Carbon dating experiment
Exceptions are those coded for by the RNA of certain viruses, such as HIV.ammonoid: Extinct relatives of cephalopods (squid, octopi, and chambered nautiluses), these mollusks had coiled shells and are found in the fossil record of the Cretaceous period.
antibacterial: Having the ability to kill bacteria.adaptive landscape: A graph of the average fitness of a population in relation to the frequencies of genotypes in it.Peaks on the landscape correspond to genotypic frequencies at which the average fitness is high, valleys to genotypic frequencies at which the average fitness is low. adaptive logic: A behavior has adaptive logic if it tends to increase the number of offspring that an individual contributes to the next and following generations.The amnion surrounds the embryo with a watery substance, and is probably an adaptation for breeding on land.amphibians: The class of vertebrates that contains the frogs, toads, newts, and salamanders.If such a behavior is even partly genetically determined, it will tend to become widespread in the population.
Then, even if circumstances change such that it no longer provides any survival or reproductive advantage, the behavior will still tend to be exhibited -- unless it becomes positively disadvantageous in the new environment.
The eggs are soft and vulnerable to drying, therefore reproduction commonly occurs in water.
Amphibian larvae are aquatic, and have gills for respiration; they undergo metamorphosis to the adult form.
For example, an allometric relation exists between brain size and body size, such that (in this case) animals with bigger bodies tend to have bigger brains.
Allometric relations can be studied during the growth of a single organism, between different organisms within a species, or between organisms in different species. amino acid: The unit molecular building block of proteins, which are chains of amino acids in a certain sequence.
adaptation: Any heritable characteristic of an organism that improves its ability to survive and reproduce in its environment.