Connect!Connect! • Where do embryos of the Where do embryos of the pictured organisms pictured organisms develop?develop?

Where Embryonic Development Where Embryonic Development OccursOccurs

• Embryonic development can occur externally or internally.

A. EXTERNAL EMBRYONIC DEVELOPMENT:

• occurs outside the female’s body

• can occur in water or on land

1. In Water

• The eggs of many fish and amphibians are fertilized externally and develop externally.

• The developing embryo’s source of food is the yolk stored in the egg.

2. On Land

• The eggs of many birds and (and a few mammals) develop externally on land after internal fertilization.

• Again, the developing embryo’s source of food is the yolk.

• Adaptations of animals that develop on land are a shell which provides protection and prevents water loss.

Chunk QuestionsChunk Questions

• What are the two types of development?What are the two types of development?• Define “external development”.Define “external development”.• Where does it occur?Where does it occur?• What type of fert and dev do amphibians What type of fert and dev do amphibians

and fish use?and fish use?• What is the function of the yolk?What is the function of the yolk?• What type of fert and dev do birds use?What type of fert and dev do birds use?• What is an adaptation for land external What is an adaptation for land external

development?development?• What functions does it serve?What functions does it serve?• Why are duckbill platypuses and spiny Why are duckbill platypuses and spiny

anteaters unusual mammals?anteaters unusual mammals?

B. B. INTERNAL EMBRYONIC DEVELOPMENTINTERNAL EMBRYONIC DEVELOPMENT

• involves the growth of the embryo inside the body of the parent

• There are 2 types of internal development: placental & marsupial

1. Placental Mammals

• These mammals have internal fertilization.

• The embryo develops internally within the uterus.

Pass folder with photo of cow Pass folder with photo of cow uterus around, for those uterus around, for those interested in looking…interested in looking…

PlacentalPlacental Mammals have Mammals have placentasplacentas!!

• The eggs of mammals have very little yolk and therefore are very small.

These eggs do not need a lot of yolk bc the placenta exchanges nutrients, wastes, and respiratory gases btwn the mother and the embryo by active transport and diffusion.

human egg –

size of sharp pencil point

•There is NO direct connection btwn maternal and embryonic blood.

•An umbilical cord, containing blood vessels, attaches the embryo to the placenta.

placenta

Umbilical cord

Notice that blood of embryo and mother do NOT mix!

So how does exchange of materials occur?

Use this diagram to help label the diagram in your notes.Use this diagram to help label the diagram in your notes.

ovary

uterus

amnion

embryo

oviduct

placenta

cervix vagina

umbilical cord

Chunk QuestionsChunk Questions• If an organism has internal development, where does If an organism has internal development, where does

fertilization occur?fertilization occur?

The following questions refer to placental mammals…The following questions refer to placental mammals…

• Where does the embryo develop?Where does the embryo develop?• Why are the eggs of placental mammals so tiny?Why are the eggs of placental mammals so tiny?• How does the embryo obtain needed nutrients and How does the embryo obtain needed nutrients and

gases?gases?• How does the embryo get rid of toxic wastes?How does the embryo get rid of toxic wastes?• By what process do OBy what process do O22 and nutrients move into the and nutrients move into the

embryo?embryo?• Explain the connection btwn mother and embryo in Explain the connection btwn mother and embryo in

the placenta.the placenta.• What does the umbilical cord do?What does the umbilical cord do?• So, what actually IS the placenta?So, what actually IS the placenta?

2. Marsupials2. Marsupials

• These mammals also have internal fertilization These mammals also have internal fertilization with with internal internal embryonic development.embryonic development.

• InternalInternal development occurs development occurs withoutwithout direct direct nourishment from the mother; instead, nourishment from the mother; instead, yolkyolk is is the source of food. the source of food.

There is NO There is NO placentaplacenta!!

• The embryo is born The embryo is born prematurelyprematurely compared to compared to placental mammals and completes its placental mammals and completes its development development externallyexternally in a pouch. The source in a pouch. The source of food in this later stage is of food in this later stage is milk milk from mammary from mammary glands located in the pouch.glands located in the pouch.

Consider a newborn koala…Consider a newborn koala…

A newborn koala is approximately the size of a gummi bear. It is born 35 days after conception and immediately crawls into its mother's pouch, where it stays for six to seven months, before taking its first peek out.

Let’s look at the development of Let’s look at the development of another marsupial, the kangaroo…another marsupial, the kangaroo…

Kangaroos have developed a Kangaroos have developed a number of adaptations to a dry, number of adaptations to a dry, infertile continent and a highly infertile continent and a highly variable climate. variable climate.

As with all marsupials, the As with all marsupials, the young are born at a very early young are born at a very early stage of development after a stage of development after a gestationgestation of 31-36 days. At this of 31-36 days. At this stage, only the forelimbs are stage, only the forelimbs are somewhat developed, to allow somewhat developed, to allow the newborn to climb to the the newborn to climb to the pouch and attach to a teat. pouch and attach to a teat.

