How do internal and external reproduction compare answers

These cells went through meiosis, an adaption of mitosis, which reduced the number of chromosomes in each reproductive cell by half, while increasing the number of cells through cell division. Complete reproductive systems were developed in insects, with separate sexes. Sperm are made in testes and then travel through coiled tubes to the epididymis for storage. Eggs mature in the ovary. When they are released from the ovary, they travel to the uterine tubes for fertilization.

Some insects have a specialized sac, called a spermatheca , which stores sperm for later use, sometimes up to a year. Fertilization can be timed with environmental or food conditions that are optimal for offspring survival. Vertebrates have similar structures, with a few differences. Non-mammals, such as birds and reptiles, have a common body opening, called a cloaca , for the digestive, excretory and reproductive systems. Coupling between birds usually involves positioning the cloaca openings opposite each other for transfer of sperm.

Mammals have separate openings for the systems in the female and a uterus for support of developing offspring. The uterus has two chambers in species that produce large numbers of offspring at a time, while species that produce one offspring, such as primates, have a single uterus.

This can occur either outside the bodies or inside the female. Both methods have advantages and disadvantages. Once fertilized, the eggs can develop inside the female or outside. If the egg develops outside the body, it usually has a protective covering over it. Animal anatomy evolved various ways to fertilize, hold, or expel the egg. The method of fertilization varies among animals. Some species release the egg and sperm into the environment, some species retain the egg and receive the sperm into the female body and then expel the developing embryo covered with shell, while still other species retain the developing offspring through the gestation period.

Skip to content Chapter Animal Reproduction and Development. Learning Objectives By the end of this section, you will be able to: Discuss internal and external methods of fertilization Describe the methods used by animals for development of offspring during gestation Describe the anatomical adaptions that occurred in animals to facilitate reproduction. External Fertilization. During sexual reproduction in toads, the male grasps the female from behind and externally fertilizes the eggs as they are deposited.

Internal Fertilization. Internal fertilization occurs most often in land-based animals, although some aquatic animals also use this method. There are three ways that offspring are produced following internal fertilization: oviparity, ovoviparity, and viviparity. This occurs in most bony fish, many reptiles, some cartilaginous fish, most amphibians, two mammals, and all birds.

Reptiles and insects produce leathery eggs, while birds and turtles produce eggs with high concentrations of calcium carbonate in the shell, making them hard. These animals are classified as oviparous. This occurs in some bony fish such as the guppy, Lebistes reticulatus , some sharks, some lizards, some snakes such as the garter snake, Thamnophis sirtalis , some vipers, and some invertebrate animals such as the Madagascar hissing cockroach, Gromphadorhina portentosa.

The offspring develops in the female and is born alive. This occurs in most mammals, some cartilaginous fish, and a few reptiles, making these animals viviparous. Internal fertilization has the advantage of protecting the fertilized egg from dehydration on land. The embryo is isolated within the female, which limits predation on the young. Internal fertilization also enhances the fertilization of eggs by a specific male. Even though fewer offspring are produced through this method, their survival rate is higher than that for external fertilization.

After the sperm reaches the egg, fertilization can then take place. Most external fertilization happens during the process of spawning where one or several females release their eggs and the male s release sperm in the same area, at the same time. The release of the reproductive material may be triggered by water temperature or the length of daylight. Nearly all fish spawn, as do crustaceans such as crabs and shrimp , mollusks such as oysters , squid, and echinoderms such as sea urchins and sea cucumbers.

Pairs of fish that are not broadcast spawners may exhibit courtship behavior. This allows the female to select a particular male. The trigger for egg and sperm release spawning causes the egg and sperm to be placed in a small area, enhancing the possibility of fertilization. Anemone fish protecting its spawn : An image of an Anemone fish protecting its spawn. The anemone fish utilizes a form of external fertilization. External fertilization in an aquatic environment protects the eggs from drying out.

Broadcast spawning can result in a greater mixture of the genes within a group, leading to higher genetic diversity and a greater chance of species survival in a hostile environment. For sessile aquatic organisms such as sponges, broadcast spawning is the only mechanism for fertilization and colonization of new environments. The presence of the fertilized eggs and developing young in the water provides opportunities for predation, resulting in a loss of offspring. Therefore, millions of eggs must be produced by individuals.

The offspring produced through this method must mature rapidly. The survival rate of eggs produced through broadcast spawning is low. Internal fertilization occurs most often in land-based animals, although some aquatic animals also use this method.

There are three ways that offspring are produced following internal fertilization: oviparity, ovoviparity, and viviparity. This occurs in most bony fish, many reptiles, some cartilaginous fish, most amphibians, two mammals, and all birds. Reptiles and insects produce leathery eggs, while birds and turtles produce eggs with high concentrations of calcium carbonate in the shell, making them hard.

These animals are classified as oviparous. This occurs in some bony fish such as the guppy, Lebistes reticulatus , some sharks, some lizards, some snakes such as the garter snake, Thamnophis sirtalis , some vipers, and some invertebrate animals such as the Madagascar hissing cockroach, Gromphadorhina portentosa. The offspring develops in the female and is born alive. This occurs in most mammals, some cartilaginous fish, and a few reptiles, making these animals viviparous.

Internal fertilization has the advantage of protecting the fertilized egg from dehydration on land. The embryo is isolated within the female, which limits predation on the young. Internal fertilization also enhances the fertilization of eggs by a specific male.