Change Over Time

Evolution Theory proposed by Charles Darwin Latin word meaning unfolding or opening out All living things on Earth are changed forms of living things that came before

Another Definition Evolution can be defined as a change in species over time. Species: a group of organisms that share similar characteristics and can interbreed to produce fertile offspring

Mutations Agents of change A change in a gene will produce a change in the offspring One major driving force behind evolution Most mutations are negative, but sometimes they improve the organism

Adaptation A change that increases an organism’s chances of survival is called an adaptation Organisms that are better adapted live longer and reproduce

New species may evolve over long periods of time Many small adaptations may occur over time…..new species evolves New species may not resemble old New species may result in the extinction of another

Populations Evolve ……not individuals

Natural Selection Process that results in adaptation of an organism to its environment by means of selectively reproducing changes in its genotype. This is the driving force behind evolution.

Natural Selection Variations that increase chances of survival and reproduction are preserved and multiplied over generations Less advantageous variations are overpowered by the better variations.

Natural Selection May arise from differences in survival, fertility, rate of development, mating success, or any other aspect of the life cycle. mutation, gene flow, and genetic drift, all of which are random processes, also alter gene abundance.

Natural Selection Ultimately over many generations the number of organisms in a population with beneficial mutations (adaptations) increases and the harmful mutations are eliminated because those organisms that carry them die off. Also known as “Survival of the Fittest” Citation (MLA). Britannica Concise Encyclopedia. Learn March

Evidence to Support Evolution Fossil Record Example: Whale-like skull found in 1983 from 50 million years ago…boney structure for hearing could not have worked under water….ancestors of modern whales must have spent time on land

Example of Fossil Evidence……armadillo and glyptodont

Anatomical Evidence Similarities in physical structure Example: The shape and arrangement of bones for a salamander, lizard, turtle, and opossum This suggests evolution from a common ancestor

Anatomical Evidence Continued: Similar Vertebrate Limbs

Evolution of Horses (Anatomy Continued)

Evolution of Horses Graph

Embryological Evidence Embryos are organisms in early stages of development Growth and development are controlled by genes Similarities in embryos indicate sharing a common ancestor

Embryological Evidence Continued

Chemical Evidence DNA molecular structure will be similar if two animals are closely related Example: Zebra-like animal from 100 years ago is 95% similar in DNA to modern day zebra….they share common ancestry that dates back 3 million years

Molecular Evidence Proteins made by genes can also be analyzed. The closer the similarity in protein structure of different organisms, the more recently their common ancestor existed

Human Karyotype: Molecular Evidence

History of Life Timeline

Have we really evolved?