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Pahoehoe
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Hawaiian name for a fast moving, liquid type of lava. |
Palmate
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In plants, a term referring to a leaf which has leaflets originating at one point, like the palm of a hand. Image can be found at LEAF SHAPE II. |
Parasite
The exploitive organism in a symbiotic relationship, which takes from its host, and returns nothing. A parasitic organism can also be harmful to its host.
Parent element
In radioactive decay, the element that is decaying. For example, in the decay of 238U to 206Pb, 238U is the parent element.
Parsec
An astronomical unit of measurement equal to 3.262 light years, or about 3.086*1016 meters. Astronomers get this number by measuring a when a stars parallax is one arcsecond.
Partial Veil
The tissue covering young gills of some fungi; as the cap expands this tissue breaks and leaves remnants in a ring around the stipe or cap margins.
Pellicle
A transparent flexible outer covering found in some protists. This acts like an exoskeleton.
Peptide
Any molecule that can hydrolyze into amino acids and form into the basis for proteins.
Perennial
Referring to any herbaceous plant that lives longer than two years.
Petal
In flowers, the sometimes colored, scented portion that protects the reproductive organs. Can often be brightly colored and scented to help attract animals.
Phosphate
Name given to a substance that contains a phosphate group (PO43-).
Phosphate group
Term referring to a grouping of phosphorous atoms bonded to four different oxygen atoms, which are themselves attached to a larger molecule.
Photoautotrophic
An organism that makes its own food by means of photosynthesis.
Photosynthesis
The process by which green plants, algae, and some bacteria combine sunlight, carbon dioxide (CO2), and water (H2O) to form carbohydrates and oxygen (O2).
Placenta
A structure that forms on the uterine wall, that provides a developing organism with food nutrients, and also can act as waste disposal.
Plant
A kingdom that primarily consists of immobile, eukaryotic, mostly photoautotrophic organisms.
Plasmodium
A multinucleate sheet of cytoplasm characteristic of some stages of such organisms as slime molds.
Plasmogamy
The fusion of two or more cells or protoplasts without the fusion of nuclei.
Plate
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In geology, any of several areas of the lithosphere that move about on the mantle. Sometimes these plates correspond to continents. This image can be found at Lecture#1. |
Plate tectonic theory
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In geology, a theory that holds that the Earths crust is made up of many plates, all of which are moving over the liquid mantle. This theory is a unifying concept, in that it explains many different geological features, such as volcanoes, volcanic island arcs, and certain types of mountain ranges. This image, along with more information about plate tectonics, can be found at the following website: A slice through the Earth: plate tectonic processes. |
Polar tube
A tube-like structure that extends out from the polar cap of some microorganisms.
Polaroplast
A specialized organelle in some single-celled animals that is filled up with water until it exerts enough pressure on the polar cap to make it rupture and extend the polar tube, through which the sporoplasm of the organism is released, so that it can infect a host.
Pollen
The microspore used by seed plants for reproduction.
Polypeptide chain
An organic compound with a sequence of three or more amino acids. Peptide bonds between them result in a regular pattern of nitrogen atoms in the carbon backbone: -N-C-C-N-C-C-. Every protein consists of one or more polypeptide chains.
Polyploid
An organism that has at least three sets of haploid chromosomes, or multiple sets of diploid chromosomes. Polyploidy can happen in a few different ways. One form happens when an organism is reproducing.
Polysaccharide
A polymer made up of monosaccharides connected by glycosidic bonds. Well known polysaccharides include: starch, glycogen, and cellulose.
Polysporoblast
A process which produces more than one sporoblast.
Pons
Portion of the brain between the midbrain and the medulla oblongata.
Posterior
The rearward facing portion of an object or organism. Compare with anterior.
Precocial
A term that refers to animals that are partially independent soon after birth.
Protein
An organic compound made up of one or more polypeptide chains.
Protein Synthesis
The process by which proteins are made.
Protist
Any eukaryotic organism not belonging to animals, fungi, or plants. Can be referred to as protoctists.
Protoctist
Any eukaryotic organism not belonging to animals, fungi, or plants. Can be referred to as protists.
Proton
A component of an atoms nucleus that has a positive charge, and provides mass.
Protoplast
The living material of a plant or bacterial cell, including the protoplasm and plasma membrane after the cell wall has been removed.
Purine
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A nucleotide base that has a double ring structure, as seen in the picture to the left. Examples of purines include adenine and guanine. |
Pyrimidine
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A nucleotide base that has a single ring structure, as seen to the image to the right. Examples of pyrimidines include cytosine and thymine. |
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