Bio Final

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prokaryotes

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organisms with cells that lack membrane-bound nuclei and organelles

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eukaryotes

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organisms with cells that have membrane-bound nuclei and organelles

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coccus

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spherical-shaped prokaryotic cells

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bacillus

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rod-shaped prokaryotic cells

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spirillum

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helical prokaryotic cells

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bacteria

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one of two prokaryotic domains; organisms with cells that lack membrane-bound nuclei

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archaea

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the other prokaryotic domain; organisms cells that lack membrane-bound nuclei but that have some features that are more eukaryotic than prokaryotic; extremophiles

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eukarya

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the domain that includes all eukaryotic organisms

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extremophiles

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organisms that live in environmental conditions so extreme that few other species can survive there

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binary fission

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in prokaryotes, a method of asexual reproduction by “division in half”

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nucleoid

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a non-membrane-bound region in a prokaryotic cell where DNA is concentrated

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plasmids

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small, circular molecules of DNA that sometimes carry genes for antibiotic resistance in the cytoplasm of bacteria

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transformation

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a method of moving genetic material between bacteria in which prokaryotes acquire genes from their surrounding environment; the foreign DNA is directly taken up by the cell and expressed; these genes can be beneficial (giving a selective advantage) or pathogenic

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pathogenic

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harmful; causing disease

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conjugation

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a method of moving genetic material between bacteria in which two living prokaryotic cells physically join with one another

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pilus

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a structure that links one cell to another at the start of conjugation (“males” have this)

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F factor

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the DNA segment that confers the ability to form pili for conjugation; when a cell has the F factor plasmid it is said to be F+, which is heritable and contagious

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transduction

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a method of moving genetic material between bacteria in which the exchange of DNA between prokaryotes is made possible by phages, which reproduce by injecting their genetic material inside the bacterial cell, multiplying, and bursting from the cell

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phages

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viruses that infect bacteria

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specialized transduction

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the process where a virus integrates in a bacterial chromosome and later removes a piece of flanking bacterial genome sequence when the virus lyses the cell

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chemo-

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prefix that means energy comes from a high-energy molecule (like glucose)

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photo-

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prefix that means energy comes from light

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auto-

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prefix that means carbon dioxide is used as a carbon source

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hetero-

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prefix that means a more complex form of carbon is used as a carbon source

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-troph

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suffix meaning nourishment

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nucleus

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he organelle of a eukaryotic cell that contains the genetic material (chromosomes); site of all gene expression

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nuclear envelope

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the double membrane that surrounds the nucleus

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nucleolus

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a specialized structure in the nucleus, consisting of chromosomal regions containing rRNA genes and ribosomal proteins; site of rRNA synthesis

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nuclear pores

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pores in the nuclear envelope that regulate traffic with the cytoplasm (mRNA exits the nucleus through these)

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endomembrane system

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the collection of membranes inside and surrounding a eukaryotic cell, related either through direct physical contact or by the transfer of membranous vesicles

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endoplasmic reticulum

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an extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane (composed of rough and smooth ER)

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smooth endoplasmic reticulum

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the portion of the ER that is free of ribosomes; synthesizes lipids and degrades toxins

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rough endoplasmic reticulum

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the portion of the ER with ribosomes attached; where proteins targeted for export are synthesized

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signal sequence

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a sequence of about 20 amino acids at or near the leading end of a polypeptide that targets it to the endoplasmic reticulum or to other organelles in the eukaryotic cell

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signal recognition protein (SRP)

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a protein-RNA complex that recognizes a signal peptide as it emerges from a ribosome and directs the ribosome to the ER by binding a receptor protein on the ER

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Golgi apparatus

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an organelle in eukaryotic cells consisting of stacks of flat membranous sacs that modify, store, and route products of the ER and helps process proteins

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glycosylation

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the process in which carbohydrates are added to proteins in the Golgi apparatus

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cis face

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the side of the Golgi apparatus where proteins enter

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cisternae

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the folds of the Golgi apparatus

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trans face

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the distal side of the Golgi apparatus where proteins leave

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secretory vesicle

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the final transport vesicle that buds from the trans face of the Golgi apparatus; these bind and fuse with the internal face of the plasma membrane by interacting with specific membrane proteins

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microfilaments

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the smallest cytoskeletal fibers; made up of actin; play a critical role in cell motility, where they facilitate cellular migration or (in muscles) contraction

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actin

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the globular protein that makes up microfilaments

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intermediate filaments

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the medium-sized cytoskeletal elements; have a thick cable-like structure; play an important role in supporting cell structures and anchoring organelles in the correct position within the cell

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microtubules

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the largest cytoskeletal elements; hollow tubes consisting of rows of paired tubulin molecules; very important to major cellular events (like mitosis) and also have a major structural role within the cell

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myosin fibers

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molecular motors that drive muscle contractions

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lysosome

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a vesicular compartment in eukaryotic cells that are involved in breaking down material

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hydrolytic enzymes

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enzymes within lysosomes that degrade material within the vesicles

