The early ancestors of horses showed the presence of digits on their limbs, while modern horses have hooves. what are likely possible reasons for this change? (more then one answer)
1.asexual reproduction
2.evolution
3.genetic mutations
4.selection
5.willful adaptation to environment

The correct answers are evolution, genetic mutation and selection.

The early ancestors of horses showed the pressence of digits and now the modern horses have hooves in their limbs. There could be many reasons for the pressence of hooves horses.

These could be due to the genetic mutations, which could have changed the shape of the digits in the limb. Sudden change in DNA can cause mutation and this mutation can change the phenotype of the horse.

There are chances that evolution took place over a period of time that changed the character in the horse.

Natural selection can also be one of the reason for the change in the phenotype of the digits on the limb of the horses.

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation: