domingo, 27 de noviembre de 2011
miércoles, 23 de noviembre de 2011
Population dynamics and Limiting Factors affecting different species
monarch butterflies:
♦. Limiting factors:
Monarch numbers can rise and fall for countless reasons. Here are some examples of limiting factors:
· Temperatures can be too hot or too cold
· Precipitation can be too high or too low
· Food Sources can be scarce or abundant
· Enemies can be many or few
· Diseases can be deadly or mild.
· Widespread and increasing use of herbicides and insecticides across North America (changing agricultural practices and land use patterns in central and eastern North America are resulting in widespread use of herbicides to sustain crops at the expense of all other competing plants, as a method of weed control along roadways, and to specifically eradicate milkweeds)
♦. Predation at the overwintering sites:
Two species of birds, the Black-headed Grosbeak (Pheucticus melanocephalus) and the Black-backed Oriole (Icterus galbula abeillei), feed extensively on Monarchs roosting at the Mexican overwintering sites. Both birds are able to circumvent the toxic properties of the Monarch (see section H), and predation is estimated to occur at a rate of up to 34,000 butterflies killed per day (Snook 1993).
♦. Monarch butterflies population:
The Monarch’s wingspan ranges from 8.9–10.2 cm (3½–4 in.). The upper side of the wings is tawny-orange, the veins and margins are black, and in the margins are two series of small white spots. The fore wings also have a few orange spots near the tip. The underside is similar but the tip of the fore wing and hind wing are yellow-brown instead of tawny-orange and the white spots are larger.
The male has a black patch of androconial scales responsible for dispersing pheromones on the hind wings, and the black veins on its wing are narrower than the female’s. The male is also slightly larger.
A color variation has been observed in Australia, New Zealand, Indonesia and the United States as early as the late 19th century. Named nivosus by Lepidopterists, it is grayish white in all areas of the wings that are normally orange. Generally it is only about 1% or less of all monarchs, but has maintained populations as high as 10% on Oahu in Hawaii, possibly due to selective predation.
Like all insects the Monarch has six legs, however it uses only four of its legs as it carries its two front legs against its body.
The eggs are creamy white and later turn pale yellow. They are elongate and subconical, with approximately 23 longitudinal ridges and many fine traverse lines. A single egg weighs about 0.46 milligrams (0.0071 gr), and measures about 1.2 millimetres (47 mils) high and 0.9 millimetres (35 mils) wide.
The male has a black patch of androconial scales responsible for dispersing pheromones on the hind wings, and the black veins on its wing are narrower than the female’s. The male is also slightly larger.
A color variation has been observed in Australia, New Zealand, Indonesia and the United States as early as the late 19th century. Named nivosus by Lepidopterists, it is grayish white in all areas of the wings that are normally orange. Generally it is only about 1% or less of all monarchs, but has maintained populations as high as 10% on Oahu in Hawaii, possibly due to selective predation.
Like all insects the Monarch has six legs, however it uses only four of its legs as it carries its two front legs against its body.
The eggs are creamy white and later turn pale yellow. They are elongate and subconical, with approximately 23 longitudinal ridges and many fine traverse lines. A single egg weighs about 0.46 milligrams (0.0071 gr), and measures about 1.2 millimetres (47 mils) high and 0.9 millimetres (35 mils) wide.
The caterpillar is banded with yellow, black, and white stripes. The head is also striped with yellow and black. There are two pairs of black filaments, one pair on each end of the body. The caterpillar will reach a length of 5 cm (2 in).
The chrysalis is blue-green with a band of black and gold on the end of the abdomen. There are other gold spots on the thorax, the wing bases, and the eyes.
Cacomixtle
♦. Limiting factors:
Cacomixtle is a nocturnal and omnivorous animal that prefers wet habitats, tropical, evergreen woodlands and mountain forests, though seasonally it will range into drier deciduous forests. It is found from southern Mexico to western Panama. It is located from the lowlands to the 2.700msnm.