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vacuole

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storage organelles in animal cells; storage organelles that also control osmotic pressure

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turgor pressure

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osmotic pressure

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mitosis

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a process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase; conserves chromosome number by allocating replicated chromosomes equally to each of the daughter nuclei

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cell cycle

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an ordered sequence of events in the life of a cell, from its orgin in the division of a parent cell until its own division into two; composed of interphase (including G1, S, and G2 subphases) and M phase (including mitosis and cytokinesis)

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M phase

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the phase of the cell cycle that includes mitosis and cytokinesis

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interphase

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the period in the cell cycle when the cell is not dividing; during interphase, cellular metabolic activity is high, chromosomes and organelles are duplicated, and cell size may increase; interphase accounts for about 90% of the cell cycle

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G1 growth phase

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the first gap, or growth phase, of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs

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S phase

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the synthesis phase of the cell cycle; the portion of interphase in which DNA is replicated

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G2 growth phase

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the second gap, or growth phase, of the cell cycle, consisting of the portion of interphase before DNA synthesis begins

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karyokinesis

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the separation of chromosomes during mitosis (the division of genetic material)

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cytokinesis

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the division of cytoplasm during mitosis

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prophase

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the first stage of mitosis, in which the chromatin condenses into discrete chromosomes visible with a light microscope, the mitotic spindle begins to form, and the nucleolus disappears but the nucleus remains intact

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chromatids

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condensed, replicated chromosomes

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centromere

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in a duplicated chromosome, the region on each sister chromatid where they are most closely attached to each other by proteins that bind to specific DNA sequences; this close attachment causes a constriction in the condensed chromosome

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mitotic spindle

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an assemblage of microtubules and associated proteins that is involved in the movement of chromosomes during mitosis

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centrosomes

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structures present in the cytoplasm of animal cells that function as microtubule-organizing centers and are important during cell division (each has two centrioles)

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prometaphase

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the second stage of mitosis, in which the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the chromosomes

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spindle microtubules

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aka spindle fibers; attach to the condensed chromosomes at the centromere during prometaphase

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metaphase

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the third stage of mitosis, in which the spindle is complete and the chromosomes, attached to microtubules at their kinetochores, are all aligned at the metaphase plate

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metaphase plate

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an imaginary structure located at a plane midway between the two poles of a cell in metaphase on which the centromeres of all the duplicated chromosomes are located

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anaphase

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the fourth stage of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell

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spindle poles

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aka centrosomes; newly freed chromatids move rapidly toward the spindle pores during anaphase in mitosis; the spindle poles then move apart

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telophase

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the fifth and final stage of mitosis, in which daughter nuclei are forming and cytokinesis has typically begun

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molecular motors

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essential agents of physical movement in cells

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tubulin

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a polymer protein that composes spindle fibers

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kinetochore

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the structure at the point on the centromere where microtubules attach to chromatids

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cleavage furrow

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the first sign of cleavage in an animal cell; a shallow groove around the cell in the cell surface near the old metaphase plate

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cyclin dependent kinase (CDK)

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a protein kinase that is active only when attached to a certain cyclin

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cyclin

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a cellular protein that occurs in a cyclically fluctuating concentration and that plays an important role in regulating the cell cycle (they keep time)

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maturation promoting factor (MPF)

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a protein complex required for a cell to progress from late interphase to mitosis; a cyclin-CDK complex

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asexual reproduction

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the generation of offspring from a single parent that occurs without the fusion of gametes; individuals produce clones

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clones

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genetically identical offspring

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sexual reproduction

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a type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from both parents via the gametes

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life cycle

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the generation-to-generation sequence of stages in the reproductive history of an organism

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genes

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discrete units of hereditary information consisting of specific nucleotide sequences in DNA

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alleles

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any of the alternative versions of a gene that may produce distinguishable phenotypic effects

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homologous chromosomes

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a pair of chromosomes of the same length, centromere, and staining pattern that have genes for the same characters at corresponding loci (1 from father, 1 from mother)

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gametes

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haploid reproductive cells, such as eggs or sperm; unite during sexual reproduction to form diploid zygotes

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meiosis

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a modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication; it results in cells with half the number of chromosome sets as the original

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diploid cells

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cells containing two sets of chromosomes (2n)

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haploid cells

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cells containing one set of chromosomes (n)

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fertilization

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the union of haploid gametes to produce a diploid zygote

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zygote

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the diploid cell produced by the union of haploid gametes during fertilization; a fertilized egg

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sister chromatids

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two copies of a duplicated chromosome attached to each other by proteins at the centromere; while joined, two sister chromatids make up one chromosome; chromatids are eventually separated during mitosis or meiosis II

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nonsister chromatids

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chromatids that are not the same duplicated chromosome

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independent assortment

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homologous pairs line up independently during metaphase I; a source of genetic variation; which chromosome (maternal/paternal) goes to each daughter cell is random

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crossing over

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aka recombination; a source of genetic variation; the reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis

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morphology

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physical appearance

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character

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a heritable feature for which variants exist (ex. Seed color)

