My Science School

Wind, moving water and sunshine are always to be found somewhere on the Earth. All of these can be harnessed to provide energy. Wind farms, consisting of fields of enormous windmills, have been set up in many parts of the world to capture the wind's energy. Hydroelectric power uses the force of water hurtling over dams. Solar panels are warmed by the Sun and can be used to heat water and homes. At the moment, these methods are not able to produce all the energy that the world needs, but they hold out hope for the future.

A renewable resource is one that can be used repeatedly and does not run out because it is naturally replaced. A renewable resource, essentially, has an endless supply such as solar energy, wind energy, and geothermal pressure. Other resources are considered renewable even though some time or effort must go into their renewal (e.g., wood, oxygen, leather, and fish). Most precious metals are renewable also. Although precious metals are not naturally replaced, they can be recycled because they are not destroyed during their extraction and use.

A renewable resource is different from a nonrenewable resource; a nonrenewable resource is depleted and cannot be recovered once it is used. As the human population continues to grow and demand for renewable resources increases. Types of biofuel include biodiesel, an alternative to oil, and green diesel, which is made from algae and other plants. Other renewable resources include oxygen and solar energy. Wind and water are also used to create renewable energy. For example, windmills harness the wind's natural power and turn it into energy.

The United States currently relies heavily on coal, oil, and natural gas for its energy. Fossil fuels are non-renewable, that is, they draw on finite resources that will eventually dwindle, becoming too expensive or too environmentally damaging to retrieve. In contrast, the many types of renewable energy resources-such as wind and solar energy-are constantly replenished and will never run out.

Most renewable energy comes either directly or indirectly from the sun. Sunlight, or solar energy, can be used directly for heating and lighting homes and other buildings, for generating electricity, and for hot water heating, solar cooling, and a variety of commercial and industrial uses.

The sun’s heat also drives the winds, whose energy, is captured with wind turbines. Then, the winds and the sun’s heat cause water to evaporate. When this water vapor turns into rain or snow and flows downhill into rivers or streams, its energy can be captured using hydroelectric power.

Living things can grow and reproduce themselves. Given the right conditions, they can continue to do this for millions of years. But some of the Earth’s resources cannot renew themselves. When they have been used up, there will be no more. Perhaps the most important of these non-renewable resources are what are known as fossil fuels. Both oil and coal were made millions of years ago when the bodies of prehistoric plants and animals were crushed under enormous pressure beneath moving rock. There is a limited supply of these fuels, making it necessary for us to develop energy sources that cannot run out.

Renewable and nonrenewable resources are energy sources that human society uses to function on a daily basis. The difference between these two types of resources is that renewable resources can naturally replenish themselves while nonrenewable resources cannot. This means that nonrenewable resources are limited in supply and cannot be used sustainably.

There are four major types of nonrenewable resources: oil, natural gas, coal, and nuclear energy. Oil, natural gas, and coal are collectively called fossil fuels. Fossil fuels were formed within the Earth from dead plants and animals over millions of years—hence the name “fossil” fuels. They are found in underground layers of rock and sediment. Pressure and heat worked together to transform the plant and animal remains into crude oil (also known as petroleum), coal, and natural gas.  

The plants and animals that became fossil fuels lived in a time called Carboniferous Period, around 300 to 360 million years ago. The energy in the plant and animal remains originally came from the sun; through the process of photosynthesis, solar energy is stored in plant tissues, which animals then consume, adding the energy to their own bodies. When fossil fuels are burned, this trapped energy is released.

Crude oil is a liquid fuel fossil fuel that is used mostly to produce gasoline and diesel fuel for vehicles, and for the manufacturing of plastics. It is found in rocks below Earth’s surface and is pumped out through wells. 

Natural gas is widely used for cooking and for heating homes. It consists mostly of methane and is found near oil deposits below Earth’s surface. Natural gas can be pumped out through the same wells used for extracting crude oil.  Coal is a solid fossil fuel that is used for heating homes and generating power plants. It is found in fossilized swamps that have been buried beneath layers of sediment. Since coal is solid, it cannot be extracted in the same manner as crude oil or natural gas; it must be dug up from the ground. Nuclear energy comes from radioactive elements, mainly uranium, which is extracted from mined ore and then refined into fuel. 

