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We talked about different levels of biodiversity in class.
We will go over genetic diversity in the future when we talk about ramifications of small population size. I also
talked about alpha and beta diversity in class-do you know what these terms refer to?
There is some discussion about numbers of individuals on page 29 but we will de-emphasize this.
On right hand side of page 29 the incredible diversity of bacteria is highlighted. Even relatively small samples
of soil may have 104 different species of prokaryotes (bacteria+archaea).
Sampled guts of three people 244 unknown species out of a total of 395 different “types.”
“On the basis of such findings, global prokaryote diversity has been argued to comprise possibly millions of
species, and some have suggested it may be many orders of magnitude more than that.” P29 (this connects to
one of the links you read)
Remember that the estimates of numbers of species we talked about basically ignore prokaryotic diversity and
only address protists (who are they?) very superficially.
Then he talks about Eukaryotic diversity (although protists are eukaryotes there is not much mention of protists
in this section…really he is talking about all non-protist Eukaryotes).
You should be able to consider material on p30 in context of what we went over in class and the paper we read
on estimating species numbers.
P30 What groups do we know well and who are we likely to be missing.
Ecological Diversity-de-emphasize perhaps.
Top left of p33 talk about idea of richness=species diversity vs eveness (the author words it differently talking
about heterogeneity which is basically how “uneven” a community is. Do you remember we went over this in
Section 2.2 Biodiversity over time. We went over the major periods in class, do you remember? And when were
the two major extinction events we emphasized? Who was around when?
Section 2.3 Patterns today on earth-we highlighted important ideas from this section in class.
CH10 EXTINCTION (this chapter was kind of rambling so I am afraid my comments below are also
kind of rambling)
Definitions of diversity again
Why do we tend to work at species level?
Issues surrounding populations-they are important too. What about loss of populations relative to loss of
species? (we went over this in class)
Box 10.1-What would be the ramifications if we just preserved a single population of each species (huge loss of
genetic diversity-something we will talk about later in semester). Populations are protected under ESA (what is
In class we talked about prairie dogs, burying beetles-why are they a good example of loss of populations?
Many, many populations must disappear before a species goes extinct.
But remember extinction is forever!
Some species come back rather easily from dramatic loss-turkeys.
Who said “the first law of intelligent tinkering is to keep every cog and wheel.”
We will talk about efforts to preserve large scale ecosystems=wildlands project, later in the semester.
P183 and p184 are important since they link with our readings! What is E/MSY-do you understand this??
Many cool species went extinct more than 15,000 years ago likely at the hand of humans in North America but
definitely Australia (Google Pleistocene extinctions). The classic data on extinction rates comes from birds in
the Pacific Islands.
I showed you some slides in class.
The next section deals with some details of how some authors have looked at extinction rates. Do remember
that the paper you read by Mora is the latest and greatest on this issue, so perhaps make sure you understand
that. Here are a couple points from the chapter…. Many islands were probably first colonized about 5,000 years
ago but good data exists for extinctions in the last 500. They make a series of interesting calculations on the
bottom of page 184?
They make an adjustment to this extinction rate because we really probably did not track all the birds for all the
years, so they say if you just use years that we knew this species then it reduces the species years to 1.6 million
species years and you get to about 85 E/MSY=slightly less than one extinction per year.
There are problems with this number. They point out that there are 1210 birds under category threatened (what
does that mean-we went over it in class) and 182 that are in critically endangered (25 of those really would have
gone extinct except for conservation interventions. Predictions are that they will likely go extinct in wild
without a lot of work.
If they did go extinct in wild then the extinction rate would be 5 species per year or 500E/MSY. It might be a
good idea to consult one of the graphs in the paper we read discussing whether we are in the midst of a 6th
extinction to see where these numbers fall out.
If all the 1300 threatened species or data deficient species were to go extinct over the next century then we
could be at 1300E/MSY. Again these are all super rough estimates but all these numbers work together to give
us what impression-what were the take-away points of the article we read?
