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Biology library
Course: Biology library > Unit 30
Lesson 5: Levels of biodiversityGenes and biodiversity
How does the gene pool contribute to biodiversity? Learn how genetic diversity within populations contributes to species survival. Video by California Academy of Sciences..
Want to join the conversation?
- Are there any alternative plant crops that could lessen our dependence on rice, wheat or corn?(11 votes)
- KEVIN, that's an outstanding question! and yes! there are many, but there are also many obstacles to transitioning to those, the least of which is that the ones you mentioned are currently subsidized by the government, so the most lucrative for farmers to grow.
"Nurturing a new cereal grain market is a lot like raising a child — it takes a village to do it right. For a new food to thrive, it takes public education, financial security, infrastructure and opportunities to grow." from this site: http://www.greenbiz.com/blog/2014/05/15/why-we-need-go-beyond-corn-wheat-and-rice hope this helps!(11 votes)
- didn't the dodo species die off from a series of dutch hunting seasons and not a drop of bio/genetic diversity?(2 votes)
- While there is some debate over the key contributing factors to the DoDo extinction, it's generally agreed hunting played a part. However, the size of the role hunting played is a moot point. Other factors cited as contributing to the Dodo's extinction are destruction of habitat by humans and competition with introduced species such as pigs.(3 votes)
- What does biodiversity mean?(2 votes)
- Biodiversity refers to having many different species (types) of living organisms rather than just a few. :)(2 votes)
- 6:20
Didn’t that already happen to the Irish?(1 vote)
Video transcript
(light music) - [Narrator] We've seen
that genes can vary. Most clearly, they differ among the major groups of organisms. That's evident because genes lead to body forms or
phenotypes, and phenotypes of these different organisms can vary. Everything from a tree to
a sand dollar, and beyond. The genes can also vary among
closely related species. Even if you look at the
hundreds of species of beetles in a single beetle genus,
each of those species has its own genetic make-up. But here, we want to talk
about how genetic diversity also occurs among distinct
populations of a single species. Or among the individuals within a species. Think of the hundreds of
different breeds of dogs, or the numerous varieties of roses. Those all represent genetic diversity within the single species of dogs, and the single species of roses. Dogs and roses, sounds like a rock group. Each individual is a little bit like a ship loaded with crew members. Some crew members are at the helm, some care for the engines, and
some are swabbing the decks. But no two ships have
exactly the same crew. Even though the ships might
look identical from a distance, each crew adds subtle
differences in the directions that their ship might
take, how well the engines are running, or even
how clean the decks are. Put all those ships into a big fleet, and you have a lot of
different crew members. You have a labor pool. Just like those ships, each
organism is unique internally, but each organism is unique
in its genetic information. If we consider all the
individuals in the population, we have a lot of different genes. Collectively, these are
known as the gene pool, the complete set of genetic information within a population of a given species, or within the species itself. The larger the gene pool, the
greater the genetic diversity. The higher the chances
are that some members of the population will
survive or even flourish in times of environmental
change and challenges. That's because some of the
individuals are gonna have traits that make them resilient
in the face of changes in the environment, more
resistant to disease, and more able to survive
changes in climate, and so on. We've already seen that
this is due to the way natural selection works,
selecting for fitter individuals that pass on their
beneficial characteristics. But now we're gonna tie that concept to the size of the population. Basically, the bigger the
population, the more likely there will be individuals
with some unique combination of genes that will allow their survival. But what happens when the
gene pool is much smaller, in other words, when the
gene pool is shallow. In the wild, in a small isolated
population of organisms, the choice of mates with whom to breed tends to be restricted to
closely related members of the same population, possibly
siblings or even cousins. So the genetic make-up of the individuals becomes more and more uniform. And what's worse, flaws or disabilities that those individuals
might be carrying in their genetic information
become expressed or appear in the population more frequently, and this is known as inbreeding. Evidence shows that maintaining
not only large numbers of species in ecosystems, but
large numbers of individuals within populations of
those species is important to preserving biodiversity overall. Lots of different studies
have shown that extinction, permanent loss of a species, is preceded by a drop in genetic diversity, a decrease in the gene pool, within
the threatened species. From the species' point of view, decreasing genetic diversity
is a sign of trouble ahead. Degradation of habitats
can cause a decrease in population size and promote inbreeding. When the population size
of a species is reduced to the point that it almost goes extinct, the species is said to have gone through a genetic bottleneck. American bison are a classic
example of such a bottleneck. The drop in the bison
population reduced their genetic diversity, which
makes them more vulnerable to environmental changes and diseases. Just as we cannot get back a species that's been lost to extinction,
it's very difficult, and in most cases impossible, to get back the genes that are
lost when that species goes extinct, or when individuals carrying unique genetic combinations die. As humans encroach on
wild habitats, populations consequently become smaller,
and so does the gene pool. This represents a loss of
options for a population to respond to stresses, whether
those are natural stresses, or stresses caused by humans. Ecosystem services arguments
go straight to this idea of conserving genetic diversity. Genes control the production of substances that we use in medicine and
food and even as energy sources. Preserving genetic diversity
increases the likelihood that new substances can be
found among wild populations, and that the supplies of useful substances we already have can be maintained. The erosion of genetic
diversity in agriculturally important species can come in two forms. One is due to artificial selection for special traits that
humans find desirable, to the exclusion of other traits. The other source of erosion is that we've focused our dependence
on only a few organisms. For example, only about
100 or so species of plants account for 90% of our food crops, and only three different species, corn, rice, and wheat account
for something close to 70% of the calories consumed by humankind. And these include 50% of
the plant proteins we eat. What if some disease attacks any of these basic sources
of our own nutrition, and those plants have
no genetic resistance? I hate to think about
the dire effects the lack of genetic diversity would
have on our own survival. (light music)