Evolution

is the process of biological change by which descendants come to Evolution is the process of biological change by which descendants come to differ from their ancestors. This change is the result of mutations

Darwin was struck by the variation of traits between species of finches in the Galapagos Islands. The most striking difference among them are their beaks.

Their beak shapes seemed well suited to their diets. These observations led Darwin to realize that species may somehow be able to adapt to their surroundings. An adaptation is a feature that allows an organism to better survive in its environment.

The Theory of Evolution by Natural Selection

Charles Darwin challenged traditional views of a young Earth inhabited my unchanging species. Many species of organisms presently inhabiting Earth are descendants of ancestral species, that is, species evolve. Darwin proposed a reasonable mechanism explaining how species evolve by natural selection.  

Organisms had more offspring than can ever survive.

Populations in nature were also limited by factors such as food, water, shelter, disease, and predators …..so organisms struggle to survive Struggle for existence

A population is all the individuals of a species that live in an area.

The individuals in a population vary in their characteristics or traits. A variation is the difference in a physical trait of an individual from those of other individuals in the population.

Individuals with the adaptation have greater fitness. Fitness describes how well an organism can survive and reproduce in its environment.

Individuals with the adaptation will be able to eat more, and produce more offspring. The adaptation will be inherited by its offspring, making the offspring better adapted to the environment.

Natural Selection Over generations, the individuals with the adaptation tend to accumulate in the population. Natural selection will result in species with adaptations that are well suited for survival and reproduction in an environment.

More and more individuals in the population will have the new adaption. In time, the number of individuals that carry the favorable adaptation will increase in the population. Simultaneously, individuals that do not have the adaptation will die, or produce fewer offspring. Eventually, the population will consists only of individuals with the adaptation. The nature of the population has changed. Evolution has occurred.

Natural selection is a mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals.

EVIDENCE OF EVOLUTION

Fossils provide evidence that Earth is very old…4.6 billion years old Life is very old…3.5 billion years old Life on Earth has changed…evolved

Fossils show a pattern of development from early ancestors to modern descendants.

The similar features of embryos in very different organisms suggest evolution from a distant common ancestor. Fish Human They share a common ancestor!

Homologous Structures Similar arrangement of bones. limbs that perform very different functions are built from the same kinds of bones. These animals share a common ancestor. WHY?

Some organisms have similar structures, however, they are not closely related. The wings of bats and insects are analogous structures.

Analogous structures are structures that perform a similar function , such as flight, but did not evolve form a common ancestor. They do not share a common ancestor.

What is one function of the pelvis? _________________ Aids in locomotion Pelvis Lion

Why do whales have a pelvis?

Whales evolved from terrestrial ancestors with four legs. Snakes evolved from lizards with four legs. The human appendix is a vestigial structure, reduced from the cecum of primate ancestors, which was involved in digestion of significant plant material.

Vestigial Structures Vestigial structure is a remnant of a structure that served an important function in the organism’s ancestor.

Hind leg bones on a whale fossil Vestigial Structure

Biological Molecules Species share a more recent ancestor Fewer amino acid sequence differences means that …. Species share a more recent ancestor amino acid amino acid Protein A in Humans amino acid amino acid Protein A’ in Chimps   amino acid amino acid Protein A ‘’ in Lemurs

All living things use the same genetic code! LET’S ALSO REMEMBER… TTA codes for Leucine in bacteria as well as in human. The most logical explanation is that all species descended from a common ancestor.

Not closely related TAIL What type of structure is it? homologous structure analogous structure vestigial structure mammal fish Not closely related TAIL

These bones an example of….. __________________________ Homologous structures Why are homologous structures important? ____________________________________ They provide evidence of a common ancestor…evolution.

Pelvic bones provide support for walking. Whales have a much reduced pelvic bones. This is an example of: Homologous structure Analogous structure Vestigial structure

What are the sources of genetic variation? Mutations: A mutation is a change in the DNA of a cell. Mutations change genes sometimes resulting in new phenotypes. Ex: Blue eyes