Unit 7 - Population Dynamics Flashcards
Describe 3 different measurements scientists use to describe populations
- Population characteristics
- Population size and density
- Mark-recapture sampling
Compare population size and population density
Population Size: the number of individuals of a specific species occupying a given area/volume at a given time
Population Density: the number of individuals of the same species that occur per unit area or volume
Why do “smaller organisms usually have higher population densities than larger organisms”?
They are smaller, so they can live closer together
They have a smaller footprint, and so can support a larger population without depleting resources
Compare crude density and ecological density. Which is typically higher?
Crude Density: population density measured in terms of number of organisms of the same species within the total area of the entire habitat
Ecological Density: population density measured in terms of the number of individuals of the same species per unit area or volume actually used by the individuals
Crude density
Define population dispersion
Population Dispersion: the general pattern in which individuals are distributed through a specified area
Explain clumped dispersion pattern
Clumped Dispersion: the pattern in which individuals in a population are more concentrated in certain parts of a habitat (most common)
Explain uniform dispersion pattern
Unifrom Disperion: the pattern in which individuals are equally spaced throughout a habitat
Explain random disperion pattern
Random Disperion: the pattern in which individuals are spread throughout a habitat in an unpredictable and patternless manner
What determines the type of disperion pattern a species exhibits in an area?
Ultimately, environmental conditions, suitable niches, and social behaviour
State the equation for the mark-recapture method
total # marked / total population = # of recaptures marked / size of second sample
M/N = m/n
What is meant by the term ‘environment’?
The surroundings or conditions in which an organism operates
State some biotic and abiotic resources that may be limited in an ecosystem at a given time
Biotic: prey, plants
Abiotic: space, light, temperature, water
Define carrying capacity
Carrying Capacity: the maximum number of organisms that can be sustained by available resources over a given period of time
What determines carrying capacity?
The environment; abiotic and biotic variability
Define fecundity
Fecundity: the potential for a species to produce offspring in one lifetime
Ex., high fecundity = starfish
Outline type 1 survivorship and provide an example
Species exhibiting a type I survivorship pattern have very low mortality rates until they are beyond their reproductive years
Ex: humans
Outline type 3 survivorship and provide an example
Species with a type III survivorship curve have very high mortality rates when they are young while those individuals that do reach sexual maturity have a greatly reduced mortality rate
Ex: sea turtles
Outline type 2 survivorship and provide an example
Type II species are intermediate between these forms and tend to show a uniform risk of mortality throughout their life.
Ex: lizards
State the formula for changes in population size
Population change = (birth + immigration) - (death+emmigration) / initial population size x 100%
Population change = (b + i) - (d + e) / n x 100%
Compare open and closed populations
Open Population: a population in which change in number and density is determined by births, deaths, immigration, and emigration
Closed Population: a population in which change in size and density is determined by natality (birth rate) and mortality (death rate) alone
What is biotic potentional?
Biotic Potential: the maximum rate a population can increase under ideal conditions
State the equation for geometric growth
N(t + 1) / N(t) = lambda (growth rate)
N(t+1) = t0 x lambdat
Define density-dependent factor
Density Dependent Factor: a factor that influences population regulation, having a greater impact as population density increases or decreases
State examples of density-dependent factors
Availability of food, predation, disease, and migration
How did Charles Drawin use density-dependent factors in his Theory of Evolution?
Darwin recognised the struggle for available resources within a growing population would inherently limit population size (natural selection, the fittest survive)
Compare interspecific vs. intraspecific competition
Intraspecific Competition: an ecological interaction in which individuals of the same species or population compete for resources in their habitat
Interspecific Competition: interactions between individuals of different species for an essential common resource that is in limited supply
Explain consequences for increased population density
More competition for resources, leading to decreased growth
Define predation
Prediation: an ecological interaction in which a predator (a member of one species) catches, kills, and consumes prey (usually a member of another species)
Explain how predation is a density-dependent factor
Example: A population of sharks searching for prey can hunt several species of fish for food. However, faster prey may escape the shark predators and survive. Fish that are slower may be easier prey for the sharks and be their food of choice. The shark population, therefore, will regulate fish populations that are their prey
Explain how disease is a density-dependent factor
A potential risk of increased population density is that it can allow disease to spread more rapidly, resulting in a reduction in population size. (spread of disease is density-dependent)
Explain the allee effect and proviede an example
Allee Effect: Allee effect density-dependent phenomenon that occurs when a population cannot survive or fails to reproduce enough to offset mortality once the population density is too low; such populations usually do not survive
Passenger pigeon: Three centuries ago, passenger pigeons were the most common bird in North America. As a result of uncontrolled hunting and destruction of the birds’ habitats, the passenger pigeon drastically declined in numbers. The population could not recover since the pigeons laid only one egg per nest and would breed only in large colonies.
