Biology Reference
In-Depth Information
Genotype.
The exact combination of alleles an organism possesses for
one or more genes.
Gill rakers.
Filter elements that are spaced so as to restrict the passage of
particulate materials of certain size from the mouth cavity to the gill
chamber in a fish.
Haplotype.
The alleles of a set of genes or the specific sequence of
genetic code shown on one chromosome.
Hardy-Weinberg expectation.
The frequency of genotypes that is
expected in a population of freely interbreeding individuals when the
alleles for a gene are of equal fitness value.
Heterozygosity.
The occurrence of different alleles of a gene on the two
members of a chromosome pair.
Homoploid speciation.
The hybridization of species with the same
chromosome number, leading to a form that is distinct and has strong
reproductive isolation without the occurrence of polyploidy.
Homozygote.
The condition in which identical alleles of a gene occur
on the two members of a chromosome pair.
Horizontal gene transfer.
Exchange of genes directly between individ-
uals rather than from parents to offspring.
Hybrid vigor.
Enhanced growth or performance of the offspring pro-
duced by the interbreeding of different species or other distant relatives.
Hyperparasitism.
Parasitism of species that are themselves parasites.
Inbreeding depression.
Reduced fitness of individual offspring result-
ing from expression of detrimental recessive characteristics due to inter-
breeding of closely related parent individuals.
Induced defenses.
Morphological or chemical deterrents to herbivore
feeding produced by plants in direct response to tissue damage by herbi-
vores.
Introgressive hybridization.
Interbreeding between two or more
species, leading eventually to the loss of genetic distinction of the species.
Invasional meltdown.
The process by which successful invaders of a
community or region facilitate the invasion of still other alien species.
Inversion (chromosomal).
A change in chromosome structure in
which a section of a chromosome becomes inverted, although it remains
at the same location.
