Evolution of Life How Organisms Survive

What Is Necessary To Survive? Variation differentVariation is an appearance of an inherited trait or behavior that makes one organism different from others in the same species. Adaptations betterAdaptations are variations that make an organism better able to survive.

Variations vs. Adaptations

How Does Evolution Work? Natural selection better adapted are more likely to surviveNatural selection is the process where the organisms that are better adapted to their environment are more likely to survive and reproduce.

Charles Darwin Theory of Natural Selection Charles Darwin is credited as discovering the mechanism, or tool, for evolution to occur. He called this the theory of natural selection.Charles Darwin is credited as discovering the mechanism, or tool, for evolution to occur. He called this the theory of natural selection. His theory can be summarized as “survival of the fittest”.His theory can be summarized as “survival of the fittest”.

Theory of Natural Selection 1.Organisms produce more offspring than can survive. Ex. Tree seeds, salmon eggs. 2.Variations exist within populations. 3.Some variations are more advantageous for survival. The struggle to survive results in competition. 4.Over time only those individuals with advantageous variations will survive and reproduce.

Natural Selection

Species Are Always Changing Evolutionchange in the hereditary featuresEvolution is the change in the hereditary features of a population of organisms over time. evolvedWhen a species changes it is said to have evolved.

How Do Species Change? mutationa permanent changeA mutation is a permanent change in a gene or chromosome that changes the organism in some way. –Ex. Size, shape, color, behavior, etc. Some mutations are harmful. Some mutations are beneficial.

Mutations

Mutation vs. Adaptation Only beneficial mutations are adaptations advantageOnly beneficial mutations are adaptations because these provide an advantage to survival.

Mutation vs. Adaptation

What Evidence Is There Of Evolution? Evolution of species is evident in: FossilsFossils Cell StructuresCell Structures DNADNA Homologous StructuresHomologous Structures EmbryosEmbryos Shared CharacteristicsShared Characteristics

Fossil Evidence of Evolution FossilsFossils are remains of life from earlier times. FossilsFossils are usually found in rock layers that provide a time reference: –Youngest (most recent) layers are on top. –Oldest layers are on the bottom. FossilsFossils provide evidence about the past climates and/or landscapes.

Fossil Evidence

Cell Structure Evidence of Evolution Studying c cc cell structures shows similarities between organisms. A comparison of ancient and modern cells shows similarities in cell membranes and cytoplasms.

Cell Structure Evidence

DNA as Evidence of Evolution DNAStudying DNA shows more similarities between organisms. DNAThe more similar the DNA, the more closely related the species are. DNA DNAEx. The DNA of Gorillas and Humans are ~92% similar whereas the DNA of any two humans is 99.9% similar.

DNA Evidence

Homologous Structures as Evidence of Evolution Homologous structuresbody partsthat aresimilar in origin and structureHomologous structures are body parts of different organisms that are similar in origin and structure. Ex: human arm, bird wing, bat wing, and dolphin flipper all have similar bone structure and function and show the relatedness of the species.

Homologous Structures

Homologous Structures

Embryo Evidence of Evolution Studying the similarity seen in the embryos of vertebrates shows that they share a common ancestor.

Embryo Evidence

Shared Characteristics as Evidence of Evolution PrimatesPrimates are a group of mammals, including monkeys, apes and humans, that share many characteristics. For example, they share: –Opposable thumbs –Flexible shoulders –Binocular vision

Opposable Thumbs