Answer: An antigen
Explanation:
A molecule that evokes immune response in the body of an organism is known as antigen. These substance can be protein, carbohydrates, lipids when asked for chemical nature.
Physically these substance can be dust particles, smoke, pollen grains, some food particles. Antigen can be defined as the substance that tends to produce immune response by the immune system of the body.
Hence, the correct answer is option D
The tick uses the dog for two reasons. 1.It uses the dog as a source of food. 2.It also uses a dog for means of transportation from one place too another. And so the dog gains nothing
The sequence of event for the evolution of the atmosphere: 1. meteorite bombardment 2. Volcanic Outgassing 3. Oceans Form 4. Banded Iron Formations Created 5. cyanobacteria evolve 6. Oxygen increases in atmosphere 7. Eukaryotes evolve
I believe it would be polyphyletic.
Polyphyletic groups are formed when two lineages convergently evolve similar character states. Organisms classified into the same polyphyletic group share phenetic homoplasies as opposed to homologies. The key difference between paraphyletic and polyphyletic groups is that paraphyletic contain their common ancestor, whereas polyphyletic groups do not.
Answer:
(a) crossing over: Meiosis I, Recombination
(b) chromatids separate at their centromeres and migrate to opposite poles: Meiosis II, Anaphase II
(c) chromosomes become aligned in pairs at the equator: Meiosis II, Metaphase II
Explanation:
Homologous recombination is a type of genetic recombination that occurs during meiosis (formation of ovum and sperm cells). The paired chromosomes of the male and female parents are aligned so that similar DNA sequences intersect. This crossing over produces an exchange of genetic material, which is an important cause of the genetic variability observed in the offspring.
Meiosis II: Anaphase II. The centromeres separate and the daughter chromatids - now individual chromosomes - move to the opposite poles of the cell. The centromeres separate, and the two chromatids of each chromosome move toward the opposite poles in the spindle.
Meiosis II: Metaphase II. Chromosomes are accommodated in the equatorial plate of metaphase, similar to what happens in mitosis. They are attached to the already fully formed meiotic spindle. Each chromosome is aligned in the equatorial plate of the metaphase, as it happens in mitosis.
