Evolution Change over Time

Natural Selection Process by which inherited characteristics are passed on more frequently and that enhance the survival and reproduction of future generations.

Alters the genetic make up of populations through time

Charles Darwin and Alfred Russel Wallace

•Both independently proposed the concept of natural selection as a mechanism for evolution•Premises for Natural Selection:

•Organisms face a constant struggle to survive and reproduce•Organisms tend to produce more offspring than can survive•Individuals of a species vary in their characteristics

Adaptation

• From one generation to the next, traits that lead to better survival and reproductive success in a given environment is called adaptation.

• An adaptive trait is a trait that promotes success

• These could be mutations, which are accidental changes in DNA, which gives rise to genetic variation in a species

• New traits can also come from sexual reproduction , with the mixing of genes in the offspring

Examples

• Peppered Moth – Light colored moths lost their

camouflage with the Industrial Revolution, where the darker moths stayed hidden

• Italian Wall Lizard– When a section of this species

was cut of on a isolated island, the lizard changed to a more vegetarian lifestyle when there was not an abundance of insects to eat

• Darwin’s Finches– Beak development changed

with the availability of seeds and their locations they were found in

• Blue Moon Butterfly of the Samoan Islands– A parasite was affecting the

males in this species, and eventually, a resistive gene was found in a few males and those survived to a reproductive age

The Selection Process

• Natural Selection– Selective pressures from

either the environment or other populations that affect the species can lead to small or large variations in populations, leading to small or large changes in their evolutionary track

• Artificial Selection– Species are bred based

on given traits that people want to maintain• Examples

– Dogs– Crops– Bacteria (insulin)

Biodiversity

• Variety of life across all levels of biological organizations– Communities– Populations– Species– Genes

• Over 1.8 million species have been described, but scientists estimate that there are over 100 million species all over the world

Speciation Process by which new species are generated

• Allopatric Speciation– New species are formed

from a physical separation of populations over a given distance

– Specimens from the same species cannot mix with other populations.

– This is long term and will take many generations to complete

– If or when the species comes back together, they can no longer breed with each other

Speciation Continued

• Allopatric speciation can occur in several ways:– Large glacial sheets – Mountain Ranges may

rise – Major Rivers change

course– Warming or cooling

trends may move whole populations

Speciation Continued

• Sympatric Speciation– When a species becomes

reproductively isolated within the same geographic region

– Examples• Some populations may

only breed at certain times of the year

• Some populations may only feed and mate on certain species of plants