Genetic Variation and Change | NCEA Level 2 Biology | StudyTime NZ
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Genetic Variation and Change | NCEA Level 2 Biology | StudyTime NZ

– Kia ora everyone,
(gentle electronic music) welcome to StudyTime’s Level Two Genetic Variation and
Change Strategy Video. I’m Hattie. – And I’m McKenzie. And as the name suggests, this Standard is really
all about genetic variaton. – It kind of breaks down
into two main areas, so there’s patterns of inheritance, which is all about genetic variation on more of an individual level, and there’s also genetic
variation within populations. – Yeah, so, because most Bio exams will be giving you three
long answer questions, usually one of them will be
on patterns of inheritance, and two of them will be
about genetic variation at the population level. – Cool. If you take on the tips in this video, you’ll be set to succeed in this exam. – Let’s get into it. So, patterns of inheritance. This is almost always the first section, and this overarching topic has a bunch of things inside of it, so, this is things like
independent assortment, segregation, crossing over. Monohybrid inheritance, and with this we have to take into consideration
things like co-dominance, incomplete dominance, multiple
alleles, and lethal alleles. Then there’s also dihybrid crosses, and with this, you have to bear in mind
the idea of linked genes. And then there’s also, lastly, mutations as a new source of alleles. Now, getting down dihybrid crosses, is something we’d really recommend, because three out of four
years of the past exam papers actually started with a
question on dihybrid crosses. – These questions will
typically go on to ask you about describing meiosis,
and aspects of meiosis which decrease or increase
genetic variation. When you’re describing meiosis, you don’t need to go into a lot of detail about what each stage involves, but it’s a good idea to be
able to draw a rough diagram of what each stage of meiosis has in it. You’ll also want to be really
familiar with things that decrease genetic variation in meiosis, so that’s things like linked genes, and things that increase it, so that’s things like crossing over, and independent assortment. As a reminder, crossing
over happens between homologous chromosomes during meiosis, and it creates new
combinations of alleles, a really common mistake is to say that it creates
new combinations of genes, don’t make this mistake, it’s not true. You want to be really clear
that you know the difference between chromosomes, alleles, and genes. – So this brings us to our
second section of the Standard, which is genetic variation
at the population level. Now, questions under this topic can be selected from
things like migration, genetic drift, natural selection, the founder effect or bottleneck effect, and mutations as a new source of alleles. Now bear in mind that
mutations can be asked in either parts or
sections of this Standard – Unlike questions on
patterns of inheritance, which are usually broken
down into sections, questions about genetic
variation on a population level, tend to be just one long
Excellent-style answer with sort of Achieved Merit
sections nestled within it. Because of this, students often miss a
key part of the question. To make sure this doesn’t happen to you, try to answer the bullet points at the bottom of the question in order, tick them off when you’re done, and if you think you need to
come back to a bullet point to add something, and you’re
not sure what to write, leave a space in your answer, so that you can see that you
needed to come back to that. One of the questions
about genetic variation on the population level is
usually about natural selection, but it won’t just be
about natural selection, it will usually combine it
with some other concepts. For example, in the 2016 exam, it was combined with
the effect of mutations, whereas in the 2017 exam,
you’re asked to talk about the effects of natural
selection, mutation, and migration all
together on a population. – So one of our last tips for getting Excellence in your question is to make sure that you’re always bringing your discussion back to the context of the question. So, it’s not enough to say something like, “The population genetic
diversity was reduced “due to the founder effect.” What we need to be saying is, “The current population, on
the Big South Cape Island, “has a low genetic diversity,
due to the founder effect.” The difference here being
that you’re just including the context of the
question in your answer. – This has been StudyTime’s Level Two Genetic Variation and
Change Strategy Video. Basically just remember that this exam comes down to two main concepts, which is genetic
variation in a population, and genetic variation due
to patterns of inheritance. We’ve covered a lot, but we haven’t quite covered everything, so we’d really recommend checking out the past few years of exams to get a feel for what to expect. – Yeah, and also, if you’re
still feeling a bit stuck, check out our walkthrough guides, and they’re available free online, or you can buy them in print
with next-day delivery, and they’re designed to walk you through everything that you need
to know for the Standard. (both) Good luck! (Hattie chuckles) Damn it, you beat me to it! (gentle electronic outro)

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