How can we help?

You can also find more resources in our Help Center.

150 terms

Bio Final 2

STUDY
PLAY
evolution
all of the changes that have transformed life over an immense time
adaptation
an inherited characteristic that improves an organism's ability to survive and reproduce in a particular environment
descent with modification
process by which descendants of ancestral organisms spread into various habitats and accumulate adaptations to diverse ways of life
natural selection
process by which individuals with inherited characteristics well-suited to the environment leave more offspring than do other individuals
fossil
preserved remains or marking left by an organism that lived in the past
fossil record
chronological collection of life's remains in sedimentary rock layers
extinct
species that no longer exists
homologous structures
structure found in more than one species that share a common ancestor
vestigial structure
remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species
population
a group of individuals of the same species living in the same area at the same time
variation
refers to differences among members of the same species
artificial selection
the selective breeding of domesticated plants and animals to produce offspring with genetic traits that humans value
gene pool
all of the alleles in all the individuals that make up a population
microevolution
a generation-to-generation change in the frequencies of alleles within a population
Hardy-Weinberg equilibrium
condition that occurs when the frequency of alleles in a particular gene pool remain constant over time
genetic drift
change in the gene pool of a population due to chance
gene flow
exchange of genes between populations
fitness
contribution that an individual makes to the gene pool of the next generation compared to the contributions of other individuals (ability to reproduce)
antibiotic
medicine that kills or slows the growth of bacteria
biological species concept
definition of a species as a population or group of populations whose members can breed with one another in nature and produce fertile offspring
macroevolution
major biological changes evident in the fossil record
speciation
formation of new species
reproductive isolation
condition in which a reproductive barrier keeps two species from interbreeding
geographic isolation
separation of populations as a result of geographic change or migration to geographically isolated places
adaptive radiation
evolution from a common ancestor of many species adapted to diverse environments
punctuated equilibrium
evolutionary model suggesting species often diverge in spurts of relatively rapid change, followed by long periods of little change
embryology
study of multicellular organisms as they develop from fertilized eggs to fully formed organisms
geologic time scale
Earth's history organized into four eras: Precambrian, Paleozoic, Mesozoic, and Cenozoic
radiometric dating
determination of absolute ages of rocks and fossils through calculations based on a radioactive isotope's fixed rate of decay
half-life
time it takes for 50 percent of a radioactive isotope sample to decay
continental drift
motion of continents about Earth's surface on plates of crust floating on the hot mantle
mass extinction
episode of great species loss
taxonomy
identification, naming, and classification of species
binomial
two-part Latin name of a species
phylogenetic tree
branching diagram, suggesting evolutionary relationships, that classifies species into groups within groups
convergent evolution
process in which unrelated species from similar environments have adaptations that seem very similar
analogous structures
similarities among unrelated species that result from convergent evolution
derived character
homologous characteristic that unites organisms as a group
cladogram
phylogenetic tree constructed from a series of two-way branch points, suggesting ancestral relationships among species
genome
complete set of an organism's genetic material
histone
small protein that dna wraps around
trisomy 21
condition in which an individual has three number 21 chromosomes, resulting in down syndrome
down syndrome
general set of symptoms in people with trisomy 21
nondisjunction
event during meiosis in which homologous chromosomes or sister chromatids fail to separate
duplication
change to a chromosome in which part of the chromosome is repeated
deletion
change to a chromosome in which a fragment of the chromosome is removed
inversion
change to a chromosome in which a fragment of the original chromosome is reversed
translocation
change to a chromosome in which a fragment of one chromosome attaches to a nonhomologous chromosome
transposon
genetic element that moves from one location to another in a genome
pedigree
family tree that records and traces the occurrence of a trait in a family
carrier
individual who has one copy of the allele for a recessive disorder and does not exhibit symptoms
genetic counselor
person trained to collect, analyze, and explain data about human inheritance patterns
growth factor
protein that initiates cell division
tumor-suppressor gene
gene that codes for a protein that stops cell division in particular situations
oncogene
cancer-causing gene
recombinant DNA technology
technology that combines genes from different sources into a single DNA molecule
plasmid
small, circular DNA molecule found in bacteria that is separate from the bacterial chromosome
restriction enzyme
enzyme that cuts sugar-phosphate bonds in the DNA backbone at specific points within particular nucleotide sequences in DNA
genomic library
complete collection of cloned DNA fragments from an organism
nucleic acid probe
radioactively labeled nucleic acid molecule used to tag a particular DNA sequence
genetically modified organism (GMO)
organism that has acquired genetic material by artificial means
transgenic
genetically modified organism whose source of new genetic material is a different species
polymerase chain reaction (PCR)
technique that makes many copies of a certain segment of DNA without using living cells
gel electrophoresis
technique for sorting molecules or fragments of molecules by length
genetic marker
specific portion of DNA that varies among individuals
DNA fingerprint
an individual's unique banding pattern on an electrophoresis gel, determined by restriction fragments of the person's DNA
operon
cluster of genes and their control sequences
promoter
control sequence on an operon where RNA polymerase attaches to the DNA
operator
control sequence on an operon that acts as a switch, determining whether or not RNA polymerase can attach to the promoter
repressor
protein that binds to the operator and blocks attachment of RNA polymerase to the promoter
transcription factor
protein that regulates transcription by binding to promoters or to RNA polymerases
gene expression
transcription and translation of genes into proteins
cellular differentiation
