Answer:
B. Second
Explanation:
In the second trimester the bony parts of the skeleton begin to form
.
Keystone predators effect their habitat by keeping the population of animals down.
Cellulose is another long polymer of glucose. Plant cells make their cell walls out of cellulose. In fact, 100 billion tons of cellulose is made every year on earth. Cellulose is indigestible in most animals, including us. Ever eat a cardboard box? You get the picture. We simply lack cellulase, the enzyme that can break it down. Some bacteria, some single-celled protists, and fungi have the enzyme. Animals that feed on cellulose harbor these microbes that help them digest it. Even though, we cannot break down this molecule, we do need cellulose in our diet. We call it “fiber”. Cellulose stimulates the colon to produce regular bowel movements and helps make the stools large and soft. A diet rich in fiber can prevent a painful intestinal disorder called diverticulosis. Hard impacted stools can sometimes cause the walls of the colon to form blind outpockets called diverticula which can periodically inflame. So what makes cellulose different from starch? Isn’t it made of glucose? Well it is but the glucose monomers are organized in an interesting fashion. The orientation of the glucose molecules alternates. So if the first one is right side up, the next one is upside down and then the next is right side up and the next one is upside down. Apparently this is a tricky arrangement for an enzyme to break.
Answer:
El híbrido va a ser esteril.
Explanation:
En la cruza entre dos especies distintas, cuando ocurre, existen distintos mecanismos de aislamiento reproductivo, que son barreras que inhiben o interrumpen el flujo génico entre especies distintas. Es decir que no habrá exito reproductivo de estas cruzas. Se trata de caracteres biológicos propios de cada especie que previenen la reproducción con otras especies.
Estos mecanismos de aislamiento reproductivo pueden ser precigóticos o postcigóticos.
1.Pre-copulatorios o pre-cigóticos:
- Ecológico o por aislamiento de hábitat;
- Por incompatibilidad de gametas.
2. Post-copulatorios o cigóticos:
- Inviabilidad del híbrido;
- Híbrido con viabilidad o fertilidad disminuido;
- Interacciones citoplasmáticas.
La mula es producto de la cruza entre dos especies distintas: una yegua (Equus ferus caballus) y un burro (Equus africanus asinus). Es un ejemplo de la accion de mecanismo poscigótico, en el cual se forma un híbrido viable esteril. Este ejemplar puede nacer, crecer y sobrevivir, pero que no puede producir gametas funcionales, por lo cual no puede reproducirse.
