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Hi.

Advanced Genetics

It's Mr. Andersen and welcome to Biology Essentials video number 30.

Advanced Genetics

This is on advanced or non-Mendelian genetics.

Advanced Genetics

I thought I'd start by tying together some of the things we've talked about this year already.

Advanced Genetics

This is a phylogenetic tree of giraffes in Africa.

Advanced Genetics

And two that I've pictured here are the reticulated giraffe and the Rothschild's giraffe.

Advanced Genetics

And what we find is that even though they look very similar, they actually lie on two different branches of the phylogenetic tree.

Advanced Genetics

And how do we know that?

Advanced Genetics

How do we know which giraffe is related to which giraffe?

Advanced Genetics

Well we don't use simple genetics.

Advanced Genetics

We use something called mitochondrial DNA.

Advanced Genetics

Mitochondrial DNA is DNA found within the mitochondria.

Advanced Genetics

It's passed from mother to mother.

Advanced Genetics

And it's found in all offspring.

Advanced Genetics

And so it allows us to trace evolutionary history.

Advanced Genetics

But it's non-Mendelian.

Advanced Genetics

In other words it's genetics that lie outside of what we would sometimes refer to as simple genetics.

Advanced Genetics

And so in this podcast I'm going to talk about some of the problems with Mendelian genetics.

Advanced Genetics

Not problems per se, but things that we didn't address in the Mendelian genetics podcast.

Advanced Genetics

First one is the idea of linked genes or genes that are found on the same chromosome.

Advanced Genetics

We'll then talk about multiple genes.

Advanced Genetics

And this is actually one of the most important things in all of genetics.

Advanced Genetics

In other words most things are not like a hitchhiker's thumb.

Advanced Genetics

Most things are not caused by just one simple gene.

Advanced Genetics

Next we'll talk about how sex chromosomes can affect inheritance.

Advanced Genetics

The example I'll give you is color blindness.

Advanced Genetics

And then finally we'll talk about non-nuclear transfer.

Advanced Genetics

In other words DNA that's not even found in the nucleus.

Advanced Genetics

Found in the mitochondria or the chloroplast and how that's passed maternally.

Advanced Genetics

And so let's start with Mendel.

Advanced Genetics

Mendel studied seven things.

Advanced Genetics

He studied the stem length of plants, seed color, pod shape, seed shape, flower color, flower position, pod color.

Advanced Genetics

In other words he studied seven different characteristics and he was able to come up with his idea of independent assortment.

Advanced Genetics

What is independent assortment?

Advanced Genetics

Well essentially it means that all of these things assort independently.

Advanced Genetics

All of these genes assort independently.

Advanced Genetics

In other words one cannot affect another.

Advanced Genetics

Now what's interesting about the seven that he chose is that all seven of them are found on different chromosomes.

Advanced Genetics

Now if he were to study most characteristics he'd find that the genes would actually be found on the same chromosome.

Advanced Genetics

If they're found on the same chromosome he never could have discovered this idea of independent assortment.

Advanced Genetics

And maybe he did find characteristics that were actually on the same chromosome and then decided not to include that data.

Advanced Genetics

We can't be for sure.

Advanced Genetics

But we do know that a number of things do travel together.

Advanced Genetics

For example red hair and freckles seem to go together.

Advanced Genetics

Why is that?

Advanced Genetics

Well they're found on the same exact chromosome and they're found very close to each other.

Advanced Genetics

And so they're going to travel together.

Advanced Genetics

And also during meiosis crossing over is not going to be able to split them apart.

Advanced Genetics

And so a lot of the time when we're doing genetics problems if they're linked that means the genes are on the same chromosome.

Advanced Genetics

Then our simple punnett squares just aren't going to work.

Advanced Genetics

Next I want to talk about multiple genes.

Advanced Genetics

But I want to start with an example of multiple genes.

Advanced Genetics

Welcome to chapter 55 over ecosystems.

AP Bio Ecosystems - Part 1

So we're going to focus on ecosystems, which is all the biotic stuff, plants, animals, as well as the abiotic stuff, the water, the rocks, the temperature, all those other conditions that the biotic stuff lives in.

AP Bio Ecosystems - Part 1

Now I also want to point out this graphic.

AP Bio Ecosystems - Part 1

I'm going to basically suggest that you guys at the end of the podcast come back and browse over this.

AP Bio Ecosystems - Part 1

Because I think this is very concise and it packs in a lot of the information that we're going to discuss into one nice graphic.

AP Bio Ecosystems - Part 1

Now I'm not going to go through all of it now because I want to do it gradually, but I think that overall it's one of the best graphics I've seen to kind of pull in the big picture.

