The right answer is D (less responsive to antigens)
It is proven that, after puberty, thymus activity (an organ that is included in the lymphatic system, producing T cells that pick up antigens) decreases and that in adult and aged people the thymus has no role. Work done in humans indicate that in fact the cellularity begins to decline from birth in favor of lymphocyte perivascular spaces and connective and adipose tissue, which leads to a decrease in the capture of antigens.
Answer:
3. haploid; diploid
Explanation:
Sperm is male gamete or often called male reproductive cell. During the process of spermatogenesis, reductional division (meiosis) occurs in the spermatocytes and spermatids are formed which further mature to sperms. Thus as a result of meiosis, their chromosome number is reduced to half and thus they become haploid cells. During oogensis, eggs are also formed as a result of meiosis which reduces the chromosome number and so eggs are also haploid.
When during fertilization, these two haploid nucleus of these cells fuse together, they form a diploid zygote.
Answer:
conservative replication model
Explanation:
In their experiment, Meselson and Stahl found that the DNA duplexes present after the first round of replication had intermediate density. This occurred since the semiconservative process of DNA replication of one DNA molecule (having both strands with 15N) forms two DNA duplexes each with one parental strand (15N) and one newly formed strand (14N).
If they had found two duplexes of two different density, this would have supported the conservative replication model. In this case, the DNA replication of the parent DNA molecule would have formed two DNA duplexes. One DNA molecule would have both the parental DNA strands with 15N while the other DNA duplex would have both newly formed strands with 14N.
<span>ileocecal valve or sphincter</span>
