I had four water-filled tanks. Two had double the amount of volume in it so the two fish could move up and down more. In other words, two tanks had 1.5 litres of water while the other two tanks had 750 millilitres of water. I used four goldfish; the cheap and basic ones. All four fish were given a small teaspoon of fish flakes everyday. I changed the water every week so the water was always clean. I measured the fish every second week for 8 weeks. The way I measured the fish was placing it into a water-filled measuring cup and measuring the increased volume. A picture was taken of every fish every week. This experiment was done to find out if fish would grow faster if it was given more space to move. The hypothesis was, “If more space is given to a fish, then it should grow faster.” The independent variable was the space the fish got; the dependent variable was how fast the fish grew.
Fish have lived on earth for a very long time and they have evolved through the years. Jawless fish are the earliest fish known. They appeared about 500 millions years ago. Some jawless fish are still living to this day. For example, lampreys and hagfish are jawless fish that are not extinct. 450 million years ago, bony fish appeared. They evolved from jawless fish. They evolved jaws 400 million years ago or 50 million years after bony fish evolved. 10 million years later, they separated into two groups, the lobe finned fish and the ray finned fish. Ray finned fish are the kind of fish most humans think of when they think of a fish nowadays. Their fins are made for swimming not for crawling. On the other hand, lobe finned fish had fleshy bases to their fins letting them leave drying pools to find other pools with water. Lobe finned fish soon evolved into amphibians. Lobe finned fish are said to be the ancestors of amphibians and all higher kinds of vertebrates such as man. Most lobe finned fish are extinct now but coelacanths and lungfishes are two lobe finned fish that still exist. On a side note, sharks, skates and rays evolved from jawless fish 390 million years ago around the same time as the bony fish separated into two groups. Sharks lost the ability to make bones and their skeletons were made of cartilage. Unlike the other fish, sharks had no swim bladder and they have to swim consistently to keep from sinking. Sharks still exist today and although some sharks are dangerous, others are a source of food. The fish used in this experiment are ray finned fish and they are considered by most to be pets. Not all ray finned fish are pets though; some ray finned fish are also a source of food nowadays. Most fish are very healthy to eat although the ones that are raised in farms can be unhealthy due to pigment and additives used to alter the fish. For example, feed dyes change the colour of salmons to pink so they look natural. Most countries have banned this practice though.
Evolution means the changing of something into a better and more complex form. Evolution takes place over millions of years. Evolutionists are people who believe in evolution. Creationists are people who believe in creationism and they are usually against all forms of evolution. Creationism is the belief in the account of creation from the Book of Genesis.
An influential and famous person in evolution was Charles Darwin. While sailing on the Beagle for five years, he collected and learned many things. His voyage changed biology for ever. Darwin’s theory was that life on earth is the result of billions of years of adaptations to changing environments. Many religious people still refuse to believe in this theory as it contradicts their beliefs. Even Darwin’s wife refused to believe this theory as she was a practicing Christian and this caused problems in their relationship. Darwin’s theory contradicted and insulted the belief that nature is the result of the kindness of God. Most creationists counter evolutionists by using the story that Darwin converted to Christianity in the last months of his life as a fact but that “fact” is just a rumour started by a woman who visited Darwin six months before he died. Some creationists also counter evolutionists by stating that evolution is just a theory and that there is no proof of its existence when there actually is proof. Another famous evolutionist was Alfred Russel Wallace. Together, Darwin and Wallace created the theory of evolution by natural selection.
The future of fish is looking good at the same time as looking bad. Fish is a source of food and fish farming creates jobs around the globe. Fish farming is more common in developing countries than in developed countries. Aquaculture, which includes the farming of fish, is the fastest growing sector in world food production. Fish is the main source of protein for around one billion people around the globe. The demand for fish is increasing every year too. Population growth, increasing incomes, and improved diets are the reasons for this increasing demand. Eating fish is no longer a luxury like it used to be. The bad side to all this is that the worldwide fish population is decreasing. Overfishing is one of the main problems and will be a major problem in the near future. To finish off, fish are important because they provide a healthy diet resulting in a longer life and it provides a source of income to poor fish farmers living in poor developing countries.