Define minimum viable population size
Minimum Viable Population Size: the smallest number of individuals needed for a population to continue for a given period of time
Define density-independent factor
Density-Independent Factors: factors that influence population regulation regardless of population density
State examples of density-independent factors
Weather, climate change resulting in population reduction, as well as insecticide use and human intervention
Define biomagnification
Biomagnification: the concentration of toxins in an organism as a result of its ingesting other plants or animals in which the toxins are more widely disbursed.
Define limiting factor
Limiting Factor: any essential resource that is in short supply or unavailable
What usually occurs when a population surpasses its carrying capacity in an environment?
Deaths increase and the number of births decline resulting in a reduction in population size
Why do biologists monior fluctuations in size and density of populations?
The natural fluctuations of such things are monitored in hopes of further understanding the natural patterns as well as predict an organism’s ability to withstand certain factors and impacts. This is especially important to environmental scientists that analyze the destructive human impact on certain species and their environments.
Define ecological niche
Ecological Niche: an organism’s biological characteristics, including use of and interaction with abiotic and biotic resources in its environment
Compare fundamental niche and realized niche
Fundamental Niche: the biological characteristics of the organism and the set of resources individuals in the population are theoretically capable of using under ideal conditions (i.e. no competition)
Realized Niche: the biological characteristics of the organism and the resources individuals in a population actually use under the prevailing environmental conditions
Interspecies competition prevents these from being identical
State the five categories of interactions between species
Define symbiosis
Symbiosis: various interactions in which two species maintain a close, usually physical, association; includes parasitism, mutualism, and commensalism
Explain the three likely results of interspecific competition
The results of interspecific competition take on several forms:
- The population sizeof the weaker competitor could decline.
- One species could change its behaviour so that it is able to survive using different resources.
- Individuals in one population could migrate to another habitat where resources are more plentiful
Explain the two ways in which interspecific competition can occur and provide an example
Interference Competition: interspecific competition that involves aggression between individuals of different species who fight over the same resource(s)
Exploitative Competition: interspecific competition that involves consumption of shared resources by individuals of different species, where consumption by one species may limit resource availability to other species
An example of interference competition is the fighting that sometimes occurs between tree swallows and bluebirds over birdhouses.
An example of exploitative competition occurs when both arctic foxes and snowy owls prey on the same population of arctic hares
What did Gause do?
- Hypothesized that two species with similar requirements could not coexist in the same community. He predicted that one species would consume most of the resources and drive the other species to extinction.
- Gause’s experiments led to the conclusion that if resources are limited, no two species can remain in competition for exactly the same niche indefinitely. This became known as Gause’s principle.
Define resource partitioning and provide an example
Resource Partitioning: Avoidance of/reduction in competition for similar resources by individuals of different species occupying different nonoverlapping ecological niches
To minimize competition for food, several species of Anolis lizard partition their tree habitats by occupying different perching sites
Define character displacement and provide an example
Character Displacement: an evolutionary divergence that occurs when two similar species inhabit the same environment. Ex., Darwin’s finches
Do resource partitioning and character displacement provide direct or indirect evidence for competition?
Character displacement: indirect, species characteristics are no longer similar which we infer is due to competition
Resource partitioning: indirect, species migrate or switch to different resources due to competition
Explain the predator-prey relationship + diagram
Predation is an example of an interspecific interaction in which the population density of one species—the predator—increases while the popu lation density of the other species—the prey—declines.
When the prey population increases, there is more food for predators and this abundance can result in an increase in the size of the predator po pulation.
As the predator population increases, however, the prey population decreases. The reduction of prey then results in a decline in the predator population, unless it has access to another food source.
In conclusion, the predator population responds to changes in prey abundance
