One recent approach to vaccine development has been production of peptide vaccines. In these vaccines, antigenic peptides are injected instead of whole bacteria or viruses. Peptide vaccines have not been particularly useful against viral pathogens because viral infections require a CD8+ T cell mediated immune response. Why is a peptide vaccine unable to create such a response?

Explanation below

Explanation:

Immunization is the process of protecting the body from infections. This can be divided into two, namely

1. Natural immunization

2. Artificial immunization

Natural immunization is the one that is being developed by the body naturally, to protect the body from infections. This is usually known as the white blood cells.

Artificial immunization is being developed through the introduction of atenuated organisms into the body, so that the body can react by producing antibodies against that infectious organisms. This is known as vaccination.

The peptide vaccines have been developed for the body to be able to produce antibodies against some infections.

It should be noted that, owing to the relatively small size of peptides, they are often weakly immunogenic by themselves and therefore require carrier molecules, to add chemical stability and adjuevating for the induction of a robust immune response.

tsd is temerature dependent sex determination.

tsd: it is a type of environmental sex determination in which the temperature experienced during embryonic/ larval development (ambient temperature for development) determine the sex of the offspring.

crocodile displays the tsd where the ambient temperature of the developing egg determines the individual's sex. for example in the american alligator's eggs, incubation at 33 ºc produces mostly males, while incubation at 30 ºc produces mostly females. so if the american alligator's egg will get the ambient temperature (33 degree celcius)during embryonic development from egg, the offspring will be male and same for the female sex determination.

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.