Answer:
Selection is a directional process that leads to an increase or a decrease in the frequency of genes or genotypes. Selection is the process that increases the frequencies of plant resistance alleles in natural ecosystems through coevolution, and it is the process that increases the frequencies of virulence alleles in agricultural ecosystems during boom and bust cycles.
Selection occurs in response to a specific environmental factor. It is a central topic of population and evolutionary biology. The consequence of natural selection on the genetic structure and evolution of organisms is complicated. Natural selection can decrease the genetic variation in populations of organisms by selecting for or against a specific gene or gene combination (leading to directional selection). It can increase the genetic variation in populations by selecting for or against several genes or gene combinations (leading to disruptive selection or balancing selection). Natural selection might lead to speciation through the accumulation of adaptive genetic differences among reproductively isolated populations. Selection can also prevent speciation by homogenizing the population genetic structure across all locations.
Selection in plant pathology is mainly considered in the framework of gene-for-gene coevolution. Plant pathologists often think in terms of Van der Plank and his concept of "stabilizing selection" that would operate against pathogen strains with unnecessary virulence. As we will see shortly, Van der Plank used the wrong term, as he was actually referring to directional selection against unneeded virulence alleles.
When prey is abundant, predator populations increase because more young are able to survive. More predators kill more prey, which, along with food scarcity, decreases the population. When prey becomes more scarce, the predator population declines until prey is again more abundant. Therefore, the two balance each other.
If your immune system attacks your own body parts, then it's called 'autoimmune disease'.
Autoimmune disease can happen at many times due to many problems the body can have. If one thing goes wrong with your body, it can go to another.
Answer:
pulmonary circuit, systemic circuit
Explanation:
The circulatory system consists of 2 circuits -
pulmonary circuit
systemic circuit.
The pulmonary circuit carries deoxygenated blood. The right auricle receives the impure blood by superior and inferior vena cava, then the blood enters the right ventricle. From the right ventricle, the deoxygenated blood moves to the lungs by the pulmonary artery.
In the lungs, the deoxygenated blood gets oxygenated and enters the left ventricle through pulmonary veins. The pureblood then passes into the left ventricle and then the ventricle pumps the oxygenated blood to different parts of the body. This blood passes to the body aways from the heart by aorta. When the blood gets deoxygenated, it again enters the right auricle. In this way, double circulation occurs and both types of blood do not mix together.
