Answer:
Natural selection is generally limited to modifying structures that were present in previous generations and in previous species
Explanation:
The basic idea of biological evolution is that populations and species of organisms change over time. Today, when we think of evolution, we are likely to link this idea with one specific person: the British naturalist Charles Darwin.
In the 1850s, Darwin wrote an influential and controversial book called On the Origin of Species. In it, he proposed that species evolve (or, as he put it, undergo "descent with modification"), and that all living things can trace their descent to a common ancestor.
Natural selection, genetic drift, and gene flow are the mechanisms that cause changes in allele frequencies over time. When one or more of these forces are acting in a population, the population violates the Hardy-Weinberg assumptions, and evolution occurs. The Hardy-Weinberg Theorem thus provides a null model for the study of evolution, and the focus of population genetics is to understand the consequences of violating these assumptions.
New gene variants (i.e., alleles) are produced by random mutation, and over the course of many generations, natural selection may favor advantageous variants, causing them to become more common in the population.
Answer: 3. The half- life of the isotope must be long enough to capture the age of the rock. and
4. their should be more than one unstable isotope.
In radioactive dating proces, the parent isotope is in unstable state which undergoes decay process to give stable daughter isotopes. Half-life is the amount of time it takes for half of the parent isotopes to decay. The rock dating requires a long lived parent isotope so that it can capture the exact rock age.
One rock when get decayed in the daughter isotope other will be available identify the age.
I believe the answer is head-on and port (left). The side lights are usually visible to vessels approaching from the front or the side. The red light usually indicates a vessel's port (left) side while the green light indicates a vessel's starboard (right) side. These lights ensure that there is safety at night as the vessels navigate.