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trait

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a particular variant for a character (ex. Yellow seeds, green seeds)

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self-fertilize

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an organism fertilizing itself (ex. Pea plants transferring pollen from the stamens to the carpel on the same flower—Mendel had to control this)

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P generation

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100. P generation- parental generation; the true-breeding (homozygous) parent individuals from which F1 hybrid offspring are derived

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true-breeding

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all of the offspring of that individual have the same trait as the parent when the offspring are produced by self-pollination

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F1 generation

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the first filial, hybrid (heterozygous) offspring arising from a parental cross

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dominant trait

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the trait expressed in the F1 generation

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f2 generation

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the offspring resulting from interbreeding of the hybrid F1 generation

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recessive trait

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the trait that reappears in the F2 generation

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dominance test

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to test dominance, you cross two parents that are true-breeding for different traits; whichever phenotypic trait is found in the hybrid F1 generation is dominant

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homozygous

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having two identical alleles for a given gene

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heterozygous

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having two different alleles for a given gene

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genotype

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the genetic makeup, or set of alleles, of an organism

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phenotype

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the observable and physiological traits of an organism, which are determined by its genetic makeup

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dominant allele

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111. Dominant allele- an allele that is fully expressed in the phenotype of a heterozygote

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recessive allele

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an allele whose phenotypic effect is not observed in a heterozygote

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mendelian traits

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traits with simple dominant/recessive patterns

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monohybrid cross

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involves the crossing of individuals and the examination of a single character in their offspring

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punnett square

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a useful tool for predicting the genotypes and phenotypes of offspring in a genetic cross involving Mendelian traits

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test cross

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used to determine the genotype of an individual with a dominant trait; an individual with the dominant phenotype is crossed with a fully recessive individual

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dihybrid cross

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a cross between two organisms that are each heterozygous for both of the characters being followed

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the law of segregation

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alleles on homologous chromosomes will segregate during meiosis I

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the law of independent assortment

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if the genes for different characters reside on different chromosomes (or are far apart on the same chromosome, they will independently assort during meiosis as well

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rule of multiplication

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multiply individual probabilities of independent events together to find the probability of both events happening

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rule of addition

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if an event can occur in more than one way, the probability of that event occurring is equal to the sum of the probabilities of each way the event can occur

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wild type

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the phenotype most commonly observed in natural populations; also refers to the individual with that phenotype

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mutant phenotype

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a phenotype that is not wild type (can be dominant or recessive)

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sex chromosomes

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chromosomes responsible for determining the sex of an individual (X and Y)

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sex-linked genes

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genes located on either sex chromosome; most are on the X chromosome

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autosomes

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all chromosomes that are not sex chromosomes

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X-Y system

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system of sex determination in mammals; X and Y chromosomes pair together with little crossing over during meiosis; XX is female, XY is male

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hemizygous

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males are said to be this for sex-linked genes (as opposed to homo/heterozygous)

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X-O system

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system of sex determination in some insects; females have 2 copies of the X chromosome and males have only one copy; the sex of the offspring is determined by whether or not an X chromosome is present in the sperm that fertilizes the ovum

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Z-W system

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system of sex determination in some birds, insects, and fish; females are ZW, males are ZZ; therefore, it is the female (not the male) who determines the sex of the offspring

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haplo-diploid system

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system of sex determination in bees and ants; females develop from fertilized eggs and are diploid, males develop from unfertilized eggs and are haploid

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Barr body

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a dense object lying along the inside of the nuclear envelope in cells of female mammals, representing a highly condensed, inactivated X chromosome

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XIST gene

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the gene for the inactivation of the X chromosome

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genetic map

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an ordered list of genetic loci along a chromosome

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nucleotides

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nitrogenous bases (A, C, T, G)

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crossing over

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the reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis

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genetic recombination

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general term for the production of offspring with combinations of traits that differ from those found in either parent

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recombinant chromosomes

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a chromosome created when crossing over combines DNA from two parents into a single chromosome

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linked genes

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genes located on the same chromosome and that tend to be inherited together

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recombination frequencies

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frequencies of recombinant phenotypes in a population

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linkage map

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portrays the sequence of genes along a chromosome without giving the precise location of the genes

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map units

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1 map unit is equal to a 1% recombination frequency (1 centiMorgan)

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complete dominance

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the situation in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable (ex. Yellow and green seeds)

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incomplete dominance

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the situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele (ex. Pink flowers)

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codominance

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the situation in which both alleles are expressed in the phenotype of heterozygotes (ex. Blood groups)

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blood groups

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M, N, MN; distinguished by the presence of two specific proteins on the surface of red blood cells

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multiple alleles

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when more than two alleles exist within a population (ex. ABO blood groups)

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pleiotropy

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the ability of a single gene to have multiple effects (ex. Albinism and crossed eyes)

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epistasis

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a type of gene interaction in which the phenotypic expression of one gene alters that of another independently inherited gene (ex. Pigment in horses)

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quantitative character

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a heritable feature that varies continuously over a range rather than in an either-or fashion (ex. Skin color)

