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| The fin rays of cartilaginous fishes, are long horny rays composed of a material similar to that comprising the dorsal spines of sharks. |
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| The rays of bony fishes; consist of jointed bony dermal scales aligned end to end. |
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| having many tiny projections on the edge like the teeth of a comb, as in many bony fishes |
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Cycloid scales are thin and overlapping, permitting more flexibility. Unlike ganoid scales, cycloid scales grow as the fish grows, and in some species, show annual growth rings.
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Definition
| The inner layer of the scale is made of lamellar bone. On top of this lies a layer of spongy or vascular bone and then a layer of dentine-like material called cosmine. The upper surface is keratin. The coelacanth has modified cosmoid scales that lack cosmine and are thinner than true cosmoid scales. |
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Definition
| Ganoid scales are similar to cosmoid scales, but a layer of ganoin lies over the cosmine layer and under the enamel. Ganoin scales are diamond-shaped, shiny, and hard. Within the ganoin are guanine compounds, iridescent derivatives of guanine found in a DNA molecule. The iridescent property of these chemicals provide the ganoin its shine. |
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Definition
| Placoid scales are found on cartilaginous fish including sharks. These scales, also called denticles, are similar in structure to teeth, and have one median spine and two lateral spines. |
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Definition
Fertilized egg remain in body of female, young - born alive (e.g. mammals).
- Nutrients trasferred from body of mother to offspring
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Definition
Egg-laying (e.g. bird)
- Large, yolky egg in protective case
- Developement occurs outside mother's body
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Definition
Yolky fertilized egg is retained in body if female
- Young develope in uterus and are born alive
- Embryo is nourished by its own yolk
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Definition
| A principal taxonomic category that ranks above class and below kingdom. |
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Definition
| a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding. The species is the principal natural taxonomic unit, ranking below a genus and denoted by a Latin binomial, e.g., Homo sapiens. |
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| the process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth. |
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| a change by which an organism or species becomes better suited to its environment |
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| Similar in position, structure, and evolutionary origin but not necessarily in function: a seal's flipper is homologous with the human arm. |
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Definition
| Similarity due to any cause other than common anscestry; similar in funtion but not origin or developement |
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| A trait that appears in a stem anscestor from which aroes an array of subsequent species, some of which may retain the trait. |
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| Plesiomorphic Characteristic |
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Definition
| Applied to a character state that is based on features shared by different groups of biological organisms and inherited from a common ancestor. |
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When a new character evolves.
e.g. Hair:
- Derived/apomorphic for mammals
- Plesiomorphic for rodents/carnivores/primates, etc.
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| A shared apomorphic trait (e.g. shared by anscestor and all descendants) |
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| Monophyletic group; a group of organisms believed to have evolved from a common ancestor |
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| Share the same immediate common anscestor; branch includes anscestor |
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Definition
| group of living organisms and their descendants; clade of interest |
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Definition
| Other groups not in crown group |
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| Outgroup nearest to crown group; sister clades. |
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Term
| (basal and radial) pterygiophores |
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Definition
The bones or cartilages with which the base of the rays of the median fins articulate; the connecting points for the dorsal and anal fin rays.
- Basal: the base of the finrays
- Radial: The radials protruding out of the basals
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Definition
| One or a pair of pneumatic sacs filled with gases derived directly or from the atmosphere; has a function of buoyancy. |
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