Answer:
In the first step of meiosis I, the chromosomes/genetic material of the cell condenses into a visible form, into a form called heterochromatin. The nucleolus also disappears.
In the second step, a process called synapsis occurs. This is when homologous chromosomes align themselves, gene by gene.
In the third step, crossing over occurs. Segments of corresponding DNA are cut and exchanged between non-sister chromatids of the formed tetrads.
In the fourth step, the nucleus fragments, the nuclear envelope fragments, the two centrosomes (if we're talking about an animal cell) separate from each other as their asters and mitotic spindles (mostly microtubules (kinetochore and non-kinetochore) lengthen. The microtubules extending from the centrosomes can now connect to chromosomes.
Answer:
B12 (cobalamin): Perhaps the most well-known of all the B vitamins, B12 is vital for neurological function, DNA production and red blood cell development. B12 is found naturally in animal sources like meats, eggs, seafood and dairy.
A) The crust and outer part of the mantle make up the lithosphere
The new species come from old ancestors of the animals that were there, over time they slowly evolved, and they adapted to that new environment.