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polygenic inheritance

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an additive effect of two or more genes on a single phenotypic character (polygenic traits are encoded by multiple genes)

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pedigree

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a diagram of a family tree with conventional symbols, showing the occurrence of heritable characters in parents and offspring over multiple generations

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carriers

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individuals who are heterozygous at a given genetic locus for a recessively inherited disorder; the heterozygote is generally phenotypically normal for the disorder but can pass on the recessive allele to offspring

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cystic fibrosis

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a human genetic disorder caused by a recessive allele for a chloride channel protein; characterized by an excessive secretion of mucus and consequent vulnerability to infection; fatal if untreated; the heterozygous state might have been advantageous many years ago

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phenlyketonuria (PKU)

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a disease observed in individuals that are homozygous for the recessive allele; the main symptom is mental retardation; symptoms can be prevented by proper nutrition

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sickle cell disease

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a recessively inherited human blood disorder; common in people of African ancestry; heterozygotes are less susceptible to malaria

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Huntington's disease

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a hereditary disease that causes progressive damage to the nervous system; develops late in life; caused by a dominant allele

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polar molecule

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a molecule with an uneven distribution of charges in different regions

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covalent bond

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bonds that involve the sharing of electrons

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hydrogen bond

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a type of weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule or in another region of the same molecule

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cohesion

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the linking together of like molecules, often by hydrogen bonds

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surface tension

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resistance to disruption at the surface

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specific heat

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the amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1 degree Celsius

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heat of vaporization

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the quantity of heat a liquid must absorb for 1 g of it to be converted from the liquid to the gaseous state

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solvent

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the dissolving agent of a solution (water is the most versatile)

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hydrophilic

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dissolving readily in water

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hydrophobic

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not interacting with water

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amphipathic

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having the ability to be both hydrophobic and hydrophilic

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inorganic compounds

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compounds that do not contain carbon

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organic compounds

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compounds that contain carbon

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electrons

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negatively charged parts of an atom

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valence

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the bonding capacity of a given atom (# of unpaired electrons in the outermost shell)

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macromolecules

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giant molecules formed by the joining of smaller molecules (four classes: carbohydrates, lipids, proteins, nucleic acids)

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anabolism

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the general process of joining monomers to form polymers

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catabolism

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the general process of breaking down a polymer into its monomers

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condensation synthesis

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an anabolic reaction in which two molecules become covalently bonded to each other with the removal of a water molecule

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hydrolysis

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a catabolic reaction whereby a polymer is broken down by the addition of water

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carbohydrate

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a sugar or one of its dimers or polymers; general formula of C(H2O)n; can be used for energy storage and as structural molecules

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nucleic acids

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organic compounds that make up RNA and DNA

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monosaccharides

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simple sugars; the basic monomeric units of carbohydrates

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disaccharide

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a sugar formed by a condensation reaction between two monosaccharides

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polysaccharide

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polymers consisting of up to several thousand monomers of simple sugars

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lipids

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any of a group of large biological molecules, including fats, phospholipids, and steroids, that mix poorly, if at all, with water

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triacylglycerols

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formed when three fatty acid molecules and one glycerol molecule join via condensation synthesis

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saturated fats

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fats that do not have double bonds

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unsaturated fats

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fats that have double bonds

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phospholipids

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a type of biomolecule that makes up the cell membrane; made up of two fatty acid molecules and glycerol attached to a hydrophilic “head”

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steroids

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a group of lipids characterized by fused ring structures

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proteins

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biologically functional molecules consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure

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amino acid

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an organic molecule possessing both a carboxyl and an amino group; the monomers of polypeptides

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polypeptides

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polymers (chains) of amino acids

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peptide bond

Back 192

the covalent bond between the carboxyl group on one amino acid and the amino group on another, formed by a dehydration reaction

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deoxyribonucleic acid (DNA)

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a double-stranded, helical nucleic acid molecule, consisting of nucleotide monomers with a deoxyribose sugar and the nitrogenous bases adenine, cytosine, guanine, ant thymine; capable of being replicated and determining the inherited structure of a cell’s proteins

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ribonucleic acid (RNA)

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a type of nucleic acid consisting of a polynucleotide made up of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine, cytosine, guanine, and uracil; single-stranded; functions in protein synthesis, gene regulation, and as the genome of some viruses

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nitrogenous bases

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ringed structures consisting of nitrogen, carbon, and hydrogen (A,C,T,G,U)

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origins of replication

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sites where the replication of a DNA molecule begins, consisting of a specific sequence of nucleotides

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helicases

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enzymes that untwist the double helix of DNA at replication forks, separating the two strands and making them available as template strands

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single strand binding proteins

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proteins that bind to the unpaired DNA strands during DNA replication, stabilizing them and holding them apart while they serve as templates for the synthesis of complementary strands of DNA

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primases

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enzymes that join RNA nucleotides to make a primer during DNA replication, using the parental DNA strand as a template

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DNA polymerase

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an enzyme that catalyzes the elongation of new DNA by the addition of nucleotides to the 3’ end of an existing chain