Unfortunately, human society is—for the time being—dependent on nonrenewable resources as its primary source of energy. Approximately 80 percent of the total amount of energy used globally each year comes from fossil fuels. We depend on fossil fuels because they are energy-rich and relatively cheap to process. But a major problem with fossil fuels, aside from their being in limited supply, is that burning them releases carbon dioxide into the atmosphere. Rising levels of heat-trapping carbon dioxide in the atmosphere is the main cause of global warming. 

Alternative energy sources, such as wind and solar energy, are a possible solution to the depletion of nonrenewable sources. Both of these clean energy sources are available in unlimited supply.

In many parts of the world, life expectancy — the number of years that a person can expect to live — is increasing. A thousand years ago, 40 might have seemed a good age for an adult to reach. Now we expect to live twice as long. Of course, these are just averages. Since records began there have been exceptional people who lived to 80 and beyond, but for most people, the dangers of dying of disease, accident, war or starvation were very high. Childhood in particular was a dangerous time. A woman might give birth to more than 10 children, none of them living to adult-hood. We must not forget that there are parts of the world where this is still true, and billions of people still die each year from lack of food or medical care.

Demographic research suggests that at the beginning of the 19th century no country in the world had a life expectancy longer than 40 years. Every country is shown in red. Almost everyone in the world lived in extreme poverty, we had very little medical knowledge, and in all countries our ancestors had to prepare for an early death.

Over the next 150 years some parts of the world achieved substantial health improvements. A global divide opened. In 1950 the life expectancy for newborns was already over 60 years in Europe, North America, Oceania, Japan and parts of South America. But elsewhere a newborn could only expect to live around 30 years. The global inequality in health was enormous in 1950: People in Norway had a life expectancy of 72 years, whilst in Mali this was 26 years. Africa as a whole had an average life expectancy of only 36 years, while people in other world regions could expect to live more than twice as long.

The decline of child mortality was important for the increase of life expectancy, but as we explain in our entry on life expectancy increasing life expectancy was certainly not only about falling child mortality – life expectancy increased at all ages.

Such improvement in life expectancy — despite being exclusive to particular countries — was a landmark sign of progress. It was the first time in human history that we achieved sustained improvements in health for entire populations. After millennia of stagnation in terrible health conditions the seal was finally broken.

Now, let’s look at the change since 1950. Many of us have not updated our world view. We still tend to think of the world as divided as it was in 1950. But in health — and many other aspects — the world has made rapid progress. Today most people in the world can expect to live as long as those in the very richest countries in 1950. The United Nations estimate a global average life expectancy of 72.6 years for 2019 – the global average today is higher than in any country back in 1950. According to the UN estimates the country with the best health in 1950 was Norway with a life expectancy of 72.3 years.

The three maps summarize the global history of life expectancy over the last two centuries: Back in 1800 a newborn baby could only expect a short life, no matter where in the world it was born. In 1950 newborns had the chance of a longer life if they were lucky enough to be born in the right place. In recent decades all regions of the world made very substantial progress, and it were those regions that were worst-off in 1950 that achieved the biggest progress since then. The divided world of 1950 has been narrowing.

Globally the life expectancy increased from less than 30 years to over 72 years; after two centuries of progress we can expect to live much more than twice as long as our ancestors. And this progress was not achieved in a few places. In every world region people today can expect to live more than twice as long.

The global inequalities in health that we see today also show that we can do much better. The almost unbelievable progress the entire world has achieved over the last two centuries should be encouragement enough for us to realize what is possible.

Human beings are mammals, which mean that their young develop inside the mother until they are ready to be born. This development takes place inside the womb or uterus, where the baby gains the nutrients and oxygen it needs for growth from its mother’s own blood, supplied through the umbilical cord.

