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

Figure 9-2

Example of an important feedback between the biosphere and the cryosphere (or hydrosphere) and climate

Methanogenesis

Metabolic production of methane, an important greenhouse gas A major source of methane in Earth’s atmosphere

Note that CH4 + O2 CO2 + 2H2O

1. Which term below characterizes the largest group?

(a) population

(b) species

(c) biosphere

(d) ecosystem

(e) community

Short Question 26

Ecosystem

Biosphere

Tropical rainforest

Temperate forest

Savannah

Mountains

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).

Ecosystem

fern frog

bacterium

communities

Ecosystem

fern frog

bacterium

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??

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?

Chapter 10 - Origin of the Earth and Life on Earth

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).

Figure 10-3

Disk around a star – imaged by light scattering (e.g. dust)

Stars have a life cycle!

Figure Box 10-2

Figure 10-4

Figure Box 10-1

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!

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 self-replicate.

Can life be made from basic elements found on early Earth?

Prebiotic synthesisMiller-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