Keystones Flashcards
science
organized way of gathering and analyzing evidence about the natural world
observations
the act of noticing and describing events or processes in a careful, orderly way
inference
logical interpretation based on what scientists already know
hypothesis
a scientific explanation for a set of observations that can be tested in ways that support or reject it
controlled experiment
an experiment that keeps track of various factors or variables that can change
independent variable
the variable that is deliberately changed
dependent variable
the variable that is observed and that changes in response to the independent variable
control group
a group exposed to the same conditions as the experimental group except for one independent variable
data
detailed records of experimental observations (gathering information)
theory
well tested explanation that unifies a broad range observations and hypothesis, and enables scientists to make accurate predictions about new situations
bias
a particular preference or point of view that is personal, rather than scientific
biology
the study of life
DNA
the complex information organisms need to live, grow, and reproduce in a genetic code written in a molecule
stimulus
a signal to which an organism responds
sexual reproduction
when cells form two parents unite to form the first cell of a new organism
asexual reproduction
when a single organism produces offspring identical to itself
homeostasis
relatively constant internal physical and chemical conditions that organisms maintain
metabolism
the combination of chemical reactions through which an organism builds up or breaks down materials
biosphere
part of earth in which life exists in luring land, water and air or atmosphere
atom
the basic unit of matter
nucleus
the center of an atom, where the protons and neutrons…
electron
a negatively charged particle
element
a pure substance that consists entirely of one type of atom
isotope
atoms of the same element that differ in the number of neutrons they contain
compound
a substance formed by the chemical combination of two or more elements in definite proportions
ionic bond
one or more electrons are transferred from one atom to another
ions
positively and negatively charged atoms
covalent bonds
moving electrons travel about the nuclei of both atoms
molecule
the smallest unit of most compounds
van der Waals forces
intermolecular forces of attraction
hydrogen bond
attraction between a hydrogen atom with a partical positive charge and another atom with a partical negative charge
cohesion
an attraction between molecules of the same substance
adhesion
an attraction between molecules of different substances
mixture
a material composed of two or more elements or compounds that are physically mixed together but not chemically combined
solution
type of mixture in which all the components are evenly distributed
solute
substance that is dissolved
suspensions
mixtures of water and nondissolved material
pH scale
scale with values from O-14, used to measure the concentration of H+ ions in a solution
acid
any compound that forms H+ ions in a solution
base
a compound that produces hydroxide ions in a solution
buffers
weak acids or bases that can react with strong acids or based to prevent sharp, sudden changes in pH
monomers
small chemical unit that makes up a polymer
polymer
molecules composed of many monomers; makes up macromolecules
carbohydrates
compounds made up of carbon, hydrogen, and oxygen atoms, usually in a ratio of 1:2:1
monosacchoricles
simple sugar molecules
lipids
a large and varied group of biological molecules that are generally not soluble in water
nucleic acids
macromolecules containing hydrogen, oxygen, nitrogen, carbon, and phosphorus; polymers assembled from nucleotides
nucleotides
subunit of which nucleic acids are composed; made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base
proteins
macromolecules that contain nitrogen as well as carbon, hydrogen, and oxygen
amino acids
compounds with an amino group one end a carboxyl group on the other end
chemical reaction
a process that changes, or transforms, one set of chemical into another
reactants
the elements of compounds that enter into a chemical reaction
products
the elements of compounds produced by a chemical reaction
activation energy
the energy needed to get a reaction started
catalyst
a substance that speeds up the rate of a chemical reaction
enzymes
proteins that act as biological catalysts (speed up chemical reactions that take place in cells)
cells
the basic unit of life
cell theory
a fundamental concept of biology
cell membrane
thin flexible barrier that surrounds all cells, regulates what goes in and out
nucleus
a large membrane enclosed structure that contains genetic material in the form of DNA; controls many of the cell’s activities
eukaryotes
cells that enclose their DNA in nuclei
prokaryotes
cells that do not enclose DNA in nuclei
cytoplasm
the portion of the cell outside the nucleus
organelles
specialized structure that performs important cellular functions within a cell
vacuoles
large, saclike, membrane-enclosed structures that store materials like water, salts, proteins, and carbohydrates
lysosomes
small organelles filled with enzymes
cytoskeleton
