Glossary

58 terms beginning with G · showing 1–40

1. gamete

   Cell that fuses with another during fertilization in organisms employing sexual reproduction, e.g., an egg or sperm cell.

2. Gammarus

   Large genus of amphipod crustacean in the family Gammaridae of which members occur in both fresh and salt water. An important source of food for many fishes.

   Used in 2 profiles

3. gang valve

   Plastic or metal, adjustable valve used to split a length of air line, and allowing two or more air-driven devices to be operated at once. Also known as an air-control valve.

4. ganoid scale

   Hard, shiny, enamel-like scale. Found in gars, bichirs and reedfishes, for example.

5. gape

   The width of the space between the jaws when open to their maximum extent.

   Used in 10 profiles

6. gape length

   Straight-line measurement from the snout tip to the angle of the mouth.

7. gas bladder

   Gas-filled sac with 1-3 chambers, situated just below the vertebral column in most ray-finned fishes. Its primary function is to aid in buoyancy by offsetting the weight of heavier structures such as bone, but is also used for respiration or sound production in some species. Often reduced in benthic fishes and sometimes absent altogether. Also known as the air or swim bladder.

   Used in 104 profiles

8. gastropod

   Any member of the mollusc class Gastropoda.

   Used in 9 profiles

9. Gastropoda

   Class of molluscs of which the majority of members possess a flattened, muscular foot for locomotion and a head bearing specialised sensory tentacles, with some also having a univalve, coiled shell. Includes all snails, whelks, limpets, conches, and slugs.

10. gender

    The condition of being male or female; sex.

    Used in 49 profiles

11. gene

    Basic hereditary unit comprising a sequence of nuceleotides within a strand of DNA or RNA and occupying a fixed position on a chromosome. Generally determines a particular character or trait present in an organism by directing production and activity of RNA.

    Used in 10 profiles

12. genealogy

    An account of the direct descent of an individual or group from an ancestor; study or investigation of the evolutionary development of an organism(s) from older, related forms; a record, chart, or table depicting a pattern of descent.

13. genera

    Plural of genus.

    Used in 874 profiles

14. general hardness

    Measure of the overall concentration of calcium, magnesium and other ions in a water sample with values usually quoted in units of degrees (dGH), of which 1 dGH corresponds to 17.848 ppm. Also referred to as total or permanent hardness.

    Used in 59 profiles

15. generic name

    The scientific name of a taxon with the rank of genus; the first part of a binomen or trinomen.

    Used in 299 profiles

16. genetics

    Branch of biology concerned with the study of heredity and variation of organisms; the genetic constitution of a single organism, species, or other taxonomic group.

    Used in 4 profiles

17. genital

    Of or relating to the genitals or the process of biological reproduction.

    Used in 74 profiles

18. genital papilla

    Small tube arising from the urogenital opening in some fishes through which male or female gametes are expelled. May only be visible during the reproductive period depending on taxon. Its shape can sometimes used as a feature to identify the gender of an individual.

    Used in 114 profiles

19. genitalia

    The reproductive organs, especially used in reference to external sex organs.

20. genitals

    The genitalia.

    Used in 8 profiles

21. genus

    Taxonomic group into which a family is divided and which contains one or more species characterised by a shared trait or traits. The generic name is used, either alone or followed by one or two specific epithets, to form a binomen or trinomen.

    Used in 1,386 profiles

22. gestation

    Period of embryonic development in a viviparous organism.

    Used in 31 profiles

23. GH

    Abbreviation for general hardness.

    Used in 53 profiles

24. gill

    Respiratory organ of fishes and some other aquatic organisms comprising a highly-vascularised membrane or outgrowth.

    Used in 314 profiles

25. gill arch

    Bony or cartilaginous arch in the pharynx to which the gill filaments and rakers are attached.

    Used in 162 profiles

26. gill chamber

    Chambers located on either side of the head into which the gill filaments project.

    Used in 2 profiles

27. gill cover

    See operculum.

28. gill filament

    Comb-like lamellae found in the gills, through which oxygen is extracted and carbon dioxide expelled.

    Used in 38 profiles

29. gill net

    Type of net normally suspended vertically in such a way that fish become ensnared by their gills.

30. gill opening

    Opening connecting the gill chamber to the exterior environment. Also referred to as the gill slit.

    Used in 83 profiles

31. gill raker

    Any of the bony processes located on the gill arch which function to either retain food items or otherwise prevent solid matter from entering the gill chamber. Vary in number and size depending on taxon and therefore useful in identification.

    Used in 88 profiles

32. gill slit

    See gill opening.

33. girth

    The distance around something; circumference; size; bulk.

    Used in 1 profile

34. gland

    Cell, cell group, or organ secreting a substance used elsewhere in the body.

    Used in 83 profiles

35. gnathal

    Of or relating to the jaw.

36. gonad

    Any organ that produces gametes, e.g., a testicle or ovary.

    Used in 11 profiles

37. Gondwana

    Former supercontinent also known as Gondwanaland existing from approximately 510 to 180 Mya and comprising the majority of the landmasses in today's Southern Hemisphere, including Antarctica, South America, Africa, Madagascar and the Australian continent, plus the Arabian Peninsula and Indian subcontinent.

    Used in 8 profiles

38. gonopodium

    Modified anal fin used in copulation for the transfer of male gametes to a female. In many cases only the anterior part of the fin is modified.

    Used in 24 profiles

39. gram-negative

    Of, relating to, or being a bacterium that does not retain the crystal violet dye used in Gram's method of staining.

40. gram-positive

    Of, relating to, or being a bacterium that does retain the crystal violet dye used in Gram's method of staining.