Lecture 4: biomes and ecological concepts Flashcards
In plant terms, what is a biome?
communities considered to be the ‘climax vegetation’ and associated vegetation types (at stable equilibrium)
What are the biggest controls on biomass?
Temperature then precipitation
Glaciers are not counted as a biome, but what reasons imply they should be?
- cover 10% lands surface
- vary with temperature and precipitation
- Iron reduction occurs under glaciers as anoxic microbes present
Describe the tundra ecosystem.
Low temperatures and rainfall. Bare surfaces or very specific plants, growth season is brief.
Why does permafrost not develop in alpine tundra? What characterises this environment?
The sun results in high levels of evaporation. Low productivity, low diversity, simple structure, cold tolerance mechanisms.
What does Hutchinson describe a niche as?
an n-dimensional hypervolume where n represents the number of environmental factors required for survival and reproduction of a species.
What is a fundamental and a realised niche?
a fundamental niche = hypervolume, whereas a realized niche is one which includes interactions such as competition that may restrict environments where a species lives.
What is interspecific competition and how might this be reduced?
Occurs where the niche of two species overlap and can be reduced by spatial or temporal separation
What is the difference between allopatric, sympatric and contiguous allopatric distribution?
Allopatric - no overlap
Sympatric - overlap and competition
Contiguous allopatric - results from competition
What are the relative impacts of interspecific and intraspecific competition?
Interspecific - distribution, population dynamics
Intraspecific - number, spacing of individuals
What is carrying capacity of an ecosystem determined by?
Disease, predators, availability of resources.
How do competitors affect population growth, and hence K?
Intra specific - set K by changing exponential growth rates to logarithmic
Interspecific - by reducing effective K
What is the effect of intraspecific competition on individuals?
Development time increase, survival rates and body length decline under increasing number of competitors.
What is competitive exclusion?
No species can occupy an identical niche, therefore where one species is prevented from occupying an area by another.
What is the effect of resources on competition?
Organisms that both need the same non-shareable resource necessarily compete. Where resources are limited, both parties suffer reduced growth, survival and / or reproduction.
