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So once you are born - you are you = no more evolution for you, individuals don't evolve. But .... over time natural selection (remember what that is?) acts on individuals and over time the population changes.
Population = a group of organisms from the same species living in the same area. Species = groups of organisms that can mate and produce viable fertile offspring.
This means that allele frequencies change = that is evolution. It can happen on a small scale - micro evolution and large scale - macro evolution.
Eventually new species form from our different changing populations.
So how do our populations get to be so different that they become reproductively isolated = speciation has occurred - and we have new species.
Step 1 : have a look at the following .... lots of information and a lot of terms = we'll look at those in more detail later. (Learn)
Mission 1 : Okay lets see what you understand form that - read and complete the work on Populations as units of evolution and Speciation and Reproductive isolation. (Learn)
As a extra .... It was firstly a theoretical concept - a cline within a species so that the ends of the cline didn't interbreed = separate species - but along the cline interbreeding did happen. A so called "Ring Species. Several species were put forward as being ring species but no .... and then they found one.
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.
For a population to end up as 2 new species they must end up being reproductively isolated form each other. There are several mechanisms for this - known as RIM's = Reprodictive Isolating Mechanisms. This can happen prezygotic = before the egg gets fertilized or postzygotic = after a zygote forms.
They sound complex and have fancy names but are really quite "simple".
Step 2 : Have a look as they are explained. (Learn)
Mission 2 : Is it really that simple - what have you understood? Read and complete the questions on Modes of Reproductive isolation and Postzygotic isolating mechanisms. (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.
When we met speciation before you may remember hearing the terms Allopatric and Sympatric speciation. These are 2 mechanisms of how speciation occurs.
Allopatric is perhaps the easiest to get to grips with = 2 populations somehow become geographically isolated ie they end up physically separated form each other - there is some sort of barrier to the original populations meeting. My memory tip is .... My mate Patrick is over the fence (Barrier) = I have to call out to him "Hello Patrick" - silly but it works for me.
Sympatric = the new species form with out geographical isolation ..... they are still in a Similar location.
Step 3 : So lets go and meet the "Patricks" Have a look at what follows. (Learn)
Mission 3 : Now read and complete the "Patrick" pages - Allopatric and Sympatric speciation. (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 4 : In between the "Patrick" pages we have some work on the formation of NZ's landmass and how this has played a role in the speciation of our parrots. This is the application of the knowledge learned all ready so far this topic. Here are some more explanations of this. (Learn)
The NZ giant land snails and the Northland Stag beetle are also good examples of allopatric speciation .....
Mission 4 : Now put this information to use as you complete the work on Speciation events in NZ and the pages on Speciation in NZ Parrots and Penguin Speciation. (Learn)
The Kakapo is one of our rarer birds - a good example to use for The Bottleneck Effect. But perhaps one of the reasons its numbers are low could be .....
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.
So far we've looked at speciation that takes a long time to happen. There is a way for a new species to arise overnight!!
Highly unlikely to happen in animals .... but it can and does happen in plants.
Remember the terms Haploid and Diploid? How about Triploid and Tetraploid? Well if an organism has more than a Diploid chromosome number a general term that we use is Polyploid = having more than 2 sets of chromosomes.
Only organisms from the same species ... and with the same number of chromosomes can successfully interbreed. If we get a polyploid event = we get a new species!
This can polyploid event can happen in a variety of ways. But if it happens within a single species - we call it Autopolyploidy. However if it is a result of a hybidisation event between 2 separate species - we have Allopolyploidy.
This can have advantages for the new species and for us (seedless varieties of fruit are created using polyploidy). Plus we met hybrid vigour before - this can apply here too.
Step 5 : Here is it all explained - watch and see what happens. (Learn)
Mission 5 : Read and complete the work on Instant speciation - Polyploidy and Polyploid advantage. (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.
Now what happens if we combine ancestral humans domesticating food crops and polyploid events ?? We get the convoluted pathway to the modern wheat crops of today.
Step 6 : Two are short - a summary, the other is longer but has the full story = watch the wheat journey. (Learn)
Mission 6 : Can you follow the journey of wheat? Read and complete the Hybrid Vigour and Bread Wheat pages in 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.
Here is a summary video of pretty much this whole section - good for revision. (Learn)
Step 7 : 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 7 : Have a go at the practice test at the end of this section. (Learn)
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