1. Observa la figura anterior e identifica cuatro cadenas tróficas en la figura. 2. En la siguiente tabla señala los niveles tróficos para cada una de las cadenas tróficas que
identificaste.
Cuarto
Tercero
Segundo
Primero
Nivel Trófico
Cadena 1
Cadena 2
Cadena 3
Cadena 4​

Proteins are the workhorses of the cell, controlling virtually every reaction within as well as providing structure and serving as signals to other cells. proteins are long chains of  amino acids  , and the exact sequence of the amino acids determines the final structure and function of the protein. instructions for that sequence are encoded in  genes  . to make a particular protein, a messenger ribonucleic acid (mrna) copy is made from the gene (in the process called  transcription  ), and the mrna is transported to the  ribosome  . protein synthesis, also called  translation  , begins when the two ribosomal subunits link onto the mrna. this step, called initiation, is followed by elongation, in which successive amino acids are added to the growing chain, brought in by transfer rnas (trnas). in this step, the ribosome reads the  nucleotides  of mrna three by three, in units called  codons  , and matches each to three nucleotides on the trna, called the anticodon. finally, during termination, the ribosome unbinds from the mrna, and the  amino acid  chain goes on to be processed and folded to make the final, functional protein

In order to understand the problems of unwanted infertility in a country — the gambia — where the desire for children and the fertility is very high, a population-based survey was undertaken. all infertile women in 24 randomly selected enumeration areas were assessed. the study included a review of the problems faced and coping mechanisms employed by infertility clients and types of health care available for infertile couples in the different types and levels of the formal and traditional health system. half of the infertile couples failed to seek formal health care, and they have to reach a certain level of care in order to be properly managed. alternative care is often sought. child fostering is also a frequent solution to childlessness. in-depth interviews revealed that traditional care like healers and spiritual leaders are frequently consulted long before formal health care. this delay could be a problem in those cases where infertility is caused by infections.