Biogeography and Ecology
Why Carnivores Are Lesser than Herbivores In the Food Chain
The energy in the ecosystem comes from a single source; hence the rest is passed from one food chain level to the next. However, a certain fraction of this energy is lost before it gets to the next level (Redman, 2020). When herbivores consume, only a small percentage of their energy is transformed into a new mass, and the rest is wasted through activities such as walking and running. Also, when carnivores eat, only a small portion of this energy becomes a new mass. Therefore, organisms in the food chain tend to receive more energy than they pass on to higher organisms through body mass. A carnivore, therefore, has to consume more herbivores to get enough energy to sustain it through its lifetime (Redman, 2020). As a result, the higher you go in the food chain, the less available the food and energy.
The Uniqueness Of Australia’s Fauna
The high level of endemism for the various organisms in Australia is related to the aftermath of the country’s geographical isolation, tectonic stability, and the different climatic regimes within the environment. The land was on the southern part of the Gondwana supercontinent. When the supercontinent began to break around 140 million years ago, the country separated until the Indo-Australian plate had a collision with Asia (Britannica, n.d.). Later, through the various episodes of evolution experienced by diverse living organisms as they tried to adapt to the surrounding, the uniqueness of Australia’s fauna cannot be ignored. During the drift, the country is believed to have escaped the influence of global warming. As a result, the native organisms that once existed in Gondwana had a higher chance of survival in Australia. After the Miocene that occurred at around 5.3 million years ago, the Asian species that remained in Australia also were able to adapt and establish there (Britannica, n.d.). The Wallace Line that marks the boundary between the Eurasian and Indo-Australian plates shows an apparent zoogeographical disparity between Asian species and those that exist in Australia. Also, the mid-Oligocene incident that occurred during the last approximately 15 million years ago heavily influence the Australian climate, which became extraordinarily arid or extremely and seasonally wet (Britannica, n.d.). With these regimes, the environment allowed some unique species to grow, some became arid-specialized, and others adapted to the wet conditions.
The Earth’s Biome
The Earth’s biome is a combination of a variety of habitats. A biome can be defined as a distinctive community of biological organisms that share a uniform response to the physical surrounding. The universal community establishes the presence and condition of individual plants and vegetation due to influence resulting from temperature, precipitation, and the availability of other plants and animals (Lumen, n.d.). The Earth’s biomes can either be terrestrial or aquatic (Lumen, n.d.). Adaptation is the primary existence key to these organisms; therefore, there are some special vegetation adaptation features which are all dictated by temperature and precipitation variations. As a result, these two abiotic features are used when predicting the various biomes, which concludes that biomes have no boundaries (Lumen, n.d.). Regardless of geographic distinction, similar biomes occur in regions that experience the same temperature regimes. The difference between tropical wet forests and Savanna is significant in the plan forms and vegetation structure present in the two (Lumen, n.d.). While tropical rainforests have elevated levels of precipitation and humidity, savanna regions are characterized by less number of trees and prolonged dry seasons. In the tropical rainforests, the vegetation has broad uniform leaves and shed leaves all year round (Lumen, n.d.). Also, for these regions, the sunlight is not seasonal, and there are no photoperiodic regimes; therefore, plants thrive (Lumen, n.d.). The long dry seasons of the Savanna hinder the growth of trees. Since wildfires have become a constant bother to this vegetation, plants have adapted by developing root systems that guarantee re-sprouting after fires.
Criticism of MacArthur and Wilson’s (1967) Theory of Island Biogeography
The theory fails to address the disparity between immigration and extinction. Since the approach is based on the rudimentary concept of the relative staticity of species composition, it, therefore, proposes that a community structure was built on the effect of immigration and extinction. The two then went deeper to explain the dynamic equilibrium of the resisting forces of immigration and extinction.
Significance Of Allopatric Speciation To Evolution
Allopatric speciation is the process where similar species in a habitat get separated due to geographical barriers for a prolonged period. Later, these two groups adapt to their new environments and become so different from each other due to genetic variations. Therefore, this process is considered one of the significant influences on natural selection, which dictates evolution. Moreover, after the geographic separation that results in allopatric speciation, these organisms are obliged to go on separate ways where they experience different types of evolutionary changes (PBS, n.d.). Genetic mutations due to the subjective pressure on these organisms transform them; therefore, becoming so different even physically, whereby if these organisms ever met, they would not interbreed (PBS, n.d.). As a result, new species are formed due to this reproduction separation.
References
PBS. (n.d.). Allopatric Speciation. Retrieved June 2020, from Evolution Library: https://www.pbs.org/wgbh/evolution/library/05/2/l_052_03.html
Lumen. (n.d.). Terrestrial Biomes. Retrieved June 2020, from Lumen Boundless Biology: https://courses.lumenlearning.com/boundless-biology/chapter/terrestrial-biomes/
Britannica. (n.d.). Australia. Retrieved June 2020, from Encyclopaedia Britannica: https://www.britannica.com/place/Australia/The-Mesozoic-and-Cenozoic-eras
Redman, L. (2020). There Are More Herbivores Than Carnivores In a Food Chain … Do You Know Why? Retrieved June 2020, from 3P Learning: https://www.3plearning.com/blog/there-are-more-herbivores-than-carnivores-in-a-food-chain-do-you-know-why/