Chapter 3

Question 1

What does abiotic mean?

Answer 1

Non living

Question 2

What are the seven characteristics shared by all life-forms?

Answer 2

1. Order
2. Harnesses and utilizes energy
3. Reproduces
4. Responds to stimuli
5. Exhibits homeostasis
6. Grows and develops
7. Evolves

Question 3

What does biotic mean?

Answer 3

Living

Question 4

Why are viruses not considered to be true living organisms?

Answer 4

They display many of the properties of life, but the characteristics of life of viruses are based on its ability to infect cells.
They infect other cells and steal their organisms to survive
Ex: viruses contain nucleic acids but they lack the cellular machinery and metabolism to use that genetic information to synthesize their own proteins so they infect living cells and hijack their machinery

Question 5

Why are the seven properties of life considered emergent?

Answer 5

They come about, or emerge, from many simpler interactions that, in themselves, do not have properties found at higher levels

Ex: the ability to harness and utilize energy is not a property of molecules or proteins or biological membranes in isolation, rather the ability emerges from the interactions of all three of these parts together

Question 6

What type of earth do scientists believe life began?

Answer 6

They believe cells with the characteristics of life arise out of a mixture of molecules that existed on primordial earth

Question 7

Why is earth so perfect for harbouring life?

Answer 7

• Earth developed an atmosphere that could cool the planet to a temperature life could survive on
• earth is situated in a position where heat from the sun allows for surface temperatures to be within a range that allows water to exist in a liquid state

Question 8

What are all forms of life composed of?

Answer 8

Major macromolecules such as
Nucleic acids
Proteins
Lipids
Carbohydrates

Question 9

What is the first hypothesis for the origin of life: reducing atmosphere?

Answer 9

Two scientists proposed that organic molecules formed the atmosphere of primordial earth and named it a reducing atmosphere because of the presence of large concentrations of molecules such as hydrogen, methane and ammonia
These molecules contain an abundance of electrons and hydrogen would have entered into reactions with eachother which led to larger and more complex organic organisms

Question 10

What is the second hypothesis for the origin of life: deep-sea vents?

Answer 10

Suggests the origin of life fame from deep sea (hydrothermal) vents

• they release super heated nutrient-rich water and reduced molecules such as methane, ammonia and hydrogen sulfide
• today the areas around these vents support a remarkable diversity of life

Question 11

What is the third hypothesis for the origin of life: Extraterrestrial Origins?

Answer 11

• each year more than 500 meteorites impact earth many of which are rich in organic molecules
• Murchison meteorite in Victoria Australia contained amino acids

Question 12

What are monomers?

Examples

Answer 12

Monomers are the building blocks of polymers that are simpler and easier to synthesize
Amino acids
Nucleotides
Monosaccharides

Question 13

What are polymers?

Examples

Answer 13

Macro molecules formed from the binding together of individual monomers
Nucleic acids
Proteins
Polysaccharides or carbs

Question 14

What type of environment could have provided the necessary things for polymerization to occur?

Answer 14

Solid surfaces

Especially clay

Question 15

What is the difference between reducing atmosphere and oxidizing atmosphere?

Answer 15

The oxidizing atmosphere is rich in oxygen which prevents complex, electron rich molecules from being formed
The lack of oxygen of the reducing atmosphere means it had no ozone layer

Question 16

What is a protobiont?

Answer 16

A group of abiotically produced organic molecules that are surrounded by a membrane structure

Have formed spontaneously without energy on primordial earth

Question 17

What are ribozymes?

Answer 17

A group of RNA catalysts that can catalyze reactions on the precursor RNA molecules that lead to their own synthesis

Question 18

What are the three reasons cells that evolved the ability to use the information present in RNA to direct the synthesis of proteins turned out to be a tremendous advantage?
Also the reasons that proteins are the dominant structural and functional molecule of the modern cell

Answer 18

1. The catalytic power of most enzymes is much greater than that of a ribozyme
2. A typical cell synthesizes a huge array of different proteins
3. Amino acids can interact chemically with eachother in bonding arrangements not possible between nucleotides

Question 19

What are the three reasons DNA is better to store information than RNA?

Answer 19

1. Each strand of DNA is chemically more stable and less likely to degrade
2. DNA uses thymine not uracil so it can detect damaged uracil and repair it
3. DNA is double stranded so if a mutation occurs on one strand it can use the complementary strand to repair it

Question 20

Where is the earliest conclusive evidence of life found in? What are these?

Answer 20

Stromatolites

Type of layered rock that is formed when microorganisms bind particles of sediment together, forming thin sheets

Question 21

What are heterotrophs?

Answer 21

Organisms that obtain carbon from organic molecules

Humans are heterotrophs

Question 22

What are autotrophs?

Answer 22

Organisms that obtain carbon from the environment in an inorganic form (CO2)

Plants are autotrophs

Question 23

What is the earliest type of photosynthesis?

Answer 23

Anoxygenic photosynthesis

Uses hydrogen sulfide and ferrous iron as electron donors for the light reactions of photosynthesis

Question 24

How were ancient stromatolites formed?

Answer 24

Cyanobacteria

Photosynthetic bacteria

Question 25

What is oxygenic photosynthesis?

Answer 25

Photosynthesis that relies on the oxidation of water as the source of electrons

Cyanobacteria uses this

Question 26

Why was oxygenic photosynthesis huge on the evolution of life?

Answer 26

It gave the organism using it the ability to grow anywhere it could get sunlight

Question 27

What is panspermia?

Answer 27

The name given to the hypothesis that very simple forms of life are present in outer space and that these may have seeded early earth

Question 28

What is an extremophile?

Answer 28

General term given to an organism that is found growing in environments that are lethal to most other organisms

Question 29

What are the three domains that all present day organisms can be placed into? Where do they all connect?

Answer 29

Archaea
Bacteria
Eukarya

They connect at the last universal common ancestor (LUCA)

Question 30

What are the seven common attributes all life forms share?

Answer 30

1. Cells made of lipid molecules brought together by bilateral
2. A genetic system based on DNA
3. A system of Info transfer DNA to RnA to protein
4. A system of protein assembly from amino acids
5. Reliance on proteins
6. Use of ATP as chemical energy
7. Breakdown of glucose by glycolysis to produce ATP

Question 31

What are the six lines of evidence that support the theory of endosymbiosis?

Answer 31

1. Morphology- form or shape of mitochondria and chloroplasts is similar to that of bacteria and archaea
2. Reproduction- can’t synthesize M or C
3. Genetic information- M and C contain their own DNA
4. Transcription and translation- both M and C compete these cycles
5. Electron transport- both have electron transport chains
6. Sequence analysis- sequencing of RNA that makes of ribosomes of C and M

Question 32

What is the model of endosymbiosis?

Answer 32

States that the prokaryotic ancestors of modern mitochondria and chloroplasts were engulfed by larger prokaryotic cells

Question 33

What is genome?

Answer 33

The complete complement of an organisms genetic material

Question 34

Where was the endomembrane system derived from?

Answer 34

The plasma membrane

Pockets of the plasma membrane may have extended inward and surrounded the nuclear region