occurs when members of two or more species interact to gain access to the same limited resources such as light, food, and space
Occurs when a member of one species (predator) feeds directly on all or part of a member of another species (the prey)
Occurs when one organism (the parasite) feeds on the body of, or the energy used by, another organism (the host), usually by living on or in the host
An interaction that benefits both species by providing each with food, shelter, or some other resource
An interaction that benefits one species but has little, if any, effect on the other
Competitive exclusion principle
States that although different species may share some aspects of their niches, no two species can occupy exactly the same ecological niche for very long. If one species can take over the largest share of one or more key resources, the other competing species must migrate to another area, shift its feeding habits or behavior through natural selection to reduce or alter its niche, suffer a sharp population decline, or become extinct in that area.
Predator-prey relationship
Relationship has evolved between two organisms, in which one organism has become prey for the other, the latter called the predator
When populations of two different species interact in this way over such a long period of time, changes in the gene pool of one species can lead to changes in the gene pool of the other species. Such changes can help both sides to become more competitive or can help to avoid or reduce competition.
Resource partioning
Occurs when species competing for similar scarce resources evolve specialized traits that allow them to use shared resources at different times, ways, and places
Population dynamics
A study of how these characteristics (i.e. distribution, numbers, age structure, density) of populations change in response to changes in environmental conditions (such as temperature, disease presence, resource avaliability, arrival/disappearance of competing species)
Desert vegetation around a spring, cottonwood trees along streams, wolf packs, flocks of birds, fish schools
Four variables that govern change in population size
Age structure
The proportions of individuals at various ages
Biotic potential
Capacity for population growth under ideal conditions
Intrinsic rate of increase
Rate at which the population of a species would grow if it had unlimited resources
Carrying capacity
The maximum population of a given species that a particular habitat can sustain indefinitely without being degraded
Environmental resistance
The combination of all factors that act to limit the growth of a population
Exponential growth
Starts slowly but then accelerates as the population increase because the base size of the population is increasing
Logistic growth
Involves rapid exponential population growth followed by a steady decrease in population growth until the population size levels off
R-selected species
Species with a capacity for a high rate of population increase; have many, small offspring and give them little care or parental attention
K-selected species
Tend to reproduce later in life; small # of offspring with long life spans. Offspring develop inside their mothers, are born fairly large, are protected/cared for by both parents, and sometimes live in herds or groups until they reach reproductive age
Founder effect
Can occur when a few individuals in a population colonize a new habitat that is geographically isolated from other members of the population
Demographic bottleneck
Occcurs when only a few individuals in a population survive a catastrophe; Lack of genetic diversity may limit the ability of these individuals to rebuild the population.
Genetic drift
Involves random changes in the gene frequencies in a population that can lead to unequal reproductive success
Occurs when individuals of a small population mate with one another
Density independent
Some(abiotic)factors that can kill members of a population regardless of population density
Population growth explodes to a high peak and then crashes to a lower more stable level
Bottom-up regulation
The size of predator and prey populations is controlled by the scarcity of one or more resources
Edge habitats
Borders between two ecosystems
Ecological succession
The gradual change in species composition in a given area
Primary succession
Involves the gradual establishment of biotic communities in lifeless areas where there is no soil in a terrestrial ecosystem or no bottom sediment in an aquatic ecosystem
Secondary succession
A series of communities or ecosystems with different species develop in places containing soil or bottom sediment
The ability of a living system to survive moderate disturbances
The ability of a living system to be restored through secondary succession after a moderate disturbance.
Tipping point
Where any additional stress can cause a system to change in an irreversible and usually abrupt way that often involves collapse
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