Super Continental Theory (Pangaea)

By Reshma Dahal

The aim of this article is to inform readers about the process in which the continents of the globe drifted to their current positions explaining the geological discovery and its impact to human kind.

The Earth is a truly extraordinary planet. There are rivers, the lakes that flourish onto the beaches. There are colossal mountains which stand strong and proud marking their territory. The hills, the forests, the seas; they are all remarkable puzzle pieces that unite to create the spherical globe, which we call Planet Earth.

Our planet is astonishing and beautiful. But it is also very mysterious. Unlike in the past, now in the twenty first century our understanding of our planet has grown significantly due to the numerous discoveries scientist have unravelled. It is clear that, in the early days, the reasoning of natural disasters such as tsunamis, earthquakes and volcanic eruptions were not properly understood. Even the most famous geologists in those times could not begin to comprehend the cause of these occurrences. Why would the ground shake so abruptly? What was the reason for gallons of water to splatter and sweep away the precious lives and essential resources? These all questions which deserve evidence based answers, but none were given until the year of 1915.

Professor Alfred Wegener, a German scientist, was always fascinated in geophysics.  He accumulated evidence to answer the question as to why the land masses on earth stand where they are today. For example: why Australia is situated near the South Pole and not the North Pole. There are four principle evidences^1,2 which Professor Wegener accumulated that gave birth to the “Pangaea” or “Super Continental” theory.  They are:

1.  There is a close fit between the coastlines of Africa and South America (see Figure 1). 

2. There are identical plants and animal fossils found on opposite sides of the Atlantic, on South America and Africa.  

      3.  There are the same types of mountains on both sides of the Atlantic Ocean, the Appalachian mountains of Eastern North America and the Scottish Highlands, and the distinctive rock strata of the Karroo system of South Africa are identical to those of the Santa Katarina system in Brazil

      4. 250 million years ago there was ice that covered south Africa, India, Australia and South America. The only way these warm climate countries, could have had ice is if they were closer to the South Pole. 

The basis of Pangaea theory is that about 300 million years ago, the continents had formed a single mass, called Pangaea (See Figure 2). Though slowly, Pangaea begun to split (See Figure 3-5), and now rests in the position of our current continents (See Figure 6).

He also has reason to believe that even until now, the shape of the Earth surface is still changing, and it will be forever, as long as the mantle underneath the Earth's crust gets heated and convection currents in the magma keeps dragging the plates.  When the Pangaea theory was first proposed, it was treated with much scepticism, but since then, there have been many forms of evidence to support Wegener’s Theory^1,2. 

Our Earth is a fascinating Planet, and as the years go by we discover more and more information about the construction of our Globe. Alfred Wegener, made a significant contribution in 1915, and it is due to his theory and reasoning that scientists have now expanded on this theory and have proven that the Earth’s present continents were once together as Pangaea.

What impact has this innovation made to Global Society? Firstly, it has expanded our understanding on the gradual change of the continental positions, which lead to the drastic change of weather from region to region thereby forcing inhabitants to adapt according to their respective environment.  Secondly, this innovation influenced urbanization, the development of scientific technology, global communication, and transportation.  However, this innovation has also increased the risk factor of possible natural calamities due to the continuous change in the shape of the earth’s surface. 

References:

      1.  Miller, R. 1983. Continents in Collision. Time-Life Books, Alexandria, Virginia
2. Hughes, P.  1994. The Meteorologist Who Started a Revolution, Vol. 47, Weather-wise.

BPA: A Harmful Chemical

On your next trip to the grocery store... think twice before stocking up on canned goods and plastic bottles.

One chemical under scrutiny by Health Canada is bisphenol-A (BPA), a substance used to make polycarbonate plastics -- tough, high-performance plastic material found in the lining of tin cans and used to create reusable, high-performance plastic containers.

Ingesting BPA is a concern because this chemical is classified as an endocrine disruptor -- a substance that interferes with the body's natural hormone system. BPA has estrogenic properties and will bind to the body's estrogen receptors. In short, our bodies think this chemical is the natural hormone and will use it to regulate our entire endocrine system. According to the World Health Organization, endocrine disruptors are linked to decreased sperm quality, early puberty, neurobehavioral problems and cancer.

Of particular concern is this chemical in baby bottles. Infants are more at risk from this chemical. Studies have linked low-dose BPA exposure with such effects as: permanent changes to genital tract; increase prostate weight; decline in testosterone; breast cells predisposed to cancer; prostate cells more sensitive to hormones and cancer; and hyperactivity. Environmental Defence Canada said that, based on its findings, parents should avoid polycarbonate plastic and shift to alternatives, such as glass bottles and plastics labelled BPA free.

