alternation
of generations A life cycle involving alternation of a multicellular haploid stage (gametophyte) with a multicellular diploid stage (sporophyte). Occurs in most plants and some protists.
amoeboid
motion A sliding movement observed in some protists accomplished by the formation of cytoplasmic extensions of the cell called pseudopodia. One form of cell crawling.
bioluminescence
The emission of light by a living organism via an enzyme-catalyzed reaction.
carbon
sink A resorvoir that stores carbon-containing compounds for an indefinite period of time.
decomposer
...
detritus
A layer of dead organic matter that accumulates at ground level or on seafloors and lake bottoms.
direct
sequencing A technique for identifying and studying microorganisms that cannot be grown in culture. Involves detecting and amplifying copies of specific genes in the microorganisms' DNA, sequencing these genes, and then comparing the sequences with the known sequences from other organisms.
endosymbiosis
An association between organisms of two different species in which one lives inside the cell or cells of the other.
endosymbiosis
theory The theory that mitochondria and chloroplasts evolved from prokaryotes that were engulfed by host cells and took up a symbiotic existence within those cells, a process termed primary endosymbiosis. In some eukaryotes, chloroplasts may have originated by secondary endosymbiosis; that is, when a cell engulfed a chloroplast-containing protist and retained its chloroplasts.
eukarya
One of the three taxonomic domains of life, consisting of unicellular organisms (most protists, yeasts) and multicellular organisms (fungi, plants, animals) distinguished by a membrane-bound cell nucleus, numerous organelles, and an extensive cytoskeleton. Compare with Archaea and Bacteria.
fertilization
Fusion of the nuclei of two gametes (often haploid) to form a zygote with a nucleus (often diploid). Exceptions to the haploid and diploid rule are seen in polyploid species.
flagellum
(plural: flagella) A long, cellular projection that undulates (in eukaryotes) or rotates (in prokaryotes) to move the cell through an aqueous environment. See axoneme.
food
chain A relatively simple pathway of energy flow through a few species, each at a different trophic level, in an ecosystem. Might include, for example, a primary producer, a primary consumer, a secondary consumer, and a decomposer. A subset of a food web.
gametophyte
In organisms undergoing alternation of generations, the multicellular haploid form that arises from a single haploid spore and produces gametes by mitosis and cell division. Compare with sporophyte.
lateral
gene transfer Transfer of DNA between two different species. Compare with chromosome-level mutation and point mutation.
life
cycle The sequence of developmental events and phases over the life span of an organism, from fertilization to offspring production.
malaria
A human disease caused by five species of the protist Plasmodium and passed to humans by mosquitoes.
monophyletic
group An evolutionary unit that includes an ancestral population and all of its descendants but no others. Also called a clade or lineage. Compare with paraphyletic group and polyphyletic group.
multicellularity
The state of being composed of many cells that adhere to each other and do not all express the same genes, resulting in some cells having specialized functions.
paraphyletic
group A group that includes an ancestral population and some but not all of its descendants. Compare with monophyletic group.
parasite
An organism that lives on a host species (ectoparasite) or in a host species (endoparasite) and that damages its host.
phagocytosis
Uptake by a cell of small particles or cells by invagination and pinching off of the plasma membrane to form small, membrane-bound vesicles; one type of endocytosis.
picoplankton
Plankton cells that are between 0.2 and 2.0 microns in diameter.
plankton
Drifting small or microscopic organisms that serve as a food source in aquatic environments (includes animals, plants, protists, archaea, and bacteria).
plantae
The monophyletic group that includes red, green, and glaucophyte algae, as well as land plants.
primary
producer Any organism that creates its own food by photosynthesis or from reduced inorganic compounds and that is a food source for other species in its ecosystem. Also called autotroph.
protist
Any eukaryote that is not a land plant, animal, or fungus. Protists are a diverse paraphyletic group. Most are unicellular, but some are multicellular or form aggregations called colonies.
pseudopodium
(plural: pseudopodia) A temporary bulge-like extension of certain protist cells used in cell crawling and ingestion of food.
sessile
Permanently attached to a substrate; not capable of moving to another location.
shell
A hard, protective outer structure.
spore
(1) In bacteria, a dormant form that generally is resistant to extreme conditions. (2) In eukaryotes, a single haploid cell produced by meiosis; it is distinct from a gamete, however, in being able to grow into a multicellular, haploid organism through mitotic divisions directly (no fertilization required).
sporophyte
In organisms undergoing alternation of generations, the multicellular diploid form that develops by mitotic divisions after fertilization produces a zygote. Compare with gametophyte.
symbiosis
(adjective: symbiotic) Any close and prolonged physical relationship between individuals of two different species. See commensalism, mutualism, and parasitism.
synapomorphy
A shared, derived trait found in two or more taxa that is present in their most recent common ancestor but is missing in more distant ancestors. Useful for inferring evolutionary relationships.-