To unlock cells – you need a key (updated!)
So, we are getting towards the end of our first unit of study – Genetics & Natural Selection. We’ve looked at the relationship between evolution & natural selection. To finish this unit of study, we need to understand how cells propagate – how one cell becomes more.
This process is called cell division, and there are two main types: Mitosis and Meiosis. But before we get too far into this topic, you may want to revise the important concepts of Genetics. Here is a post that covers the genetics topics – I strongly suggest you go back and read it (and watch the videos!) – not doing this will do bad things to your results…
So, back to the cell division topic – what do you have to know? The problem is is you look this topic up on the internet, you will find far more information than you need at year 10 – information about what the different phases are, what happens during each phase, a lot of details. You should try and learn this information if you plan on studying biology during VCE, but otherwise you only need to know the basics.
- Cell preparation: the cell prepares to divide by making extra of all critical parts: organelles and DNA
- Cell organisation: the parts of the cell are all arranged and prepare to split – the Chromosomes (DNA) line up, and are pulled apart
- Cell splitting: the cell divides into two smaller new cells, each with half of the material of the parent cell.
This is what you need to understand of the process of mitosis. This the “what is mitosis” that you must be able to explain. You also need to know the mitosis occurs in two situations – each with a different outcome. In unicellular life (e.g. bacteria), mitosis is a process by which the population grows – this is how more bacteria are made. In multicellular life (e.g. Humans, or other creatures made up of more than one cell), mitosis is the way damaged cells are replaced – this is how the organism grows and repairs injuries, or replaces cells that are too old.
There is another process of cell division, meiosis, which only happens in multicellular life that reproduces sexually. Meiosis is the process by which gametes (sex cells such as sperm and ovum) are produced. Because sperm and ova contain only half the genetic information of standard cell, it is easiest to think of the process of meiosis as similar to mitosis but with a second splitting after the first – this means that the process of meiosis will result in four sex cells at the end (unlike mitosis which produces only 2).
The final issue that you need to understand is that populations that grow by asexual reproduction ( mitosis) (i.e. unicellular lifeforms) can grow much more quickly than populations that grow by sexual reproductions (meiosis). This is an advantage because they can quickly grow to take advantage of environmental opportunities. The downside is that because cells produced by mitosis are identical to the parent cell, a population can also die rapidly if exposed to a threat – the lack of variation between the population means that they are much slower to evolve when faced by a (natural ) selective pressure.
See you in class!
One last thing – if you have not submitted your two assignments and do not have your genetics letter and frog selection experment report ready to submit on the first class of term 2, you will automatically have your name placed in SWOP. Also remember that your glossary will be checked in week 1!
Update: Here is the Sunny Meadows Population Simulator – if you can attain a high score, and explain why and how your populations are stable, that would be a demonstration of competence that would do good things for your semester report…Cytology, Year 10