The life cycle of vertebrates

The life cycle of vertebrates

The life cycle of vertebrates starts with the production of the reproductive cells of an individual and ends with the production of the reproductive cells of the next generation.

Biology

Keywords

vertebrates, life cycle, development, ontogeny, reptile, amphibian, bird, mammal, fishes, common carp, kangaroo, grass snake, thrush, red deer, chicken, edible frog, nidicolous, placental, adult, marsupial, precocial, egg, embryo, tadpole, gill, lung, fertilization, mating, soft-shelled egg, bird egg, breast, breast milk, placenta, fetus, incubation, nest, morula, fry, animal, spine, biology

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Scenes

  • - It develops from the fertilized egg. Initially, it takes nutrients from the yolk sac found under the stomach.

Fishes are gonochoric animals but generally there is only little difference between female and male individuals. The spawning of fishes depends on water temperature.

The process starts with the the female and the male releasing their reproductive cells into the water. The male fish uses external fertilization to fertilize the eggs laid by the female.

Most fishes have a simple life cycle, that is, they do not go through metamorphosis. The offspring resemble the adults but they are smaller and weaker.

Amphibians have spectacular courtship rituals and use mostly external fertilization.

Amphibians develop by metamorphosis. Larvae that hatch from the fertilized eggs are called tadpoles; they undergo major changes before reaching their adult form. The fish-like tadpoles breathe through gills. As they grow, their legs gradually develop while the gills and the tail disappear.

Reptiles use internal fertilization; that is, during mating, the male discharges its reproductive cells inside the female’s body. The fertilized egg is soon surrounded with a nutrient-rich yolk and a soft shell.

Most reptiles lay their eggs into the ground and the ideal incubation temperature for the eggs is provided by solar radiation.

Reptiles have a simple life cycle, that is, they do not go through metamorphosis. Their development does not depend on the presence of water.

  • - It has a light color and weighs about 50–60 g. (1.8–2.1 oz)
  • - The male is called a rooster and the female a hen. Males are larger than females and have brightly colored plumage and a large, red comb. Females have less colorful plumage, mostly brown; and a smaller comb. Egg cells are constantly developing in the hen's body. They become eggs even if they are not fertilized. However, chicks only develop from fertilized eggs.

Birds are gonochoric animals, that is, there are separate female and male individuals. Sexual dimorphism is usually present: males typically have a colorful plumage while females are more dull-colored.

Birds use internal fertilization, i.e. during mating, the male discharges its reproductive cells inside the female’s body through the cloaca. The fertilized egg is soon surrounded with a nutrient-rich yolk and calcified shell. The ideal incubation temperature for the eggs is provided by the body heat of the brooding parent.

Birds have a simple life cycle, that is, they do not go through metamorphosis.

The offspring of precocial birds are developed enough to follow their parents soon after hatching.

  • - It is bluish green with brownish red spots and weighs about 6–7 g (0.2–0.3 oz)
  • - Male blackbirds have black plumage and orange beaks, while females have brownish gray plumage. Males take a bigger role in raising the chicks. Common blackbirds can raise three broods a year.

Birds are gonochoric animals, that is, there are separate female and male individuals. Sexual dimorphism is usually present: males have a colorful plumage while females are more dull-colored.

Birds use internal fertilization, i.e. during mating, the male discharges its reproductive cells inside the female’s body through the cloaca. The fertilized egg is soon surrounded with a nutrient-rich yolk and calcified shell. The ideal incubation temperature for the eggs is provided by the body heat of the brooding parent.

Birds have a simple life cycle, that is, they do not go through metamorphosis.

When the offspring of altricial birds hatch, they are undeveloped and are not capable of feeding on their own for a long time.

  • - The newborn fawn weighs 7–15 kg (15.4–33.1 lb) and can walk soon after birth.

Mammals derive their name from the mammary glands, which are modified sweat glands. The young are fed milk produced by the the mother's mammary glands.

The offspring of placental mammals develop in the mother’s uterus for a long period of time and are born relatively developed. Placental mammals derive their name from the placenta which provides nutrients to the fetus.

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