Many phenotypic traits are genetically variable within species, they can readily evolve by natural selection and genetic drift.

TLS Online TPP Program

#Id: 123

#Unit 5. Developmental Biology

The head ectoderm is competent to respond to the paracrine factors made by the optic vesicles & induced to form the lens of the eye.

TLS Online TPP Program

#Id: 124

#Unit 5. Developmental Biology

The optic vesicle is able to induce lens formation in the anterior ectoderm but not in the presumptive trunk and abdomen.

TLS Online TPP Program

#Id: 125

#Unit 5. Developmental Biology

If the optic vesicle is removed, the surface ectoderm forms either an abnormal lens or no lens at all.

TLS Online TPP Program

#Id: 126

#Unit 5. Developmental Biology

The prospective lens cells secrete paracrine factors that instruct the optic vesicle to form the retina. 

TLS Online TPP Program

#Id: 164

#Unit 5. Developmental Biology

The two major parts of the eye (lens and retina) co-construct each other, and the eye forms from reciprocal paracrine interactions.

TLS Online TPP Program

#Id: 165

#Unit 5. Developmental Biology

First inducers of the lens are foregut endoderm and cardiac mesoderm that underlie the lens-forming ectoderm during the early and mid gastrula stages.