What is Life?

Taken from “Life on Earth… and Elsewhere?”

Earth’s life forms all…

• are carbon-based.

• have a membrane or wall that creates an internal environment.

• use energy to maintain an internal state.

• require liquid water.

• able to extract energy from the environment.

Earth’s life forms all…

• carry out metabolic processes such as the exchange of gases and solid materials (i.e. consuming raw materials and producing wastes.)

• exhibit growth, cell division, reproduction, or replication.

• able to have a population evolve and adapt to the environment.

In a Nut Shell….

• Things needed to sustain life are:

• Food (for energy)

• Water

• Shelter

What does life need to exist?

• Liquid water and a method for cycling water (atmospheric, geothermal) so that necessary chemicals can be transported – All known life requires a temp. between [-15°C

(5°F) to 115°C (239°F)] liquid water possible in this range.

• Energy– Light energy from a star (sun): needs to live at the

surface but still be in the correct temperature range and be protected from harmful UV rays and solar wind

– Chemical energy -breaking complex compounds into simpler ones (ex. Food energy)

• Nutrients – raw materials to construct and maintain bodies

Wild, Wacky, Wonderful Water!

• Most organisms are 50% to 95% water.• Water’s ability to absorb and retain heat (regulates

climate)• Water is polar. (has a negative charge on one end

and a positive charge on the other)– Water is the universal solvent. (Lots of substances can

dissolve in it.)– Polarity causes surface tension.

• only substance that can exist as a solid, liquid, or gas at normal temperatures on Earth.

• solid form (ice) is less dense than the liquid form.

Carbon is Cool!

• Living things are made up mostly of four elements: hydrogen, oxygen, carbon, and nitrogen. When you take away the water, living things are mostly carbon.

Graphite (pure carbon)

Graphite pencil

Sugar cube (C6H12O6)

Carbon is Unique.

• Its structure is the main reason why life is based on it.

• It can form complex molecules.

• Carbon is the smallest element that has this ability.

Structure of a diamond (all carbon)

Amorphous carbon containing molecule

That Crazy Carbon!!!

• Carbon can form 4 bonds (the most possible) because there is room for four more electrons in its outer shell.

Carbon bonding with 4 hydrogen atoms

4 available bonding locations

Carbon Containing Compounds

• Carbon dioxide (reactant in photosynthesis)

• Amino acids (building blocks of proteins)

• Nucleic acids (like DNA)

Carbon Containing Compounds

• Carbohydrates (sugars and starches)

• Lipids (fats and steroids)

• Carbon is also found in rocks like limestone.

Starch molecule

Steroid molecule

Movies about life on other planets.

Search for ET

• Astrobiology – the study of all living things within the universe, where they might be found and how they were formed.

• Astrobiologists look for habitable conditions and direct evidence of life when searching for ETs.

Habitable Zone

• Distance from a star where water can exist as a liquid, or the distance between the points where there is too much and too little sunlight.

What have we found so far?

• Currently, the only life we have found in the universe is located on Earth.

Remember the Inverse Square Law?

• Light intensity decreases by the square of the distance.

Planet or Moon Distance from Sun (AU)

Light Intensity (relative to Earth)

Watts per Square Meter

Mercury 0.39 6.575 9008

Venus 0.72 1.929 2643

Earth & Moon 1.0 1.000 1370

Mars 1.5 .444 603

Jupiter and its moons 5.2 0.037 51

Saturn and its moons 9.5 0.011 15

Uranus 19.2 0.0027 3.7

Neptune 30.1 0.0011 1.5

Pluto 39.5 0.0006 0.8

What makes a world habitable?

• Besides the basic requirements of life (energy, nutrients and liquid water), a planet or moon also must have:– A temperature range from -15 to 115°C (too

high and organic molecules break down; too low and chemicals don’t function properly)

– An atmosphere to provide nutrients and protect from ultraviolet radiation and small meteor impacts.

