The best answer is D, birds.
For more information and details on the way a bird's respiratory system works:
https://asknature.org/strategy/air-flow-patterns-facilitate-efficient-gas-exchange/
From the given choices above, the portion that is not readily penetrated by the sunlight is the river's or the stream's mouth. The plant life usually are on the surface of the water. The middle portion is occupied by the fish and other aquatic lives.
They should repeat their experiments, use their results to disprove the existing theory, and publish an extensive paper to bring attention to their discoveries.
The lowest level of biological organization that can survive and reproduce is the cell of an organism.
<h3>What is a cell?</h3>
A cell is the most basic functional unit of an organism that works to maintain homeostatic (internal equilibrium) by performing different metabolic activities such as for example, differentiation and reproduction.
In conclusion, the lowest level of biological organization that can survive and reproduce is the cell of an organism.
Learn more about the cells as functional units here:
brainly.com/question/3562162
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Site-specific recombination systems all of the choices are correct i.e.
A. do not depend on extensive nucleotide sequence homology.
B. depend on enzymes that are often specific for sequences within the host.
C. are features of some viruses.
- An exchange between two specified sequences (target sites), either on the same DNA molecule or on two separate DNA molecules, is known as site-specific recombination.
- DNA sequences may be integrated, excised, or inverted as a result of the exchange.
- A site-specific recombinase that can work by itself or with the aid of additional components or enzymes shapes the DNA target during recombination.
- The recombinase is chemically bonded to the ends of the intermediate DNA after DNA breakage at the recombination site; when this process is reversed, the intermediate DNA is resealed to form the recombinant and the recombinase is released.
- During this recombination process, neither replication nor repair are necessary.
learn more about Site-specific recombination here: brainly.com/question/11458760
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