Their average length is 793 mm males and females 756 mm; range: 616-811 mm. And their weight range is 0.9-1.3 kg. It feeds from invertebrates, fruit, and other parts of plants, small mammals and possibly birds.
The breeding season begins in February. The gestation period is 51 to 54 days. In every birth are born from two to four puppies, but can be from one to five. Their nests are usually inside trunks of trees.
♦. Treats:
Loss of habitat due to deforestation is a major threat. In Mexico the rate of forest clearance is tremendously high and forest fragmentation is also a major problem. In addition, it is hunted in Honduras and Mexico for its fur and for meat by indigenous people.
it is also listed as an endangered species in Costa Rica. In Belize it is covered by the Wildlife Protection Act. It is not protected by law in Panama. Elsewhere the situation is unknown. Cacomistles are known to occur in the proposed Volcano Baro National Park in Panama, in the Monte Cristo National Park in El Salvador and in the Cockscomb Basin Reserve in Belize and may be living in a number of protected areas where there is suitable habitat.
it is also listed as an endangered species in Costa Rica. In Belize it is covered by the Wildlife Protection Act. It is not protected by law in Panama. Elsewhere the situation is unknown. Cacomistles are known to occur in the proposed Volcano Baro National Park in Panama, in the Monte Cristo National Park in El Salvador and in the Cockscomb Basin Reserve in Belize and may be living in a number of protected areas where there is suitable habitat.
Black-tailed prairie dogs:
Once numbered in the hundreds of millions – maybe even over 1 billion – and were possibly the most abundant mammal in North America. But due to a variety of reasons, their numbers have decreased by over 95%. Today they may number around 10-20 million.
Black-tailed prairie dog colonies were once found across the Great Plains from southern Canada to northern Mexico. Their colonies once occupied probably 40-80 million acres within this 400 million acre region, and were often tens of miles long. Today their small, scattered colonies occupy 1-2 million acres within this region. They have been eradicated completely from Arizona but survive in small numbers (relative to historic numbers) in the other 10 U.S. states, 2 Mexican states, and 1 Canadian province. Limiting factors Prairie dogs mainly live in altitudes ranging from 2,000-10,000ft above sea level.The areas in which they live can get as warm as 100F degrees in the summer and as cold as -35F degrees in the winter. As prairie dogs live in areas that are prone to environmental threats including hailstorms, blizzards, and floods as well as drought and prairie fires, burrows provide important protection for them.
Black-tailed prairie dog colonies were once found across the Great Plains from southern Canada to northern Mexico. Their colonies once occupied probably 40-80 million acres within this 400 million acre region, and were often tens of miles long. Today their small, scattered colonies occupy 1-2 million acres within this region. They have been eradicated completely from Arizona but survive in small numbers (relative to historic numbers) in the other 10 U.S. states, 2 Mexican states, and 1 Canadian province. Limiting factors Prairie dogs mainly live in altitudes ranging from 2,000-10,000ft above sea level.The areas in which they live can get as warm as 100F degrees in the summer and as cold as -35F degrees in the winter. As prairie dogs live in areas that are prone to environmental threats including hailstorms, blizzards, and floods as well as drought and prairie fires, burrows provide important protection for them.
Being the primary diet in prairie species such as the Black-footed Ferret, Swift Fox, Golden Eagle, American Badger, and Ferruginous Hawk. Other species, such as the Mountain Plover and the Burrowing Owl, also rely on prairie dog burrows for nesting areas. Even grazing species such as Plains Bison, Pronghorn, and Mule deer have shown a proclivity for grazing on the same land used by prairie dogs.