In comparison, a human embryo In comparison, a human embryo at a similar stage of at a similar stage of development would be about 7 development would be about 7 weeks old, and premature weeks old, and premature babies born at less than 23 babies born at less than 23 weeks are usually not mature weeks are usually not mature enough to survive.enough to survive.

• The joey will usually stay in the pouch for about 9 The joey will usually stay in the pouch for about 9 months or (for the Western Grey) 180 to 320 days, months or (for the Western Grey) 180 to 320 days, before starting to leave the pouch for small periods before starting to leave the pouch for small periods of time. It is usually fed by its mother until the age of time. It is usually fed by its mother until the age of 18 months. of 18 months.

• Examples of marsupials include kangaroos Examples of marsupials include kangaroos and opossums and opossums (only marsupial native (only marsupial native to North America)to North America)

Chunk QuestionsChunk Questions

• What type of fert and dev do marsupials have?What type of fert and dev do marsupials have?

• Do marsupials have a placenta?Do marsupials have a placenta?

• How do the embryos get nourishment?How do the embryos get nourishment?

• Describe marsupial embryos.Describe marsupial embryos.

• Name some marsupials.Name some marsupials.

• What is the gestation period for kangaroos and What is the gestation period for kangaroos and koalas?koalas?

• How is marsupial development different from How is marsupial development different from placental?placental?

• How is marsupial development similar to placental?How is marsupial development similar to placental?

Image SourcesImage Sources

• Bunny - oregonjon.wordpress.com/.../Bunny - oregonjon.wordpress.com/.../

• Apple - organic-center.org/.../ripe-red-apple.jpg Apple - organic-center.org/.../ripe-red-apple.jpg

• Oppossum - 1.bp.blogspot.com/.../s400/oppossum.jpg Oppossum - 1.bp.blogspot.com/.../s400/oppossum.jpg

• Trout - skywalker.cochise.edu/.../image022.jpg Trout - skywalker.cochise.edu/.../image022.jpg

• Sea turtle - www.treehugger.com/2008/10/19-week/Sea turtle - www.treehugger.com/2008/10/19-week/

• Ostrich - photos.igougo.com/images/p303673-Oranjestad-O...Ostrich - photos.igougo.com/images/p303673-Oranjestad-O...

• Kangaroo - www.royalpetclub.com/blog/wp-content/uploads/...Kangaroo - www.royalpetclub.com/blog/wp-content/uploads/...

• Stink bug eggs - www.edupic.net/.../hem_stink_bug_eggs01.JPG Stink bug eggs - www.edupic.net/.../hem_stink_bug_eggs01.JPG

• Frog eggs - academic.emporia.edu/sievertg/tadpoles/devo.htm Frog eggs - academic.emporia.edu/sievertg/tadpoles/devo.htm

• Platypus photo and anteater - www.greenfieldpub.lib.in.us/.../platypus.jpg Platypus photo and anteater - www.greenfieldpub.lib.in.us/.../platypus.jpg

• Robin eggs www.wbu.com/chipperwoods/photos/robin.htm Robin eggs www.wbu.com/chipperwoods/photos/robin.htm

• Sea turtle eggs - naturescrusaders.files.wordpress.com/2009/06/... Sea turtle eggs - naturescrusaders.files.wordpress.com/2009/06/...

• Patchwork platypus - www.olliverlyle.com/.../images/platy5.gif Patchwork platypus - www.olliverlyle.com/.../images/platy5.gif

• Duckbill cartoon - www.cartoonstock.com/lowres/shr0115l.jpg Duckbill cartoon - www.cartoonstock.com/lowres/shr0115l.jpg

• Arthur and Baby Kate - http://pbskids.org/arthur/Arthur and Baby Kate - http://pbskids.org/arthur/

• Placenta diagram – E. ThomasPlacenta diagram – E. Thomas

• Embryo diagram and placenta sketch (modified by E. Thomas) - en.wikibooks.org/.../Reproductive_System Embryo diagram and placenta sketch (modified by E. Thomas) - en.wikibooks.org/.../Reproductive_System

• Slide 13 and 14– diagrams (modified by E. Thomas) - http://www.mikecurtis.org.uk/biol0image4_2.gifSlide 13 and 14– diagrams (modified by E. Thomas) - http://www.mikecurtis.org.uk/biol0image4_2.gif

• Types of marsupials - visual.merriam-webster.com/images/animal-king. Types of marsupials - visual.merriam-webster.com/images/animal-king.

• Koala with baby - www.itee.uq.edu.au/~adc2010/koala.jpg Koala with baby - www.itee.uq.edu.au/~adc2010/koala.jpg

• Newborn koala/gummi bear - www.koalajo.com/images/gummibear.jpg Newborn koala/gummi bear - www.koalajo.com/images/gummibear.jpg

• Joey in pouch - en.wikivisual.com/images/4/4f/Joey_in_pouch.jp, blogs.courierpostonline.com/fishhead/files/20... , Joey in pouch - en.wikivisual.com/images/4/4f/Joey_in_pouch.jp, blogs.courierpostonline.com/fishhead/files/20... ,

• Kangaroo cartoon - www.cartoonstock.com/lowres/ato0120l.jpg Kangaroo cartoon - www.cartoonstock.com/lowres/ato0120l.jpg

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