a network of protein filaments in a eukaryotic cell that gives the cell it’s shape and internal organization and is involved in movement
centrioles
structures in an animal cell that helps to organize cell division
ribosomes
small particles of RNA and protein found throughout the cytoplasm in all cells
endoplasmic reticulum
internal membrane system found in eukaryotic cells; place where lipid components of the cell membrane are assembled
Golgi apparatus
organelle in cells that modifies, sorts, and packages proteins and other materials from the endoplasmic reticulum for storage in the cell or release outside the cell
chloroplasts
the biological equivalents of solar power plants that capture the energy from sunlight and convert it into food that contains chemical energy in a process called photosynthesis
mitochondria
the power house of the cell; converts the chemical energy stored in food into compounds that are more convenient for the cell to use
cell wall
a strong supporting layer around the membrane
lipid bilayer
a double layered sheet that gives cell membranes a flexible structure that forms a strong barrier between the cell and its surroundings
selectively permeable
property of biological membranes that allows some substances to pass across it while others cannot
diffusion
the process by which particles move from an area of high concentration to an area of lower concentration
facilitated diffusion
the process in which molecules that cannot directly diffuse across the membrane pass through special protein channels
aquaporins
water channel proteins that allow water to pass right through them
osmosis
the diffusion of water through a selectively permeable membrane
isotonic
when the concentration of two solutions is the same
hypotonic
when comparing two solutions, the solution with the lesser concentration of solutes
osmotic pressure
the net movement of water out of or into a cell produces a force
tissue
a group of similar cells that performs a particular function
organ
group of tissues that work together to preform closely related functions
organ system
a group of organs that work together to preform a specific function
receptor
on or in a cell, a specific protein to whose shape fits that of a specific molecular messenger, such as a hormone
hypertonic
when comparing two solutions, the solution with the greater concentration of solutes
adenosine triphosphate
(ATP) compound used by cells to store and release energy
heterotrophs
organisms that obtain food by consuming other living things
autotrophs
organisms that make their own food
photosynthesis
the process by which autotrophs use the energy of sunlight to produce high-energy carbohydrates -sugars and starches- that can be used as food
pigment
light absorbing molecule used by plants to gather the sun’s energy
chlorophyll
the plants’ principle pigment
thykaloid
saclike photosynthetic membranes found in chloroplasts
stroma
fluid portion of the chloroplast, outside the thykaloid
NADP+
carrier molecule that transfers high-energy electrons from chlorophyll to other molecules
light-dependent reactions
set of reactions in photosynthesis that use energy from light to produce ATP and NADPH
light-independent reactions
set of reactions in photosynthesis that do not require light; energy from ATP and NADPH is used to build high-energy compounds such as sugar
photosystems
clusters of chlorophyll and proteins found in thylakoids
electron transport chain
series of electron carrier proteins that shuttle high-energy electrons during ATP-generating reactions
ATP synthase
cluster of proteins that span the cell membrane and allow hydrogen ions (H+) to pass through it
Calvin cycle
light-independent reactions of photosynthesis in which energy from ATP and NADPH is used to build high-energy compounds such as sugar
calorie
the amount of energy needed to raise the temperature of 1 gram of water 1 degree celsius
cellular respiration
the process that releases energy from food in the presence of oxygen
aerobic
pathways of cellular respiration that requires oxygen
anaerobic
pathways of cellular respiration that does not directly require oxygen, nor does it rely on an oxygen-requiring electron
glycolysis
the first set of reactions in cellular respiration; during glycolysis, one molecule of glucose, a 6-carbon compound, is transformed into 2 molecules of pyruvic acid, a 3-carbon compound; literally means “sugar breaking”
NAD+
an electron carrier; nicotinamide adenine dinucleotide; accepts a pair of high-energy electrons and becomes NADP
Krebs Cycle
the second stage of cellular respiration; pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions
matrix
the innermost compartment of the mitochondrion and the site of the Krebs cycle reactions
fermentation
the combined process of the pathway where oxygen is not present and glycolysis is followed by a pathway that make it possible to continue to produce ATP, and glycolysis; in the absence of oxygen, fermentation releases energy from food molecules by producing ATP
cell division
the process by which a cell divides into two new daughter cells
asexual reproduction
process of reproduction involving a single parent that results in offspring that are genetically identical to the parent
sexual reproduction
type of reproduction in which cells from two parents unite to form the first cell of a new organism
chromosome
