Investigating the relationship between cell size and rate of diffusion
Investigating the relationship between cell size and rate of diffusion Aim: To plan and carry out an investigation to show the relationship between volume, surface area, and diffusion; and to demonstrate, using diffusion, why the size of cells is limited. Hypothesis: In this experiment, I expect to find that when the surface area to volume of a cell reaches a certain level, diffusion alone won't be able to supply the cell materials needed, and as single-celled organisms take in and release substances by means of diffusion across the cell membrane, this process limits cell size. I predict that as the rate of diffusion will be too slow to deliver materials to the center of the cell in the larger cells, it could result in cell malfunction. Variables: In this investigation, the variable I am manipulating, the independent variable are the dimensions of surface area to volume ratio of the agar cube. The variable I am observing/recording, the dependent variable, is the rate of diffusion (NaOH turns the agar cube pink as it disperses into it). The controlled variables will be keeping the concentrations of the Sodium Hydroxide constant, to use agar jelly from the same batch (so the type of agar jelly is exactly the same), and to keep the time even for all cubes so the NaOH has the same amount of time to disperse into the cube. Apparatus: 3 agar cubes containing pH indicator
Pro-natalist Australia
Pro-natalist, Australia Background Information Australia is considered the most sparely populated continent in terms of the population density, 2.6 persons per km2. Like most of the developed countries are having problems with the issues of population, Australia is not exceptional. In fact, there has been the substantial fall in fertility rates since 1960s. Australia's total fertility rate has declined from 3.5 in 1961 to 1.73 in 2001, and in 2007 was 1.93 babies per woman with two child families the most common type. Also, there are concerns of the ageing of the Australian population, implying that there are fewer babies being born compared with a number of elderly population increased by life expectancy. Australia's population is ageing and the evidence for this demographic change is undeniable. The result of falling fertility, increasing life expectancy and the effect of the baby boomer generation moving through older age groups, has contributed to an increase in the number and proportion of people aged over 65 years. These trends are anticipated to continue and numbers of people aged over 65 years and proportions of people over 85 years are growing while proportion of the population aged between 15 and 64 years (labor force age) are falling. The main cause of the falling fertility rates is the increased empowerment of women. In Australia, greater numbers of females
China One Child Policy
Case Study China One Child Policy History China has the world's largest population, and it's cities are the most densely populated ones. It's policy is one of the most recognized policy, since is the most rigid of any country. The policy admites only one child per couple, and because of this it is called the "One Child Policy". Before 1949, before the communists had the power, China was at stage 1 of demographic transition model, and families had betwen 5 and 8 children. Also there was a high death rate, and a low life expectation. Infant mortality rate was also high, and so with death rate and birth rate, which means that the population was increasing at a very slowly rate. In these days, large families where encouraged, since the government followed a pro-natalistic population policy. Ten years later in 1960, the population increased dramatically to 100million people more, which determined China in the second stage of the demographic transition model. As a result improvements where made in medical services. In 1976, whith the death of Mao, the government decided to advocate voluntary population control to reduce the birth rate. China began to advice about limiting family sizes and to distribute information about the need to control the population growth. Finally in 1980, the One Child Policy was introduced, which provided benefits for couples which had only one
China's One Child Policy
Sasha Zouev Geography 09/11/05 China's One Child Policy China is the 3rd biggest country in the world in terms of land area. However in terms of population, China is by far the leading nation with a population of roughly 1,306,313,000 people (2005 est). Brief History of China's Population 1905 - 1978 China was founded in 1949 at a time when the country had a population of about 540 million. Within three decades the population was above 800 million. This record population boost from the 1950s to the 1970s fashioned a strong population momentum that is motivating China's population expansion in spite of already low levels of fertility. It is hypothesized that China's population will grow to some 1.48 billion. Nonetheless, all of this growth will take place during the next 25 years. In its most recent medium variant projection, the UN Population Division estimates that China's population will rise by 260 million between 1995 and 2025. This certainly causes a major crisis for China's food supply: within only three decades the nation will have to feed an additional 260 million people (equivalent to the total population of the USA). At the bottom of the Chinese population pyramid (see fig. 1) one can again see large associates that were born between 1985 and 1990. They are almost as large as the birth cohorts during the "baby boom" years. However, these large number of
Population Essay
"The new threat to the planet is not too many people but too few." Was once written by Michael Mayer. He claimed that the global population will rise to a peak and then sharply decrease. As we know at the moment it seems like there are already too many people on the world, leading to starvation, scarce natural resources, poverty, war and global competition for jobs. And it seems like the amount of people are continually increasing, but will it really last and will it be a problem? In Japan in fact the population is already starting to decrease, where the total fertility rate is only 1.2. That means that a woman in Japan will have an average of 1.2 kids in her life. One of the problems in Japan is that it is difficult to live there as an immigrant. This is due to the hard language and very few Japanese people speak English well. So it's not really attractive to migrate to Japan. And the women see kids the result for Japan is what's called an 'ageing population', where there will be older people, than younger people in the future. The picture beneath shows the current populations pyramid of Japan. As you can see, the life expectancy in Japan is high, as there are quite some people in their 85's-89's. What we can conclude from this pyramid is by the trend in it. [Source: http://www.nurse.or.jp/jna/english/nursing/images/pyramid.jpg] The number of kids in the groups of 0-15
