Fitting in with the National Curriculum of A level and AS level biology including Conservation and Classification a trip to Noah’s Ark Zoo Farm can enlighten students further to the following areas:

Distribution of plants and animals: effects of biotic and abiotic factors

There are factors that affect animals in their distribution, some of these factors are physical and are called abiotic factors. There are other factors which are due to the affect of other living organisms on the distribution of species, these are called biotic factors. Competition between a single population or between different populations is an example of a biotic factor.

These physical factors (abiotic factors) are discussed:

Temperature – the main affect of temperature is that it affects the rate of metabolic reactions, such as photosynthesis and respiration. It affects these processes since they involve the use of enzymes. Therefore just like enzymes organisms have an optimum temperature range at which they survive. Temperature is mainly offered by the sun’s radiation, and is therefore affected seasonally, daily and by the aspect. Temperature is also affected by the addition or loss of vegetation.

Plants tend to develop faster in warmer conditions, however at higher temperatures enzymes become denatured and metabolic reactions slow down or stop altogether. At lower temperatures the reactions will not occur quickly and below freezing ice crystals will form and disrupt the cells.

We can measure the temperature of an ecosystem using an electronic thermometer, which has a temperature probe that can either be pushed into the soil or placed in aquatic ecosystems at different depths.

Light – the main affect of light is that it affects the rate at which photosynthesis and therefore growth occurs, influencing primary productivity.

Gene technology

Genetic Modification (GM) is the process of changing or inserting genes. Genes carry the information about the different characteristics of an organism such as the colour of its leaves or how tall it can grow. These genes are made from a string of DNA, the material found in the cells of all living things which allows them to function, repair and reproduce themselves. Genetic Modification is done by altering DNA or by taking genes from one organism and putting them into another. Genes can be moved between organisms that are of the same or different species. For example, genes could be introduced from one plant to another plant, from a plant to an animal or from an animal to a plant. This altered genetic material is then called recombinant DNA.

Why use genetic modification?

People have been breeding animals and plants for hundreds of years with the aim of developing or removing certain characteristics. Racehorses are bred to be faster and stronger and roses are bred to give a wider range of colours. The world’s main food crops have been chosen and bred to suit the countries and conditions they are grown in and make them more tasty.

Traditional breeding methods involving mixing thousands of genes, whereas genetic modification allows just one individual gene to be changed in a pre-determined way.

For example, herbicides are used to kill weeds in fields of crops but they can also affect the growth of the crops they are intended to protect. By using genetic modification, a gene with a particular characteristic, such as resistance to a specific herbicide, can be introduced into a crop plant. When that herbicide is sprayed on the field to kill the weeds, it will not hinder the growth of the crops.

Similarly, genetic modification can be used to reduce the amount of pesticide needed by altering a plant’s DNA so it can resist the particular insect pests that attack it. For example GM Maize and Cotton that resist their primary insect predator are widely used around the world . Laying hens have chicks that have been bred so that male and female chicks are born different colours. Only the females are required for egg production, so can be separated early.

How does it work?
Paste in pics from the GM crop display

To extract the gene from the original organisms enzymes called restriction endonucleases are used. Restriction endonucleases are usually found in microorganisms. Specific restriction endonucleases cut DNA at a specific nucleotide sequences, these are called recognition sites. The enzymes cut in a staggered way so that a few base pairs are left exposed on each side of the double strand of DNA, these bases are complementary to each other and are referred to as sticky ends.

Once the gene is extracted it needs to be combined with a plasmid which is also known as a vector, since they add the new gene into a host cell transferring genes from one organism to another. Plasmids are found in bacteria and are double stranded circular bits of DNA, which are separate to the chromosomal DNA. They are used as vectors for the gene since they are small and replicate many times inside the bacteria and therefore produce many copies of the desirable gene. The gene is combined with the plasmid by using the same restriction endonuclease to cut open the plasmid that was used to extract the gene. Therefore both the plasmid and the gene have complementary sticky ends, and the bases join together with hydrogen bonds. The enzyme DNA ligase will join the gene to the plasmid with phosphodiester bonds.

The plasmid along with the inserted DNA is referred to as recombinant DNA and it is then placed into bacterial cells. The bacterial cells are more permeable to the plasmids if they are treated with calcium ions. When the bacteria cells contain the recombinant DNA they are referred to as transformed cells.

Not all of the bacteria cells will take up the recombinant DNA and these cells need to be separated from the transformed cells, which do. These can be separated by the use of a radioactive DNA probe or genetic markers such as a gene for antibiotic resistance. Once the transformed cells have been identified they need to be multiplied.

Introducing new genes into crop plants

The soil bacteria Agrobacterium tumefaciens contains a plasmid called a Ti plasmid. This is used as the vector for the gene to be introduced into and returned into the Agrobacterium tumefaciens. The transformed bacterium is introduced into leaf discs or isolated plant cells in a culture and the plasmid is transferred into the plant cells. These transformed plant cells are then grown into undifferentiated tissue and then in the right conditions are grown into plantlets, which are known as transgenic plants.

GM foods used today

GM is increasingly recognised as being useful to us, but it needs safeguards.

All commercial tomatoes are genetically modified to avoid rotting after a few days in the shop.

The most widely used barley for beer making, Golden Promise was developed by bombardment with X-rays.

Some GM could be harmful to other plants or to us, so regulations are in place to keep GM development under close scrutiny.
Implications of gene technology

With the use of gene technology many questions are raised such as ‘Is this unnatural?’ and ‘Are we interfering with nature?’