ecological succession process consisting of
consecutive changes in species composition
in a given area. (13.1)
ecology the study of the patterns of distribution and
abundance of plants, animals, and other types of
organisms on Earth. (13.1)
ecosystem community of living organisms, together
with the biotic and abiotic factors that surround
and affect the community. (13.1)
effectors structures that receive information from
the homeostasis integrator, and make changes to
the body’s internal conditions (e.g., a gland, an
organ, or a muscle). (4.1)
electron negatively charged subatomic particle,
found outside the nucleus of an atom in an
energy level. (1.1)
electron acceptor molecule that accepts an electron
from the chlorophyll areaction centre in a
photosystem. (3.3)
electronegativity measure of the relative abilities of
atoms to attract electrons. (1.1)
electron transport chain series of electron carrier
molecules that move electrons during the redox
reactions that form ATP. Also called electron
transport system. (3.1)
electron transport system seeelectron transport
chain. (3.3)
electrophoresis technique for analyzing DNA,
used to examine the variability of genes in a
population. Samples of DNA from individuals
are placed in a gel that is in turn placed in a
solution and connected to an electrical circuit.
The DNA fragments move through the gel at
varying speeds and a DNA “fingerprint” of bands
is then stained and analyzed. (11.1)
element substance that cannot be broken down into
simpler substances by chemical means. (1.1)
elongation the second step in transcription, in
which the correct number of nucleotides from a
DNA template is copied onto a messenger RNA
molecule. (8.2) Also, in translation, the name of
the second step, in which a polypeptide is
synthesized. (8.3)
embryology study of embryos (10.2)
emigration movement of individuals away from a
region; in population dynamics, a factor that
decreases the population. (14.2)
endemic regarding species, unique to a certain
region such as an island. (10.3)
endocrine glands ductless glands that secrete
hormones directly into the bloodstream. (6.1)
endocrine system body system that works in
parallel with the nervous system to maintain
homeostasis by releasing chemical hormones
from various glands. The system is composed of
the hormone-producing glands and tissues of the
body. (6.1)
endometrium the lining of the uterus. (6.3)
endothermic reaction reaction that requires an
input of energy in order to proceed. (2.1)
energy the capacity for doing work. (2.1)
entropy disorder in a chemical reaction or the
universe. (2.1)
environmental resistance situation in which biotic
and abiotic factors in an environment limit a
population’s growth. (14.3)
enzymes specialized proteins that make cellular
work possible in all cells by helping chemical
reactions to occur. (2.2)
enzyme-substrate complex the combination of the
substrate induced-fitted into the active site of an
enzyme and the enzyme itself. (2.2)
epididymis in human males, the tube within the
scrotum in which sperm mature and become
motile. (6.3)
equilibrial life history reproductive strategy in
which organisms produce a few large offspring
and care for them to ensure their survival is
favoured. This strategy is usually seen in
populations that are at their carrying capacity.
The strategy is also known as K-selected
reproduction. (14.4)
evolution the relative change in the characteristics
of populations that occurs over successive
generations. (10.1)
exaptation process by which an adaptation that
evolved for one purpose is co-opted for another
use. (12.1)
excision repair replacement by the cell of a
damaged section of DNA with a newly
synthesized correct section of DNA. (9.1)
excitatory response process in which the
neurotransmitter reaches the dendrites
of a postsynaptic neuron, and a wave of
depolarization is generated by the resultant
opening of sodium gates (5.2)
exocrine glands glands that have ducts and secrete
substances such as sweat, milk, or digestive
enzymes. (6.1)
exon the coding region of a eukaryote gene. Each
gene is composed of one or more exons. (7.4)
exothermic reaction reaction that is accompanied
by a release of energy. (2.1)
exponential growth the growth of a population
that occurs in an environment with unlimited
resources. (14.2)
expression vector plasmid that contains a
prokaryotic promoter sequence just ahead
of a restriction enzyme target site. (9.3)Glossary • MHR 575