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antiparallel

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referring to the arrangement of the sugar-phosphate backbones in a DNA double helix (they run in opposite 5’→3’ directions)

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leading strand

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the new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5’→3’ direction

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lagging strand

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a discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5’→3’ direction away from the replication fork

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replication fork

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a Y-shaped region on a replicating DNA molecule where the parental strands are being unwound and new strands are being synthesized

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primer

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a short stretch of RNA with a free 3’ end, bound by complementary base pairing to the template strand and elongated with DNA nucleotides during DNA replication

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Okazaki fragments

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short segments of DNA synthesized away from the replication fork on a template strand during DNA replication; many are joined together to make up the lagging strand of newly synthesized DNA

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ligase

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an enzyme that seals the Okazaki fragments into a continuous strand of DNA

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transcription

Back 208

the synthesis of RNA using a DNA template

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translation

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the synthesis of a polypeptide using the genetic information encoded in an mRNA molecule; there is a change of “language” from nucleotides to amino acids

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genetic code

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the nucleotide triplets of DNA and RNA molecules that carry information

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codon

Back 211

a three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code

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messenger RNA (mRNA)

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a type of RNA, synthesized using a DNA template, that attaches to ribosomes in the cytoplasm and specifies the primary structure of a protein

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template strand

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the DNA strand that provides the pattern for ordering, by complementary base pairing, the sequence of nucleotides in an RNA transcript

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RNA polymerase

Back 214

enzyme that separates the DNA strands and joins the RNA nucleotides along the exposed DNA template

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transcription factors

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regulatory proteins that bind to DNA and affect transcription of specific genes

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promoter

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a specific nucleotide sequence in the DNA of a gene that binds RNA polymerase, positioning it to start transcribing RNA at the appropriate place

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terminator sequence

Back 217

a specific RNA sequence that signals the end of RNA synthesis

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ribosomal RNA (rRNA)

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RNA molecules that, together with proteins, make up ribosomes

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transfer RNA (tRNA)

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RNA molecules that function as translators between nucleic acid and protein languages by carrying specific amino acids to the ribosome, where they recognize the appropriate codons in the mRNA

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ribosomes

Back 220

cellular structures where polypeptides form

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anticodon

Back 221

a sequence of three nucleotides that is complementary to a sequence of bases in the mRNA strand (in tRNA)

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aminoacyl tRNA synthetase

Back 222

the enzyme that insures that a given tRNA molecule picks up only its particular amino acid

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initiation

Back 223

first stage of translation; mRNA binds to the small subunit of a ribosome; an initiation codon (AUG) binds with an initiator tRNA molecule and the amino acid methionine; then a large subunit of a ribosome attaches

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elongation

Back 224

second stage of translation; the peptide grows by addition of amino acids according to the sequence of bases in the mRNA molecule; this is accomplished through codon recognition, peptide bond formation, and translocation (tRNA goes from A site to P site to E site)

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aminoacyl-tRNA

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a tRNA carrying this binds to the A-site and a peptide bond forms between the new amino acid and the end of the growing polypeptide during elongation

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termination

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third and final stage of translation; a stop codon signals the end of translation; a release factor protein binds to the stop codon and the newly synthesized polypeptide is liberated

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stop codon

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codons that signal the end of translation

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release factor protein

Back 228

proteins that bind to the stop codon (instead of a tRNA)

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gene regulation

Back 229

describes how genes can be “turned on” to synthesize a needed protein, or “turned off” to stop synthesis of a protein that is no longer needed

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population

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a group of organisms that are members of the same species and that live in the same geographical area

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species

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a group of potentially interbreeding individuals that can produce fertile offspring

Front 232

gene flow

Back 232

the transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes

Front 233

gene pool

Back 233

the aggregate of all copies of every type of allele at all loci in every individual in a population; also the aggregate of alleles for just one or a few loci in the population

Front 234

range

Back 234

the area that a species occupies

Front 235

monomorphic

Back 235

just one form of a certain gene exists within a population

Front 236

polymorphic

Back 236

multiple forms of a certain gene exist within a population

Front 237

Hardy Weinburg equation

Back 237

p2 + 2pq + q2 = 1

Front 238

genetic drift

Back 238

random changes in the gene pool

Front 239

macroevolutionary

Back 239

describes evolutionary changes that mark the appearance of a new species

Front 240

microevolutionary

Back 240

describes evolutionary changes that lead to alterations in allele frequencies

Front 241

bottleneck effect

Back 241

a type of genetic drift in which an event (such as an earthquake or fire) decimates a population and results in only a small fraction of the population surviving

Front 242

founder effect

Back 242

a type of genetic drift in which a few individuals become geographically separated from the original population and form a new colony

