Answer:
The correct answer is b. must be present in a population before natural selection can act upon the population
Explanation:
Genetic variation can be caused by mutation, recombination between chromosomes during meiosis and by fusion of two genetically different gametes during sexual reproduction.
This genetic variation is necessary for the evolution of any population. Natural selection acts on every individual and it decreases the frequency of those alleles that are not suited for the environment and increase the frequency of those alleles which helps the individual to survive in the changing environment.
Therefore genetic variation must be present in the population before natural selection act on the.
Answer:
DNA is made up of molecules called nucleotides each nucleotides contains a phosphate group a sugar group and nitrogen base
Answer:
the answer is less than 5 minutes.
Explanation:
Hope this helped Mark BRAINLEST!!
Answer:
In an organ, different tissues work together to carry out a particular function. These are the main organs, as well as their primary function:
The brain controls thoughts, memory and other organs.
The heart pumps blood around the body.
The lungs separate oxygen from the air and remove carbon dioxide from the blood.
The stomach helps to digest food.
The intestines absorb nutrients from food.
The liver removes poisons from the blood.
The kidneys filter blood and produce urine.
The bladder stores urine.
The skin protects and contains the other organs.
<span>The cell requires a barrier between itself and its environment.</span>
