Introduction
Environmental factors influence population growth and these factors include food availability and space to live and reproduce in (Begon et al. 2006, Caswell 1996). These all need to be accounted for when creating a population model, as they influence the amount of individuals that are present (Caswell 1996). A stage model is useful as it groups individuals into their different life history stages e.g. juveniles, yearlings and adults animals or growth stages for plants (Leslie 1948). Size structured models take into account that not all individuals proceed to the next age group, i.e. they have an indeterminate growth, and therefore allows for the possibility that some of the individuals may remain in the same age group for more than one consecutive year (Gotelli & Gillman 1996). The objective of this study was to compare the different results achieved when using stage structured and size structured models. Which model is most accurate at depicting a population’s growth? How is each model affected by the parameters that are entered into them?
Methods
Collecting skulls of Himalayan tahrs and sorting them according to year class obtained the data used for the stage-structured model. A total number of 159 skulls were collected and sorted into 9 age classes. A life table was then constructed to estimate the mortality (qx) and survival (px) rates for each year class. This data was then used to create an expanded Vensim model that was later simplified into 3 different year classes: juveniles, yearlings and adults. This was done by adding all individuals from age 2 and up together and then estimating the aggregate survival for animals over 2 years of age where: qx= number of skulls/ summed adult population
And
px= 1- qx (mor...
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...e parameterizations for size-and stage-structured models. Ecological Modelling,88(1), 73-82.
Crowder, L.B., Crouse, D.T., Heppel,S.S., &Martin, T.H. 1994. Predicting the impact of turtle excluder devices on loggerhead sea-turtle populations. Ecolocical Applications (4), 437-445
Gotelli, N. J., & Gillman, M.1996. A Primer of Ecology. Trends in Ecology and Evolution, 11(6), 265. Metapopulation Dynamics A Model of Metapopulation Dynamics pp 84
Leslie, P.H. 1948. Some further notes on the use of matrices in population mathematics. Biometrika, 35(3–4), 213–245.
Paulo, O. S., Dias, C., Bruford, M. W., Jordan, W. C., & Nichols, R. A. 2001. The persistence of Pliocene populations through the Pleistocene climatic cycles: evidence from the phylogeography of an Iberian lizard. Proceedings of the Royal Society of London. Series B: Biological Sciences, 268(1476), 1625-1630.
Theoretical Population Biology, 9, 129-136. Kacelnik, A. 1984. The.
Throughout the animal kingdom, adaptations take place continuously and even the smallest of changes can leave a significant impact. Examples can be seen within any plant or animal. One example would include sea turtles, specifically, the Loggerhead Turtles. These turtles are native to the Indian, Atlantic, and Pacific Oceans as well as the Mediterranean Sea (Deurmit L 2007). They thrive in either temperate or tropical climates and can live in a myriad of biomes (Deurmit L 2007). These biomes include the pelagic, reef, coastal, and brackish water (Deurmit L 2007). Loggerhead turtles are omnivores and can eat anything from insects to aquatic crustaceans, to macro algae (Deurmit L 2007). According to Deurmit (2007) Caretta caretta is classified into Animalia Kingdom, Chordata Phylum, Vertebrata Subphylum, Reptilian Class, Testudines’ Order,
The efforts taking place through different conservation organizations and the State of Florida are making a mixed impact on the survival of Manatees and Sea Turtles. The decline in manatee population has decreased, but due to low reproduction rates, more needs to be done to avoid extinction. The sea turtle outlook is more species specific. Some species of turtle are seeing stabilization in population, while others are not. The State of Florida has a large array of custom license tags that support the conservation efforts taking place within the State. The proceeds go to benefit the local marine life in Florida. With financial resources, state and local cooperation, and through constant research and observation, we are able to learn more about both of these gentle animals. With human awareness of those living in Florida, these two animals will survive
Tanner, J.M. and G.R. Taylor, Time-Life Books. Growth, New York: Life Science Life, 1965. p.64.
Loggerhead turtles are becoming endangered more and more often. Not many people understand the dangers that these turtles are in, especially when the females are nesting. Nesting takes an important role in the lives of these turtles and is an amazing process that occurs during the season. Unfortunately, many factors disturb the process of these hatching eggs. This paper explains these factors in depth to educate the audience about the dangers involved in loggerhead nesting. Light pollution, natural disasters, and predators are described and explained as to why they affect the process of nesting. Many organizations are trying to share their knowledge on these loggerhead-nesting dangers with people and are trying to help keep the loggerheads alive.
The green sea turtles have been taken out of the Atlantic Ocean for several years, so now they are an endangered species. Today, the green sea turtles population is growing and in the Florida Refuge they counted up to over 12,000 turtle nests. It is shocking to see how much the refuges care about the green sea turtles. They have been looking out for the turtles for 35 years. It was interesting to find out that these green sea turtles live for a really long time. It takes the turtles 25 years just to mature. This article caught my eye because I love science and animals. Knowing that people are taking care of what used to be endangered animals really means a lot to me. I hate seeing animals hurt or struggling to survive. Because of the refuges
Spencer, Herbert. “A Theory of Population, Deduced from the General Law of Animal Fertility.” Westminster Review. LVII (1852): 250-68.
Tanner, J.M. and G.R. Taylor, Time-Life Books. Growth, New York: Life Science Life, 1965. p.64.
All animals are quite different, especially in appearance. Common features may be found if major differences can be looked past. If the smooth, slimy skin of a hagfish and the hard, ridged shell of a snapping turtle are stripped away, some shared characteristics may arise. Hagfish and snapping turtles have certain similarities and differences in important life processes that all animals depend on to live, such as procuring and digesting nutrients, supporting themselves, and their sense organs.
Raup, D.M.(1979). Conflicts between Darwin and Paleontology. Field Museum of Natural History Bulletin,50, (l), 25.
When fishers throw their nets, the turtles get caught in the nets causing damages to their body or drowning them. When juvenile loggerheads head to their foraging area in the water, they are highly exposed to bycatching, international longlines, and illegal, unreported and unregulated (IUU) longline fisheries causing high mortality rates (Peckham et al. 2008). Though juveniles have a higher mortality rate due to bycatch, longlines and trade since they are still maturing, adults are easily exposed to these threats as
Works Cited Bates, D. (1957, December 17). Letter from Roy Wilkins. Little Rock, Arkansas, United States of America. Beals, M. P. (1994). The Species of the World.
and stand maturity for pool-breeding amphibians in forested landscapes. Canadian Journal of Zoology, 84(11), 1604-1615. Retrieved from http://search.proquest.com/docview/220513124?accountid=34939
Southwick, C. H. (1996). "Chapter 15: Human Populations." Global Ecology in Human Perspective. Oxford University Press, 159-182.
This includes birds, reptiles and many other animals. A type III curve, is characterized by a decreasing concave line. This curve shows a higher death rate early in life, if the organism survives, it has higher chances for a longer life. This is seen in small mammals and marine invertebrates. “The general shape of the survivorship curve is fixed for each species, however, the convexity of the curve is highly sensitive to environmental conditions and the genetic constitution of the population. This fact suggests that the general shape of the life table may provide information about the genetic variability in the population, the range of environmental factors that impinge on the population or the incidence of random events in the lifetimes of different individuals” (http://www.nature.com/nature/journal/v275/n5677/abs/275213a0.html) . Here, we will view the survivorship between urban and rural population’s pre and post