Evolution Lesson 1-3

All populations show [blank_start]variation[blank_end]. It can be seen in an individual's [blank_start]DNA[blank_end]. DNA varies through [blank_start]mutation[blank_end] and [blank_start]recombination[blank_end].

There will always be [blank_start]competition[blank_end] for resources in [blank_start]life[blank_end].

Charles [blank_start]Darwin[blank_end] created the theory of natural [blank_start]selection[blank_end] based on observations of [blank_start]populations[blank_end].

Organisms with the most beneficial traits survive [blank_start]longer[blank_end] and reproduce more [blank_start]successfully[blank_end].

The advantages or disadvantages of a trait is determined by the [blank_start]environment[blank_end] in which the organism lives in. Beneficial traits are called [blank_start]adaptations[blank_end].

Darwin's idea was that today, all species are [blank_start]descended[blank_end] from older [blank_start]extinct[blank_end] types. All species are [blank_start]connected[blank_end] to each other in a family [blank_start]tree[blank_end].

Adaptation is a [blank_start]trait[blank_end] that improves an organism's ability to [blank_start]survive[blank_end] and/or [blank_start]reproduce[blank_end]. [blank_start]Evolution[blank_end] is the process in which organisms change overtime.

Natural selection is the process in which organisms better [blank_start]adapted[blank_end] to the [blank_start]environment[blank_end] survives.

If an organism is born with [blank_start]traits[blank_end] that help it [blank_start]survive[blank_end] or attract [blank_start]mates[blank_end], it will produce [blank_start]more[blank_end] offspring than individuals that do [blank_start]not[blank_end] have these traits. Over long periods of [blank_start]time[blank_end], these [blank_start]beneficial[blank_end] traits will spread throughout the [blank_start]species[blank_end].

Evolution is a [blank_start]process[blank_end] from which [blank_start]modern[blank_end] species have [blank_start]descended[blank_end] from ancestral [blank_start]extinct[blank_end] species while accumulating [blank_start]adaptations[blank_end] for their environment.

Natural selection occurs in [blank_start]4[blank_end] steps. Natural selection changes a species to help it [blank_start]survive[blank_end].

Step 1: A species lives in a particular [blank_start]environment[blank_end]. Individuals compete for resources such as [blank_start]food[blank_end], water, space, and [blank_start]mates[blank_end]. Some show variation in their [blank_start]physical[blank_end] traits.

Step 2: A [blank_start]change[blank_end] occurs in their environment. The change can be [blank_start]biotic[blank_end] (living) like a new [blank_start]predator[blank_end] or food source. The change could also be abiotic ([blank_start]nonliving[blank_end]). Climate changes, change in pH, or more acidic water or soil are some examples of [blank_start]abiotic[blank_end] changes.

Step 3: An individual born with a [blank_start]mutation[blank_end] that somehow [blank_start]changes[blank_end] one of its traits. The change allows this particular individual to survive [blank_start]longer[blank_end], and therefore, [blank_start]reproduce[blank_end] more often. The individual produces more offspring [blank_start]compared[blank_end] to others.

Over many generations, individuals possessing the "[blank_start]better[blank_end]" adaptation will become more [blank_start]common[blank_end]. Individuals without the better [blank_start]adaptation[blank_end] reproduce less. They can't [blank_start]compete[blank_end] with the adapted individuals and get less resources. The species has now [blank_start]changed[blank_end] and the adaptation can be seen [blank_start]throughout[blank_end].