Primary cell walls
A cell wall is a fairly rigid layer surrounding a cell, located external to the cell membrane,
which provides the cell with structural support, protection, and acts as a filtering
mechanism.
Primary consumer
An herbivore; an organism in the trophic level of an ecosystem that eats plants or algae.
Primary germ layers
The three layers (ectoderm, mesoderm, endoderm) of the late gastrula, which develop into
all parts of an animal.
Primary growth
Growth initiated by the apical meristems of a plant root or shoot.
Primary immune response
The initial immune response to an antigen, which appears after a lag of several days.
Primary meristems
Meristematic tissue in vascular plants that is derived from an apical meristem, such as the
procambium, protoderm, and ground meristem.
Primary pit fields
The parenchyma cell in the very center (arrow) appears to be filled with a weblike mesh, but
in fact we are looking at either the front or the back wall, and virtually the entire wall is a set
of primary pit fields.
Primary producer
An autotroph, which collectively make up the trophic level of an ecosystem that ultimately
supports all other levels; usually a photosynthetic organism.
Primary productivity
The rate at which light energy or inorganic chemical energy is converted to the chemical
energy of organic compounds by autotrophs in an ecosystem.
Primary structure
The level of protein structure referring to the specific sequence of amino acids.
Primary succession
A type of ecological succession that occurs in an area where there were originally no
organisms.
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