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Environment and Competition

The major characteristic of any given ecosystem is usually its climatic conditions. This is the reason why similar biomes are found in similar geographical regions that experience similar climatic conditions. Consequently the climate dictates the plants, animals, and even micro-organisms communities as these organisms usually thrive only in distinct climatic conditions. Temperature and precipitation levels directly influence the nature and amount of flora and fauna in different areas. It is in fact these climatic conditions that define different biomes. The Tundra biome for instances experiences very low temperatures, sometimes below the freezing point and very low precipitation ranging from 0 to 25mm per annum. The low temperatures in this biome as well as the short growing seasons hinder tree growth. The typical tundra vegetation therefore comprises of widely scattered trees amid which dwarf sedges, shrubs, grasses, mosses, liverworts and lichens grow. Nematoceras sulcatum and Nematoceras dienemum are the only orchids and arguably the only colorfully blossomed plants that thrive in the biome. The animal life in the tundra is also peculiar with various mammals such as seals, cats and rabbits as well as birds such as penguins and Antipodean albatross inhabiting the arctic and Antarctic tundra (World Wildlife Fund). The desert biome on the other hand gets the same level of precipitation as the tundra regions (0- 25 mm) but has extremely high temperatures that range from 70C to 380C. It is the temperature level, therefore which causes the distinct differences in flora and fauna between the deserts and the tundra. The desert plants are mainly characterized by their adaptive features such as salt, and drought resistance. Some of the most common shrubs in desert biomes include Desert Holly, Prickly Pears, and Brittlebushes. Unlike the tundra vegetation, the plants here often bear conspicuously colored blossoms. The fauna comprises of hardy xerocoles such as jack rabbits, kangaroo rats, camels, coyotes, and many snakes and lizards. The deviations in animal and plant life between the tundra and the desert biomes prove just how big a role temperature levels have in defining a biome.

Similarly, the levels of precipitation often define different biomes and mark the distinction between different biomes that have the same temperature ranges such as the savanna and rainforest biomes. The two experience temperature levels that fall in the same range but have precipitation levels that are widely different. The difference in vegetation and animal life is however quite different. While the savanna is a grassland ecosystem with trees that are widely spaced and thus with no closed canopies allowing for vigorous foliage growth, the rainforests are characterized with various layers including the canopy layer formed by the closely spaced trees that hinder vigorous undergrowths. The plant and animal species are also quite different.  Rainforests support much more life with many species of flora and fauna, living here including various families of mammals such as primates and felids, bird families such as Cuculidae and vangidae, reptiles such as turtles, chameleons and snakes such as boa constrictors, and numerous invertebrate families. Plant life in these biomes include enormous trees that sometimes exceed 45m in height sometimes with girths of over 3m in diameter, some shrubs and fungi that feed on the decomposing matter (Saha, 2003). The savanna on its part, supports growth of grass, shrubs and widely spaced trees. These in turn support numerous grazers and browsers and their predators. The massive differences between the two biomes and is therefore as a result of difference in precipitation.

Begon (1996) observes that in general, the numbers of predators and prey exhibit a clearly explicable trend. Generally, holding all factors constant, the number of predators decreases when the prey numbers are low. This is mainly due to the fact that the predators cannot get enough to eat and some therefore starve to death.  This is explicit from the fact that when the prey population is at its lowest at 7 600 during the study year 18, the predator population is also at among its lowest populations during the study period at 15 800.  Similarly high numbers of predators cause a cause a decline in the number of prey as depicted by the period between years 4 and six of study. At year 4, the numbers of prey are quite high at 77, 400. This causes a rise in the predator population from 35 200 in year 4 to 59 400 in year 5. The increase in predator population has a direct impact on the prey population and the latter declines from 77 400 to 36 300. The high number of predator population in year 5 causes further decline in prey population from 36 300 to 20 600 in year 6. However, the continuous decline in the number of prey takes it toll on the predator population and it reduces from 59 400 in year 5 to 41 700 in year 6.

Survey Year Prey (x1000) Predator (x1000)
4 77.4 35.2
5 36.3 59.4
6 20.6 41.7

The data proves that periodic cycles exist in the numbers of predators and prey. Such a cycle at the beginning may have a small number of predators and a small number of preys. Due to adequate resources and little predation, the number of the prey rises significantly. As the number of prey rises, the number of the predators rises as they can now get enough to eat and hence their prolificacy and survival rate is increased. A rise in the number of predators triggers a fall in the number of prey as they are being predated upon at a high rate. The fall in the number of prey in turn causes the fall in the number of predators since the predators cannot now get enough to eat and hence their reproductive power is greatly reduced. The in the number of predators in turn cause a reduction in the number of prey. The cycle then repeats itself (Begon, 1996). Though the cycle is in many instances affected by other factors such as diseases, human encroachment and droughts, the trend has often been observed in many ecological studies.

Competition within a species has a direct impact on the survival rate of organisms within the species. Such competition is usually over food, habitat and mates. Competition however may involve siblings born together in a single birth as is the case in Felis Catus where competition for survival starts soon after birth. The number of offspring per birth is usually a function of the age of the mother. As a rule, the older the mother the fewer the number of offspring she usually gets per birth. Older Felis catus mothers therefore give birth to a fewer number of offspring. The competition for mother’s milk and care is therefore limited since she can look for food more comfortably for fewer off spring. The survival rate in older mothers is consequently much higher than in younger mothers who usually give birth to a high number of offspring at a time. The litter size in mothers who have just reached puberty averages at six while the litter size of females at the end of their reproductive cycle is on average 3. At the same time, Felis catus are domestic animals and hence when the size litter is too large, their owners may not be in a position to offer the level of care they would to a smaller litter.