A woman’s ovaries usually release one egg each month. As it travels through the fallopian tube towards the uterus, it may be fertilized by a sperm that has enter her bady during sexual intercourse.

As soon as it is fertilized, the egg call begins to divide, until it becomes a ball of cells called a blastocyst. This ball then implants itself in the wall of the uterus.

After four weeks, the blastocyst has become an embryo. Its brain, spin and limbs are already forming and its heart will soon begin to beat.

At 12 week, the embryo is now called a foetus. All its organs are formed. For the rest of the time before it is born, it simply has to grow.

From 38 weeks onwards, the baby is ready to be born. It moves down into the pelvis. At birth, the cervix gradually opens and the baby is born through the vagina.

The characteristics of individual human beings are passed from one generation to the next in their chromosomes. Each of our parents gives us 23 chromosomes, making 46 in all. That means that we have two versions of each of our genes, but one is often dominant. We see the effect of the dominant gene, but the other (recessive) gene is still there and can be passed to our children.

The Law of Inheritance – Mendel’s Law, is significant in comprehending how characteristics or traits are genetically passed from one generation to the next. Heredity is the process through which a new individual acquires traits from its parents during the event of reproduction.

Every individual has 23 pairs of chromosomes, each of which comes from the father and the mother. As genes are present on chromosomes, we receive two copies of each gene from paternal and maternal side respectively and one pair of sex chromosomes from each parent to form 46 chromosomes on the whole.

Traits acquired through inheritance are determined by rules of heredity. These traits are coded in our DNA and hence can be passed to the offspring (eye color, hair color, height etc.). Thus for each trait, there are two versions in a child. During the cell division process, genetic information (DNA structure) containing chromosomes are transferred into the cell of the new individual, therefore, passing traits to the next generation.

Gestation is the length of time between conception — the fertilization of an egg by a sperm — and the birth of the baby that grows from the fertilized egg. The length of gestation varies according to the species.

Gestation, in mammals, the time between conception and birth, during which the embryo or fetus is developing in the uterus. This definition raises occasional difficulties because in some species (e.g., monkeys and man) the exact time of conception may not be known. In these cases the beginning of gestation is usually dated from some well-defined point in the reproductive cycle (e.g., the beginning of the previous menstrual period).

The length of gestation varies from species to species. The shortest known gestation is that of the Virginian opossum, about 12 days, and the longest that of the Indian elephant, about 22 months. In the course of evolution the duration of gestation has become adapted to the needs of the species. The degree of ultimate growth is a factor, smaller animals usually having shorter periods of gestation than larger ones. Exceptions are the guinea pig and related South American rodents, in which gestation is prolonged (averaging 68 days for the guinea pig and 111 days for the chinchilla). The young of these species are born in a state of greater maturity than are those of the rat with its period of 22 days. Another factor is that, in many species with restricted breeding seasons, gestation is adjusted so that birth coincides with the period when food is most abundant. Thus the horse, a spring breeder with 11 months’ gestation, has its young the following spring, as does the sheep, a fall breeder with a five months’ gestation. Animals that live in the open tend to have longer gestations and to bear young that have reached a state of greater maturity than do animals that can conceal their young in underground burrows or in caves. Marsupials generally have short gestations—e.g., 40 days for the largest kangaroos. The young, born in an extremely immature state, transfer to the pouch in which gestation may be said to continue.

Embryos of some species experience an arrest in development that greatly prolongs gestation. This is especially true of the fur-bearing carnivores the martens and weasels. Embryos of the European badger and American marten, which breed in July and August, develop for a few days, and then lie dormant in the uterus, being implanted in January. Birth occurs in March. Of the total gestation period of 250 days, growth occurs during only 50. Delayed implantation also occurs in mice and other small rodents that become pregnant while they are still suckling a litter.

