Entrance Examination for April 2021

1st Application

Examination Questions
Graduate School of Environmental and Life Science(Master's Course)

OKAYAMA UNIVERSITY

SubjectDNA

RFLP

RAPD

AFLP

SSR

SNP

QTLDNADNA

SubjectSpecies diversity has two primary components: species richness
in a community) and species composition(the number of species(the list of species and their relative abundances ina community). While most research on the relationship between ecosystem diversity and stability has
focused on species richness, it is variation in species composition that provides the mechanistic basis toexplain the relationship between species richness and ecosystem functioning. Species differ from one
another in their resource use, environmental tolerances, and interactions with other species, such thatspecies composition has a major influence on ecosystem functioning and stability.
The traits that characterize the ecological function of a species are termed functional traits, andspecies that share similar suites of traits are often categorized together into functional groups. Whenspecies from different functional groups occur together, they can exhibit complementary resource use,
meaning that they use different resources or use the same resources at different times. In
the case of plants, all species may utilize the same suite of resources (space, light, water, soil nutrients,etc.) but at different times during the growing season. Increasing species diversity can influence
ecosystem functions — such as productivity — by increasing the likelihood that species will use
complementary resources and can also increase the likelihood that a particularly productive or efficient
species is present in the community. For example, high plant diversity can lead to increased ecosystemproductivity by more completely, and/or efficiently, exploiting resources.
Theoretical models suggest that there could be multiple relationships between diversity andstability, depending on how we define stability. Stability can be defined at the ecosystem level — forexample, a rancher might be interested in the ability of a grassland ecosystem to maintain primary
production for cattle forage across several years that may vary in their average temperature andprecipitation. Figure shows how having multiple species present in a plant community can stabilize
ecosystem processes if species vary in their responses to environmental fluctuations such that anincreased abundance of one species can compensate for the decreased abundance of another.
Biologically diverse communities are also more likely to contain species that confer resilience to that
ecosystem because as a community accumulates species, there is a higher chance of any one of themhaving traits that enable them to adapt to a changing environment. Such species could buffer the systemagainst the loss of other species. Scientists have proposed the insurance hypothesis to explain thisphenomenon.

SubjectDiversecommunity

Community
dominatedby “black”
species
Communitydominatedby “white”
speciesYear 1:
Averageclimate year

Year 2: Warm year Year 3: Cold year

Time; Each rectangle represents a plant community containing individuals of either black orwhite species and the total number of individuals corresponds to the productivity of the ecosystem.
White species increase in abundance in warm years, whereas black species increase in abundance incold years such that a community containing only black or white species will fluctuate in biomass when
there is inter-annual climate variability. In contrast, in the community containing both white and black
individuals, the decrease in one species is compensated for by an increase in the other species, thus
creating stability in ecosystem productivity between years. Note also that, on average, the diverse
community exhibits higher productivity than either single-species community. This pattern could occur
if black or white species are active at slightly different times, such that competition between the twospecies is reduced. This difference in when species are active leads to complementary resource
utilization and can increase total productivity of the ecosystem.
Elsa E. Cleland

Biodiversity and Ecosystem Stability

Nature Education Knowledge 3(10): 14(2011)

speciesecosystemmechanistic

functioning

toleranceinteraction

ecological

functional

complementary

productivity

theoreticalranchergrassland

forageprecipitation

stabilize

fluctuationcompensate

biologicallyresilience

conceptualfluctuate

biomassvariability

Subject

species richness

species composition
15

resource

Figure2520

Year 1Figureresource use

130

FigureFigure2200