Because an antibody is "made" relative to the antigen, but kept at low levels when you are exposed the first time ("primary immune response"). The second time you're exposed to the same antigen, memory cells recognize it and the body produces a high level of antibodies, and the level of antibodies usually remains higher for a longer time ("secondary immune response"). This is your basic immune response (primary and secondary).
This explains exactly why vaccines are effective to extremely effective.
The Central Nervous system is made out of spinal cords that connect to the brain.
Answer:
NeanderthalsThese artistic innovators were probably Neanderthals. Dated to 65,000 years ago, the cave paintings and shell beads are the first works of art dated to the time of Neanderthals, and they include the oldest cave art ever found
Explanation:
Which hominids created art? The first human artist on Earth is believed to have drew on a cave wall with red ochre over 65,000 years ago, as a Neanderthal reached out and drew on it. There is no evidence that the modern human is the only species to express itself through art, as is widely believed.
Answer:
he organisms that can fix energy from inorganic sources into organic molecules are called autotrophs. Organisms that cannot make their food from inorganic sources but depend on energy rich organic molecules synthesized by autotrophs for their energy needs are called heterotrophs.
The only source of energy for all the ecosystems of the earth is the sun. Light falling on the plants is trapped by the producers or autotrophs in the presence of chlorophyll and is used in synthesizing the organic food called glucose by the process of photosynthesis. By photosynthesis radiant energy of sunlight is transformed into potential energy of food. A part of this energy is trapped by the producers while the rest of the energy is dissipated. The remaining part of energy which is used in the synthesis of plant biomass is called photosynthate which is then available to the next trophic level in the food chain that is the consumers or heterotrophs. In an ecosystem there is a unidirectional flow of energy.
<span>More than 50</span>. There are more than 7000 chemicals in cigarette smoke, 250 of which are known to be detrimental to health and 69 chemicals are carcinogenic (can cause cancer). Some of the carcinogenic chemicals in cigarette smoke are: Arsenic, Cadmium, Chromium, Formaldehyde and Nickel.