threadlike structures of DNA and protein that contains genetic information; in eukaryotes, chromosomes are in the nucleus; in prokaryotes, chromosomes are in the cytoplasm
chromatin
substance found in eukaryotic chromosomes that consists of DNA tightly coiled around histones
cell cycle
series of events in which a cell grows, prepares for division, and divides to form two daughter cells
interphase
period of the cell cycle between cell divisions
mitosis
part of eukaryotic cell division during which the cell nucleus divides
cytokinesis
division of the cytoplasm to form two selects daughter cells
prophase
first and longest phase of mitosis in which the genetic material inside the nucleus condenses and the chromosomes become visible
centromere
region of a chromosome where the two sister chromatids attach
chromatid
one of two identical “sister” parts of a duplicated chromosome
centriole
structure in an animal cell that helps to organize cell division
metaphase
phase of mitosis in which the chromosomes line up across the center of the cell
anaphase
phase of mitosis in which the chromosomes separate and move to opposite ends of the cell
telophase
phase of mitosis in which the distinct individual chromosomes begin to spread out into a tangle of chromatin
cyclin
one of a family of proteins that regulates the cell cycle in eukaryotic cells
growth factor
on of a group of external regulatory proteins that stimulate the growth and division of cells
apoptosis
process of programmed cell death
cancer
disorder in which some of the body’s cells lose the ability to control growth
tumor
mass of rapidly dividing cells that can damage surrounding tissue
embryo
developing stage of a multicellular organism
differentiation
process in which cells become specialized in structure and function
totipotent
cells that are able to develop into any type of cell found in the body (including the cells tat make up the cells that make up the extra embryonic membranes and placenta)
blastocyst
stage of early development in mammals that consists of a hollow ball of cells
pluripotent
cells that are capable of developing into most, but not all, of the body’s cell types
multipotent
cells with limited potential to develop into many types of differentiated cells
stem cells
unspecialized cell that can give rise to one or more types of specialized cells
genetics
scientific study of heredity
fertilization
process in sexual reproduction in which male and female reproductive cells join to form a new cell
trait
specific characteristics of an individual
hybrid
offspring of crosses between parents with different traits
gene
sequence of DNA that codes for a protein and thus determines a trait
allele
one of a number of different forms of a gene
principal of dominance
Mendel’s 2nd conclusion, which states that some alleles are dominant and others are recessive
segregation
separation of alleles during gamete formation
gamete
sex cell
probability
likelyhood that a particular event will occur
homozygous
having two identical alleles for a particular gene
heterozygous
having two different alleles for a particular gene
phenotype
physical characteristics of an organism
genotype
genetic makeup of an organism
punnet square
diagram that can be used to predict the genotype and phenotype combinations of a genetic cross
independent assortment
one of Mendel’s principals that states genes for different traits can segregate independently during the formation of gametes
imcomplete dominance
situation in which one allele is not completely dominant over another allele
codominance
situation in which the phenotype produced by both alleles are completely expressed
multiple alleles
a gene that has more than one allele
polygenic trait
trait controlled by two or more genes
homologous
term used to refer to chromosomes in which one set comes from the male parent and one set comes from the female parent
diploid
term used to refer to a cell that contains two sets of homologous chromosomes
haploid
term used to refer to a cell that contains only a simple set of genes
meiosis
process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell
tetrad
structure containing four chromatids that forms during meiosis
crossing over
process in which homologous chromosomes exchange portions of their chromatids during meiosis
zygote
fertilized egg
transformation
process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria
bacteriophage
kind of virus that infects bacteria
base pairing
principle that bonds in DNA can form only between adenine and thymine and between guanine and cytosine
replication
process of copying DNA prior to cell division
DNA polymerase
principal enzyme involved in DNA replication
telomere
repetitive DNA at the end of a eukaryotic chromosome
RNA
nucleic acid that consists of a long chain of nucleotides
messenger RNA
type of RNA that carries copies of instructions for the assembly of amino acids into proteins from DNA to the rest of the cell
ribosomal RNA
type of RNA that combines with proteins to form ribosomes
transfer RNA
type of RNA that carries each amino acid to a ribosome during protein synthesis
transcription
synthesis of an RNA molecule from a DNA template
RNA polymerase
enzyme that links together the growing chain of RNA nucleotides during transcription using a DNA strand as a template
promoter