AP Bio Ecosystems - Part 1

There'll be details it lacks.

AP Bio Ecosystems - Part 1

Now starting off we've got trophic structures.

AP Bio Ecosystems - Part 1

These are the levels of kind of what's eating what, where the energy is being transferred to.

AP Bio Ecosystems - Part 1

So we'll start off when we typically got our primary producers, otherwise known as autotrophs, commonly plants on terrestrial ecosystems.

AP Bio Ecosystems - Part 1

In aquatic ecosystems this would be more like algae, in some cases even cyanobacteria.

AP Bio Ecosystems - Part 1

So the other name for these is primary producers.

AP Bio Ecosystems - Part 1

So don't freak out if you see that.

AP Bio Ecosystems - Part 1

It's basically the same thing as saying autotrophs.

AP Bio Ecosystems - Part 1

Now there's individuals that we call consumers or hydrotrophs that will eat those plants.

AP Bio Ecosystems - Part 1

Herbivores is the common name.

AP Bio Ecosystems - Part 1

We'll also call them primary consumers because they're the first guys to consume stuff.

AP Bio Ecosystems - Part 1

They're consuming these autotrophs.

AP Bio Ecosystems - Part 1

You then have your first layer of actual predators, guys that eat other animals, other consumers.

AP Bio Ecosystems - Part 1

And so we're going to call those guys consumers yet again, but they're just going to be called secondary because they're oftentimes eating these primary consumers.

AP Bio Ecosystems - Part 1

And then up at the top there you can have several individuals that we'd call tertiary, which means ultimately they're eating the guys that eat other guys.

AP Bio Ecosystems - Part 1

These are some of our biggest predators that we'll have.

AP Bio Ecosystems - Part 1

And generally speaking you're not going to go too much higher than this.

AP Bio Ecosystems - Part 1

Occasionally you can have another layer or two as you get to bigger and bigger predators if it's a very energetic ecosystem.

AP Bio Ecosystems - Part 1

But you're not normally going to go past about six levels as the max.

AP Bio Ecosystems - Part 1

And we'll discuss why in terms of energy coming up here, although we've mentioned it before that there's always this loss.

AP Bio Ecosystems - Part 1

And then pretty much all of these guys up at the top here are going to die at some point and go down to what we call decomposers, detritivores.

AP Bio Ecosystems - Part 1

You might see them called saprobes.

AP Bio Ecosystems - Part 1

But these are the guys that are going to break down and eat the dead stuff.

AP Bio Ecosystems - Part 1

And it's not so much that they're recycling energy.

AP Bio Ecosystems - Part 1

Most of the energy is gone by the time you get to the top here.

AP Bio Ecosystems - Part 1

There's a bit left to keep them alive, but that's about it.

AP Bio Ecosystems - Part 1

A lot of what's really important about this is this takes nutrients from all of these guys and allows those nutrients to be broken down and released back into the soil.

AP Bio Ecosystems - Part 1

So that autotrophs can use those nutrients and then they can be passed on up to the rest of the consumers.

AP Bio Ecosystems - Part 1

So that's our trophic structure.

AP Bio Ecosystems - Part 1

Now some of the other things you might see is a food chain versus a food web.

AP Bio Ecosystems - Part 1

Now food chains are much more simplistic.

AP Bio Ecosystems - Part 1

It's one possible pathway.

AP Bio Ecosystems - Part 1

So this is a terrestrial pathway.

AP Bio Ecosystems - Part 1

Grass, grasshopper insects, some more carnivorous insects.

AP Bio Ecosystems - Part 1

From there you've got a frog, a snake, and then you've got a hawk.

AP Bio Ecosystems - Part 1

So this is one pathway energy can take within an ecosystem.

AP Bio Ecosystems - Part 1

In an aquatic ecosystem it's similar.

AP Bio Ecosystems - Part 1

It's just going to be this plankton like phytoplankton.

AP Bio Ecosystems - Part 1

Okay, so here we're going to talk about viruses that infect eukaryotic cells, so whether it be mammals or plants or other things that are eukaryotes.

Viruses AP Biology Topic 6.4

But a virus, it's important to remember that a virus is not a cell.

Viruses AP Biology Topic 6.4

So when we think about the characteristics of a cell, like all cells have a cell membrane, all cells have a cytoplasm and ribosomes and DNA, a virus does not meet those qualifications.

Viruses AP Biology Topic 6.4

So when we look at, well, what is a virus?

Viruses AP Biology Topic 6.4