Natural selection is the process by which individuals with characteristics that are advantageous for reproduction in a specific environment leave more offspring in the next generation, thereby increasing the proportion of their genes in the population gene pool over time. Natural selection is the principal mechanism of evolutionary change, and is the most important idea in all biology. Natural selection, the unifying concept of life, was first proposed by Charles Darwin, and represents his single greatest contribution to science.
Natural selection occurs in any reproducing population faced with a changing or variable environment. The environment includes not only physical factors such as climate or terrain, but also living factors such as predators, prey, and other members of a population.
Mechanism of Natural Selection
The mechanism of natural selection depends on several phenomena:
• Heredity: Offspring inherit their traits from their parents, in the form of genes.
• Heritable individual variation: Members of a population have slight differences among them, whether in height, eyesight acuity, beak shape, rate of egg production, or other traits that may affect survival and reproduction. If a trait has a genetic basis, it can be passed on to offspring.
• Overproduction of offspring: In any given generation, populations tend to create more progeny than can survive to reproductive age.
• Competition for resources: Because of excess population, individuals must compete for food, nesting sites, mates, or other resources that affect their ability to successfully reproduce.
Given all these factors, natural selection unavoidably occurs. Those members of a population that reproduce the most will, by definition, leave more offspring for the next generation. These offspring inherit their parents' traits, and are therefore also likely to succeed in competition for resources (assuming the environment continues to pose the same challenges as those faced by parents). Over several generations, the proportion of offspring in a population that are descended from the successful ancestor

Uloborid spider eggs and spiderlings. In any given generation, populations tend to create more offspring than can survive to reproductive age.
increases, and traits that made the ancestor successful therefore also increase in frequency. Natural selection leads to adaptation, in which an organism's traits conform to the environment's conditions for existence.
The correct answer is option d. "Elastic channels".
Explanation:
The vascular plants uses xylem and phloem cells that carry water and nutrients to all the parts of the plant, which are present in the leaves of the plant. Stomata is part of the vascular system of a plant, but it serves for gas exchange instead of water and nutrients exchange. Palisade mesophyll is a structural component that contains columnar cells with spaces between them, located in the leaves of vascular plants as well. A component that is not part of the vascular plant leaf anatomy are the elastic channels.
Both dinosaur and the trees are the living organisms which share many characteristics of the living organisms.
Among the given choices, the most common things between these two different species of the living organism are that they are made of the same constituents which makes the lowest organization of life on earth that is the cell.
Since the cells of both tress and the dinosaur are made up of the same matter or the constituent elements arranged in similar fashion therefore, the selected option is the correct answer.
