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Biodiversity | California Academy of Sciences
Course: Biodiversity | California Academy of Sciences > Unit 8
Lesson 2: Biodiversity and the tree of life- Discovering the tree of life
- Understanding the past to preserve the future
- Sea slug evolution and conservation – what’s the link?
- Test your knowledge: biodiversity and the tree of life
- Exploration questions: biodiversity and the tree of life
- Glossary: biodiversity and the tree of life
- Selected references: biodiversity and the tree of life
- Answers to exploration questions: biodiversity and the tree of life
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Understanding the past to preserve the future
Learn how comparisons of evolutionary relatedness can help us protect the greatest amount of biodiversity. Video by California Academy of Sciences.
Video transcript
(serene classical music) - [Narrator] We've
mentioned this many times, saving biodiversity comes down to choices, hard choices about what
biodiversity to save. Unfortunately, so much
of the natural world is threatened by human activities, we have to make choices between what to prioritize for
protection, we cannot save it all. There's ongoing discussion
about what criteria and, most importantly,
what tools we have at hand that we can and should use to help us make intelligent choices, choices that maximize ecosystem function, and along with that, ecosystem services. What do we actually focus on saving, a species, an ecosystem? A saved species isn't really
saved if its ecosystem or habitat remains at risk. After all, you could lock all those endangered
species safely in a zoo and keep their lineages
going for quite a long time, but that doesn't really help
the planet or us overall. What we're talking about is
focusing on the preservation of functioning ecosystems. Most people would agree that we want to keep organisms in
their native habitats, fulfilling functions so that
the ecosystem sustains itself. A self-sustaining web of interactions in which species have connected but differing functions in that web. With limited resources such as time, money, and space available
for protecting biodiversity, we're gonna have to
decide if some ecosystems are more important to save than others. How do we choose? It's a nasty little question, but with the accelerating speed of this current sixth mass extinction, we really do need to address it quickly. One of the things that
scientist have discovered is that in a healthy ecosystem, a diversity of things are going
on among different species, and that leads to production of biomass. That's one measurement that scientists have been able to make. A healthy ecosystem tends
to produce more biomass than a less healthy ecosystem. With more biomass, you have
a more stable foundation to support more organisms
within that ecosystem, and you're also sequestering more carbon that might otherwise
add to climate change. So, higher biomass in an ecosystem is regarded as a good thing, at least in terms of a simple
measure of ecosystem health. And as it turns out, recent
carefully controlled experiments have shown that ecosystems made up of more distantly related species
result in greater biomass. The reason for this is that
distantly related organisms are more likely to fulfill functions in different, non-overlapping niches. In other words, they're not competing with closely related species that, because of their common ancestry, have similar tastes or needs
for resources in the ecosystem. But how do you know that things are more or less distantly related? That's where phylogeny,
the study of lineages, or evolutionary lineages, comes in. And I'm going to give you a little example that illustrates how this
can be an important tool in our efforts to make decisions about where to focus our
energies in saving ecosystems. Let's consider three lakes,
Lake A, Lake B, and Lake C. And Lake A over here has
a bunch of fish in it. Let's say there are four species, we're gonna call them A1, A2, A3, and A4. And then in Lake B, we've
got four other species. And finally, in Lake C over here, we have yet another different
set of four species of fish. Local governmental
agencies want to preserve the healthiest ecosystem
among these lakes, but due to the limited funding and staff they have to work with, they can only focus on saving
one lake, that's the problem. If they only consider species richness, there's equal diversity. Four different fish species
in each of these lakes. How do you decide which lake should receive your limited
resources to preserve it? Well, we can do that
by using phylogenetics. So we study all 12 of these fish species, and we build a phylogenetic tree using the latest and greatest of molecular and morphological methods. All these data help us to build a tree of life, this phylogeny. The first thing you can observe is that the four species in Lake A are more closely related to each other than they are to anything else. And the same is true for
the four species in Lake B. But we've got one species from Lake C that's more closely
related to those in Lake A, and another C species that's more closely
related to the B species. And interestingly, the
two remaining species from Lake C are closely
related to each other, but form a group that is
only distantly related to the species in either Lake A or Lake B. It's pretty obvious that the
evolutionary distinctiveness, or diversity, among the
four species from Lake C is much greater than the
distinctiveness among the species in either Lake A or B. So if you wanna preserve
really distinct species that most likely function
in distinct niches that enhance biomass production
and ecosystem health, our friendly government agencies should focus on efforts on
protecting the Lake C ecosystem. Of course, real life is
always more complicated than this simple example in which we've only varied the degree of evolutionary relatedness among species in each of the lakes. In real life, you have many factors that should be considered in decisions about what to protect, factors ranging from the total number of species in an ecosystem, to the value of the services
provided by that ecosystem. But the point here is
that we have a valid, powerful scientific tool, the
study of phylogenetic lineages that can help us understand
how different ecosystems possess different levels of productivity depending on the types
of species they contain. As a scientist trying to
deal with the enormity of the problems we face
and the daunting task of trying to protect as
many things as possible, I'm happy about new scientific tools that can help us make these
most difficult choices. We need all the help we can get in trying to reduce the
loss of biodiversity that we humans are causing because we are now arguably
the most influential ever of all the species in the tree of life.