Front 243

inbreeding

Back 243

the mating of closely related individuals

Front 244

mutation

Back 244

a change in an organism’s DNA

Front 245

positive assortative mating

Back 245

a mating scheme where individuals of like phenotypes mate

Front 246

negative assortative mating

Back 246

a mating scheme where individuals of like phenotypes do not mate

Front 247

fitness

Back 247

reproductive success

Front 248

stabilizing selection

Back 248

selection that favors intermediate variants by acting against extreme phenotypes

Front 249

directional selection

Back 249

selection that favors individuals that are at one end of the phenotypic range, usually during periods of environmental change

Front 250

diversifying selection

Back 250

selection that favors individuals at both extremes of the phenotypic range, usually during periods of environmental change

Front 251

balancing selection

Back 251

selection that works to maintain a dynamic state of balance between advantageous and disadvantageous alleles (ex. Sickle-cell anemia)

Front 252

heterozygotic advantage

Back 252

as with sickle-cell disease, when carriers of a recessive allele have an advantage over homozygotes

Front 253

frequency-dependent selection

Back 253

an example of balancing selection, in which if a trait provides prey to with an ability to avoid predation, their fitness is increased; if the frequency of this trait becomes too high, more predators will have adapted and it will no longer increase fitness

Front 254

sexual selection

Back 254

the selection of a mate based on a specific heritable trait; not a mode of natural selection; based on secondary sex characteristics

Front 255

sexual dimorphism

Back 255

differences in secondary sex characteristics

Front 256

cladogenesis

Back 256

the process of a new species arising and the new species and parental species coexisting

Front 257

speciation

Back 257

an evolutionary process in which one species splits into two or more species

Front 258

biological species concept

Back 258

defines a species as a group of individuals who interbreed or have the potential to interbreed in nature

Front 259

morphological species concept

Back 259

defines a species as a group of individuals with shared morphologies (appearances)

Front 260

evolutionary species concept

Back 260

defines a species as a group with shared evolutionary history

Front 261

reproductive isolation

Back 261

the existence of biological factors (barriers) that impede members of two species from producing viable, fertile offspring

Front 262

prezygotic barrier

Back 262

reproductive isolation that blocks fertilization

Front 263

hybrid

Back 263

offspring that results from the mating of individuals from two different species or from two true-breeding varieties of the same species

Front 264

postzygotic barrier

Back 264

reproductive isolation that prevents complete development after a hybrid zygote has been formed

Front 265

habitat isolation

Back 265

prezygotic barrier in which two species don’t interbreed because they occupy an overlapping territory but use different habitats

Front 266

temporal isolation

Back 266

prezygotic barrier in which two species don’t interbreed because they are receptive to mating at different times of the day or year

Front 267

behavioral isolation

Back 267

prezygotic barrier in which two species don’t interbreed because they exhibit different behaviors

Front 268

gametic isolation

Back 268

prezygotic barrier in which two species don’t interbreed because their gametes do not form a zygote

Front 269

mechanical isolation

Back 269

prezygotic barrier in which two species don’t interbreed because differences in size and shape of genitalia (or flower structures) prevent successful mating

Front 270

reduced hybrid viability

Back 270

postzygotic barrier in which hybrids lack vigor and rarely, if ever, reach sexual maturity

Front 271

reduced hybrid fertility

Back 271

postzygotic barrier in which hybrids are usually sterile

Front 272

hybrid breakdown

Back 272

postzygotic barrier in which hybrids are capable of reproducing but their offspring have either reduced fertility or reduced viability

Front 273

allopatric speciation

Back 273

type of speciation that occurs when populations become physically isolated due to some sort of geographical barrier

Front 274

sympatric speciation

Back 274

type of speciation that occurs when populations become genetically isolated, even though their ranges overlap

Front 275

adaptive radiation

Back 275

the relatively rapid evolution of many new species from a single common ancestor into diverse habitats

Front 276

polyploidy

Back 276

a chromosomal alteration in which the organism possesses more than two complete chromosome sets; the result of an error in cell division

Front 277

exaptations

Back 277

structures that arise and are used in one context but in another context have different or additional functions

Front 278

homeotic genes

Back 278

genes that determine the placement of body parts

Front 279

homeosis

Back 279

the general term for any mutation that results in a misplaced organ

Front 280

heterochrony

Back 280

an alteration in time, or a change in order, of one or more events

Front 281

paedomorphosis

Back 281

a condition in which the timing of sexual maturity is altered

Front 282

allometric growth

Back 282

disproportionate growth; not all parts of the organ and/or organism grow at the same rate

Front 283

plate tectonics

Back 283

the movement of landmasses by geological activity

Front 284

continental drift

Back 284

the continents constantly arranging themselves as a result of crust movement

Front 285

pangaea

Back 285

the supercontinent comprising all landmasses 250 million years ago

Front 286

fossils

Back 286

preserved remnants of organisms or whole organisms embedded where bacteria can’t decompose them, or other forms (such as a footprint)

Front 287

sedimentary rock

Back 287

rock formed by layers of minerals that settle in water (best source of fossils)

