Autochthonous and allochthonous production

North American Photosynthesis

All biotic communities depend on a supply of energy for their activities. In most terrestrial systems this is contributed in situ by the photosynthesis of green plants - this is autochthonous production. Exceptions exist, however, particularly where colonial animals deposit feces derived from food consumed at a distance from the colony e.g. bat colonies in caves, seabirds on coastland - guano is an example of allochthonous organic matter dead organic material formed outside the ecosystem . In...

Unitary and modular organisms

Duckweed Lifecycle

Our 'ecological fact of life', though, implies by default that all individuals are alike, which is patently false on a number of counts. First, almost all species pass through a number of stages in their life cycle insects metamorphose from eggs to larvae, sometimes to pupae, and then to adults plants pass from seeds to seedlings to photosynthesizing adults and so on. The different stages are likely to be influenced by different factors and to have different rates of migration, death and of...

Competition between Paramecium species

Caudatum And Bursaria

The fourth example comes from the classic work of the great Russian ecologist G. F. Gause, who studied competition in laboratory experiments using three species of the protozoan Paramecium (Gause, 1934, 1935). All three species grew well alone, reaching stable carrying capacities in tubes of liquid medium. There, Paramecium consumed bacteria or yeast cells, which themselves lived on regularly replenished oatmeal (Figure 8.3a). When Gause grew P. aurelia and P. caudatum together, P. caudatum...

Detritivores and specialist microbivores

Images Detritivores

The microbivores are a group of animals that operate alongside the detritivores, and which can be difficult to distinguish from them. The name microbivore is reserved for the minute animals that specialize at feeding on microflora, and are able to ingest bacteria or fungi but exclude detritus from their guts. Exploitation of the two major groups of microflora requires quite different feeding techniques, principally because of differences in growth form. Bacteria and yeasts show a colonial...

A logistic model of interspecific competition

Interspecific Competition Zero Isocline

The 'Lotka-Volterra' model of interspecific competition Volterra, 1926 Lotka, 1932 is an extension of the logistic equation described in Section 5.9. As such, it incorporates all of the logistic's shortcomings, but a useful model can none the less be constructed, shedding light on the factors that determine the outcome of a competitive interaction. contains, within the brackets, a term responsible for the incorporation of intraspecific competition. The basis of the Lotka-Volterra model is the...

Foundercontrolled and dominancecontrolled communities

In response to disturbances, we can postulate two fundamentally different kinds of community response according to the type of competitive relationships exhibited by the component species - founder controlled and dominance controlled (Yodzis, 1986). Founder-controlled communities will occur if a large number of species are approximately equivalent in their ability to colonize an opening left by a disturbance, are equally well fitted to the abiotic environment and can hold the location until...

Chemical pesticides target pest resurgence and secondary pests

Pest Resurgence

Chemical pesticides are a key part of the armory of pest managers but they have to be used with care because population theory see, in particular, Chapter 14 predicts some undesirable responses to the application of a pesticide. Below we discuss the range of chemical pesticides and herbicides before proceeding to consider some undesirable consequences of their use. The use of inorganics goes back to the dawn of pest control and, along with the botanicals below , they were the chemical weapons...

Dispersal of seeds and pollen

Mutualisms

Very many plant species use animals to disperse their seeds and pollen. About 10 of all flowering plants possess seeds or fruits that bear hooks, barbs or glues that become attached to the hairs, bristles or feathers of any animal that comes into contact with them. They are frequently an irritation to the animal, which often cleans itself and removes them if it can, but usually after carrying them some distance. In these cases the benefit is to the plant which has invested resources in...