Teenagers may carry the highest levels of bisphenol A – about 30 per cent more than the rest of the population, according to the first national survey about the compound conducted by Statistics Canada, but exposure to the estrogen-mimicking chemical is widespread, with detectible levels in 91 per cent of Canadians. It has also been found in the urine of 95% of Americans tested. Food is considered the major source of BPA. Teenagers had the highest average amounts, possibly because they eat more food relative to their body size or have metabolic differences.

Statistics Canada said its data, based on urine samples collected from more than 5,400 people aged 6 to 79, suggest there is “continual widespread exposure in the Canadian population” to BPA. The Statscan sampling is the largest such effort done to date in the world.

Canada was the first country in the world to take action on bisphenol A by proposing a series of actions to reduce BPA exposure to newborns and infants, including a prohibition on the importation, sale and advertising of polycarbonate baby bottles containing BPA.

Here are some ways you could reduce your exposure BPA:

• Don’t microwave polycarbonate plastic food containers. Polycarbonate is strong and durable, but over time it may break down from over use at high temperatures.
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  Polycarbonate containers that contain BPA usually have a #7 on the bottom
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  Reduce your use of canned foods.
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  When possible, opt for glass, porcelain or stainless steel containers, particularly for hot food or liquids.
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  Use glass baby bottles or baby bottles that are BPA free.
  
  
  

  

  By Tanya Kunwar

Mechanism of determining sex - Male or Female?

All over the world, plants and animals of different species from varied environments reproduce. One thing that is different across species is the mechanism that determines sex - male or female. 


In all mammals, including humans, male or female is determined by the fusion of XX or XY chromosomes.  Females have two X chromosomes while males have one X chromosome and one Y chromosome.  The offspring, whether be male or female is determined by the sperm cell, passed down from the male. If the male sperm contributes a Y chromosome, the result comes to be YX- male offspring, but if X chromosome, the result comes to be XX- the female offspring.
 
Birds are exactly the opposite of humans, in that the sex of their offspring is determined by egg cells rather than sperm cells. The females are homozygous, having two identical sex chromosomes, whereas males are heterozygous, having two different sex chromosomes. These chromosomes are labeled as W and Z. 
Cockroaches and some species of grasshoppers determine the sex of their offspring in a different way. There is only 1 type of chromosome: the X chromosome.  A female has two X chromosomes, while a male has only one. The gender of offspring is determined by whether or not the male passes on his chromosome.  If he does not, the offspring is male. 
In many other animals, chromosomes do not determine the sex of the offspring. For example, the sex of the offspring of the crocodile and turtle depends on the egg temperature during incubation. If the egg is incubated in high temperature, the offspring will be female. If it is incubated in low temperatures, then it will be male.
Unlike most other living species, most plants are hermaphroditic, meaning that they have both male and female sex organs.
For some plant species, genetic makeup determines gender; for others, environment plays a central role.


                                                                                                                                        Shreya Dahal

Influences of Advertisements on Teenagers

Advertisements have huge impacts on peoples' lives. Teenagers have more chances of being affected as they are still at the developing stage, both emotionally and physically. They tend to buy products advertised on television because they misunderstand how the product might affect them in the long run. In most cases it doesn’t work that way. 
Peers play enormous roles in teenagers’ lives. Friends affect the way they react to advertisements and to be more specific, the products they want to buy.  It's true that it is hard to balance out friends and family and, sometimes advertised products may lead to fights and money problems. Teenagers feel the need to "fit in" with the group, by purchasing the items their friends' possess. Sometimes this may lead to bullying and harassment.
FOOD. Ahhh……..Food is one of the most affective advertisements. I am sure that all of us have caught ourselves drooling over some mouth-watering junk that’s extremely harmful to our health. But when you actually go out and consume the product, it's not really as good as the advertisment is it? That’s exactly what advertisers are trying to achieve. They are using the media to try and get you to believe that their product is absolutely the best thing you could ever have.
One of the most common and effective ways that advertisers use to get you to buy the product is to feature a currently famous star in their advertisements. That way, teenagers really want to buy it because they think their idol is using the product.
In conclusion, advertisements can influence teenagers in many different ways, both directly and indirectly. So next time you see an apealling advertisement, it's good to think about it before you buy it.
- By Supriya Aryal