<span>main function of the circulatory system in multicellular organisms is to circulate blood and oxygen in our body .so the right option is
</span><span>A) to bring oxygen into the lung
</span>hope this helps
Answer: parasitism
Explanation: Because it's relationship between two species of plants or animals in which one benefits at the expense of the other, sometimes without killing the host organism.
They have hooks so that the seeds can spread around, get carried away and land in a place be planted and grow.
The ileocecal valve prevent the back flow of materials from the large intestine to the ileum of the small intestine.
Answer:
Increased frequency of the allele for sickle cell anemia
Explanation:
Sickle cell anemia is fatal in homozygous genotype. The homozygous genotype having two copies of the allele for sickle cell anemia is not favored by natural selection due to its reduced survival success.
However, the heterozygous genotype for sickle cell anemia with one allele for the disease exhibit malaria resistant. The presence of one allele is not fatal for the organisms as the presence of one normal allele ensures the formation of some normal hemoglobin protein and RBCs to support the oxygen delivery to the body parts.
The increased survival success of heterozygous genotype in malaria-prone regions allowed their natural selection. This increased the frequency of allele for the sickle cell anemia in the gene pool of the local population and increased the frequency of heterozygous dominant genotype.
