Internal fertilization has the advantage of protecting the fertilized egg from dehydration on land. This occurs in most mammals, some cartilaginous fish, and a few reptiles. The offspring develops in the female and is born alive. Fertilized eggs are retained inside the female, and the embryo receives nourishment from the mother’s blood through a placenta.This occurs in some bony fish, some sharks, some lizards, some snakes, some vipers, and some invertebrate animals. Fertilized eggs are retained inside the female’s body, but the embryo receives nourishment from the egg’s yolk and the young are fully developed when they are hatched.This occurs in most bony fish, many reptiles, some cartilaginous fish, most amphibians, two mammals, and all birds. Fertilized eggs are laid outside the female’s body and develop there, and the embryo receives nourishment from the yolk that is a part of the egg.There are three ways that offspring are produced following internal fertilization: Internal fertilization occurs most often in land-based animals, although some aquatic animals also use this method. (credit: “OakleyOriginals”/Flickr) Internal Fertilization In other species, including many amphibians, individual males court individual females to induce the female to release the eggs, at which point the male releases the sperm to fertilize that individual female’s eggs.ĭuring sexual reproduction in toads, the male grasps the female from behind and externally fertilizes the eggs as they are deposited.In this situation, males and females are often not interacting with each other as individuals, but massed together so that all sperm and all eggs are in the same location. In some species, including some fish, crustaceans, mollusks, and other invertebrates, there are environmental (water temperature, length of daylight) or biological (pheromones) cues that cause males and females to release gametes at the same time.Getting the sperm and egg together requires that the gametes be released at the same time and in the same location to increase the likelihood of fertilization (otherwise all those gametes are wasted!) How does that happen? Water protects the eggs from drying out during development. The information below is adapted from OpenStax Biology 43.2Įxternal fertilization occurs in aquatic environments where both eggs and sperm are released into the water, a process called spawning.
Fertilization can occur either inside ( internal fertilization) or outside ( external fertilization) the body of the female. Sexual reproduction starts with the combination of a sperm and an egg in a process called fertilization. Describe different ways that males compete for mates.Define sexual selection, and give examples of secondary sexual characteristics.Define biological fitness and parental investment, and explain why females are more likely than males to be “choosy” about mates.Differentiate between internal and external fertilization.However, the plantations are unattractive to local people, not because the people are ' choosy' but because they can't live on the pittances offered as wages.įrom high-end jewelry artisans to women with a penchant for being " choosy," the latest crop of Atlanta designers proves that building a business can start at home. "That's where the dance can go wrong with some couples - if the male signals are not strong enough, or if the female system is too ' choosy'." PRINCE: The courts are kind of choosy about which cases are appropriate for a class action, but this has all the makings.ĭuring a dialogue session with Yew Tee residents yesterday, Mr Shanmugam jumped to the defence of foreigners and blamed locals for being " choosy" about jobs instead.īut some apparently healthy sperm failed to activate these changes, leading to the suggestion that the female system can be " choosy" about its biological mate, she said.
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