Front 288

geological time scale

Back 288

how the explosions of life or mass extinctions mark the general age of Earth

Front 289

precambrian, paleozoic, mesozoic, cenozoic

Back 289

the four great eras of the geological time scale

Front 290

isotopes

Back 290

variations of an element with different numbers of neutrons

Front 291

radiometric dating

Back 291

the procedure of using elements with radioactive isotopes that decay at known rates to date various rocks, including those containing fossils

Front 292

half life

Back 292

the amount of time it takes for one-half of the parental atom population to decay into daughter atoms

Front 293

radiocarbon dating

Back 293

radiometric dating using carbon-14, which decays into nitrogen-14

Front 294

dendrochronology

Back 294

an absolute dating technique that relies on the fact that tree growth occurs in spurts; trees have annual growth rings that reflect their ages and often reveal something about past climate conditions

Front 295

isomer

Back 295

one of several compounds with the same molecular formula but different structures and therefore different properties

Front 296

amino acid racemization

Back 296

the chemical conversion of L-form amino acids to D-form amino acids; knowing this rate for a given amino acid allows scientists to date some fossils

Front 297

metabolism

Back 297

v=all of the chemical reactions that occur in an organism

Front 298

energy

Back 298

that which can or does move matter; the capacity for doing work

Front 299

kinetic energy

Back 299

energy that is associated with moving matter

Front 300

potential energy

Back 300

energy that is stored

Front 301

thermodynamics

Back 301

the physics of energy transformations that occur in a collection of matter

Front 302

first law of thermodynamics

Back 302

states that energy is neither created nor destroyed; in other words, the amount of energy in the universe is constant

Front 303

second law of thermodynamics

Back 303

states that all energy-affected matter in the universe is becoming matter; in other words, the total entropy in the universe is increasing

Front 304

entropy

Back 304

a measure of disorder or randomness; a spontaneous reaction will increase this

Front 305

free energy

Back 305

the energy available (or required) to do work in a given system

Front 306

endergonic

Back 306

describes a reaction in which deltaG is positive (energy enters the system); a nonspontaneous reaction

Front 307

exergonic

Back 307

describes a reaction in which deltaG is negative (energy leaves the system); a spontaneous reaction

Front 308

spontaneous reaction

Back 308

an exergonic reaction (negative deltaG); energetically favorable

Front 309

enthalpy

Back 309

the total energy in a system

Front 310

exothermic

Back 310

describes a reaction with a negative deltaH (heat is released)

Front 311

endothermic

Back 311

describes a reaction with a positive deltaH (heat is absorbed)

Front 312

mechanical work

Back 312

type of work that contracts muscle cells

Front 313

transport work

Back 313

type of work that moves substances across the cell membrane

Front 314

chemical work

Back 314

type of work that causes nonspontaneous reactions between molecules

Front 315

adenosine triphosphate (ATP)

Back 315

a major source of chemical energy for work; a 5-carbon sugar attached to a nitrogenous base (adenine) and a group of 3 phosphates

Front 316

energy coupling

Back 316

the use of an exergonic process to drive an endergonic process

Front 317

non-spontaneous

Back 317

describes a reaction that is energetically unfavorable

Front 318

cellular respiration

Back 318

a catabolic pathway comprised of a series of steps that convert chemical energy in glucose into the energy contained in ATP

Front 319

redox

Back 319

the transfer of electrons that occurs during many chemical reactions

Front 320

reduction

Back 320

gain of electrons

Front 321

oxidation

Back 321

loss of electrons (the conversion of an aldehyde to a carboxylic acid group is this kind of reaction)

Front 322

electronegativity

Back 322

the affinity for electrons

Front 323

dehydrogenase

Back 323

in the presence of this enzyme and hydrogen, NAD+ can be reduced to NADH

Front 324

cytosol

Back 324

the protein-rich, semi-fluid part of the cell in which the cell’s organelles are immersed; where glycolysis takes place

Front 325

glycolysis

Back 325

first step of cellular respiration; involves the initial breakdown of glucose to pyruvate

Front 326

pyruvate

Back 326

glucose is broken down into this during glycolysis

Front 327

substrate-level phosphorlyation

Back 327

the enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism

Front 328

fermentation

Back 328

a catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid; NAD+ is regenerated

Front 329

alcohol fermentation

Back 329

glycolysis followed by the reduction f pyruvate to ethyl alcohol, regenerating NAD+ and releasing carbon dioxide

Front 330

lactic acid fermentation

Back 330

glycolysis followed by the reduction of pyruvate to lactate, regenerating NAD+ with no release of carbon dioxide

Front 331

Krebs cycle

Back 331

the second stage of cellular respiration; a chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing acetyl CoA to carbon dioxide; occurs within the mitochondrial matrix

Front 332

FAD

Back 332

an electron carrier in the Krebs cycle

Front 333

mitochondrion

Back 333

an organelle in eukaryotic cells that serves as the site of cellular respiration; uses oxygen to break down organic molecules and synthesize ATP

Front 334

electron transport chain

Back 334

a sequence of electron carrier molecules that shuttle electrons down a series of redox reactions that release energy used to make ATP

Front 335

protons

Back 335

positively charged hydrogen atoms (H+)

Front 336

charge differential (voltage)