Either a single factor or a great number of minor factors, all culminating at or near one date, determine the length of gestation. Several minor variations are known: in man, gestation for males is three to four days longer than that for females; and in cattle, bulls are carried about one day longer than heifers. In both species gestation of twins is five to six days less than for singlet’s. In animals such as the rabbit or pig, which bear many young at a time, gestation is shorter for larger litters than for smaller ones. Heredity also influences gestation; in cattle the mean gestation period for Holstein-Friesians is 279 days; for Brown Swiss, 290 days; other breeds fall between these extremes. When hybrids are produced by crossing two species with different gestation periods, the hybrid is carried for a period lying somewhere between those of the two parents and tending toward the mother’s species. Thus a mare carries a mule foal (fathered by a jackass) about 10 days longer than the normal period for the horse (about 337 days). For human gestation, see pregnancy.

Human beings are far from being the longest-living animals. The giant tortoise can reach 150 years, while several aquatic creatures, such as the killer whale and some species of sea anemone, can survive for well over 80 years. At the other end of the scale, the adult mayfly lives for less than two days. The plant kingdom has far longer-living species. Several trees, such as the yew and giant sequoia, live for thousands of years.

There are tortoises alive today that were 25 to 50 years old when Charles Darwin was born. There are whales swimming the oceans with 200-year-old ivory spear points embedded in their flesh. There are cold-water sponges that were filter-feeding during the days of the Roman Empire. In fact, there are a number of creatures with life spans that make the oldest living human seem like a spring chicken in comparison.

Greenland shark: This shark lives in Arctic waters and slowly grows to an average length of 16 feet. It scavenges for its food and is attracted to the smell of rotting meat in the ocean. It's also known to primarily live in deeper ocean depths compared to other sharks. A group of scientists conducted radiocarbon testing on the eye lens of 28 female sharks and determined its life span to reach at least 272 years. They concluded that the Greenland shark is the longest-living vertebrae known to man.

Geoducks: These large saltwater clams that are native to the Puget Sound and have been known to live for at least 160 years. They are characterized by their long 'necks', or siphons, which can grow to more than 1 meter long.

Tuatara: The word "dinosaur" is commonly used to describe an old person, but when it refers to tuataras, the term is perfectly metaphorical. The two species of tuatara alive today are the only surviving members of an order that flourished about 200 million years ago — they are living fossils. They are also among the longest-lived vertebrates on Earth, with some individuals living for between 100 and 200 years.

Lamellibrachia tube worms: These colorful deep sea creatures are tube worms (L. luymesi) that live along hydrocarbon vents on the ocean floor. They have been known to live 170 years, but many scientists believe there may be some that have lived for more than 250 years.

Red sea urchins: The red sea urchin or Strongylocentrotus franciscanus is found only in the Pacific Ocean, primarily along the West Coast of North America. It lives in shallow, sometimes rocky, waters from the low-tide line down to 90 meters, but they stay out of extremely wavy areas. They crawl along the ocean floor, using their spines as stilts. If you discover one, remember to respect your elders — some specimens are more than 200 years old.

Bowhead whales: Also known as the Arctic whale, the bowhead is by far the longest living mammal on Earth. Some bowhead whales have been found with the tips of ivory spears still lodged in their flesh from failed attempts by whalers 200 years ago. The oldest known bowhead whale was at least 211 years old.

Koi: Koi are an ornamental, domesticated variety of the common carp. They are common in artificial rock pools and decorative ponds. Amazingly, some varieties are capable of living more than 200 years. The oldest known koi was Hanako, a fish that died at the age of 226 on July 7, 1977.

Tortoises: Tortoises are considered the longest living vertebrates on Earth. One of their oldest known representatives was Harriet, a Galápagos tortoise that died of heart failure at the age of 175 years in June 2006 at a zoo owned by the late Steve Irwin. Harriet was considered the last living representative of Darwin's epic voyage on the HMS Beagle. An Aldabra giant tortoise named Adwaita died at the rumored age of 250 in March 2006.

Two things affect the way in which living things grow and age. The first is their genetic make-up — the genes that they have inherited from their parents. The DNA in their chromosomes controls the way that cells divide to cause the growth of the young organism, its coming to maturity and its aging. The other important factor is the environment and conditions that the organism experiences — how much of the right kind of food it eats, where it lives, the climate and the kinds of events and accidents that happen to it.

