Life Sciences lab classes explained

In your next 109 workshop (workshop 5) you will see that an exponential equation  (that describes an exponential graph)  has been converted to a straight line equation by using logarithms.  It is going to be useful for you to be able to do this conversion yourselves - and I will go through this in my next post - but before I do that I want to make sure you are ok with how to manipulate logarithms... Here are some of the laws of logarithms: 1.  Log 10  (m x n)    =     Log 10 m +  Log 10 n proof: Log 10  (100 x 100)  =   Log 10  (10000) =   4 which is the same as: Log 10  (100 x 100)  =   Log 10 100  +   Log 10 100   =   2 + 2  =   4 2.  Log 10  (m / n)    =     Log 10 m -  Log 10 n proof: Log 10  (1000 / 100)    =     Log 10 10  =  1 ...

Following on from my previous post, Biologists actually prefer to know  the  factor by which the rate increases for every  10 degrees  i ncrease in temperature. So, a Biologist might say that  'the Q10 for this reaction is 2'  - what this means is that for every 10  ° C increase in temperature, the rate of the reaction increases by a factor of two i.e. doubles. Now, if we are dealing with Q10 rather than k, this means our equation above needs to be re-written slightly to take this into account: All that we have done is write  Q10  instead of  k , and divided the temperature difference by 10 to take into account the fact that we are interested in the factor by which the rate increases for every 10 degrees increase in temperature.

In your next 109 workshop you will be looking at the effect of temperature on biological rates... Here is a graph showing how growth rate varies with increasing temperature. Between points  a  and  b  there is an exponential increase in growth rate - this means that the growth rate keeps increasing by the same factor for every jump up in temperature. Remember what exponential increase is? Here is an example of a set of numbers that are increasing exponentially: 2,4,8,16,32,64,128.... For this example the factor by which these numbers increase each time is two - i.e. the numbers keep doubling which means the gap between them keeps getting bigger and bigger. So back to the graph above, between a and b the growth rate is increasing exponentially with increasing temperature. The equation that describes this part of the graph can be written like this:  Where  Rt2  is the  rate of growth at temperature 2 Rt1  is the ...

Exponential growth is coming up again in 109 workshop 5..... perhaps you want me to go over what exponential growth is, and what the formula is that describes it.... First of all, what is exponential growth? Look at this set of numbers... 2, 4, 8, 16, 32, 64, 128 These numbers are increasing exponentially i.e. they are increasing each time by a set factor which is 2. The factor by which these numbers increase is always the same (it is a constant) . When numbers keep increasing like this, it is called exponential growth. We actually came across exponential growth in Application 2 in 109 workshop 3 (Keeping Track of Weeds). Remember, you drew a graph that looked something like this: So this graph shows how the number of weeds increased over a number of weeks. You can see that it has a curve that increases in steepness as time progresses. This is because the number of weeds are  increasing exponentially  - i.e.  by a set facto...

Chi squared is the other statistical test you are coming across in your first year.... I have already written  a post on the t-test ,   and how this can be used to see if means from different data sets are significantly different. But the t-test only works with   measurement data   (bummer!) . These are data that are continuously variable - i.e. can take any numerical value within a range, like between 1mm and 2mm you can have any value eg 1.5mm or 1.0000003mm or 1.8585mm......... So what about when you have data that is  discontinuous .  For example eye colour, motile or non-motile cells, Marmite lover or Marmite detester. In these cases we are dealing with numbers of individuals in defined classes - therefore these data can only have particular values with nothing in-between.  In these cases, the questions you might have are;  Do my results reflect what I expected?  or,  Are my results significantly different from what I...