ORCHIDS:
♦. Population and Population dynamics:
Based on worldwide evidence, scientists have declared that humankind is facing the sixth extinction event in the history of the planet, and that orchids are facing among the most severe of threats. Orchid conservation is a worldwide concern, but the leading research is performed in Australia, with a particular emphasis on species occurring in the Southwestern Australia floristic region (SWAFR), a global biodiversity hotspot. Biodiversity hotspots are areas boasting a proliferation of plant and animal species, and were estimated to once cover 12% of the globe, but current estimates are only 1-4%. Although this area contains comparatively few orchids when compared to tropical forests of northern South America, the SWAFR does harbor the highest number of terrestrial species of anywhere in the world. A departure from their epiphytic cousins (growing on the branches of trees or on rocks), terrestrial orchids (species that grow in the soil) represent special, but difficult cases of species conservation due to a complex blend of intrinsic and extrinsic factors.
♦. Limiting factors:
Extrinsic factors are the reasons most frequently sited in the extinction of orchids. Upon European colonization, massive tracts of land in the SWAFR were converted to wheat plantations, destroying prime orchid habitat. Suppression of fire, competition from invasive species, increasing soil salinity, and climate change has also reduced orchid numbers. Despite the obvious effects of extrinsic factors, Current research indicates that extrinsic factors may play a secondary role to the intrinsic factors of terrestrial orchid conservation.
Of the intrinsic factors affecting orchid conservation, one of the most limiting factors is the relationship between orchids and mycorrhizae. Mycorrhizae are ubiquitously occurring fungi that form symbiotic relationships with the roots of many seed-bearing plants. Plants receive supplemental nitrogen, phosphorus, carbon assimilates, and water from fungi; all are necessary to support the growth of all plants. There remains debate concerning what fungi receive in return, but studies have shown that different forms of carbon move from the roots of plants to fungi.
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| Rhizanthella gardneri |
Terrestrial orchids have developed some of the most complex relationships of all. Species such asRhizanthella gardneri do not produce green leaves and manufacture food through photosynthesis and are thus entirely dependant on a specific fungus from Melaleuca forests for nutrition.In Australia, conservation of orchids occurs by managing existing orchid populations (in situ), assisted migration (moving) of orchid species to new sites, and the development of propagation methods for both orchid and mycorrhiza (ex situ). In situ conservation is considered to most efficient and preferred method of orchid species conservation. In situ conservation focuses on identifying existing orchid species populations that are particularly vulnerable to disappearance, and formulating conservation strategies that result in long term persistence of the population.
An example is Rhizanthella gardneri. This species faces danger of extinction in the wild because soils in its habitat are subject to increasing salt content, and the extinction of the mammal responsible for spreading seeds of this species to new areas. Although assisted migration of this species failed, scientists were able to successfully propagate this species by replicating the conditions ex situ. Cultivation attempts require the successful culture of the Melaleuca tree, and the symbiotic fungus. Although many orchid species are considered impossible to grow in cultivated settings, success with Rhizanthella has provided a glimpse of hope to conserving other fastidious orchid species (Melaleuca tree).
An example is Rhizanthella gardneri. This species faces danger of extinction in the wild because soils in its habitat are subject to increasing salt content, and the extinction of the mammal responsible for spreading seeds of this species to new areas. Although assisted migration of this species failed, scientists were able to successfully propagate this species by replicating the conditions ex situ. Cultivation attempts require the successful culture of the Melaleuca tree, and the symbiotic fungus. Although many orchid species are considered impossible to grow in cultivated settings, success with Rhizanthella has provided a glimpse of hope to conserving other fastidious orchid species (Melaleuca tree).
Bristlecone Pine:
The bristlecone pine is a tree native from United States. It is quite known for being the living organisms with the greater life expectancy (up to 5,000 years).
There are three species of bristlecone pine:
· Pinus aristata, located in the Rocky Mountains (Colorado and northern New Mexico)
· Pinus longaeva or Great Basin Bristlecone Pine located in Nevada, Utah, and eastern California
· Pinus balfouriana or Foxtail Pine from California
Although they belong to different species, they are so closely related that hybrids of these species have been found in the wild. Depending on their species, bristlecone pines can grow between 5 and 20m (some have reach 35m!) and have a trunk diameter of up to 2m.