Every living organism begins life as a single cell. Unicellular organisms may stay as one cell but they grow too. Multicellular organisms add more and more cells to form more tissues and organs as they grow.

The Growth and development of living organisms are not the same things. Growth is the increase in size and mass of that organism. Development involves the transformation of the organism as it goes through the growth process.

Think of a newly born baby. It has all the features of a fully-grown adult, but they are very tiny. As the years go by, they become big and become a young person like you, and later on, into a fully grown adult, maintaining all the features that they are born with. This is growth. But in their mummy’s tummy, they started off as a single cell and transformed into a zygote and into a foetus before transforming into a tiny baby.

In some organisms, growing involves drastic transformation. Think of a butterfly for instance. It starts off as a cell (egg). Then it transforms into a caterpillar, then into a pupa (chrysalis), and then pops out as a beautiful butterfly.

Plants often start from a tiny seed, and grow into a big tree. One thing common to all organisms is that they grow or develop to look just like their parent species, even though there may be some slight variations resulting from the mixing of cells by the parents. 

Cell growth and development include its repair. As cells grow old, they wear off. Sometimes they suffer injury and bruises, but they are able to repair themselves by growing new cells in a process called Mitosis.

As living things grow, they undergo a process called aging (age). As they get close to the end of their lifespan, their ability to carry out life functions reduces. Eventually, they die to end the process of life.

You can help to make the world a safer, cleaner place. Just remember to: Reduce, Reuse and Recycle.

Reduce waste by only buying the things you need. Try to reuse items or find new uses for them.

Recycle anything you cannot reuse.

 

Buy local foods and reduce packaging.

Reduce rubbish by encouraging your family to buy goods in local markets. Supermarkets often buy their foods from far-away countries. Lots of packaging is needed to protect the goods on the long journey. Foods grown locally often have less packaging, so why not buy them instead.

 

 

Reuse pots and containers.

All kinds of boxes, pots and bottles can find new uses at home. Cardboard boxes can be used to store books, toys or CDs. Plastic ice cream tubs can become lunch boxes. Glass bottles and jars can be used to hold pencils or flowers, or you can use them to grow plants. Decorate them with bright paints or stick on pictures from magazines.

 

Recycle old clothes.

Clothes you have grown out of can be taken to a local charity shop. They may be sold to raise money for the charity, or sent to a developing country.

Unwanted books, toys and household items can also be recycled at charity shops. Even old vinyl records can be recycled —they can be melted down and turned into bank cards.

Plastic is cheap, tough and hard-wearing. No wonder so many things are made of plastic these days!

Plastic does not rot, however. So it often ends up in landfills. There are many different kinds of plastic. Some are hard to recycle.

Cloth is easier to recycle. It can be cut up and put into mattresses.

These sheets are made from recycled plastic.

A single bottle may contain several different types of plastic. So, at the recycling plant, plastics are sorted by hand or machine. The plastic is shredded into tiny flakes, which are melted and made into new things.

 

 

Your boots may contain recycled plastic.

Recycled plastic has many uses. Some is used to make garden chairs, fence posts, waterproof boots or new bottles. Other plastics provide stuffing for pillows and duvets or are made into fleecy coats.

 

Old clothes are cut into rags. They can be used for cleaning.

Worn-out clothes and other textiles can also be recycled. You can reuse them as cleaning cloths at home or send them for recycling.

Some old clothes are cut into rags and used to wipe machinery. Other clothes are ripped up and the threads woven to make new clothes or used to stuff seats and mattresses.

 

If you use cloth bags it cuts down on litter.

Most supermarkets hand out plastic bags to their customers to carry home their shopping. Because the bags are free, we often just throw them away at home.

Some supermarkets have started charging for the bags. This encourages people to reuse them or to use strong cloth or canvas bags instead. This cuts down on the litter and waste caused by old plastic bags.

Picture Credit : Google