Back 336

this is created in the inner mitochondrial membrane by the movement of protons by the electron transport chain; used to synthesize ATP

Front 337

terminal electron acceptor

Back 337

the final acceptor of electrons in the ETC, usually oxygen

Front 338

mitochondrial matrix

Back 338

the part of the mitochondrion enclosed within the inner membrane, which houses the enzymes and substrates for the Krebs cycle

Front 339

chemiosmosis

Back 339

an energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP

Front 340

ATP synthase

Back 340

a protein complex that functions in chemiosmosis with adjacent electron transport chains, using the energy of a proton concentration gradient to make ATP

Front 341

oxidative phosphorylation

Back 341

the generation of ATP from chemiosmosis

Front 342

activation energy

Back 342

the amount of energy that reactants must absorb before a chemical reaction will start

Front 343

catalysts

Back 343

chemical agents that selectively increase the rate of a reaction without being consumed by the reaction

Front 344

enzymes

Back 344

macromolecules serving as catalysts; most are proteins

Front 345

substrate

Back 345

the reactant on which an enzyme works

Front 346

active site

Back 346

the specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs

Front 347

enzyme-substrate complex

Back 347

the unit that forms when an enzyme and its substrate(s) join

Front 348

coenzymes

Back 348

organic molecules serving as cofactors; required for normal catalytic functioning of enzymes

Front 349

feedback inhibition

Back 349

a form of metabolic regulation in which a reaction’s end products inhibit the reaction itself by halting it when a certain amount of product has accumulated

Front 350

allosteric regulation

Back 350

noncompetitive inhibition; an inhibitor binds to a site distant from the active site and causes a conformational change in the enzyme thereby decreasing its ability to bind with the substrate and hence catalyze the reaction

Front 351

allosteric enzymes

Back 351

enzymes that change their conformation upon the binding of an effector

Front 352

phosphofructokinase (PFK)

Back 352

an important enzyme that is involved in the early stages of glycolysis

Front 353

kinases

Back 353

a family of enzymes that moves phosphate groups from energy-containing molecules (like ATP) to other organic molecules)

Front 354

endosymbiosis

Back 354

a process in which a unicellular organism (the “host”) engulfs another cell, which lives within the host cell and ultimately becomes an organelle in the host cell

Front 355

serial endosymbiosis

Back 355

sequential endosymbiotic events

Front 356

extant

Back 356

currently existing

Front 357

cyanobacteria

Back 357

a group of bacteria that is capable of photosynthesis

Front 358

photosynthesis

Back 358

the conversion of light energy to chemical energy that is stored in sugars or other organic compounds; occurs in plants, algae, and certain prokaryotes

Front 359

photochemistry

Back 359

the sun’s energy being transformed into electrical energy

Front 360

algae

Back 360

a diverse grade of photosynthetic protists, including unicellular and multicellular forms

Front 361

wavelengths

Back 361

the peak-to-peak distance between oscillations

Front 362

thylakoids

Back 362

flattened, membranous sacs inside chloroplasts, in which photosynthesis occurs

Front 363

chloroplasts

Back 363

organelles found in plants and photosynthetic protists that absorb sunlight and use it to drive the synthesis of organic compounds from carbon dioxide and water

Front 364

grana

Back 364

stacks of thylakoids in chloroplasts

Front 365

photosystems

Back 365

light-capturing units located in the thylakoid membrane of the chloroplast or in the membrane of some prokaryotes, consisting of a reaction-center complex surrounded by numerous light-harvesting complexes

Front 366

photosystem II

Back 366

system in which light is absorbed by pigments and its energy is channeled to chlorophyll, where it excites an electron

Front 367

photosystem I

Back 367

a light-capturing system in which electrons end up at another type of chlorophyll molecule

Front 368

Z scheme

Back 368

the two electron transport chains (named for their shape when diagrammed)

Front 369

NADP+

Back 369

the final acceptor of electrons in photosynthesis

Front 370

NADPH

Back 370

the reduced version of the final acceptor of electrons in photosynthesis

Front 371

photophosphorylation

Back 371

process in which energy is harvested from protons moving across the membrane to make ATP from ADP and phosphate

Front 372

Calvin cycle

Back 372

the second of two major stages in photosynthesis (following the light reactions) involving fixation of atmospheric CO2 and reduction of the fixed carbon into carbohydrate

Front 373

ribulose biphosphate (RuBP)

Back 373

the recycled molecule in the Calvin cycle

Front 374

chromatography

Back 374

the technique used to determine which molecules had incorporated the C14

Front 375

rubisco

Back 375

the enzyme that fixes carbon in photosynthesis

Front 376

stomata

Back 376

pores in leaves that carbon dioxide enter through

Front 377

glyceraldehyde 3 phosphate (G3P)

Back 377

a 3-carbon molecule that carbon dioxide is reduced to during the Calvin cycle

Front 378

carbon cycle

Back 378

the relationship, on a global scale, between carbon dioxide constantly being fixed into sugars and sugars being oxidized back into CO2