Essay Example on 2 Extinct Organisms: Why They Vanished From Earth

Name two extinct organisms from different geological ages and explain why each probably became extinct.

A significant percentage of organisms that have ever stepped foot on earth are extinct. The evolution of newer species as a result of the ever-changing ecological niches forced older species to get wiped out of the earth. However, in the history of the planet, the extinction rate can be regarded as being far from constant. Over the last 500 million years, several organisms/species on earth have vanished in a geological blink of an eye (Koch, 1967). The extinction of the organisms during the various geological ages is termed as 'mass extinctions.' In essence, they refer to catastrophic and deadly events that allow for the formation of new life and hence more unique species of organisms. One of the mass extinctions that wiped out the majority of the significant organisms is the cretaceous-Paleogene extinction, which occurred approximately 66 million years ago. Some of the primary species/organisms that became extinct include the Nonavian Dinosaurs and other dinosaur species. The extinction of the dinosaurs gave room for the emergence of a different life - mammals and birds got the opportunity to quickly diversify and evolve for survival (Koch, 1967). The other organism that became extinct is the Trilobite, a macroscopic arthropod. The Trilobite happens to be among the oldest species of organisms, and their extinction took place right during the early part of the Paleozoic era, about 500 million years ago (Feist, 1995).

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Trilobites - Initially, microscopic single-cell plants and animals developed sediment-trapping structures known as Stromatolites, which have fossils in the shallow waters of Northern Arkansas (Feist, 1995). Trilobites were a group of arthropods that had significant dominance over the other macroscopic organisms for about ten years before becoming extinct. Their numbers started to drop because of the complex-growing ecosystem. The key reason for their extinction was the competition for food as well as living space from other marine creatures who were apparently better adapted (Feist, 1995).

Nonavian Dinosaur - The dinosaur was a dominant species back then. This organism got extinct in the late Mesozoic Era. Their sudden demise is generally linked to climate change. The climate change theory happens to be a justifiable reason as to why the dinosaur got extinct. Since time immemorial, the dinosaur flourished in the earth's continually humid, tropical climate. It is believed that during the Mesozoic era, the planet got cooler (Koch, 1967). Such low temperatures led to the formation of ice in both the North and South poles.

Consequently, the oceans became cooler as well. Since the dinosaurs were cold-blooded, the only source of heat (the sun), as well as air, were not able to sustain them. Thus, the dinosaur became extinct.

Explain how each of the five major population characteristics shapes population dynamics.

Population dynamics refers to the variation of populations over time, and it depends on the biological as well as environmental processes that influence population changes. The five significant characteristics that shape population dynamics include population size, population density, spatial distribution, sex ratio, and age structure. These factors influence population dynamics in the following ways:

Population Size and Density - Refers to a measure of the number of individuals per unit area. Size and density are both essential in describing the current status of the population and, potentially, for making predictions about how the population could change in the future. Larger populations can be more stable compared to smaller populations because they have a high probability of possessing more considerable genetic variability hence bearing more potential to adapt to changes in the environment through natural selection (Nikita, 2020). Also, an organism in a low-density population, particularly where members are scattered, may have trouble getting a mate to reproduce with compared to an individual found in a high population density. However, a high population might lead to increased competition for food and space.

Spatial Distribution - Other than population size and density, it is essential to determine the spatial distribution of organisms. The dispersion patterns, as well as distribution patterns, are components of spatial distribution, and they explain how members of a population are distributed in space at a given time (Nikita, 2020). The member organisms present in a population could more or less equally spaced, dispersed randomly with no predictable pattern, or clustered in groups. These are commonly referred to as uniform, random, and clumped dispersion patterns, respectively. Most organisms that adopt uniform dispersion tend to stake out and defend their territories. The organisms that take random dispersion are those that live in a favorable environment, with adequate resources. As for clumped distribution, organisms group themselves according to the availability of necessary resources.

Age Structure - Refers to the composition of a population in terms of the proportions of individuals of different ages. The growth rate of a given population is strongly determined by the proportions of members of particular ages. A more even age structure is likely going to result in a more stable number of births in the population. The age structure containing younger individuals (who are at or close to the reproductive age) is likely to lead to rapid growth in the population (Nikita, 2020).

Natality (Birth Rate) - Natality is also known as the birth rate in a population, and it refers to the number of individuals born per year. This factor increases the population size. The higher the Natality, the larger the population because more members can reproduce. Moreover, Natality varies from one organism to another, and it depends on the population density as well as environmental factors. There exists a general rule that if the population density is low, then the birth rate would be low as well (Nikita, 2020). This is because the chances of mating between opposite sexes are low. However, if the population density is exceedingly high, then the birth rate can also be low because of the poor nutrition and psychological problems emanating from congestion. Maximum Natality is experienced where the organisms live under ideal ecological as well as genetic conditions (Nikita, 2020).

