Comparative Embryology

What is an embryo?

• An early stage of development of a multicellular organism.

• A sex cell that begins to grow and diversify.

• The genome of an organism before birth.

• The fluid sac surrounding a developing organism in its earliest stages.

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What is comparative embryology?

• Compares embryos of different species, showing how all animals are related.

• Medical research that uses embryonic stem cells.

• The study of environmental influences on embryos.

• The act of sequencing DNA of embryos.

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The most recent ancestral form or species from which two different species evolved is known as ________________________.

• a common ancestor.
• an embryonic stage.
• development.
• evolution.

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Common ancestry relates to evolution because

• evolution only happens when there are common ancestors.
• Common ancestors make evolution happen more quickly.
• evolution can never take place with common ancestors.
• the more two organisms have in common, the more recent is their common ancestor during their evolution.

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In stage one (top row) of these embryos, most of the embryos________

• look very similar.
• have very different features.
• show different stages of development.
• have only a tail if they are non-human.

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In stage 2 (middle row) fish embryos _________

• are very different from bird and mammal embryos.

• are still very similar to bird and mammal embryos.

• show arm and leg buds.

• are the only embryos with tails.

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In the the third embryonic stage (bottom row), mammal embryos _____

• have more characteristics in common with each other than with reptiles or birds.
• are still hard to tell from reptiles and birds.
• have the same features as fish, reptiles, and birds.
• do not have tails.

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The more similar the stages of embryonic development, the more likely that organisms share ____________

• a common ancestor.
• embryos.
• eggs.
• embryology.

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This period is generally divided into three: germinal, embryonic, and fetal.

• common ancestry
• egg
• embryonic stages
• development

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According to the images shown, which species are most related?

• calf and rabbit

• fish and human

• pig and tortoise

• salamander and chick

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