astrobio exam2

What are the six properties of life?

Order; reproduction; growth and development; energy utilization; response to environment; evolutionary adaptation.

What is order as a property of life?

Living systems have organized, structured components.

What does reproduction mean as a property of life?

Living organisms can produce offspring or replicate.

What is growth and development?

Organisms increase in size and undergo changes through their life cycle.

What is energy utilization?

Life uses energy to power its activities and metabolism.

What is response to environment?

Organisms react to environmental conditions and stimuli.

What is evolutionary adaptation?

Populations change over generations as traits affecting reproductive success become more common.

What did Anaximander propose about life?

Life originated in water and evolved from simpler to more complex forms.

What did Aristotle believe about species?

Species were fixed, independent, and did not evolve.

What was Lamarck's idea of evolution?

Organisms adapt during life and pass acquired characteristics to offspring.

What theory is Charles Darwin associated with?

Evolution by natural selection; published in The Origin of Species in 1859.

What did Darwin's Galápagos finches illustrate?

Related species from one ancestor adapted to different island environments.

What are the two key facts behind natural selection in the slides?

Overproduction/struggle for survival and individual variation.

What is the result of natural selection?

Unequal reproductive success among individuals.

What is artificial selection?

Humans choose organisms with desired traits to reproduce.

How are geological eras/epochs separated in the lecture's framing?

By changes in the dominant forms of life.

What definition of life is offered in the lecture?

Something that can reproduce and evolve through natural selection.

Why are viruses difficult to classify as alive?

They require host cells to survive and reproduce.

Why is a mule a tricky case in defining life?

It is a living offspring but is sterile and cannot reproduce.

Why are rock crystals not generally considered alive?

They can grow, but growth alone does not meet the full criteria for life.

Why is fire not considered alive despite using energy and growing?

It does not reproduce and evolve through natural selection as organisms do.

What does evolution unify in biology?

Living things share ancestors and their relationships are explained by evidence of evolutionary change.

What makes a scientific theory scientific according to the slides?

It is supported by evidence and makes testable, falsifiable predictions.

What is science's basic assumption about the universe?

The universe follows rules that can be investigated through observation.

How do the slides contrast science and religion?

Science builds testable, evidence-based explanations of the natural world; religion often addresses supernatural beliefs and moral frameworks.

What does it mean that science is amoral?

Science itself is not inherently moral or immoral; it can be used for good or bad.

Why are creationism/intelligent design not considered science in the lecture?

They do not make falsifiable predictions and invoke supernatural explanations rather than testable natural mechanisms.

What did Lord Kelvin estimate about Earth's age in 1862?

About 100 million years.

How did Kelvin's estimate of Earth's age change by 1897?

He revised it downward to about 24 million years.

Why did Kelvin underestimate the Sun's age?

He did not know that nuclear fusion powers the Sun.

Why did Kelvin underestimate Earth's age?

He did not know about radioactive heating from nuclear decay.

Who proposed that radioactivity heats Earth?

Ernest Rutherford suggested this in 1904.

Who recognized nuclear fusion as the Sun's power source in 1938?

Hans Bethe.

Which four elements make up about 96% of living mass?

Oxygen, carbon, hydrogen, and nitrogen (O, C, H, N).

Why is oxygen especially abundant in living organisms?

Because water (H₂O) is abundant in living matter.

Why is carbon well suited to organic chemistry?

It has four bonding sites and can form stable chains, networks, and strong double bonds.

Why is silicon considered less suitable than carbon for complex life chemistry?

Silicon-silicon chains are less common and its bonds are weaker; it does not form comparable strong double bonds.

What are carbohydrates used for?

Sugars and starches provide energy; cellulose provides cellular structure.

What are two major roles of lipids?

Store energy as fats and form membranes that separate cells and regulate exchange.

What are proteins made from?

Sequences of amino acids; there are 20 types used in life on Earth.

What do proteins do in cells?

Perform most cellular work; enzymes are protein catalysts.

What is DNA's role?

Stores the genetic code.

What is RNA's role in modern cells?

Helps carry out genetic instructions.

What is molecular handedness?

Molecules can occur in left- and right-handed forms that are mirror images.

What handedness do amino acids in Earth life use?

Living cells use left-handed amino acids.

What does the shared left-handedness of Earth's amino acids suggest?

All Earth life likely descended from the same original biochemical building blocks.

What is a prokaryote?

An organism whose cells lack a membrane-bound nucleus; bacteria and archaea are prokaryotes.

What is a eukaryote?

An organism whose cells contain a membrane-bound nucleus.

Were prokaryotes or eukaryotes first?

Prokaryotes appeared first.

Are all eukaryotes multicellular?

No. Eukaryotes can be single-celled, such as amoebas.

What are the three domains of life?

Bacteria, Archaea, and Eukarya.

Which domain is genetically more similar to Eukarya than Bacteria is?

Archaea.

What is metabolism?

The chemical reactions occurring within living organisms.

