Answer: Layer a is 500 million years old.
Explanation:
Trilobite is a member of the group of extinct arthropods found as fossils and they can be identified by the three-lobed as well as three segmented forms. These were the marine animals. These were appeared initially in the Cambrian Period. They used to live 542 million years ago so the fossils can be estimated to be aged of 500 above years old. These animals used to dominate in the sea area.
<span>Compound Microscope
Compound microscope is commonly used in the schools and colleges.
It comes under the category of microscopes used in biology.
It has two lenses namely the objective lens and the ocular lens.
It provides a magnification of 1500X.
Eyepiece lens is of 10X or 15X power.
It is used to observe bacterial, protozoa, various cells, etc.
</span><span>Dissecting Microscope
It is also called stereo microscope.
Its magnification power is less than the other microscope.
It gives a 3 dimensional picture.
Due to the low magnifying power they are used to observe little bigger objects than other microscopes.
They are used in the surgeries, dissection, forensic science etc.</span>
T cells
The immune response to a transplanted organ consists of both cellular (lymphocyte mediated) and humoral (antibody mediated) mechanisms. Although other cell types are also involved, the T cells are central in the rejection of grafts. The rejection reaction consists of the sensitization stage and the effector stage.
Answer:
Human nutrition is the process of which substances are Transformed into tissues and energy which are used up to mental and physical activities!
The environment provides the selective pressure in natural selection. Artificial Selection is a type of choice in which people effectively pick which characteristics ought to be passed onto posterity. People have utilized particular rearing some time before Darwin's Postulates and the disclosure of hereditary qualities. It is the rearing of plants and creatures to deliver attractive qualities. Living beings with the coveted characteristics, for example, size or taste, are misleadingly mated or cross-pollinated with creatures with comparable wanted attributes.
