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EMBRYONIC DEVELOPMENT

UNIT 4. The reproduction function. EMBRYONIC DEVELOPMENT. Natural Science 2. Secondary Education. UNIT 4. Embryonic development. EMBRYONIC DEVELOPMENT. There are three types, depending on where it takes place. OVOVIVIPAROUS. OVIPAROUS. VIVIPAROUS. Click on each box to find out more.

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EMBRYONIC DEVELOPMENT

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  1. UNIT4 The reproduction function EMBRYONIC DEVELOPMENT Natural Science 2. Secondary Education

  2. UNIT4 Embryonic development EMBRYONICDEVELOPMENT There are three types, depending on where it takes place OVOVIVIPAROUS OVIPAROUS VIVIPAROUS Click on each box to find out more Natural Science 2. Secondary Education

  3. UNIT4 Embryonic development Oviparous animals • These animals hatch from an egg which the mother lays in the environment. • The embryo feeds on the nutritive stores contained in the yolk of the egg. • Once it has developed, it hatches, which is when the new individual breaks the shell and emerges from the egg. • There are two types of eggs: • Eggs without a shell: these are found in aquatic animals and must be laid in a wet environment or they will dry up. • Eggs with a shell: they are laid on land so they do not dry up. Toads are oviparous: they lay their eggs in the water, as their eggs do not have shells and would dry up on land. Natural Science 2. Secondary Education

  4. UNIT4 Embryonic development The structure of the egg Amnion: this forms the amniotic sac, which holds the amniotic fluid where the embryo floats. Yolk Vitelline membrane: this encloses the yolk, which the embryo feeds on. Embryo Shell: keeps the embryo from drying out but allows O2 and CO2 to pass through. Membranes:they serve as the egg’s excretory system, collecting waste, and the respiratory system, letting CO2 out and O2 in. Go back to the Start menu Natural Science 2. Secondary Education

  5. UNIT4 Embryonic development Viviparous animals • The embryos of these animals develop inside the mother’s uterus. • The embryo feeds on nutrients that pass from the mother through the placenta. • When the new individual has developed, it comes out of the mother’s body: this is called birth. • All mammals, with the exception of monotremes (the platypus and the echidna) and some sharks, are viviparous. Boars are viviparous animals. Natural Science 2. Secondary Education

  6. UNIT4 Embryonic development The embryo in viviparous animals Amnion:forms the amniotic sac, which holds the amniotic fluid where the embryo floats. Embryo Umbilical cord: connects the embryo to the placenta. Placenta: extracts nutrients and oxygen for the embryo from the mother’s blood. Go back to the Start menu Natural Science 2. Secondary Education

  7. UNIT4 Embryonic development Ovoviviparous animals • These animals develop inside an egg, but the mother keeps the egg inside her body until it hatches. • The embryo feeds on the food reserves contained in the egg. When the embryos are fully developed, hatching takes place, just as it does in oviparous animals. • The young are alive when they come out of the mother. • Certain sharks, vipers and some insects are ovoviviparous. Many sharks are ovoviviparous. Go back to the Start menu Natural Science 2. Secondary Education

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