Date palm
Seedlings of the date palm normally produce fruit that is fit only for feeding camels. Furthermore, this palm has a breeding cycle of six years, and its vegetative propagation is very slow. The palm is also dioecious, meaning that each palm is either male or female, but not both. Choosing a male parent on the basis of fruit quality is possible but very difficult. Date palms also occupy a lot of space. Amateurs could be involved in the screening of existing populations of seedling date palms...
Reversible and Irreversible Ecosystem Damage
We must make a clear distinction between reversible and irreversible damage to ecosystems. If the damage is within the resilience capabilities of the ecosystem, it is reversible, and the ecosystem will recover. Occasionally, however, an ecosystem can suffer damage beyond the limits of its resilience, and beyond its capacity for recovery. Some ecosystems are fragile, and they can easily be triggered into collapse. During the Holocene pluvial period 12,000-9,000 years ago , Lake Chad was the size...
Demonstration of a GeneforGene Relationship
A gene-for-gene relationship can be demonstrated genotypically or phenotypically. A genotypic demonstration of a gene-for-gene relationship requires genetic studies in both the host and the parasite. Such studies can be a lengthy business, often requiring many years of painstaking work. Genetic studies in the parasite are often extremely difficult, as with aphids or rusts, for example. In many other parasites, genetic studies are impossible because the reproduction is entirely asexual. A...
The PersonHabgood differential interaction
Having applied the Habgood 1970 nomenclature for the host and parasite differentials to the pairs of genes in a gene-for-gene relationship, Robinson 1976 rearranged the Person 1959 differential interaction on the basis of the Habgood nomenclature. There was then a greatly increased simplicity, and he called this the Person Habgood differential interaction Fig. 4.4 . Intriguingly, the patterns within the differential interaction are reproducible with the techniques of cellular automata see 2.2...
