Rules in Ecology
: Ecology is the scientific study of the interactions that exist between living organisms and their surroundings. The term “Ecology” was coined by Ernst Haeckel. A number of fundamental principles and rules govern ecological processes and interactions within ecosystems. Some of the prominent rules are listed below.
Rules in Ecology
1. Allen’s Rule:
Allen's rule is a biological principle named after the late-nineteenth-century American zoologist Joel Asaph Allen. The rule describes how endothermic or warm-blooded animals' body shape or size varies with temperature across geographical regions. It is frequently used to explain patterns of adaptation and variation in body shape among related species living in various climates. According to Allen's rule, endothermic animals from colder climates have more compact body shapes and shorter appendages (limbs, tails, and ears) than those from warmer climates. Animals from warmer climates, on the other hand, have more elongated body shapes and longer appendages. The rule is thought to be an adaptation to aid in the regulation of heat exchange with the environment. A more compact body shape with shorter appendages reduces the surface area-to-volume ratio in colder climates, reducing heat loss and conserving body heat. In warmer temperatures, on the other hand, a longer body shape and longer appendages increase the surface area-to-volume ratio, facilitating the dissipation of heat and keeping the animal cool. This phenomenon has been observed in a variety of animal groups, including mammals and birds. The Arctic fox (
Vulpes lagopus
), has shorter ears and limbs than its relative, the fennec fox (
Vulpes zerda
), which lives in the hot deserts of North Africa.
2. Bergmann’s Rule:
Bergmann's rule is another biological principle named after Carl Bergmann, a German biologist who developed it in the mid-nineteenth century. Bergmann's rule, like Allen's rule, describes patterns of variation in body size among related species, but it is only applicable to endothermic animals. Bergmann's rule states that individuals from colder climates have larger body sizes or masses than those from warmer temperatures within a species or among closely associated species. In other words, populations of a species that live in colder environments have larger individuals, whereas populations that live in warmer environments have smaller individuals. This phenomenon is considered to be an adaptation to help regulate heat in various climates. Larger bodies have a lower surface area-to-volume ratio, which helps to reduce heat loss in cold environments. Larger animals have a lower surface area relative to their body mass, resulting in less heat loss to the environment and vice versa. Bergmann's rule has been observed in a variety of animal taxonomic groups, including mammals and birds. Polar bear populations in the Arctic, for example, are generally larger and heavier than brown bear populations in more temperate and warmer regions.
3. Gloger’s Rule:
Gloger's rule is a biological principle that describes a pattern of variation in the coloration or pigmentation of animals within a species based on geographic distribution. The rule is named after the German zoologist Constantin Wilhelm Lambert Gloger, who proposed it in the early nineteenth century. According to Gloger's rule, animals that live in warmer and more humid environments have more heavily pigmented or darker coloration, whereas those that live in colder and drier environments have lighter coloration. In other words, populations of a species in hot and humid climates have darker fur, feathers, or skin, whereas populations in colder and drier climates have lighter coloration. Gloger's rule is commonly observed in a variety of animal groups, including mammals, birds, and insects. Many bird species in tropical rainforests, for example, have darker plumage, whereas closely related species in arid regions have lighter plumage. Gloger's rule, like other ecological rules, can have exceptions due to various factors such as evolutionary history, migration patterns, and local adaptation. Nonetheless, the rule provides valuable insights into how animals have adapted to different environmental conditions over time.
4. Shelford’s law of tolerance:
Shelford's law of tolerance, proposed by American zoologist Victor Ernest Shelford in 1911, is an ecological principle that describes how the most limiting environmental factor within a species' range of tolerance determines its abundance and distribution. This concept is crucial for comprehending an organism's ecological niche and ability to survive and thrive in a variety of environmental conditions. According to the law of tolerance, every organism has a set of environmental conditions in which it can survive, grow, and reproduce. This tolerance range includes upper and lower limits for a variety of environmental factors such as temperature, humidity, pH, salinity, and other specific requirements. These factors influence the organism's ability to survive and perform ecological functions as a whole. The prefix steno and eury have been used generally for comparing the relatively narrow and wide degree of tolerance, respectively of an organism to a given environmental factors.
5. Gause's hypothesis:
Gause's hypothesis, also known as the competitive exclusion principle or Gause's law, was proposed in the 1930s by Soviet ecologist Georgy Gause. The principle states that two species competing for the same limited resources cannot coexist in the same ecological niche indefinitely. Eventually, one species will outcompete and displace the other, resulting in the exclusion of the weaker competitor.
The competitive exclusion principle is based on the idea that no two species can occupy the same ecological niche, which refers to a species' role and position within its ecosystem, including interactions with other species and resource use. The competitive exclusion principle proposed by Gause is critical for understanding the dynamics of ecological communities and species coexistence. It contributes to the understanding of patterns of species distribution and abundance, as well as the process of species diversification and niche specialization over evolutionary time.
6. Rensch’s Rule:
Rensch's rule, also known as Rensch's size rule, is a principle of ecology and evolution named after the German zoologist Bernhard Rensch. He developed this rule after observing sexual size dimorphism (SSD) in various animal species. According to Rensch's rule, the degree of size difference between the sexes increases with body size in species where males are larger than females (positive sexual size dimorphism). In other words, as the species grows larger, the relative size of males versus females becomes more pronounced.
In species where females are larger than males (negative sexual size dimorphism), the size difference between the sexes decreases as body size increases. As the species grows larger, the size difference between males and females becomes less pronounced. Rensch's Rule can be observed in a wide range of animal taxa, including mammals, birds, and insects. In many bird species, for example, where males typically compete for female access or defend territories, larger males may have an advantage in securing mates or resources, resulting in greater size dimorphism.