Mortality (Death Rate) - Mortality refers to the death rate of a population. It relates to the death of individuals of a population under existing environmental conditions or because of nature (physiological longevity). Mortality is influenced by several factors, including population density, disease, competition, predation, and environment (Nikita, 2020). Mortality varies among organisms and is correlated with birth rates. The population is said to be stationary, where the Natality is equal to the mortality rate.

Explain some examples of non-symbiotic and symbiotic mutualisms. What is at least one way that mutualisms affect your daily life?

Mutualism refers to a relationship in which two or more organism species benefit from interacting with one another (Cushman & Beattie, 1991). In such a case, the organisms are interdependent. Physically close mutualism is what is known as symbiosis. An excellent example of symbiosis is the microbes in the tracts of the human digestive system (Cushman et al., 1991). The human body hosts the bacteria, and they, in turn, help in the digestion of food in the body, and both parties are in very close physical contact. Also, there can exist mutualism with benefits without necessarily having close proximity; this is also known as non-symbiotic mutualism (Cushman et al., 1991). An example of non-symbiotic mutualism can be demonstrated by bees that pollinate flowers. They search for nectar from flowers, and in the process, they help flowers carry out pollination.

My digestive tract is full of microbes that help in the digestion of food necessary for normal body function. Food provides energy, growth, and protection against diseases when digested. Therefore the process of digestion is essential to my body, and it can only be achieved with help from the microbes. Otherwise, without digestion, my body would not survive for long.

What is a keystone species? What types of organisms does this term often apply to? Identify one such keystone species that supports organisms that are important to you and explain why.

A keystone species refers to a plant or animal that plays a unique and essential role in the functionality of an ecosystem (Mills, Soule, & Doak, 1993). Besides, a keystone species bears a strong or wide-reaching impact far out of proportion to its abundance - it helps hold the ecosystem together. Without the existence of keystone species, then the ecosystem would be dramatically different or cease to exist altogether. Also, without keystone species, new organisms could come into the habitat and drive out the native species. Even though all species in an ecosystem or a habitat are essential and rely on each other, the contributions of keystone features are substantial compared to the species' prevalence in the habitat (Mills et al., 1993). Moreover, a small number of keystone species can bear a significant impact on the environment.

In most cases, secondary as well as tertiary consumers are considered keystone species because they determine/control the population of the species found in the lower trophic level. Trophic cascade refers to predators at the high trophic levels, and they indirectly promote populations of low trophic levels by keeping species at intermediate trophic levels in check (Mills et al., 1993).

Bees happen to be an essential keystone species to me. Bees play a significant role in reproduction among flowers. Most of the plants are food for human beings. The removal of bees from our ecosystem signifies a lack of reproduction among plants hence no seed-producing plants. It means that humans are going to lack food to consume.

Different types of biomes might form in a particular place on land. What factors most strongly influence which biome forms? In a given location, what factors contribute to the type of aquatic system that may form? Give and explain a concrete example.

The biome is a large, naturally occurring community of flora and fauna occupying a primary habitat (Jackson, Canadell, Ehleringer, Mooney, Sala, & Schulze, 1996). It consists of a significant regional complex of similar communities - a large scale ecological unit recognized fundamentally by its plant type and vegetation structure. Factors such as temperature and precipitation determine the type of biome that forms in a particular place on land (Jackson et al., 1996).

Aquatic systems refer to the biomes present in the oceans, along the coastal lines, and also in freshwater systems. The marine systems are shaped by salinity, water temperature, wave action, dissolved nutrients, depths, light levels, currents, and types of substrates such as the muddy, rocky bottom, or sandy (Carr, Duthie, & Taylor, 1997).

References

Carr, G. M., Duthie, H. C., & Taylor, W. D. (1997). Models of aquatic plant productivity: a review of the factors that influence growth. Aquatic Botany, 59(3-4), 195-215. Retrieved from https://doi.org/10.1016/S0304-3770 (97)00071-5

Cushman, J. H., & Beattie, A. J. (1991). Mutualisms: assessing the benefits to hosts and visitors. Trends in Ecology & Evolution, 6(6), 193-195. Retrieved from https://www.sciencedirect.com/science/article/pii/016953479190213H

Feist, R. (1995). Effect of paedomorphosis in eye reductio...