A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community. Another name for food web is consumer-resource system.
Answer:
Fossil records provide evidence of an increase in animal species at the same time that atmospheric oxygen levels increased.
Explanation:
A huge diversification among animal species occurred with the increase in the levels of atmospheric oxygen. The reason why the number of species increased drastically was that a whole new world opened up, the land. The land was open for exploitation and taking over, with every single niche free, so animals diversified and filled in pretty much all of the niches. The fossil records give us clues when this happened, as from only microorganisms there is a sharp rise in complex animals, coinciding with the increase of oxygen levels.
If it wasn't for the increase of atmospheric oxygen though this wouldn't have been possible. The oxygen in the atmosphere enabled animals to breathe on land. Also, it cooled off the global temperatures which were too high before the increase of atmospheric oxygen, making them suitable for life. And last but not least, the atmospheric oxygen resulted in the formation of the ozone layer, a layer that started to act as protection from the UV rays.
In the absence of tryptophan, the genes trpA-E will not be transcribed.
If there were a mutation in the operator region of the trp operon, there would be a nucleotide change in the sequence of the operator. Mutations in the repressor that prevent its binding to the operator will lead to constitutive expression Mutations that prevent binding of the inducer without affecting the ability to bind to the operator lead to a non‑inducible phenotype.
The tryptophan binds to the trp repressor and causes it to change shape, converting into its active form. The trp repressor with the bound tryptophan attaches to the operator, blocking RNA polymerase from binding to the promoter and preventing transcription of the operon.
To learn more about tryptophan, here
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The greenhouse effect is a natural process that warms the Earth's surface. When the Sun's energy reaches the Earth's atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases. The absorbed energy warms the atmosphere and the surface of the Earth.
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D replace toxic chemicals