How do cells accelerate chemical reactions?

They gather raw materials, provide energy, and use enzymes as catalysts.

What happens when ATP becomes ADP?

ATP → ADP + energy; energy is released for cellular work.

How is ATP regenerated from ADP?

ADP + energy → ATP.

What molecule supplies energy for chemical manufacturing in all known life?

ATP (adenosine triphosphate).

What does photo- mean in metabolism terms?

Energy is obtained from light.

What does chemo- mean in metabolism terms?

Energy is obtained from chemical reactions.

What is an autotroph?

An organism that obtains its carbon by making organic matter from inorganic carbon, such as CO₂.

What is a heterotroph?

An organism that obtains carbon by consuming other organisms or organic matter.

What is a chemo-heterotroph?

Gets energy from chemicals/food and carbon from organic matter; animals are examples.

What is a photo-autotroph?

Uses light energy and fixes CO₂ into organic molecules; plants are examples.

What is a photo-heterotroph?

Uses light for energy but obtains carbon from organic food; found among some prokaryotes.

What is a chemo-autotroph?

Gets energy from chemical reactions and carbon from CO₂; some prokaryotes do this.

What is oxidation?

A chemical process in which an atom, ion, or molecule loses electrons.

What are three roles of water in Earth life?

Allows chemicals to contact/dissolve, transports materials into and out of cells, and participates in reactions such as photosynthesis.

What is DNA's overall shape?

A double helix made of two intertwined strands.

What forms DNA's backbone?

Alternating deoxyribose sugar and phosphate groups.

Where is genetic information encoded in DNA?

In the sequence of its nitrogenous bases.

What are DNA's four bases and pairing rules?

Adenine pairs with thymine (A–T); guanine pairs with cytosine (G–C).

What did Watson and Crick describe in 1953?

The double-helix structure of DNA.

Why might extraterrestrial life not use DNA?

Heredity and evolution require an information system, but DNA is the known system for Earth life—not necessarily all life.

What are lithophiles?

Organisms associated with rock environments ('rock lovers').

When may life have originated on Earth according to the slides?

Around 3.85 billion years ago.

What are two proposed settings for life's origin?

Underwater thermal vents and surface pools/ponds.

When was Earth's last global sterilization period estimated?

About 3.9–4.2 billion years ago.

What three lines of evidence are used for ancient life?

Carbon isotope ratios, stromatolites, and microfossils.

What is the significance of a low ¹³C/¹²C ratio in ancient rocks?

Life preferentially metabolizes carbon-12, leaving biological material relatively depleted in carbon-13.

What is the normal abundance ratio ¹³C/¹²C given in the slides?

About 1/89.

Why is isotope evidence for ancient life uncertain?

Metamorphism can alter the rocks; volcanic origins may erase or complicate the biological signature.

What are stromatolites?

Layered structures formed by microbial colonies that trap or induce mineral sediment layers.

How old are some of the ancient stromatolite-like rocks discussed?

About 3.5 billion years.

Where are stromatolites typically associated with in the slides?

Shallow-water environments such as tidal flats.

Why can stromatolites be ambiguous evidence?

Non-biological sedimentation can potentially mimic layered structures.

What are microfossils?

Microscopic structures in ancient rocks interpreted as possible fossilized microorganisms.

Why can proposed microfossils be controversial?

Non-biological processes may create similar structures, and some samples formed near deep-sea vents.

Why was early Earth's lack of atmospheric oxygen helpful for prebiotic chemistry?

Oxygen destroys or oxidizes many organic compounds.

What did the Miller–Urey experiment demonstrate?

Simple organic monomers can form abiotically through chemical reactions under simulated early-Earth conditions.

When was the Miller–Urey experiment performed?

1953.

What products did Miller–Urey produce after about a week?

Several biological amino acids, non-biological amino acids, formaldehyde, and sugars.

What gases were used in the classic Miller–Urey setup?

Methane (CH₄), ammonia (NH₃), hydrogen (H₂), and water vapor.

What was a limitation of the classic Miller–Urey atmospheric model?

Early Earth's atmosphere may have been mostly CO₂ with some CH₄, producing fewer organics in experiments.

What handedness did Miller–Urey amino acids have?

Equal amounts of left- and right-handed amino acids.

What did Juan Oró show in 1961?

HCN + NH₃ + energy can produce adenine, a component of RNA, DNA, and ATP.

What does the Murchison meteorite show about organic molecules?

Meteorites can contain abundant organic compounds, including more than 50 amino acids in this case.

What are two possible non-atmospheric sources of amino acids?

Meteorites/space-delivered material and chemical reactions near deep-sea vents.

Why are deep-sea vents considered possible origin sites?

They provide abundant chemical energy and protection from ultraviolet radiation.

How can monomers become polymers in proposed origin-of-life settings?

Concentration and dehydration, aided by evaporation, freezing, or mineral-surface catalysis.

How might hot springs help form polymers?

Evaporation concentrates organic molecules in the remaining solution.