increasing specialization in structure and function of cells during development of a multicellular organism
stem cell
cell with the potential to develop into one of several types of differentiated cells
homeotic gene
master control gene in many organisms that directs development of body parts
trait
a variation of a particular inherited character
genetics
the study of heredity
cross fertilization
when sperm from the pollen of one flower fertilizes the eggs in the flower of a different plant
hybrid
the offspring of two different true-breeding varieties
monohybrid cross
a pairing in which the parent plants differ in only one character
homozygous
when two of your alleles are the same for a certain characteristic
heterozygous
when two of your alleles are different for a certain characteristic
dominant
an allele in a heterozygous individual that appears to be the only one affecting that trait
recessive
an allele in a heterozygous individual that doesn't appear to affect a trait
punnett square
a type of diagram that shows all possible outcomes of a genetic cross
phenotype
an observable trait, the physical appearance
genotype
the genetic makeup, or combination of alleles
testcross
breeds an individual of unknown genotype, but dominant phenotype with a homozygous recessive individual
dihybrid cross
crossing organisms differing in two characters
codominance
inheritance pattern in which a heterozygote expresses the distinct traits of both alleles
polygenic inheritance
when two or more genes affect a single character
chromosome theory of inheritance
generalization that genes are located on chromosomes and that the behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns
gene locus
specific location of a gene on a chromosome
genetic linkage
the tendency for the alleles on one chromosome to be inherited together
sex-linked gene
gene located on a sex chromosome
virus
package of nucleic acid wrapped in a protein coat that must use a host cell's machinery to reproduce itself
bacteriophage
virus that infects bacteria
deoxyribonucleic acid (DNA)
molecule responsible for inheritance; nucleic acid that contains the sugar deoxyribose
nucleotide
building block (monomer) of nucleic acid polymer
nitrogenous base
a single or double ring of carbon and nitrogen atoms with functional groups
pyrimidine
single-ring nitrogenous base
purine
double-ring nitrogenous base
double helix
two strands of nucleotides wound about each other; structure of DNA
DNA replication
process of copying DNA molecules
DNA polymerase
enzyme that makes the covalent bonds between the nucleotides of new DNA strands
ribonucleic acid (RNA)
any nucleic acid containing the sugar ribose
transcription
process by which a DNA template is used to produce a single-stranded RNA molecule
messenger RNA
RNA molecule transcribed from a DNA template
RNA polymerase
transcription enzyme that links RNA nucleotides together
intron
internal noncoding region in RNA transcript
exon
coding region in RNA transcript
RNA splicing
process by which the introns are removed from RNA transcripts and the remaining exons are joined together
transfer RNA
RNA that translates the three-letter codons of mRNA to amino acids
anticodon
in tRNA, a triplet of nitrogenous bases that is complementary to a specific codon in mRNA
ribosomal RNA
RNA component of ribosomes
mutation
any change in the nucleotide sequence of DNA
mutagen
physical or chemical agent that causes mutations
asexual reproduction
process in which a single cell or set of cells produces without sex
sexual reproduction
process in which genetic material from 2 parents combines and produces offspring that differ genetically from either parent
chromatin
combination of DNA and protein molecules, in the form of long, thin fibers, making up the genetic material in the nucleus of a eukaryotic cell
chromosomes
condensed threads of genetic material formed from chromatin as a cell prepares to divide
sister chromatids
one of a pair of identical chromosomes created before a cell divides
centromere
region where 2 sister chromatids are joined tightly together
cell cycle
sequence of events from the production of a eukaryotic cell to the time the cell itself reproduces
interphase
stage of the cell cycle during which a cell carries out its metabolic processes an performs its functions in the body
mitotic phase
stage in the cell cycle when a cell is actively dividing
mitosis
process by which the nucleus and duplicated chromosomes of a cell divide and are evenly distributed, forming 2 daughter nuclei
cytokinesis
process by which the cytoplasm of a cell is divided in 2; usually follows mitosis and meiosis
spindle
framework of microtubules that guide the movement of chromosomes during mitosis and meiosis
centrosome
region of cytoplasmic material that in animals cells contain structures called centrioles
prophase
first stage of mitosis and of meiosis I and II, when the already replicated chromosomes condense
metaphase
second stage of mitosis and of meiosis I and II when the spindle is fully formed and all of the chromosomes are held in place
anaphase
third phase of mitosis and meiosis I and II, in which the sister chromatids separate and move toward the poles of the spindle
telophase
final stage of mitosis and of meiosis I and II, in which the chromosomes reach the spindle poles, nuclear envelopes, form around each set of daughter chromosomes, and the nucleoli reappear
cell plate
disk containing cell wall material that develops in plant cells during cytokinesis, eventually dividing the cell into 2 daughter cells
benign tumor
mass of cells that remain at their original site
malignant tumor
mass of abnormal cells resulting from uncontrolled cancer cell division
cancer
disease caused by severe disruption of the mechanisms that normally control the cell cycle
metastasis
spread of cancer cells beyond their original site in the body
meiosis
type of cell division that produces 4 cells, each with half as many chromosomes as the parent cell
karyotype
display of a person's 46 chromosomes
homologous chromosomes
one of matching pair of chromosomes, one inherited form each parent
sex chromosome
1 of 2 chromosomes of the 23rd pair of human chromosomes, which determine an individual's gender
diploid
having 2 homologous sets of chromosomes and inheriting all chromosomes from parents
zygote
diploid cell formed when the nucleus of a haploid sperm cell fuses with the nucleus of a haploid egg cell
haploid
having a single set of chromosomes
fertilization
the fusion of the nuclei and cytoplasm of a haploid sperm cell and a haploid egg cell, forming a diploid zygote
tetrad
group of 4 chromatids formed during prophase I of meiosis by the 2 sister chromatids in each of the 2 homologous chromosomes
crossing over
exchange of genetic material between homologous chromosomes during prophase I of meiosis
genetic recombination
new combination of genetic information in a gamete as a result of crossing over during prophase I and and meiosis