specific region of a gene where RNA polymerase can bind and begin transcription
intron
sequence of DNA that is not involved in coding for a protein
exon
expressed sequence of DNA, codes for a protein
polypeptide
long chain of amino acids that makes proteins
genetic code
collection of condons of mRNA, each of which directs the incorporation of a particular amino acid to be incorporated into a protein
codon
group of three nucleotide bases in mRNA that specify a particular amino acid to be incorporated into a protein
translation
process by which the sequence of bases of an mRNA is converted into the sequence of amino acids of a protein
anticodon
group of three bases in a tRNA molecule that are complementary to the three bases of a codon of mRNA
gene expression
process by which a gene produces its product and the product carries out its function
mutation
change in the genetic material of a cell
point mutation
gene mutation in which a single base pair in DNA has been changed
frameshift mutation
mutation that shifts the “reading frame” of the genetic message by inserting or deleting a nucleotide
mutagen
chemical or physical agents in the environment that interact with DNA and may cause a mutation
polyploidy
condition in which an organism has extra sets of chromosomes
operon
in prokaryotes, a group of adjacent genes that share a common operator and promoter and are transcribed into a single mRNA
operator
short DNA region, adjacent to the promoter of a prokaryotic operon, that binds repressor proteins responsible for controlling the rate of transcription of the operon
RNA interference
introduction of double stranded RNA into a cell to inhabit gene expression
differentiation
process in which cells become specialized in structure and function
homeotic gene
a class of regulatory genes that determine the identity of body parts and regions in an animal embryo. Mutations in these genes can transform one body part into another
homeobox gene
the homeobox is a DNA sequence of approximately 130 base pairs, found in many homeotic genes that regulate development. Genes containing this sequence are known as homeobox genes, and they code for transcription factors, proteins that bind to DNA, and they also regulate the expression of other genes
Hox gene
a group of homeotic genes clustered together that determine the head to tail identity of body parts in animals. All hox genes contain the homeobox DNA sequence
evolution
change over time; the process by which modern organisms have descended from ancient organisms
fossils
preserved remains or traces of ancient organisms
artificial selection
selective breeding of plants and animals to promote the occurrence of desirable traits in offspring
adaptation
heritable characteristics that increases an organism’s ability to survive and reproduce in an environment
fitness
how well an organism can survive and reproduce in its environment
natural selection
process by which organisms that are most suited to their environment survive and reproduce most successfully; also called survival of the fittest
biogeography
the study of past and present distribution of organisms
homologous structures
structures that are similar in different species of common ancestry
analogous structures
body parts that share a common function; but not structure
vestigial structure
structure that is inherited from ancestors but has lost much of all of its original function
extinct
term used to refer to a species that has no living members
paleontologist
scientist who studies fossils
relative dating
method of determining the age of a fossil by comparing its placement with that of fossils in other rock layers
index fossil
distinctive fossil that is used to compare the relative ages of fossils
radiometric dating
method for determining the age of a sample from the amount of a radioactive isotope to the nonradioactive isotope of the same element in a sample
half-life
length of time required for half of the radioactive atoms in a sample to decay
geologic time scale
timeline used to represent earth’s history
era
major division of geologic time; usually divided into two or more periods
period
division of geologic time into which eras are subdivided
plate tectonics
geologic process, such as continental drift, volcanoes, and earthquakes, resulting from plate movement
macroevolutionary patterns
changes in anatomy, phylogeny, ecology, and behavior that take place in clades larger than a single species
background extinction
extinction caused by slow and steady process of natural selection
mass extinction
event during which many species become extinct during a relatively short period of time
gradualism
the evolution of a species by gradual accumulation of small genetic changes over long periods of time
punctuated equilibrium
pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change
adaptive radiation
process by which a single species of a small group of species evolves into several different forms
convergent evolution
process by which unrelated organisms independently evolve similarities when adapting to similar environments
coevolution
process by which two species evolve in response to changes in each other over time
endosymbiotic theory
theory that proposes that eukaryotic cells formed from a symbiotic relationship among several different prokaryotic cells
