Answer: A. Brain - Organ level
B. Neurons - Cellular level
C. Neurotransmitters - Chemical level
D. Neurons and neuroglial cells - Tissue level
E.Brain combined with the spinal cord and spinal nerves - Organ System level
Explanation: There are five levels of organisation of life; cell, tissue, organ, system and organism.
The smallest unit is cell. Neurons are nerve cells.
Aggregation of cells forms a tissue. Neurons and neuroglial cells aggregate to form nervous tissues and are hence at tissue level.
Aggregation of tissues forms an organ. Brain is an example of organ. It is formed from aggregation of nervous tissues.
Tissues aggregate to form organs while aggregation of organs constitute a system. The nervous system consist of brain combined with spinal cord and spinal nerves.
The nervous system release chemicals called neurotransmitters.
Answer:
The correct answer will be option-Crossover region
Explanation:
Recombination is a complex process which leads to the exchange of the genetic material between sister chromatids.
The recombination process is mediated by the recombinase enzyme which recognize the specific sites and allows the formation of the protein-DNA complex called synaptic complex.
The synaptic complex contains the short asymmetric sequence called the crossover region, which represents the rejoining and the DNA cleavage site.
Since crossover region represents the recognition sequence which is flanked is known as the crossover region.
Thus, the crossover region is the correct answer.
Answer:
a. 1/2 b. The organism is an animal
Explanation:
a. What is the medullary index for an organism that has a medulla width of 2cm and hair shaft width 4cm?
Medullary index = diameter of medulla/diameter of hair.
Given that diameter of medulla = medulla width = 2cm and diameter of hair = hair shaft width = 4cm,
Medullary index = diameter of medulla/diameter of hair = 2 cm/4cm = 1/2
b. Is this organism human or animal?
Since the medullary index = 1/2 > 1/3 (if it is ≤ 1/3 it is human hair and ≥ 1/2 it is animal hair), it is animal hair. So, the organism is an animal.
Enzymes. They don't need it
Answer: Organisms are born with variation.
