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Romashka [77]
3 years ago
7

According to most scientific models, how many years ago did the first simple cells appear on Earth?

Biology
1 answer:
alexandr402 [8]3 years ago
7 0

About 3.6 billion years ago, one billion years after the formation of Earth, the first simple cells (prokaryotes) appeared on Earth. Hope this helps!

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A signaling pathway that stimulates cellular growth and division is positively regulated by a GTPase encoded by an autosomally l
Romashka-Z-Leto [24]

Answer:

The correct answer is: a.

Explanation:

  • A Diploid organism possess two copies ( also called alleles) of each  autosomal gene, of which one copy of the gene is obtained from one of its parents and the other copy from its other parent.
  • During the process of replication, one of the alleles of the GTPase encoding gene undergoes a mis-sense mutation.
  • A Mis-sense mutation can be defined as a non-synonymous mutation in which one of the nucleotide in the sequence of the gene gets altered such that it causes a change in the amino acid encoded by the codon (triplet nucleotide message encoding for a single amino acid)  formed by the mutated nucleotide. A single amino acid change in the protein, if occurs in the functional site of the protein, can render a protein non-functional.
  • Hence, the mis-sense mutation in one of the alleles encoding for the GTPase gene causes the resulting protein produced from the mutated allele to have drastically reduced function (1%).
  • A heterozygous cell is one which has one copy of the normal allele and the other copy of the mutated allele of the GTPase encoding gene.
  • As one copy of the normal GTPase allele is present in such an individual, it can produce the normal GTPase protein that can assist in the process of cell growth and division.
  • Hence, the phenotype(expressed character) of  the heterozygous cell will not be affected due to the mutation and it will be able to grow and divide normally.
8 0
3 years ago
Explain how the reduction in biodiversity can effect the ecological balance in the dam
hodyreva [135]
<span>Damming a river has a variety of effects on the freshwater ecosystem, more than just altering the flow from A to B.  Dams create calm bodies of water, changing overall temperature regimes and sediment transport, leading to conditions which tend to favour generalist species. Loss of specialist species, particularly endemics, changes the community structure and leads to biotic homogenization.  A dam will withhold sediment in the reservoir, not just decreasing the amount of substrate available to local freshwater species, but even impacting diadromous, estuarine and marine species much further downstream.  The competition between resident species for food and breeding sites will increase as damming isolates populations, and perhaps more importantly, damming completely restricts migratory fish species.  Isolation may lead to decreases in genetic diversity and therefore puts species at greater risk from disease.  All of these effects may be exacerbated by changes in the surrounding land use.  Overall, damming river flow will lead to both a loss of native species, but also an increase in exotic species which are more likely to become established in degraded habitats. For this reason, dams are one of the greatest global threats to freshwater biodiversity.</span>
6 0
4 years ago
Which statements are additions to cell theory, called modern cell theory? Check all that apply.
Marysya12 [62]
1.    All cells are similar in structure and function. 

2.   Cell contains hereditary information that is passed from cell to cell during cell division. 
 
3.    Living cells can be created from dead cells. All cells perform similar metabolic activities.

hope this helps
5 0
3 years ago
Read 2 more answers
You have batch of pea plants with purple flowers that you grew by crossing plants that had purple flowers (PP) with plants that
nordsb [41]
If I have a batch of pea plants with purple flowers that I grew by crossing plants that had purple flowers (PP) with plants that had white flowers (pp), purple flowers (dominant) will be expressed in this batch of pea plants.
3 0
4 years ago
Mice that have been given morphine are very likely to develop blood poisoning because bacteria that normally reside in the intes
Hitman42 [59]

Answer:

Which of the following, if discovered to be true, would most seriously weaken the support for the researchers’ prediction?

The correct answear is B. Naltrexone inhibits morphine from triggering the migration of intestinal bacteria into the bloodstream.

Explanation:

Naltrexone is a non-selective opioid antagonist, it competes with these at the level of the receptors and thus reduces their effects.

The responses A, C, D and E does not weaken the support for the

researches ´ predictions, and are not relevant to the argument.

4 0
3 years ago
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