In my opinion, I think that coal is the most important mineral of all. It keeps us warm during winter and it helps train transport food and other goods that we need.
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<span>A key difference between active transport and diffusion is that active transport needs energy</span>
Answer :Four characteristics were to be used for the classification of all viruses:
Nature of the nucleic acid in the virion.
Symmetry of the protein shell.
Presence or absence of a lipid membrane.
Dimensions of the virion and capsid.
Explanation:
Answer:
Species separated by a physical barrier for a long time, suffer allopatric speciation, so they can not interbreed anymore.
Explanation:
Allopatric speciation consists of the geographic separation of a continuous genetic background giving place to two or more new geographically isolated populations. These separations might be due to migration, extinction of geographically intermediate populations, or geological events. In this speciation, some barriers impede genetic interchange, or genetic flow, as the two new populations that are separated can not get together and mate anymore. These barriers might be geographical or ecological.
Vicariance is the geographical separation of an original population into two or more new groups. Discontinuities in the physical environment like rivers, mountains, water, etc., are physical barriers that impede genetic flow between the separated groups.
The process of allopatric speciation involves different steps:
- The emergence of the barrier.
- Interruption in the genetic interchange
- The occurrence of new mutations and their accumulation in time in each population. Slow and gradual differentiation.
- Genetic divergence by natural selection and reproductive isolation makes it impossible for the two groups to mate even if the barrier disappears.
- Prezigotic isolation mechanisms favored by selection once occurs a secondary contact between the new species in formation.
Chromosome is to cactus as gene is to needle.
