Fossil record of the first possible bipeds is the evidence exists that state humans are evolved in Africa. Modern humans arose in Africa at least 250,000 to 300,000 years ago, fossils and DNA are the evidence that reveals. Scientists have been unable to pinpoint a more specific homeland because the earliest Homo sapiens fossils are found all across Africa.
Humans first evolved in Africa, and much of human evolution occurred on that continent. The fossils of early humans who lived between 6 and 2 million years ago come entirely from Africa. Most scientists currently recognize some 15 to 20 different species of early humans found from Africa.
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Answer:
Below
Explanation:
mRNA is a complimentary copy of a DNA segment (gene) and consequently can be used to deduce the gene sequence. For converting a sequence from mRNA to the original DNA code, apply the rules of complementary base pairing: Cytosine (C) is replaced with Guanine (G) – and vice versa. Uracil (U) is replaced by Adenine (A).
The codon is the three nucleotide sequence in the mRNA that indicates which amino acid should be incorporated in the growing polypeptide chain. The anticodon is the complementary three nucleotide sequence in the appropriate tRNA.
Answer: Substances that are protein based cannot cross the lipid cell membrane, but can exert their effect by binding to the proteins based receptors present on the lipid bilayer.
Explanation:
Hormones such as calcitonin , Parathyroid hormone and pituatry horomones are proteins and water soluble.They cannot cross lipid bilayer but can bind to ligand binding protein receptors.
These receptors are protein macromolecules that are specific in nature for specific hormones.
After binding to the receptors, these hormone-recpetor complexes activate second messengers and regulate the downstream effects.
Antagonsitic effect/interaction/response
In order to combat antiobiotic resistance, and to possibly enhance the activity of antibiotics, they are sometimes used in combinations during treatment. However, three possible responses or effects can manifest.
First is antibiotic synergy, where the combined effect of the antibiotics enhances the activity/potency of the treatment compared to when the antibiotics are administered singly.
The effect is also distinguished from another type of response, which is additive effect, where the combined effect of the antibiotics is more or less equal to the combined activity/potency of each of the antibiotic when applied singly. Antibiotic synergy results in even greater enhancement of the activity of the combined antibiotics compared to additive effect.
Lastly, there is the antagonistic effect or response, where the combined effect of the antibiotics results in the weakening of the potencies of the antibiotics relative to the combined (additive effect) potencies of each of the antibiotics.
