For the natural regulation of numbers of individuals in a population, the Australian school (Davidson and Andrewartha) argued that density-independence was most important because:
Thrip populations in south Australia had a high correlation with the rainfall of a given season.
The theory of density-depend population regulation, as developed by David Lack, was based on the observation that:
The numbers of nesting pairs of birds were remarkably constant from year to year.
Many studies of the effect of predators on large herbivores, such as carribou in northern communities, indicate that predators such as wolves typically:
Cull the herds only of the old, sick, and very young. Thus the breeding stock tends to be preserved.
An example of K selection was demonstrated in the Solbrig and Simpson study of dandelions on the University of Michigan campus. The best example was the D biotype which:
Grew larger and set less seed than the three other biotypes &dominated the remote, rarely visited meadow site.
Clutch size in the European Robin is always
Dependent on latitude, the number of eggs in the clutch increasing as one goes north.
In terms of population regulation, territorial behavior:
promotes maximum reproduction for individuals possessing territories. & prevents reproduction by an often large population that does not possess a territory. & usually prevents food resources from being depleted. & sets a nearly constant upper limit to population.
An altricial bird:
must be fed in the nest by the parents for a long time, cannot forage for itself, and is usually found among hawks, eagles, seed-eating songbird species, etc.
The experiments on predator removal of the starfish (sea star) Pisaster in the intertidal zone of Washington state demonstrated that:
the number of prey species decreases after the removal of the predator.
Sexual reproduction is postulated to have arisen in the very ancient Archaen seas flooded with high levels of UV light. The original function of sexual reproduction was to:
Repair damaged DNA.
Female animals are generally larger than male animals because of the energetic investment made for eggs, etc.
A large young reproductive strategy necessarily implies:
Tansley, who coined the term ecosystem performed one of the earliest predator removal experiments in which plots of English pasture were kept rabbit-free for 6 years. The results of this experiment were:
Decrease in the number of plant species as the tall grass Zerna grew well without rabbit-copping and it then shaded out low-growing competitors.
Fresh water animals noted for reproducing parthenogentically (asexually), water fleas and rotifers, will turn to sexual reproduction when:
winter arrives in temperate regions and the freshwater habitat either deteriorates or disappears entirely.
Quantitative chemical defense, utilizing the secondary compounds found in various plants,consists of:
Silica phytoliths deposited in plant cells.
lignin deposited in plant cell walls.
tannins deposited in leaves.
In the co-evolution of bees and various flowering plants, bees can be considered:
Among the results of the co-evolution of mutualists in a community is (are):
Species will become better adapted for “using each other”. continually co-evolve as mutualists, etc., and probably increase the number of species that can live in a community.
The cyclic oscillation in population numbers of predatory species in northern Canada, the lynxes and foxes for example, do not follow the trends predicted by the Lotka-Volterra predator-prey equations. This is the case because the peak numbers of the real predators:
Coincide with the peak numbers of the prey species, making the predator a “helpless captive of its resources”.
Qualitative chemical defense, utilizing the secondary compounds found in various plants, consists of:
Plants producing toxins to ward off predators (herbivores).
an organism that reproduces once during its lifetime.
a regular cycle of change in population density of arctic lemmings. Typically the lemmings reach a peak population density every three or four years followed by a population crash.
A major effect a predator has on prey species is to increase the diversity of all the prey species. The predator prevents any prey species from becoming dominant and this prevents the working of monopoly competition.
Primordial Trait Hypothesis:
It states that sexual reproduction is part of the fundamental architecture of eukaryote cells and organisms. It cannot be remove by natural selection. It is supposedly in the same category as the enzymes, etc. required by eukaryotes.
The behavior of an animal that returns to its area of birth to reproduce. Considered a form of inbreeding.
Red Queen Hypothesis:
The statement that the environment is constantly changing and natural selection is continually altering the genotype of an organism to maintain its fitness for its ecological niche. Given as an explanation for sexual recombination and it contribution to fitness. Thus, no organism is ever perfectly adapted to its ecological niche.
The 50% cost of meiosis:
A statement of the fact that when a female/male undergoes sexual reproduction (s)he gives up half of his or her fitness to the male or female (s)he is mating with.