Excerpt from âOn the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection,â by Charles Darwin [Read July 1st, 1858]. To give an imaginary example from changes in progress on an island:âlet the organisation of a canine animal which preyed chiefly on rabbits, but sometimes on hares, become slightly plastic; let these same changes cause the number of rabbits very slowly to decrease, and the number of hares to increase; the effect of this would be that the fox or dog would be driven to try to catch more hares: his organisation, however, being slightly plastic, those individuals with the lightest forms, longest limbs, and best eyesight, let the difference be ever so small, would be slightly favoured, and would tend to live longer, and to survive during that time of the year when food was scarcest; they would also rear more young, which would tend to inherit these slight peculiarities. The less fleet ones would be rigidly destroyed. I can see no more reason to doubt that these causes in a thousand generations would produce a marked effect, and adapt the form of the fox or dog to the catching of hares instead of rabbits, ... So would it be with plants under similar circumstances. If the number of individuals of a species with plumed seeds could be increased by greater powers of dissemination within its own area (that is, if the check to increase fell chiefly on the seeds), those seeds which were provided with ever so little more down, would in the long run be most disseminated; hence a greater number of seeds thus formed would germinate, and would tend to produce plants inheriting the slightly better-adapted down.
2 examples must be provided for each question. One for each species.
DarwinâNatural Selection
Questions:
What are the two Species? What trait varies within the species?
What is the selective pressure? (In other words, what causes some individuals to produce more offspring than others?)
How would the population change over time?
Excerpt from âOn the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection,â by Charles Darwin [Read July 1st, 1858]. To give an imaginary example from changes in progress on an island:âlet the organisation of a canine animal which preyed chiefly on rabbits, but sometimes on hares, become slightly plastic; let these same changes cause the number of rabbits very slowly to decrease, and the number of hares to increase; the effect of this would be that the fox or dog would be driven to try to catch more hares: his organisation, however, being slightly plastic, those individuals with the lightest forms, longest limbs, and best eyesight, let the difference be ever so small, would be slightly favoured, and would tend to live longer, and to survive during that time of the year when food was scarcest; they would also rear more young, which would tend to inherit these slight peculiarities. The less fleet ones would be rigidly destroyed. I can see no more reason to doubt that these causes in a thousand generations would produce a marked effect, and adapt the form of the fox or dog to the catching of hares instead of rabbits, ... So would it be with plants under similar circumstances. If the number of individuals of a species with plumed seeds could be increased by greater powers of dissemination within its own area (that is, if the check to increase fell chiefly on the seeds), those seeds which were provided with ever so little more down, would in the long run be most disseminated; hence a greater number of seeds thus formed would germinate, and would tend to produce plants inheriting the slightly better-adapted down.
2 examples must be provided for each question. One for each species.
DarwinâNatural Selection
Questions:
What are the two Species? What trait varies within the species?
What is the selective pressure? (In other words, what causes some individuals to produce more offspring than others?)
How would the population change over time?
