Tugas Terstruktur 1_BioDas II - Biologi Dasar II Semester...

Biologi Dasar II
Semester Genap 2015/2016
Tugas Terstruktur 1
TT1 - Topic 1
Could Nonvascular Plants Have Caused Weathering of Rocks and Contributed to Climate
Change During the Ordovician Period?
[T.M. Lenton, et al, First plants cooled the Ordovician. Nature Geoscience 5:86-89 (2012)].
The oldest traces of terrestrial plants are fossilized spores formed 470 million years ago.
Between that time and the end of the Ordovician period 444 million years ago, the atmospheric
CO2 level dropped by half, and the climate cooled dramatically. One possible cause of the drop
in CO2 during the Ordovician period is the breakdown, or weathering, of rock. As rock
weathers, calcium silicate (Ca2SiCO3) is released and combines with CO2 from the air,
producing calcium carbonate (CaCO3). In later periods of time, the roots of vascular plants
increased rock weathering and mineral release by producing acids that break down rock and
soil. Although nonvascular plants lack roots, they require the same mineral nutrients as vascular
plants. Could nonvascular plants also increase chemical weathering of rock? If so, they could
have contributed to the decline in atmospheric CO2 during the Ordovician.
How the Experiment Was Done
The researchers set up experimental and control microcosms, or small artificial ecosystems, to
measure mineral release from rocks. First, they placed rock fragments of volcanic origin, either
granite or andesite, into small glass containers. Then they mixed water and macerated
(chopped and crushed) moss of the species Physcomitrella patens . They added this mixture to
the experimental microcosms (72 granite and 41 andesite). For the control microcosms (77
granite and 37 andesite), they filtered out the moss and just added the water. After 130 days,
they measured the amounts of various minerals found in the water in the control microcosms
and in the water and moss in the experimental microcosms.
Data from the Experiment
The moss grew (increased its biomass) in the experimental microcosms. The table shows the
mean amounts in micromoles (µmol) of several minerals measured in the water and the moss
in the microcosms.

Interpret the Data
1. Make two bar graphs (for granite and andesite) comparing the mean amounts of each
element weathered from rocks in the control and experimental microcosms.
2. Overall, what is the effect of moss on chemical weathering of rock? Are the results similar or
different for granite and andesite?
3. “Life has profoundly changed the Earth.” Explain whether or not these experimental results
support this statement.
TT1 - Topic 2
What Can Genomic Analysis of a Mycorrhizal Fungus Reveal About Mycorrhizal Interactions?
[F. Martin et al., The genome of Laccaria bicolor provides insights into mycorrhizal symbiosis, Nature
452: 88–93 (2008)]
The first genome of a mycorrhizal fungus to be sequenced was that of the basidiomycete
Laccaria bicolor . In nature, L. bicolor is a common ectomycorrhizal fungus of trees such as
poplar and fir, as well as a free-living soil organism. In forest nurseries, it is used in large-scale
inoculation programs to enhance seedling growth. The fungus can easily be grown alone in