Chapter 5 - 9

09 Biology

listen to a lecture in a biology class. fill in the diagram with the information that you hear.

M: Today, I want to talk to you about the importance of genetic diversity in animals.

If a population of animals is said to be “genetically diverse,” that just means there is a great variation in the genes of that species.

Typically, very large populations of animal show genetic diversity, while smaller populations do not show such great diversity.

Genetic diversity allows animals to adapt to changes in an environment, to build up resistances to diseases… we’ll discuss that more in a second.

It actually affects a lot of different systems in animals… especially the reproductive process.

One of the most prevalent concerns scientists have regarding endangered species is their lack of genetic diversity.

Many animal species are now either threatened or endangered, which, of course, leaves a much smaller number of animals to reproduce and continue the species.

At first, a reduced population isn’t too much of a problem, uh, well, in terms of genetic diversity at least.

But… but, uh, eventually, all the animals start to have the same genetic lineage.

So they are lacking the introduction of new genetic material.

Basically, the old material just gets recycled, over and over again.

So what, then, is the effect of reduced genetic diversity?

There are many, actually.

First, animals are more susceptible to disease when the gene pool is reduced−when there’s little genetic diversity.

Usually, when different strains of viruses or diseases hit, the species survives through its eclectic mix of genetic material.

The diversity enables them to survive, because there are usually some families of animals that are more tolerant of the disease than others.

These animals survive, and then reproduce, which passes this immunity on to the others in their species.

If there isn’t a wide variety of genetic diversity, and all the… they all have the same characteristics, they will also all have the same weaknesses.

This puts the species in danger of complete extinction by a single, particularly potent disease that they don’t have a resistance to.

This susceptibility gets worse as the genetic diversity decreases, meaning that the problem gets worse with every generation.

The originally unique genetic material gets… well, watered−down.

To move on to another negative affect: because of this lack of genetic diversity, and the subsequent watering-down of the original genetic information, the animals’ offspring are born with more deformities.

The genetic information gets corroded.

Hmm, let me explain that. Without a source of new genetic material, the body has fewer options when it is forming.

Instead, the genes recombine in defective ways, producing multiple genetic problems.

A good example is the cocker spaniel.

These animals have such a lack of genetic diversity that many of them experience a variety of health problems as a result.

These health problems in animals with a lack of genetic diversity are not always very obvious.

The defect can be as simple as a higher disposition toward heart problems, or arthritis.

But, um, in any case, the animal’s genetic integrity is weakened.

OK… let’s see. I know I was going to make third point.

Oh, yes. All of these problems affect the overall population viability.

If the entire species has such a lack of genetic diversity that they are in poor health, that puts the whole species at risk.

All of the factors I’ve already mentioned… well, those factors make for a pretty poor outlook for the survival of the species.

The susceptibility of the animals to disease makes them prone to widespread population wipeouts.

Their compromised physical health means that many of them die before reaching old age, and the deformities cause a large number to die shortly after birth.

Or while still really young. So the entire population is threatened by the lack of diversity.

The whole situation is really pretty sad.

So, how about an example of how all of this information applies to a specific animal?

One species that is battling these problems are cheetahs.

These animals are rare in the wild, and have been bred in captivity for many years.

But because the overall number of cheetahs is so small, they have a severe lack of genetic diversity.

Scientists actually estimate that as many as eighty percent of all cheetahs have the same genetic material.

That’s a lot! Um… really, a lot.

These animals face all of the physical problems associated with this, too.

In fact, their problem is so bad that cheetahs have a difficult time successfully reproducing at all.

Their reproductive organs have been weakened by the limited genetic information.

1) How does the professor organize the information he presents to the class?

2) How does the professor organize his point about disease?

3) How does the professor explain his point about population viability?