Biology ISU 11
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What is population density?
The number of individuals per unit of volume or area.
How can ecologists determine population density?
By counting the number of individuals in a smaller sample and making an average.
What are transects?
samples taken along a long rectangle or line. Researcher chooses a random starting point and walks the length counting the species. (Useful when density is low or organisms are large)
What are quadrats?
An area of specific size used for sampling, multiple quadrats may be placed. (Useful for sessile animals)
What is the formula for finding density in a quadrat? How can we extrapolate this information?
Dp=N (sum of individuals)/ A (size of quadrat)
Estimated density x total area
How can we determine relative density?
Indirect factors such as feces and tracks can help determine the relative density, which is an estimate compared to the absolute density.
What is mark recapture?
Animals are captured, marked then released. They are then retrapped and scientists compare the number of mark to the number of unmarked.
What is the formula used when analyzing mark recapture?
N (population size) = (# originally marked x total in recapture)/ marked in recapture
What is a distribution pattern?
The pattern in which a population is distributed or spread in an area. 3 types: uniform, random, clumped. Influenced by two factors: distribution of resources and interactions among members of a population.
What causes clumped distribution?
populations gather around resources, populations that exist in packs. Based off positive interactions.
What causes uniform distribution?
resources are evenly distributed but scarce. species defend food and shelter ( negative interactions)
What causes random distribution?
neutral interactions, evenly distributed resources, rarely occurs in nature.
How would one describe distribution patterns?
fluid, constantly changing
What is life history?
Understanding survivorship and reproductive patters of individuals to predict population size.
What is fecunduity?
average number of offspring produced by a female over her lifetime.
What is survivorship?
The percent of organisms that live to a given age. A cohort is when ecologists follow a group of species born at a similar time to study this.
Three types of survivorship, what are they?
- Type 1 - live to be mature, few offspring
- Type 2 - risk of mortality is constant throughout lifetime
- Type 3 - die young, many offspring
What are the four factors that affect population size?
immigration (movement into), emmigration (movement out), birth and death
A change in population can be determined by what formula?
N/T = B-D
A Change in population for humans might be determined by what formula?
N = (B+I) - (D + E)
What formula is used to measure per capita growth rate?
Cgr = (Birth - death)/ Total people
What is biotic potential?
Highest possible per capita growth rate for a population (ideal conditions), related to fecunduity
What is exponential growth?
The growth pattern exhibited by a population growing at its biotic portential (J shaped). Occurs in unlimited environments
What is logistic growth?
exhibited by environments with limited carrying capacity. Lag phase- few organisms to produce followed by rapid growth. Resources become limited, equals out when carrying capacity is reached. S shaped.
What are r-selected species?
Live close to biotic potential, short life span, sexually mature at a young age, large broods of offspring, little parental care.
What are k-selected species?
Live close to carrying capacity, long life span, sexually mature later in life, few offspring, lots of parental care.
What is a density independent factor?
an abiotic factor that affects population growth regardless of population density.
What is a density dependent factor?
biotic factors that depend on density, like competition or predation. Larger populations will be more greatly affected by biotic factors. (As pop increases, more competition for resources)
What is intraspecific vs interspecific competition?
- Intra- competition amongst members of the same population
- Inter- competition amongst members of different pops for the same resource
What are population cycles?
limited prey means limited predators. The alternating periods of large and small population sizes results in sinusodial growth
What is parasitism?
parasite benefits, host is harmed. Similar to predator prey cycles
What is mutualism?
both species benefit from the relationship. Growth in one population spurs growth in the other and vv.
What is commensalism?
- One partner benefits, one is unaffected. growth of host = growth of symbiont
- growth of symbiont does not affect growth of host.
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