Extremophiles!

• Organisms that live at the limits of what is acceptable for life.

• Most are microorganisms.• They’re found in Antarctica, in hydrothermal

vents, and deep in the Earth’s crust.

Some love heat…

Some love cold…

Some love salt…

These are solar evaporation ponds near Salt Lake City, Utah. They are shallow ponds that use solar energy to evaporate the water and leave behind salt. As the salinity of the ponds increases, the bacteria species change, creating different colors. These type of bacteria are called Halophiles.

Some love acid…

And lots of other crazy things!!!

These bacteria are acidophiles, or acid loving bacteria. This particular species has been found in environments, such as underground caves, with a pH of 0.

What about sending Earth microbes to colonize other worlds?

• Pros – help create an atmosphere– add oxygen to the environment – detoxify harmful compounds– establish a food supply – extract useful materials from

the planet’s or moon’s crust

• Cons– may interfere with learning about extraterrestrial life– Earth life forms may out compete ET life forms,

causing them to become extinct– space travel may negatively impact new colony (may

pollute the colony planet)

1. All living things are composed of..?

Boro

n

Car

bon

Oxy

gen

nitr

ogen

0% 0%5%

95%A. Boron

B. Carbon

C. Oxygen

D. nitrogen

2. Consuming raw materials and producing waste is a living process

called:

Eat

ing

and th

e...

Mec

hanis

ms

photo

synt

hesi

s

met

abol

ism

37%

58%

0%5%

A. Eating and then pooping

B. Mechanisms

C. photosynthesis

D. metabolism

3. For life to exist the temperature range needs to be:

-15

oC-115

oC

1oC-1

00oC

5oF-2

15oF

32o

F-106

oF

89%

0%11%

0%

A. -15 oC-115oC

B. 1oC-100oC

C. 5oF-215oF

D. 32oF-106oF

4. Four elements living things are made of:

Hel

ium

, oxy

gen...

Hyd

roge

n, oxy

g...

Phosp

horus,

ni..

.

Sodiu

m, a

lum

in...

0% 0%5%

95%A. Helium, oxygen,

nitrogen, calcium

B. Hydrogen, oxygen, nitrogen, carbon

C. Phosphorus, nitrogen, chloride, oxygen

D. Sodium, aluminum, hydrogen, carbon

5. How many bonds can carbon form?

1 2 3 4

11%

84%

0%5%

A. 1

B. 2

C. 3

D. 4

6. ____energy needs to be in the right temperature range and UV

range for life to exist:

Chem

ical

Nucl

ear

Lig

ht

ele

ctric

al

11%

0%

79%

11%

A. Chemical

B. Nuclear

C. Light

D. electrical

7. Solid water is ____dense than liquid water.

More

Les

s

Equal

ly

aw

esom

ely

26%

0%0%

74%A. More

B. Less

C. Equally

D. awesomely

8. Scientists who look for habitable conditions and for evidence that life

exists:

Bio

logis

ts

Phys

icis

ts

Envi

ronm

enta

li...

ast

robi

ologi

st...

5%

89%

5%0%

A. Biologists

B. Physicists

C. Environmentalists

D. astrobiologists

9. The distance from a star where life and water can exist in liquid form and the distance between

where there is too much or too little sun is:

The

fun z

one

The

habita

t zone

The

habita

ble z

one

The

end zo

ne

0%

11%

63%

26%

A. The fun zone

B. The habitat zone

C. The habitable zone

D. The end zone

10. Which of the following is not a benefit to sending microorganisms to

inhabit other planets?

Adds

oxygen

to th

e e.

..

Est

ablis

hes

a fo

od s...

Spac

e tra

vel m

ay p

oll...

Det

oxify

har

mfu

l co...

16% 16%

63%

5%

A. Adds oxygen to the environment

B. Establishes a food supply

C. Space travel may pollute other planets

D. Detoxify harmful compounds