The maintenance and ecological effects of flight

Once flight originated, for its ecological effects to be expressed it had to be maintained. Loss of flight is an interesting phenomenon, for it has occurred very frequently in insects and birds, and not at all in bats (nor probably in pterosaurs). The obvious difference between these two groups of organisms is that the former (insects and birds) retained a functional distinction between the flight apparatus and the legs they can both walk or run without using their wings. In pterosaurs and bats...

Evolution of the biosphere a brief history

The origin of the biosphere and of earth's ecology occurred between 3.8 and 3.5 billion years ago. Both autotrophic and heterotrophic origins have been proposed. Previously the heterotrophic use of organic molecules synthesized in the pre-biotic broth was a popular idea (see Lazcano and Miller 1999). More recently, autotrophic theories have re-emerged, for two reasons first, early cell membranes would probably have lacked sufficient permeability to transport large molecules. Second, it is now...

Cichlids and evolutionary ecology

The cichlid story illustrates many of the broader features of evolutionary ecology, the science that involves both ecological and evolutionary knowledge. Evolutionary biology is the field concerned with understanding how biological lineages change through time (anagenesis), split (cladogenesis), and ultimately go extinct. Ecology is concerned with the interaction of organisms with their environment. The organisms can be considered at various levels of a hierarchy, comprising the individual, the...

Sexual selection in plants

This discussion of plant reproduction is convenient for the next subject sexual selection. Sexual selection was another brainchild of Darwin (1871) who realized that characters that made organisms successful at acquiring a mate might be selected for, and that this can account for some of the extraordinary exaggerated traits of organisms, such as antlers of deer and long tails and colourful plumage of pheasants. The first person to explicitly model female choice as the exaggerating process was...

The origins and maintenance of mutualism

Figures 10.3, 10.4) are those interactions in which both partners accrue increased fitness relative to individuals that do not engage in it. How might selection favour the expression of traits that help other individuals of a different species, given a prior relationship that was more nearly neutral or even antagonistic Frank (1997) has suggested that two processes act to help the spread of such traits first, an initially high level of expression on first meeting in both...

Evidence for dispersal evolution

What evidence supports these predictions It must be admitted that the theoretical richness of dispersal evolution, while matching easily that on sex ratios, is not yet supported by the same wealth of evidence. The reason is primarily the difficulty of measuring the variables sex ratios simply require counts of males and females, whereas direct measurement of dispersal rates or distances is extremely problematic. Most studies have used some sort of morphological marker for dispersal ability,...