Bristlecone pines grow in isolated groves. They usually are near (or are) the tree line. Because of cold temperatures, dry soils, high winds, and short growing seasons, the trees grow very slowly. The wood is very dense and resinous, and thus resistant to invasion by insects, fungi, and other potential pests.
♦. Climate change: The effects of current and future climatic conditions on Great Basin and the Rocky Mountains regeneration are uncertain. Climate change may be hindering regeneration on sites in the interior Great Basin. Although with the climate change it would be expected a drop in the population of bristlecone, recent studies have concluded that the population of bristlecone trees is stable. And in some cases such as the Nevada Great Basin Bristlecone Pine, the population has increased.
♦. Population can be affected by parasitism and disease. Bristlecone pine is at great risk of a White Pine Blister Rust infection. Other insects and/or disease agents are mountain pine beetle, dwarf mistletoe, and wood decay fungi. Nevertheless, the dry high-elevation sites of most Bristlecone pine currently serve to slow fungal growth and wood decay.
In addition to its susceptibility to diseases, Bristlecone pine population can be threatened by wildfires. Though they are at risk of wildfires, the fires rarely reach the Bristlecone pines because of the high elevation they are in.
References:
martes, 1 de noviembre de 2011
Research population: Monterrey population
1.- What age groups make up the largest part of the population? The smallest?
Monterrey has one of the biggest group of young people reaching almost 400,000 (393738) persons between the 14 and 19 years old only in 2010. On the other hand Monterrey has a age group of only 125,158 people between 60 and 65, sadly in the next 20 years this age group would be decreasing and maybe old people would be in a dangerous place being between the fifty thousand and one hundred thousand people, but luckily this numbers will increase again because the expectations of life are increasing for young people, less people die young (in Monterrey) and more people are giving birth at early ages.
2.- Which gender has the highest population numbers? Why do you think so? (Females tend to have higher population numbers due to their general longer life expectancies, as well as other socio-economic factors.)
Between women and men, women are taking head by only one hundred persons above the men.
3.- What trends may be predicted for the population over the next 20 to 50 years? Do you expect to have more people in older age groups?
There are more young men than women we can infer with this information that in 20 years the men population will be higher than women but in 50 year women will again head the leadership in what population is related.
4.- If you have researched migration, life expectancy, and other population features, what do you expect to happen in this country in the next 25 to 50 years? Will the population pyramid still be a pyramid or more like a box?
The population in Monterrey is 3.7 millions that is the 94% of the total population of Nuevo León that is 4,199,292; 62% of this population has from 15 to 59 years and according to the graph the life expectancy is 75 years. In the last 5 years around 2.8% arrived recently to Monterrey, from that 2.8%, 97.2% had already lived in Monterrey so they came back, 2.6% lived in another state, and 0.2% came from U.S.A.
According to the official population statistics the growth rate is 1.4% per year, so it is expected that the graph became a box between 25 and 50 years more or less because there are a lot of factors that are affecting the emigration and immigration like the insecurity, people are emigrating for a better life expectancy etc, there are also lots of diseases that are related with death rate and affect directly but there are a lot of services like the IMSS, ISSSTE or any other health service.
Because Monterrey is a city; it ranks third in the bigger cities of México, that’s why we have more life expectancy because of the resources so we are expected to become more people and graph to become a box.
5.- What effect on population would better housing, income, medicine/health care have on the overall population?
It has long been established that man's most basic needs are food, clothing and shelter, however housing represents a very influential factor in determining social attitudes in our population and the type of community in which the family is raised. Informal rental housing has been characterized as overpriced, overcrowded and inadequate, while formal rental housing often disproportionately caters to upper income groups and foreign workers, so if housing gets better and cheaper, there would be enough space for a population to grow and develop properly. Another aspect to considerate is the income that for example a family earns and that they spend daily to survive, this means, the effect that have on population will determine their financial position in the society and for the last aspect to considerate is the effect of medicine and health care in populations. They are factors that impact health on a population-level, such as environment, social structure, distribution, etc but they also provide longer lives for people, more cures to treat serious diseases, better conditions that they give for the life but as always, is not equal for everyone. We have to see the reality, this three main effects affect population in different ways and become more visible in some regions but they are all related to each other, so finally, I think that there’s positive effects on how a population may grow according to the factors of their environment.
