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From our "family tree" we know that evolution has been at work - but how exactly does evolution operate?
Through the process of Meiosis we all have a different collection of alleles (we have the same genes - just different versions of them). These differences = the genetic variation present in our population allows some of us to do things "better" than others. We live in a changing world, those organisms that are "better" suited to the conditions they live in are deemed to be more "fit" for survival = are more likely to pass on their genetics to the next generation.
So a combination of nature and variation leads to evolution.
Lets go look at the mechanisms of evolution in more detail.
As mentioned Genetic Variation is key to evolution. So where do we get this variation?
There are 2 main sources of all variation = Sexual reproduction and Mutation.
Remember Meiosis? From the random processes of Independent assortment, Crossing over, and Segregation we get our individual genetic combinations.
Step 1(a) : Time for a refresher - if you don't remember have a look as processes are explained to us. (Learn)
Step 1(b) : Lets not forget about Mutations - what do you remember? Need a refresher = have a look at this. (Learn)
Mission 1 : Now that we've remembered all that = time to read and answer the questions on The importance of Genetic Variation and Mutations in your books. (Learn)
Done that? = Share with your teacher.
Yes = now its time for your next Step/Video clip/Challenge/Mission.
No = go back and complete the Step/Video clip/Challenge/Mission please.
We notice evolution because we see the differences between species - often these species began as 1 species.
The normal variation or diversity in a population is the "stuff" that natural selection works with to give us evolution. We are looking at things that change the spread of alleles in a population = alter the allele frequency = change the number of alleles in the gene pool (total of all the alleles in a population). So what can do that?
Gene flow is one - individuals (and their alleles) move in = Immigrate or out = Emigrate of a population.
Step 2(a) : So here is a chance to remind yourselves about gene flow. (Learn)
If you need a hand with figuring out how to calculate the frequencies try this ....
In any population we get random changes in the numbers of different alleles = Genetic Drift - this is more noticeable in small populations. We'll get less differences within a population and more between populations. Two key events - Founder effect or Bottleneck effect commonly lead the occurrence of genetic drift.
Step 2(b) : They are explained here as well. (Learn)
Mission 2 : Read and complete the work on Gene Flow and Genetic Drift in your workbooks (Learn)
Done that? = Share with your teacher.
Yes = now its time for your next Step/Video clip/Challenge/Mission.
No = go back and complete the Step/Video clip/Challenge/Mission please.
We've had the term Natural Selection used a few times - so what exactly is it? Simply put its natures way of choosing the best genes to keep ..... with variation some organisms survive better than others = the are a better fit to the environment - we call this genetic Fitness. When under selection pressure = the fittest survive and pass on their genetics to the next generation.
In any population there are extremes - but most are sort of in between = we get the classic "Bell" shaped curve.
There are generally 3 possible outcomes of natural selection - the extremes lose out = the averages survive (Stablising), or one extreme is better = it becomes the "new" average (Directional), or we get both extremes being better = averages die (Disruptive).
Step 3 : Watch as this is explained and demonstrated to you. (Learn)
Mission 3 : Now its time to see how "Fit" you are as you answer the questions on Natural Selection and Three general outcomes of selection. (Learn)
Done that? = Share with your teacher.
Yes = now its time for your next Step/Video clip/Challenge/Mission.
No = go back and complete the Step/Video clip/Challenge/Mission please.
I'm predicting that with each generation the human race is getting more and more attractive = why = Everyone is looking for that attractive someone to make babies with!!
Look around you = I'm right!
But in nature there is a definite selection for appearance is some species - even to the point of ridiculous extremes = Peacocks tails. Not only does being survival fit help you pass on you genetics, but being chosen for looks helps too = Sexual Selection.
Step 4 : Want to see this in action for yourself - be my guest. (Learn)
Or the human version - perhaps??
Mission 4 : So what have you remembered - answer the questions on Sexual selection on your workbook. (Learn)
Done that? = Share with your teacher.
Yes = now its time for your next Step/Video clip/Challenge/Mission.
No = go back and complete the Step/Video clip/Challenge/Mission please.
Step 5 : At the end of this section of your workbook you'll find (maybe) a puzzle page or two, a review planning page then a practice copy of the end of topic test. Complete these pages plus don't forget the definition page found at the start of the topic = you'll be ready for the test. (Learn)
Mission 5 : Have a go at the practice test at the end of this section. (Learn)
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