Biology Questions

Heritable variation is one of the four most important factors that affect whether natural selection can occur. These factors include

1) Heritable variation

2) Descent with modification

3) Struggle for survival, and necessarily if the others are satisfied

4) Survival of the fittest.

Heritable variation allows for possibly beneficial, negative, or even neutral mutations to get filtered during each generation by natural selection--weeding out negative mutations, passing on positive and neutral ones. Without heritable variation, species would quickly fall victim to parasites who take advantage of identical genetic material in a population and evolution would not occur.

Variation is the raw material of evolution.

Because arteries have to have thick walls for use of protection. Its when you get to veins where the walls get thinner. And the use of the heart is to pump blood to all of the cells and organs in the body so it would be to transport blood away from the heart.

i.e. 

Arteries = Away from the Heart 
Veins = Back to the Heart.

A sarcomere is the basic unit of striated muscle tissue. It is the repeating unit between two Z lines.

Skeletal muscles are composed of tubular muscle cells (myocytes called muscle fibers or myofibers) which are formed in a process known as myogenesis. Muscle fibers contain numerous tubular myofibrils. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as alternating dark and light bands. Sarcomeres are composed of long, fibrous proteins as filaments that slide past each other when a muscle contracts or relaxes.

A muscle fiber from a biceps muscle may contain 100,000 sarcomeres.

Translation occurs in the cytoplasm whereas transcription occurs in the nucleus.

Transcription and Translation:

Terms transcription and translation in biology are generally related to the DNA and its properties. Human cells replicate. In order to do that, they have to produce the same constituents for the new cell that is to be made. The only way to do that is by producing proteins.

The proteins are produced in the process that is called protein synthesis. The first step is in the nucleus where a particular gene is being expressed so it enables all protein factors to come and to replicate that part of a chromosome. This is finished when mRNA, the same single-stranded genetic code of a particular gene, is formed. This is transcription.

Right after that, the mRNA enters the cytoplasm through nuclear pores. There, it could be translated into proteins by ribosomes. This process is called translation.