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actin filaments
rope-like structures composed of two intertwined polmers of the protein actin. Their location is concentrated just beneath, and often attached to, the plasma membrane where they become and important part of a eukaryotic cell's cytoskeleton
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microtubules
cylindrical (tubular) structures composed of the protein tubulin. Due to their tubular nature they are stiff structures that form an important part of a eukaryotic cell's cytoskeleton.
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endocytosis
invagination of the outer membrane to the point that materials outside the cell are brought into the cell enclosed in a membrane-bounded vesicle.
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endoplasmic reticulum
a highly convoluted membrane-bounded cavity that surrounds the nuclear space in eukaryotic cells.
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nucleus
a membrane-bound compartment of a eukaryotic cell that contains DNA and is connected to the rest of the cytoplasm by nuclear pores.
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kinetosome
a short cylindrical array of microtubules (plus their associated proteins) found at the base of eukaryotic flagella (or cilia). It serves as the nucleation site for the growth of a flagella's microtubule core (the axoneme)
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(eukaryotic) chromosome
a linear (the two ends are not connected) two-side DNA molecule that contains only a portion of a cell's genome. (in other words, when the DNA that makes up a cell's genome is broken up into more than one two-sided DNA molecules, and each linear molecule is called a chromosome.)
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mitotic cell division
mitosis, cell division that uses a microtubule-based distribution system to move DNA, and each daughter cell ends up with all the DNA present in the original cell. (ploidy level remains constant across cell division.)
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endosymbiont
symbiosis means living together, and endo-means inside, so and endosymbiont is an organism that lives inside another organism.
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mitochondrion
membrane-bounded organelle, about the size of bacteria and containing DNA and the machinery of protein synthesis, where the KRebs cycle and oxidative phosphorylation takes place and is consequently the site where most of the ATP production in eukaryotic cells takes place.
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chloroplast
membrane-bounded organelle, about the size of bacteria and contining DNA and the machinery of protein synthsis, where water-splitting photosynthesis--bother light phase (noncyclic photophosphorylation) and dark phase (Calvin-Benson cycle)-- takes place in eukaryotic cells.
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ploidy level
the number of complete genomes contained within a cell.
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homologous chromosomes
two chromosomes that contain the same portion of a cell's genome. (In sexual reproduction, a cell receives one chromosome of each homologous pair from its mom and the other from its dad.)
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meiotic cell division
meiosis- cell division that uses a microtubule-based distribution system to move DNA, and each daughter cell ends up with one-half the number of genomes found n the original cell. (ploidy level is reduced by one-half across cell division. Note that a haploid cell could not undergo meiotic cell division.)
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tetrad
an alignment of two homologous chromosomes each in their duplicate form that occurs at the beginning (prophase I) of the first meiotic division. It is in this arrangement that recombination between homologous chromosomes can occur.
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outcrossing population
a sexual population where individuals typically avoid mating with close relatives.
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inbreeding depression
the increased chance of matings between close relatives producing offspring that die or suffer abnormalities. It is found in normally outcrossing populations.
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interstitial space
the space in multicellular organisms that is inside the outer sheet of cells, but outside any cells.
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anchoring junctions
structures that hold adjacent cells together by ooking into each cell's cytoskeleton. They are the relatively strongest form of cell-cell connections.
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extracellular matrix
regions of interstitial space consisting of a collagen framework filled in by an interconnected and highly hydrated gel-like structure (formed from the interaction between water molecules and proteoglycans).
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fibroblasts
cells that specialize in secreting the collagen and proteogycan components of extracellular matrix.
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development
the regeneration of a multicellular form from a starting point that has fewer cells, fewer cell types, and less complex arrangement. Development commonly starts with a single cell.
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cell differentiation
process through which cells within the same developing multicellular organism become different from each other (e.g., muscle cells, liver cells, nerve cells, etc.). The differences are generated by a unique pattern of turning on and off genes in a different cell lines.
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pattern formation
the process by which the "right" cell types come to be in the "right" place to form a functional multicellular organism. (e.g., muscle cells come to be where muscles need to be, etc.)
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germ-line cells
the lineage of cells that throughout development retains the ability to serve as a starting cell for the next generation. In sexual organisms, germ-line cells form gametes.
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somatic cells
those cell types that are formed anew in each multicellular generation through differentiation from germ-line cells. A coherently functioning multicellular organism is formed by the collective action of the various forms of somatic cells.
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flagellation constraint
a cell that for some reason does not retain its flagella while undergoing cell division. As a consequence the cell can not swim" and reproduce at the same time.
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triploblastic organism
any organism that has an outer cell layer (known as the ectoderm), and inner cell layer surrounding the gut (known as the endoderm), and a distinct third tissue layer, consisting largely of muscle cells and connective tissue, sandwiched in between (known as the mesoderm). Also know as a three-layered organism.
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alternation of generations
a form of sexual reproduction that include both a multicellular haploid phase (organism) and a multicellular diploid phase (organism) within each reproductive cycle.
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sporophyte
a multicellular diploid organism within an alternating generation reproductive cycle that produces haploid cells by meiosis that go off and act as spores.
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spore
a reproductive cell that can develop into a multicellular organism without fusing with another cell.
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gametophyte
a multicellular haploid organism within an alternating generation reproductive cycle that produces haploid cells by mitosis that go off and act as gametes.
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stomata
stoma- an opening created on the outer surface of most terrestrial plants by guard cells pulling apart. Stomata are typically found on the underside of leaves and along photosynthetic stems. Such openings allow interior cells to exchange materials (such as carbon dioxide) with their environment.
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transpiration
or evapotranspiration- the diffusional movement of water molecules out of a plant's stomata.
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embryophyte
any phototroph in which early sporophyte development is supported by the gametophyte. All plants are embryophytes
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vascular plant
any plant that develops regions of conducting tissue known as phloem and xylem.
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gene for a trait
a particular gene, or form of a gene, makes a difference in the development of a trait. For instance, the protein coded for by the gene in some way plays a causal role in the development of a certain trait. (In many cases, a gene for a trait can also be viewed as a necessary, but not sufficient, interactant in a trait's development)
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locus
the location of a particular gene. That is, what chromosome it is on, and where it is along that specific chromosome.
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allele
one of the alternative forms of a gene found in a sexual population
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variable gene
any gene where more than one allele exists within a sexual population.
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homozygous
the term used to indicate that a gene within a diploid individual (a gene pair) has two copies of the same allele.
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heterozygous
the term used to indicate that a gene within a diploid individual (a gene pair) is filled with two different alleles.
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additive interaction
when a heterozygous individual (all else being equal) develops a phenotype intermediate to those developed by individuals homozygous for either allele.
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dominance-recessive interaction
when a heterozygous individual (all else being equal) develops the same phenotype as individuals homozygous for one of the two alleles.
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sex chromosome
any chromosome that contains genetic information involved in determining an individual's sex
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poikilothermic
organisms that do not always maintain body temperature at their thermal optimum.
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homeothermic
organisms that maintain body temperature close to their thermal optimum despite environmental fluctuations in temperature.
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hormone
any chemical signal that uses the circulatory system to travel between the monitor that released it and whatever effectors respond to it
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neurotransmitter
any chemical signal released from the end of a nerve cell that influences how the postsynaptic cell will respond to neurotransmitters.
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