A-Level Biology & Chemistry and GCSE Science Tuition. A-Level Biology Revision.
Control of blood glucose is very important. Sufficient glucose must be delivered to cells for respiration, but too much glucose can eventually result in coma or even death. The concentration of glucose is affected by factors such as eating and exercise, and must be brought back to the normal level of about 4mmol/L to 5.5mmol/L.... Continue Reading →
Control of body temperature is the first example of homeostasis we will look at in this series. For humans, normal body temperature is 37°C. It is important to maintain this temperature as it is the optimum temperature for enzymes involved in many metabolic processes such as respiration. Humans are endotherms, meaning that they control their... Continue Reading →
Homeostasis is the maintenance of a stable internal environment. The conditions inside the body must be stable so that cells can function properly. For example, if the temperature or pH are too high, enzymes can become denatured. It is also important to maintain blood glucose concentration and water potential, which we will look at in... Continue Reading →
In the last article we looked at natural selection, a process which leads to evolution. We saw that if an organism has advantageous alleles, it is better adapted to its environment and is more likely to survive and reproduce. In today's article we will look at the different types of adaptions that organisms can have... Continue Reading →
Natural selection is one way that evolution occurs. Evolution is the change in allele frequency over time. In this article we will look at the process of natural selection, and a few different types of selection. Note that there can be other mechanisms behind evolution as well, such as the genetic bottleneck effect described here.... Continue Reading →
Species diversity is another level at which biodiversity can be investigated (see the last article about genetic diversity for the first level). Today we will look at what species diversity means and how it can be measured. A few definitions Before we start, there are a few words which will pop up through this article... Continue Reading →
Genetic diversity is defined as the number of different alleles of genes in a population. Last week we looked at one method of introducing new alleles into a population - by genetic mutation. Today we will look at other ways that genetic diversity can be increased or decreased, and how it can be measured. Increasing... Continue Reading →
There is a huge variety of life on this planet. In this series we will look at how all that variation exists, from the DNA level to the population level. Today we are starting off with a source of variation at the DNA level. What are mutations? A genetic mutation occurs when the DNA base... Continue Reading →
We know that nerve impulses are carried along neurones in a wave of depolarisation. But how does a nerve impulse get transmitted from one neurone to the next? Well, that is where synapses come in. Structure of synapses Synapses are the microscopic gaps between neurones. The neurone before the synapse is called the presynaptic neurone,... Continue Reading →
Last time we looked at an action potential happening in a section of a neurone cell membrane. The membrane was depolarised and repolarised. However, that depolarisation must travel along the whole length of a neurone in the right direction. Today we will look at how an action potential travels in a wave of depolarisation. The... Continue Reading →
