Summary
Ectoderm, mesoderm and endoderm give rise to all animal tissues; simple animals have only two.
In depth
Diploblasts (cnidarians) have ectoderm and endoderm; triploblasts add mesoderm, enabling complex organs like muscles and circulatory systems.
Germ layers determine tissue types. Triploblasts have more organ complexity. Fate is shown in fate maps.
Remember: ectoderm is outer, endoderm inner.
Germ layers form during gastrulation. Ectoderm gives skin, nervous system and sense organs; mesoderm gives muscle, bone, blood, heart, kidneys and gonads; endoderm gives the gut lining, liver, pancreas and lungs. Cnidarians are diploblastic (with two layers and a jelly-like mesoglea), but all other animals are triploblastic. Spemann and Mangold's organiser experiments in 1924 showed that a region of the early embryo induces neural tissue.
Understanding germ layers helps in stem cell research, where cells are directed to become tissues derived from specific layers. Abnormal development of layers causes defects, such as neural tube defects. Neural crest is sometimes called the fourth germ layer for its range of derivatives.
Remember: mesoderm allowed muscles and circulatory systems and thus larger, more active bodies.
Frequently asked questions
What is Germ Layers?
Ectoderm, mesoderm and endoderm give rise to all animal tissues; simple animals have only two.
Which area of biology covers Germ Layers, and how advanced is it?
Germ Layers is one of the 53 topics in Zoology & Animal Diversity. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Vertebrates and Invertebrates, Animal Symmetry, Animal Kingdom.
Can you give an example of Germ Layers?
In vertebrates, the notochord and heart develop from mesoderm.
What should I learn before Germ Layers?
Work through the Beginner topics in Zoology & Animal Diversity first, such as Animal Kingdom, Vertebrates and Invertebrates, Sponges, then return to Germ Layers. Intermediate topics assume the Beginner vocabulary.
What topics are related to Germ Layers?
The closest topics to Germ Layers are Vertebrates and Invertebrates, Animal Symmetry, Animal Kingdom, Body Cavities. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Germ Layers?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Germ Layers. To practise the whole of Zoology & Animal Diversity, use the Zoology & Animal Diversity quiz.
How is Germ Layers different from Vertebrates and Invertebrates?
Germ Layers: Ectoderm, mesoderm and endoderm give rise to all animal tissues; simple animals have only two. Vertebrates and Invertebrates: Vertebrates have a backbone; invertebrates, which are over 95 percent of animals, do not. Read both side by side and note what each one explains.
How should I study Germ Layers step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Vertebrates and Invertebrates and explain the difference aloud. Finally, take the Zoology & Animal Diversity quiz and come back to this page for any question you miss.