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Male Dendropsophus microcephalus calling. Sexual selection in amphibians involves sexual selection processes in amphibians, including frogs, salamanders and newts.Prolonged breeders, the majority of frog species, have breeding seasons at regular intervals where male-male competition occurs with males arriving at the waters edge first in large number and producing a wide range of vocalizations ...
Diagram of stages of embryo development to a larval and adult stage. In developmental biology, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm cell (spermatozoon). [1]
As the blastopore deepens, a new embryonic cavity develops, the primitive gut, or the archenteron. It grows in length towards the future front part of the embryo. It can be seen from outside the embryo that the dorsal lip curves itself and grows, creating the side lips of the blastopore. During this time, the paraxial mesoderm enters the embryo.
Parthenogenesis (/ ˌ p ɑːr θ ɪ n oʊ ˈ dʒ ɛ n ɪ s ɪ s,-θ ɪ n ə-/; [1] [2] from the Greek παρθένος, parthénos, 'virgin' + γένεσις, génesis, 'creation' [3]) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization.
After many generations the two salamander gene pools will become mutated caused by natural selection. The mutation will change the DNA sequence of the two populations enough that the salamander populations can no longer successfully breed between each other making the populations of salamander become classified as different species.
The radiation destroyed the DNA within the sperm, but nearly normal embryos were still produced. Gunther Hertwig repeated this experiment in 1924, using crosses between different frogs. [ 1 ] A cross between a toad, Amietophrynus regularis , and a frog, Rana fusca , would not produce a viable embryo, but fertilization of a toad egg by an ...
This is common in molluscs, arthropods and fishes, and is found in most frogs. [1] Oviparity: fertilisation is internal, but the female lays zygotes as eggs with a substantial quantity of yolk to feed the embryo while it remains in the egg. The egg is not retained in the body, or only for a limited time. [1] Oviparity is found in insects, birds.
Many species of salamander, and amphibians in general, exhibit environmental neoteny. Axolotl and olm are perennibranchiate salamander species which retain their juvenile aquatic form throughout adulthood, examples of full neoteny. Gills are a common juvenile characteristic in amphibians which are kept after maturation; examples are the tiger ...