Development and Growth

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Development and Growth
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Where Do Embryos Develop?

• Growing offspring, or the embryo, may develop
  outside or inside of the parents body.
• The offspring of some animals develop inside an
  egg laid outside of the parents body.
• Most animals without backbones lay eggs.
• The eggs of land vertebrates such as reptiles and
  birds, that develop in an egg outside of the
  parents body are called amniotic eggs.

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Amniotic Egg
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Egg Retaining Animals

• In some animals, an embryo develops inside an egg
  that is kept within the parents body.
• The developing embryo gets all of its nutrients
  from the eggs yoke.
• What are some egg-retaining mammals that you can
  think of?

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Placental Mammals

• In placental mammals the embryo develops inside
  the mothers body.
• What are some examples of placental mammals?
• Materials are exchanged between the embryo and
  the mother through an organ called the placenta.

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Placental Mammals

• Blood carrying food and oxygen from the mother
  flows to the placenta and then the embryo.
• Blood carrying wastes and carbon dioxide from the
  embryo flows to the placenta and then to the
  mother.
• The mothers blood does not mix with the embryos
  blood and the placental mammal develops inside
  the mothers body until its body systems can
  function on their own.

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Placental Mammals
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How Do Young Animals Develop?

• Some animals look like small versions of adults.
• Other animals go through a process of
  metamorphosis, or major body changes, as they
  develop from young organisms into adult
  organisms.
• What are some examples of animals that undergo
  metamorphosis?

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Crustaceans

• Most crustaceans such as lobsters begin their
  lives as tiny, swimming, larvae that do not
  resemble adults.
• Through metamorphosis, crustacean larvae develop
  into adults.

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Insects

• Insects undergo complete or incomplete
  metamorphosis.

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Complete Metamorphosis

• Complete metamorphosis had 4 stages egg, larva,
  pupa, and adult.
• In the pupa stage the insect is enclosed in a
  protective covering and major changes in body
  structures are taking place.
• The pupa does not eat and moves very little.

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Incomplete Metamorphosis

• Incomplete metamorphosis has no distinct larval
  stage and has 3 stages egg, nymph, and adult.
• An egg hatches into a nymph which usually looks
  like an adult without wings.
• As the nymph grows it may shed its exoskeleton
  several times.

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Amphibians

• Amphibians such as frogs begin their life cycles
  as fertilized eggs in water.
• The larva of a frog is called a tadpole.
• The frog undergoes metamorphosis to become an
  adult.
• Does a frog go through complete or incomplete
  metamorphosis?

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How Do Animals Care For Their Young?

• Most amphibians and reptiles do not provide
  parental care, while most birds and mammals
  typically care for their offspring.
• Offspring that do not receive parental care must
  be able to care for themselves from their time of
  birth.

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Parental Care

• Most bird species lay their eggs in nests that
  one or both parents build.
• Some species can move around and find food right
  after they hatch while others are helpless and
  must be fed by the parent.
• Most parent birds feed and protect their young
  until they are able to care for themselves.

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Parental Care

• Most mammals are usually quite helpless for a
  long time after they are born.
• All young mammals are fed with milk from the
  mothers body and one or both parents may
  continue caring for their offspring until the
  young animals are independent.