A2.1 origins of cells (HL)

Question 1

how was early earth believed to be?

Answer 1

• 4.5 billion years old
• been formed from a swirling mass of smaller particles that collided with one another and formed larger masses
• no atmosphere
• various objects from space impact the surface of earth causing temp to raise

Question 2

earths state 4 billion years ago

Answer 2

• impacts on the Earth’s surface began to decrease
• developing atmosphere at this time was thick with water vapour and other compounds being released by volcanic eruptions
• regular Lightning
  -carbon dioxide and methane, which were present in higher concentrations than today, allowed ultraviolet light to penetrate the early atmosphere and retained heat, resulting in high surface temperature

Question 3

possible compounds of earths early atmosphere

Answer 3

1. Methane
2. Ammonia
3. Water vapour
4. Carbon dioxide
5. Hydrogen sulfide
6. Hydrogen
7. Nitrogen

Question 4

possible compounds of earths early atmosphere (formulas)

Answer 4

1. CH4
2. NH3
3. H2O
4. CO2
5. H2S
6. H2
7. N2

Question 5

functions of life that unicellular and multicellular organisms carry out

Answer 5

1. metabolism
2. growth
3. reproduction
4. response
5. homeostasis
6. nutrition
7. excretion

Question 6

metabolism

Answer 6

Metabolism includes all the chemical reactions that occur within the organism. As a result of metabolism, cells can convert energy from one form into another.

Question 7

growth

Answer 7

growth refers to the increase in size or mass of an organism, which can involve cell division, enlargement, and differentiatio

Question 8

Reproduction

Answer 8

Reproduction involves hereditary molecules that can be passed to offspring.

Question 9

response

Answer 9

Responding to stimuli (or survival and adaptation, involving behaviors, physiological changes) in the environment is essential for an organism to survive.

Question 10

homeostatis

Answer 10

maintanance of a constant internal environment. ( to control fluctuating temperature and acid-base levels to create a constant internal environment)

Question 11

nutrition

Answer 11

Using a source of compounds with many chemical bonds that can be broken down to provide an organism with the energy necessary to maintain life is the basis of nutrition.

Question 12

Excretion

Answer 12

Excretion is essential to life because it enables those chemical compounds that an organism cannot use or that may be toxic or harmful to be released from the organism’s system.

Question 13

cell theory

Answer 13

• all organisms are composed of one or more cells
• cells are the smallest units of life
• all cells come from pre-existing cells.

Question 14

Robert Hooke use of the microscope

Answer 14

in 1665, after looking at cork through a self-built microscope he first described cells

Question 15

Antonie van Leeuwenhoek

Answer 15

observed the first living cells and referred to them as “animalcules”, meaning little animals

Question 16

botanist Matthias Schleiden

Answer 16

1838, botanist Matthias Schleiden stated that plants are made of “independent, separate beings” called cells. Matthias Schleiden made a similar statement about animals.

Question 17

louis Pasteur

Answer 17

louis Pasteur in the 1880s, have performed experiments to support the third principle. After sterilizing chicken broth (soup) by boiling it, Pasteur showed that living organisms would not “spontaneously” reappear. Only after exposure to pre-existing cells was life able to re-establish itself in the sterilized chicken broth.

Question 18

process that evolved to a cell

Answer 18

1. The synthesis of small carbon compounds from abiotic (non-living) molecules, such as demonstrated in the Miller-Urey experiment.
2. Small organic molecules joining to form large-chain molecules called polymers.
3. Polymers becoming contained by membranes, creating a protective homeostatic environment around the polymers, separate from their surroundings.
4. The development of self-replicating molecules so that inheritance and control can
   occur.

Question 19

enzymes

Answer 19

Enzymes are proteins that act as biological catalysts and accelerate chemical reactions. Enzymes are carbon compounds, which means they always contain the elements carbon and hydrogen, usually along with other elements.

Question 20

why is it doubtful that enzymes existed when protocells first formed

Answer 20

Scientists have been able to produce polymers from simple compounds by exposing them to hot sand, clay or rock. This vapourizes water from the simple compounds, and molecule chains are formed, suggesting that polymers could have formed on early Earth even if no enzymes were present.

