Key Questions
What are the characteristics of life that allow to interact
with the other Earth systems to help create a habitable
planet?
How is the biosphere structured?
How is energy transferred within the biosphere?
What is an ecosystem?
What is biodiversity and how is it ‘measured’?
Some important characteristics of life
It spreads exponentially, 2  4  8  16  32….
It needs energy – the ‘food chain’ starts with either
photosynthesis (sunlight) or chemosynthesis (ocean
thermal vents)
It “pollutes” the physical environment
It is versatile – e.g. evolution/natural selection
Life can be categorized taxonomically (e.g. by species,
genera, families, etc.), it can also be categorized on the basis
of ways in which organisms obtain and metabolize energy
Autotrophs – primary producers that take CO2 and water
and make hydrocarbons, either using the sun or sulfur. Key
– they convert inorganic carbon to organic carbon.
Organic carbon is a way to store this solar or chemical
energy for later conversion at a time that it is needed
(“metabolized”)
Heterotrophs – controlled ‘burning’ of the energy stored in
organic molecules produced by the autotrophs. Requires an
oxidant (O2, nitrate, sulfate, iron, manganese oxides)
Table 9-1
Ecosystem
Community
Population
Species
Figure 9-1
Biosphere hierarchy
Ecosystem – Subset of the global biosphere (e.g. forest and all
plants, animals, fungi, microbes and their interactions)
Community – two or more groups of interacting species. May
include any combination of animals, plants, fungi, and
microbes. regions with characteristic plant community is
called a ‘biome’…e.g. desert, tropical rainforest,…
Population – all the members of a given species
Species – one specific kind of plant, animal, fungus, or
microbe
Example of an important feedback between the biosphere
and the cryosphere (or hydrosphere) and climate
Figure 9-2
Methanogenesis
Metabolic production of methane, an important
greenhouse gas
A major source of methane in Earth’s atmosphere
Note that
CH4 + O2  CO2 + 2H2O
Short Question 26
1. Which term below characterizes the largest group?
(a) population
(b) species
(c) biosphere
(d) ecosystem
(e) community
Ecosystem
Tropical rainforest
Mountains
Biosphere
Savannah
Temperate forest
Ecosystems exist on a variety of scales. An example of a
small scale ecosystem (micro) is a pond. A medium scale
ecosystem (meso) could be a forest. The tropical rainforest is
an example of a very large ecosystem (biome).
fern
frog
bacterium
Ecosystem
communities
fern
frog
bacterium
Ecosystem
communities
Ecosystem 1
Ecosystem 2
“ecotone” – the transition between two ecosystems
Common aspects of ecosystems
- energy flow (autotrophs/heterotrophs)
- food chain
- symbiotic relationships
- diversity
Energy Flow in an Ecosystem
Pollution
“Food chain”
Energy flows from trophic
level to trophic level
“trophic” - of or involving
the feeding habits or food
relationship of different
organisms in a food chain.
Other examples
Particle production from dimethyl sulfide (DMS)
- stuff that makes a beach smell like a beach
Reduction of erosion by plants
Others??
Chapter 10 - Origin of the Earth and Life on Earth
How old is the Earth?
How did the solar system form?
How did the atmosphere and oceans form?
How has the composition of the atmosphere
changed over time?
When and how did life originate?
Why did early life prefer hot environments?
EON
Formation of Solar System - review
Eagle Nebula
Scientists believe that the solar system was formed when a cloud
of gas and dust in space was disturbed, maybe by the explosion
of a nearby star (called a supernova).
Disk around a star – imaged by light scattering (e.g. dust)
Figure 10-3
Stars have a life cycle!
Figure Box 10-2
Figure 10-4
By studying meteorites, which
are thought to be left over from
this early phase of the solar
system, scientists have found
that the solar system is about
4,600 million years old!
Figure Box 10-1
Eventually, the cloud grew hotter and denser in the center, with a disk of gas and
dust surrounding it that was hot in the center but cool at the edges. As the disk got
thinner and thinner, particles began to stick together and form clumps. Some
clumps got bigger, as particles and small clumps stuck to them, eventually forming
planets or moons .
Eventually, the cloud grew hotter and denser in the center, with a disk of gas and
dust surrounding it that was hot in the center but cool at the edges. As the disk got
thinner and thinner, particles began to stick together and form clumps. Some
clumps got bigger, as particles and small clumps stuck to them, eventually forming
planets or moons .
Near the center of the cloud, where planets like Earth formed, only rocky material
could stand the great heat. Icy matter settled in the outer regions of the disk along
with rocky material, where the giant planets like Jupiter formed.
As the cloud continued to fall in, the center eventually got so
hot that it became a star, the Sun, and blew most of the gas and
dust of the new solar system with a strong stellar wind.
The Moon is critical for Earth’s climate!
Figure 10-5
Early Earth’s atmosphere – probably He and H2 left over from
formation, would gradually escape to space as gravity is too weak to
keep these light elements close to the surface. Plus, Earth still did not
have a differentiated core (solid inner/liquid outer core) which creates
Earth's magnetic field (magnetosphere = Van Allen Belt) which
deflects solar winds.
Second atmosphere – outgassing from volcanoes and impacts to make
H2O, CO2, SO2, CO, S2, Cl2, N2, H2 and NH3 (ammonia) and CH4
(methane). No free O2 at this time (not found in volcanic gases).
Today’s atmosphere – green plants! Photosynthesis produces O2,
which causes exposed iron in rocks to rust (turn red!)
Ocean Formation - As the Earth cooled, H2O produced by out
gassing could exist as liquid in the Early Archean, allowing oceans to
form.
Evidence - pillow basalts, deep marine sediments in greenstone belts.
Origin of life
To be “alive”, something
must be able to selfreplicate.
Can life be made from
basic elements found on
early Earth?
Prebiotic synthesis
Miller-Urey experiment –
amino acids from ammonia
and methane, evolves into
something more complex
Interplanetary dust? (the cosmic ‘ride’)
Hydrothermal vents (‘black smokers”) (due to FeS)
Chapter 11 – Effect of Life on the Atmosphere: The Rise of
Oxygen and Ozone
Key Questions
• How did early forms of life on earth affect atmospheric
composition?
• When did oxygen become more abundant?
• When did the ozone layer form and how did it affect life on
earth?
• How much has atmospheric oxygen changed over the past 540
million years?
• What determines the abundance of atmospheric oxygen today?
"It is widely believed that 2000 million
years ago the cyanobacteria, oxygen
eliminating photosynthetic prokaryotes that
used to be called blue-green algae...effected
one of the greatest changes this planet has
ever known: the increase in concentration of
atmospheric oxygen from far less than 1%
to about 20%. Without this concentration of
oxygen, people and other animals would
have never evolved"
Margulis, Lynn and Karlene V. Schwartz. Five Kingdoms, 2nd
edition. W. H. Freeman and Company 1988. p28.
also at Gaia by Brig Klyce
Universal tree of life
PCR – Polymerase chain
reaction