A2.1 HL only

Question 1

Prebiotic age

Answer 1

hypothetical set of conditions present on the Earth around 3.7 to 4.0 billion years ago

Question 2

Proto-Earth

Answer 2

encompassing Earth in its first one billion years

Question 3

Extraplanetary objects

Answer 3

an astronomical object that exists outside the Solar System.

Question 4

Hadean Eon

Answer 4

the oldest eon and dates from 4.5–4.0 billion years ago. This time represents Earth’s earliest history, during which the planet was characterized by a partially molten surface, volcanism, and asteroid impacts

Question 5

inorganic molecules

Answer 5

Inorganic molecules are generally simple and are not normally found in living things. Although all organic substances contain carbon , some substances containing carbon, such as diamonds, are considered inorganic

Question 6

organic molecules

Answer 6

a complex molecule that is primarily made of carbon atoms bonded with other elements and/or other carbon atoms. All living things on Earth are composed of organic molecules

Question 7

unicellular

Answer 7

composed of a single cell

Question 8

multicellular

Answer 8

an organism that is made of many cells, such as plants, animals or fungi

Question 9

organelles

Answer 9

a subcellular structure that has one or more specific jobs to perform in the cell

Question 10

compartmentalization

Answer 10

the separation of the cell interior in distinct compartments with specific local conditions that allow the simultaneous occurrence of diverse metabolic reactions and processes

Question 11

Subcellular components

Answer 11

specific structures that take on sets of tasks within the cell, or they can be local regions of the cell defined by the concentration of molecules or distinct physical characteristics and proportions

Question 12

binary fission

Answer 12

the process of one cell simply dividing into two. It is most commonly used in archaea and bacteria, which are both prokaryotic organisms

Question 13

mitosis

Answer 13

the process by which a cell replicates its chromosomes and then segregates them, producing two identical nuclei in preparation for cell division.

Question 14

gametes

Answer 14

a reproductive cell of an animal or plant. In animals, female gametes are called ova or egg cells, and male gametes are called sperm

Question 15

paradox

Answer 15

contradictory-yet-interrelated elements that exist simultaneously and persist over time

Question 16

proto-cell

Answer 16

self-organized, endogenously ordered, spherical collection of lipidsproposed as a rudimentary precursor to cells

Question 17

Spontaneous generation theory

Answer 17

hypothetical process by which living organisms develop from nonliving matter

Question 18

LUCA

Answer 18

the hypothesized common ancestral cell from which thethree domains of life, the Bacteria, the Archaea, and the Eukarya originated

Question 19

Primordial Soup Theory

Answer 19

if energy is added to the gases that made up Earth’s early atmosphere, the building blocks of life would be created

Question 20

Polymerization

Answer 20

any process in which relatively small molecules, called monomers, combine chemically to produce a very large chainlike or network molecule, called a polymer

Question 21

Miller-Urey experiment

Answer 21

experimentalsimulationconducted in 1953 that attempted to replicate the conditions ofEarth’s earlyatmosphereandoceansto test whetherorganicmoleculescould be created abiogenically, that is, formed fromchemical reactionsoccurring betweeninorganicmolecules thought to be present at the time

Question 22

Scientific models

Answer 22

a physical and/or mathematical and/or conceptual representation of a system of ideas, events or processes

Question 23

Extraplanetary carbon compounds

Answer 23

organic compounds found on meteorites

Question 24

Panspermia theory

Answer 24

the concept that life may have originated elsewhere in the universe and reached Earth through space travel, potentially by microorganisms or even advanced extraterrestrial beings

Question 25

Monomers

Answer 25

atoms or small molecules that bond together to form more complex structures such as polymers

Question 26

Polymers

Answer 26

any of a class of natural or synthetic substances composed of very large molecules, called macromolecules, that are multiples of simpler chemical units called monomers

Question 27

covalent bonds

Answer 27

a chemical bond that involves the sharing of electrons to form electron pairs between atoms

Question 28

activation energy

Answer 28

The minimum energy required for a reaction to occur

Question 29

“RNA World” hypothesis

Answer 29

suggests that life on Earth began with a simple RNA molecule that could copy itself. The RNA world hypothesis suggests that life on Earth began with a simple RNA molecule that could copy itself without help from other molecules

Question 30

Phospholipids

Answer 30

a group of polar lipids that consist of two fatty acids, a glycerol unit and a phosphate group

Question 31

Hydrophilic head

Answer 31

phosphate group of a phospholipid

Question 32

Hydrophobic tails

Answer 32

fatty acid tails of a phospholipid

Question 33

Micelle

Answer 33

a collection of amphiphilic surfactant molecules that spontaneously aggregate in water in a concentration-dependent manner to produce a metastable aggregate

Question 34

Liposome

Answer 34

a tiny bubbled vesicle made up of similar material to a cell membrane and phospholipids, which are essential to the cell membrane

Question 35

lipid bilayers

Answer 35

a continuous double layer of lipid molecules in which membrane proteins are embedded

Question 36

Murchison meteorite

Answer 36

a meteorite that fell in Australia in 1969 near Murchison, Victoria. It belongs to a group of meteorites rich in organic compounds

Question 37

Ribozymes

Answer 37

catalytically active RNA molecules or RNA–protein complexes, in which solely the RNA provides catalytic activity

Question 38

Inferred evolutionary intermediate

Answer 38

steps in an evolutionary pathway that are assumed but there is no direct evidence of

Question 39

Prokaryotes

Answer 39

any organism that lacks a distinct nucleus and other organelles due to the absence of internal membranes

Question 40

Bacteria

Answer 40

single-celled microorganisms that lack a nuclear membrane, are metabolically active and divide by binary fission

Question 41

Archaea

Answer 41

single-celled microorganisms with structure similar to bacteria. They are evolutionarily distinct from bacteria and eukaryotes and form the third domain of life

Question 42

Extremophiles

Answer 42

an organism that thrives in extreme environments. Extremophiles are organisms that live in "extreme environments," under high pressure and temperature

Question 43

sedimentary rock

Answer 43

formed from pre-existing rocks or pieces of once-living organisms

Question 44

isotope

Answer 44

A form of a chemical element in which the atoms have the same number of protons (part of the nucleus of an atom) but with a different number of neutrons (part of the nucleus of an atom)

Question 45

half-life

Answer 45

The time required for a biological system, such as that of a human, to eliminate, by natural processes, half of the amount of a substance (such as a radioactive material) that has entered it

Question 46

Biomarkers

Answer 46

A biological molecule found in blood, other body fluids, or tissues that is a sign of a normal or abnormal process, or of a condition or disease

Question 47

Stromatolites

Answer 47

mineral structures built by microorganisms

Question 48

Hydrothermal vents

Answer 48

the result of seawater percolating down through fissures in the ocean crust in the vicinity of spreading centers or subduction zones

Question 49

mutation

Answer 49

a change in a DNA sequence

Question 50

Carcinogens

Answer 50

a substance, organism or agent capable of causing cancer

Question 51

Molecular clock

Answer 51

DNA and protein sequences evolve at a rate that is relatively constant over time and among different organisms

Question 52

obligate anaerobe

Answer 52

organisms that can grow and survive only in the absence of oxygen

Question 53

chemoautotroph

Answer 53

an organism that takes inorganic chemicals and transforms it into energy