It has long been established that man's most basic needs are food, clothing and shelter, however housing represents a very influential factor in determining social attitudes in our population and the type of community in which the family is raised. Informal rental housing has been characterized as overpriced, overcrowded and inadequate, while formal rental housing often disproportionately caters to upper income groups and foreign workers, so if housing gets better and cheaper, there would be enough space for a population to grow and develop properly. Another aspect to considerate is the income that for example a family earns and that they spend daily to survive, this means, the effect that have on population will determine their financial position in the society and for the last aspect to considerate is the effect of medicine and health care in populations. They are factors that impact health on a population-level, such as environment, social structure, distribution, etc but they also provide longer lives for people, more cures to treat serious diseases, better conditions that they give for the life but as always, is not equal for everyone. We have to see the reality, this three main effects affect population in different ways and become more visible in some regions but they are all related to each other, so finally, I think that there’s positive effects on how a population may grow according to the factors of their environment.
6.- What effects do immigration and emigration have on the country’s population? (Answers may include that more people moving into a country will increase the population while more people leaving will decrease the population if births and deaths are also high.)
Even if a person decides to move into another country, more than a change of land, it alters all the population in means of quantity and resources. When it does immigration to a land, it competes between more individuals resources, as he is taking more space of that space provided. An d when he leaves his basic town, produces to decrease its population of the land that he lived, and that little by little all the society that lived on the same area as he lived, will be affected, because there is one less human to reproduce, or to get resources with.
7.- What challenges are faced by countries that have an older population that outnumber the younger population?
While some countries are struggling with the increase of the population by new young members, other countries have quite a different problem. Nations, such as Belgium and Sweden, have a greater average in the age of their population. Some challenges these countries face (or will soon face) are:
· A higher demand for medical and nonmedical services. Some of these services are nursing, medical care, Long-Term Care (LTC). An example of problems with this is Croatia. Persons over the age of 65 are more than the 17% of Croatia’s population; each year there is a greater demand of LTC services, but there is neither the necessary money nor work force for it.
· Older people are likely to participate less in the labor force. Some reasons for this are retirement, sickness. Another problem arises because the younger generations are smaller and can’t possibly do as much work, or have little opportunities, etc; creating a smaller and weaker work force.
· Pensions and programs for elderly. The economy of countries wouldn’t be capable to produce the needed money for the pensions for a great part of the population. And pension-time would be greater by the increasing life expectancy.
8.- What are some challenges both developed and developing countries will have in the future with growing populations? (Answers may include environmental concerns, transportation concerns, growing medical needs, growing demands for education, shortages of resources, and shortages of housing.)
Some challenges would be like, how to get the enough resources for all the population if the population is growing and growing and it is finishing with all the resources, there won’t be any food cause the population will be ending with it, also for the transportation, if there is so much population, they would end with the petroleum that is used in almost all the transports in the planet. Also cause in the future the population would very few spaces for people on houses. Also cause is there going to be more people the countries would face the demand for education cause there is going to be more people and it would be the same spaces for schools, like we are facing in our times.
Some challenges would be like, how to get the enough resources for all the population if the population is growing and growing and it is finishing with all the resources, there won’t be any food cause the population will be ending with it, also for the transportation, if there is so much population, they would end with the petroleum that is used in almost all the transports in the planet. Also cause in the future the population would very few spaces for people on houses. Also cause is there going to be more people the countries would face the demand for education cause there is going to be more people and it would be the same spaces for schools, like we are facing in our times.
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