Dollo’s law:  A biological generalization positing that complex characters, once lost in evolution, are extremely unlikely to reappear and thus the loss of complex characters is virtually always irreversible.

TLS Online TPP Program

#Id: 10287

#Unit 4. Cell Communication and Cell Signaling

T-Cell - Cells leaving the thymus are functional, mature T cells expressing unique and specific T-cell receptors (TCRs) that are both tolerant to self and restricted to self-MHC.

TLS Online TPP Program

#Id: 4240

#Unit 12. Applied Biology

Most cells are anchorage dependent and must be cultured while attached to a solid or semi-solid substrate (adherent or monolayer culture), while others can be grown floating in the culture medium (suspension culture). 

TLS Online TPP Program

#Id: 8987

#Unit 11. Evolution and Behavior

Allele frequency when genotype frequency is given

TLS Online TPP Program

#Id: 9119

#Unit 10. Ecological Principles

TLS Online TPP Program

#Id: 1031

#Unit 5. Developmental Biology

In secondary neurulation, 

the neural tube arises from the aggregation of mesenchyme cells into a solid cord that subsequently forms cavities that coalesce to create a hollow tube.