10.2.4 Put this bird data in context of other species. What are the take-away points from this section? What does
Fig 10.1 show?
What is the situation for orchids? P 186
How many new species of mammals have been described?
10.3 There has been a debate in the literature essentially saying it is silly to calculate extinction rates from birds
on islands because they are the exceptions-they are super likely to go extinct in these areas because once people
get there they have nowhere to go. This section tries to raise some arguments to defend birds as good
representatives. Look at Figure 10.2 for one good point.
Not in particular p 187 “Low total population size, whether because of small range, local rarity or both ,
exacerbated in fragmented populations, and in those populations that fluctuate greatly from year to year likely
brings populations to he very low numbers from which they cannot recover.”
Figure 10.3…I would mainly note that many, many amphibians have small range sizes, at least relative to
mammals and birds.
I found Section 10.4 kind of weird. Main points are that there are only a very few species with really large
ranges, species with small ranges also tend to be uncommon (Connect this to class when we talked about 3kinds of rarity –Rabinowitz)
The other laws I would just skip..Do review our coverage of why biodiversity is high in tropics from lecture!
We will go over Myer’s hotspots later in semester when we talk about prioritizing areas for conservation-so I
would not ask you questions about it now.
They talk about Oceans, mainly concluding some of the same things that some quite small areas have many
10.5 talks about Future Extinctions and how we predict based on relationships between number of species and
area (Island Biogeography). They go through the example of New England deforestations and numbers of bird
species lost. Why did more bird species not go extinct? What do they mean there are really only 30 endemic
species of birds in the region.
Then they go on in 10.5.3 to think about using these species-area relationships to extrapolate extinction in the
hotspots of biodiversity. You can skip this.
10.5.4-It is not just down to area lost to estimate extinctions, introduced species drive extinction. They talk
about Guam and the brown tree snake.
Then they talk about climate-we will get to this so no need to focus on in detail now.
Carbon cycle!
Nitrogen cycle!
Water cycle!
I did not go over these in class but you should understand the basics!
Fossil groundwater, forests as humidity pumps, flood control, loss of mangrove forests affecting tusnami..New
Orleans barrier islands and plants living on those barrier islands would have slowed hurricane Katrina.
Dunes along east coast could have reduced the wave action of Hurricane Sandy.
Forests moderate seasonal downpours..keep streams constant
Loss of cover speeds up soil loss as well as water loss.
3.4 Biodiversity and Ecosystem function
Importance of functional group (probably the easiest “functional group” for you all to imagine are legumes-they
have mutualistic bacteria on their roots that take nitrogen gas from air and make it biologically available to the
plant they are living on. In other words they “fix” nitrogen. Adding a legume to your species mix in a prairie
will likely increase the nitrogen availability in your plot so they are an important group.)
Sampling-competition effect…this is just referring to the idea that more biodiverse (plots) more likely to have
one species that likely to does well (we gave the example of big bluestem in prairies).
More stable (fewer fluctuations year to year in terms of biomass…more efficient because more pathways for
energy to flow).
P57 keystone species-effect large in relation to abundance
Species may act like rivets in an airplane!
Diverse forest stands sequestering carbon more effectively
Forest dwelling bees increasing pollination services for coffee production
You can deemphasize mobile links p57!!
Box P54 Carnivores
And see otters and sea urchins
P59 ecosystem engineers beavers and woodpeckers
P59 more seed dispersal
P60 more pollinator decline-in box as well as on page-not in box
P61 lots of concern about almonds in California.
P63 More on the importance of pest control by native (hopefully) pest predators-natural enemies of crop pests
save us $54 billion
Services of vultures! (vultures declined, feral dogs increased-carry rabies)
P64 pharmaceuticals… (provisioning or regulating?)
Ecosystem change often promotes the escape of pathogens from their native environments..Nipah virus….forest
fires led to fruit failures, bats hung out on pig farms instead of fruit trees, passed the virus to pigs then to
humans Skip rest of pathogen stuff
Value-note idea of “tragedy of commons” p 65
We will talk about challenges/strategies of valuing biodiversity later..