Question 21

Inorganic compounds

Answer 21

Inorganic compounds do not usually contain carbon (an exception is carbon dioxide, which is considered to be an inorganic compound).

Question 22

Carbon compounds (often called organic compounds)

Answer 22

Carbon compounds (often called organic compounds) contain carbon and can be quite complex. It is these more complex compounds or molecules that make life possible, thus the element carbon can be said to be the keystone element for life on Earth.

Question 23

who conducted an experiment to stimulate the conditions thought to be present on early earth and when

Answer 23

1953
stanley miller
harold urey

Question 24

important concepts of the experiment

Answer 24

• the apparatus is initially charged with the simple inorganic compounds CH4, NH3 and H2, representing Earth’s early atmosphere
• heat is used to produce water vapour, which rises to the chamber containing the simple inorganic compounds
• two electrodes in this chamber produce 7,500 volts at 30 amps of electricity,
  representing the lightning that existed on early Earth
• cold water flows into the condenser to allow condensation of gaseous compounds from the chamber
• a sample is collected in the collecting device for chemical analysis.

Question 25

what did Miller identify

Answer 25

several simple organic molecules in the collecting device that are known to exist in organisms. These molecules included long chains of hydrogen and carbon, called hydrocarbons. He also found some of the building blocks of proteins called amino acids. Proteins are major biochemicals essential to all organisms

Question 26

whats the The fluid collected from the experiment called

Answer 26

The fluid collected during the experiment suggested to many scientists that life originated in a primordial soup, a water-based sea of simple organic molecules.

Question 27

why did Some scientist believe the gases used in the Miller-Urey experiment were not likely to have been present on early Earth

Answer 27

they believe the first atmosphere of our planet formed slowly over extended periods of time as a result of the release of gases from volcanoes. If this is accurate, the gases at this early stage in the Earth’s development would have originated from the planet’s mantle, an intermediate layer surrounded by the exterior crust and resting on the core.

also they beleived chemical properties of the mantle are the same today as they were in the past, and volcanic gases today do not contain methane or ammonia. If this is true, this hypothesis results in an early atmosphere that had the following composition:
* water vapour
- carbon dioxide
- sulfur dioxide
- small amounts of carbon monoxide and hydrogen sulfide.

Question 28

The Miller-Urey experiment and primordial soup theory have been questioned

Answer 28

due to concerns about protein breakdown in water, which contradicts the belief that complex molecules could form in a primordial soup environment, leading scientists to explore hydrothermal vents as a potential origin for life.

Question 29

why is Membrane formation crucial for Earth’s first cells

Answer 29

serving as a boundary between the cell and environment, enabling regulation and maintenance of cell activities.

Question 30

fatty acids

Answer 30

One of the carbon compounds thought to have been present on early Earth was a simple group known as fatty acids. These fatty acids, when present in water, display a polarity, with one end having water-attracting, hydrophilic, properties, and the other end having water-repelling, hydrophobic, properties. When large numbers of fatty acids are placed in water, they tend to organize themselves into small, cell-sized double-layer bubbles often referred to as vesicles.

Question 31

Laboratory-produced vesicles

Answer 31

Laboratory-produced vesicles can perform various processes such as engulfing organic molecules, growing, and replicating themselves.

Question 32

compartmentalization

Answer 32

compartmentalization, a boundary around a vesicle, was crucial for cell formation and evolved as cells evolved, allowing for specialization of functions within the outer protective fatty acid bilayer.

Question 33

RNA hypothesis

Answer 33

RNA, specifically ribonucleic acid, possibly played a key role in early cell formation due to its properties. RNA’s simplicity compared to DNA suggests it might have been the initial genetic material in early cells, governing their functions.

Question 34

RNA molecules display some interesting properties.

