Answer:
a.There are three signaling pathway
1- Reception in which molecule binds to receptor
2- Signal transduction in which activation of intracellular pathway and enzyme occur.
3- Cellular response in which specific response of cell occur according to receptor and ligand.
b. Three types of receptors are
1- autocrine
2- paracrine
3- endocrine.
Explanation:
autocrine receptors are signaling pathway in which cell releases its molecule and bind to its own cell receptor example cancer cells while paracrine in which ligand binds to other nearby cell receptor and it is used during development and in endocrine cell target distinct cell and travel through blood stream like hormones functioning.
Answer:
This is correct. The remaining portion:
Sympatric species that form interrelationships undergo coevolution.
Allopatric species in different environments can undergo convergent evolution.
Allopatric species in small populations and under intense environmental conditions can undergo genetic drift.
Explanation:
On the basis of geographical distance, speciation is of two major types:
- Sympatric
- Allopatric
Sympatric Speciation:
Sympatric speciation is the formation of new species with no gergraphical separation from the ancestor. The new and parent species both exist in the same environment but do not interbreed due to mechanisms of reproductive isolation. These involves both prezygotic and post zygotic barriers to reproduction such as timing of mating, sensitivity to pheromones, choice of mating sites or infertility and mismatched gametes. Species formed through sympatric speciation can form interrelationships and undergo coevolution i.e. the evolution of ones species is dependent on the other.
Allopatric Speciation:
It involves the geographical separation of the parent and new species. These species could be geographically separated by a river, mountain range or land mass.
Although, allopatric species evolve independently, they may develop similar characteristics that serve different functions. Allopatric species in radically different environments undergo convergent evolution i.e. species evolve similar characteristics without any ancestral homology.
Allopatric species that reside in small populations and are under harsh environmental pressures undergo a rapid genetic revolution i.e. genetic drift. This includes the Founder's and bottleneck effect that involve the continuation of a species from very few individuals after a drastic, sudden environmental change.
