There are two questions here; but if we look at the first one (how the eye evolved), the second one will also be answered. The simplest "eye" is simply light sensitivity. For example, some simple sea organisms can only distinguish between light and dark; if it's dark they shrink - some cells on their bodies are light sensitive and it triggers the response. It's obviously basic but better than no sensitivity to light at all. The next stage is a light sensitivity with some indication of motion; again some sea organisms have just that - some extra processing indicating which cells "see" the dark area first. Again, this is better than simply having light or dark sensitivity. One can see from this, that its possible to imagine lots of "next steps" - speed as well as direction, different directions, two eyes to be able to estimate direction, layers of transparent cells to form lenses in front of the light sensitive areas and so on. What's surprising is that examples can be found of most of the "intermediate" stages. A key point is that there's no "final" target that evolution is aiming for; the next stage is reached because the offspring that have more of the next stage present will tend to survive to reproduce and eventually a new species will arise that all have the next stage. Because modern eyes are essentially the result of millions of minor improvements of earlier models we've ended up with some odd results; in our own eye the retina is essentially back to front; the nerves which lead off to the visual context are in front of the light sensitive cones and rods - also if we wanted to design an eye, we wouldn't have a blind spot where the optic nerve joins the eyeball. The "why did the eye evolve" part of the question is that each step provides an advantage over not doing it.
Populations evolve, but individuals are selected. Natural selection affects individual organisms.
These three ideas seem to run together, so it's important that you are able to distinguish among them. The theory that organisms change over time is evolution. The mechanism by which organisms evolve is natural selection. Survival of the fittest explains how natural selection works.Answer = Natural SelectionThe process of natural selection, of course.
They adapt and evolve through the process of natural selection and learned behaviours.
The book, On The Origin Of Species, " suggested " that organisms evolve through the process of natural selection. The nonrandom survival and reproductive success of randomly varying organisms
Natural selection (survival of the fittest) means that valuable adaptations and mutations have the greatest number of surviving descendants.
Natural Selection
No, all life evolves. Bacteria evolve, viruses evolve, protists evolve, plants evolve, fungi evolve and animals evolve. Evolution is driven by Natural Selection. So, no. The evolution of all life on Earth is driven by Natural Selection: all bacteria, plants, animals, mammals, fish, insects, biochemical pathways, behaviours et cetera evolve by Natural Selection.
evolve
Natural selection
Populations evolve, but individuals are selected. Natural selection affects individual organisms.
natural selection
natural selection
natural selection
natural selection
By the process of natural variation and selection by survival of the fittest.
By the process of natural selection and adaptation to a continuously changing environment.
These three ideas seem to run together, so it's important that you are able to distinguish among them. The theory that organisms change over time is evolution. The mechanism by which organisms evolve is natural selection. Survival of the fittest explains how natural selection works.Answer = Natural SelectionThe process of natural selection, of course.