Answer 34

• RNA can assemble spontaneously from simpler organic molecules called nucleotides.
• RNA can form copies of itself, thus acting as a type of genetic material.
• RNA demonstrates the ability to control chemical reactions, thus acting in an enzymatic role

Question 35

An overview of the major stages in the origin of life

Answer 35

early Earth →
abiotic chemical compounds →
small organic molecules →
polymers of organic molecules →
protocell →
cell

Question 36

Evidence for the existence of a last universal common ancestor (LUCA) for all life on Earth

Answer 36

• DNA carries a universal genetic code shared by all cells.
• Over 300 genes or sections of DNA are common to all cells.
• Same building blocks for DNA and RNA in all cells.
• Common molecular processes within all cells, including DNA replication and protein production.
• Similar transport mechanisms for cellular materials in and out of cells.
• Other life forms with distinctive characteristics may have evolved over 3.5 billion years.

Question 37

What concept did Charles Darwin utilize in his theory of evolution?

Answer 37

Common ancestry, suggesting all life traces back to a single ancestor known as LUCA.

Question 38

When did the earliest life on Earth occur?

Answer 38

Approximately 3.5 billion years ago, according to various dating techniques.

Question 39

What dating method is considered accurate for fossils and how does it work?

Answer 39

Radiometric techniques, based on the half-life of radioactive isotopes. Isotopes accumulate in fossils when organisms are alive, and by measuring the isotope amount in fossils and comparing it with the live organism, the fossil’s age can be determined.

Question 40

What is absolute dating of a fossil’s age based on?

Answer 40

Absolute dating is based on comparing the isotope amount in fossils when alive to the amount in the fossil, using the constant rate of radioactive decay.

Question 41

How do radioactive isotopes help in determining a fossil’s age?

Answer 41

Radioactive isotopes have constant rates of uptake by organisms, so comparing the isotope amount in a fossil to the amount taken up when the organism was alive provides an estimate of the fossil’s age.

Question 42

How does relative dating of fossils differ from absolute dating?

Answer 42

Relative dating relies on sediment layers and index fossils, providing an estimate of a fossil’s age in comparison to the less exact absolute dating methods.

Question 43

What are sediments, and how are they used in relative dating?

Answer 43

Sediments are eroded rock or soil particles that form layers. In relative dating, the sequence of these layers (with the oldest at the bottom) helps estimate a fossil’s age.

Question 44

Why might relative dating provide inaccurate fossil ages?

Answer 44

Geological processes can disrupt the original sequence of sediment layers, potentially leading to inaccurate estimations of fossil ages.

Question 45

What are index fossils, and how do they aid in dating?

Answer 45

Index fossils are fossils of the same age found in strata across different parts of the world. Strata containing identical fossils are considered to be of the same age.

Question 46

How can we visualize Earth’s 4.5-billion-year existence using a 24-hour time span?

Answer 46

Using a 24-hour span to represent 4.5 billion years, each hour would represent a vast duration of time in Earth’s history, illustrating the immense length of its existence.

Question 47

What’s the proposed location for the origin of life on Earth, according to a hypothesis?

Answer 47

Hydrothermal vents, where hot water from beneath the ocean floor emerges, creating a mineral-rich environment.

Question 48

How do hydrothermal vents form, and what communities are found around them?

Answer 48

Hydrothermal vents result from cracks in the ocean floor crust, exposing seawater to heated rocks. Entire communities exist around these vents, including unique creatures like tube worms that rely on symbiotic bacteria for food.

Question 49

What was a significant discovery challenging the belief about life at the ocean bottom?

Answer 49

Discoveries of communities around hydrothermal vents disproved the notion of lifelessness due to lack of sunlight, supporting the idea of life’s potential origin in these environments.

Question 50

What evidence supports the hypothesis that the earliest life could have formed at hydrothermal vents?

Answer 50

Evidence includes ancient fossilized traces near these vents, genetic similarities in organisms suggesting a common ancestor, and a mineral-rich, chemically diverse environment conducive to life’s formation.

Question 51

What’s emphasized regarding the origin of life despite existing hypotheses?

Answer 51

Many unanswered questions persist about life’s origin. Continued research will present various hypotheses, necessitating an open-minded approach and reliance on experimentation to verify evidence.