VL 2 Flashcards
How many insects are there?
ca. 1’000’000 species are currently known, estimates from 2’000’000 to 30’000’000
Insects represent as much as 50% of all known species and 75% of known animals
What is the importance of insects?
Natural world (“the little things that run the world”)
Nutrient cycling
Plant Reproduction (pollination, seed disperal)
Community Structure / Population Dynamics (Phytophagy, seed feeding, parasitism, predation
food web
What is a pest?
Any living species whose activities, enhanced by numbers, causes economic losses to human possessions, directly threatens human health or is annoying
Name three types of pests
Aesthetic pests
Medical pests
Economic pests (Agricultural and forest)
Name examples of pests
Japanese Beetle
Stink Bug
European Corn Borer
Drosophila Suzuki
Asian Longhorn beetle
Wireworms
diseases caussed by pests:
Elephantiasis
Malaria
Bubonic plague
Population dynamics
Rate of increase (high reproductive potential)
Carrying capacity (population level that environment can sustain)
Natural enemies (presence or absence)
R-Strategist
“Ecological opportunists”
Organisms with high reproductive rate and low survival rates
Small bodies & short life cycles in order to produce large numbers of offspring quickly
Usually early colonizers of disturbed habitats, and have high dispersal ability
Thrive in ecosystems that are “unstable” or where food resources are short- lived
Populations go through huge fluctuations depending on the environment with large amounts of mortality followed by quick rebounds of population numbers.
K-strategists
Organisms with low rates of reproduction but high survival
Larger body size, longer lifespans
Found in stable, undisturbed environments (mature grasslands, climax forests)
More individuals reach sexual maturity and population levels stabilize near environmental carrying capacity
Environmental fluctuations do not cause major shifts in population levels.
Determinants of insect abundance
Effective environment
Elements in the ecosystem can also influence reproduction & survival
Factors such as weather, food quality/quantity and living space my help or inhibit population growth
Natural enemies can also inhibit population grwoth
r-Strategist vs. K-Strategists
“r” stands for “rate” (grwoth rate), r have a high r value and a low K value, they grow fast but most die
“K” stands for Kapazitätsgrenze (capacity limit) now called carrying capacity, K strategists have low r and high K. they grow slow but more survive
What are Insect population densities regulated by?
Perfectly density-dependent mortality factors
Imperfectly density-dependent mortality factors
density-independent mortality factors
Perfectly density-dependent mortality factors
A density-dependent factor that never fails to act on a population
Acts strongly to subtract numbers when the density is high and acts less strongly as density decreases.
Examples: Intraspecific competition between individuals for limited resources (usually food).
Imperfectly density-dependent mortality factors
Density-dependent factor that sometimes fails to limit numerical increase.
Examples: predators, parasites, pathogens
These factors can themselves be influenced by other environmental factors which sometimes leads to their
failures
Density-independent mortality factors
The impact of these factors do not vary across different insect densities.
Example: Weather (rainfall, temperature, humidity)
The strength of these effects is always the same with no influence from the density of the population
What are challenges in Agroecosystems?
Agroecosystems are either short lived or undergo frequent disruptions (environment unstable, abrupt changes in microclimate)
one or very few plant species, one species being dominant
plants are either non-native or have undergone intensive artificial selection for increased yield -> loss of ancestral anti-herbivore traits
uniform species with low or no genetic diversity leads to uniform phenological events
Agroecosystems frequently have added nutrients in form of fertilizers
