B4 - distributions of species Flashcards
What does scale-dependent in regards to distribution maps mean?
That the chance of an individual being found in a grid cell, depends on the size of the cell
What is an important factor to remember when depicting species distribution?
The distribution is dynamic. i.e. it changes over time, and therefore depictions must repeatedly be updated to account for this
What are the three basic kinds of range maps?
Outline: depicts a range as an irregular area - often based on dot maps
Dot: plottet points where a a species has been recorded
Contour: indicate similar levels of a variable, often an isolcline, which can illustrate variation among individuals or populations across a species range.
Describe a species ecological niche (Hutchinsons’s multidimensional niche concept)
The niche of a species can be visualized as the combination of environmental variables that allow individuals to survive and reproduce and populations to maintain their numbers. Each variable is represented by an axis in the multidimensional space.
What is the difference between the realized niche and the fundamental niche?
The realized niche is the actual environmental conditions a species survives and reproduces in, the fundamental niche is the total range of environmental conditions in which a species can survive and reproduce.
Each species has a fundamental geographic range (potential range) where it could be expected to occur, however most species only occur in its realized geographic range, why is this?
Because geographic barriers, limited dispersal and colonization abilites limits the species distribution.
Explain source and sink habitats and their functions
A source habitat is a habitat that is so favorable that it provides a surplus of individuals (i.e. birth rate exceeds death rate), this surplus can then disperse to other habitats. A sink habitat is a habitat with such poor conditions that the death rate exceeds the birth rate, but can still be inhabited if a suffient supply of immigrants is maintained
Explain exploitative competition
Individuals use up resources and make them unavailable to others
Explain interference competetion
Individuals use aggressive dominance or active inhibition to deny other individuals access to resources
What is diffuse competition?
Competition in which one species is negatively affected by numerous other species collectively depleting a shared resource.
What is a keystone species?
A species that strongly influence community structure through its direct and indirect effects.
