Evolution

Evolution Theories Jean Lamark- Proposed the first method for explaining the change of organisms over time. Lamark thought that organisms had a tendency to move toward perfection Proposed the idea of in heritance of acquired characteristics Ex. If a rat had its tail cut off that rat would produce offspring without tails

Lamark Lamark also put forth was the theory of use and disuse -Under this idea Lamark Hypothesized that organisms that used a certain body the most it would grow. Ex. Giraffes

Hutton and Lyell These scientists proposed that the earths geologic structures were formed slowly over long periods of time. They proposed that the earth was several million years old Lyell proposed that past geologic events such as the formation of mountains must be able to be explained using current observable processes Mountains formed by earthquakes, rivers, and glaciers Geologists Currently estimate the earth to be 4.5- 5 billion years old

Malthus First to bring forth the idea of carrying capacity Recognized that if any population continued to grow unchecked that the community would run out of resources required to survive

Scientific theories of evolution Darwin HMS Beagle Collected data in the form of fossils and living organisms Main place of collection were the Galapagos islands The different island had different environmental conditions

Darwin and Wallace Charles Darwin and Alfred Wallace independently came up with the revolutionary idea that organisms change over time through a mechanism of natural selection Darwin published The Origin of Species in which he proposed the mechanism for evolution, which he called natural selection.

Descent with Modification Darwin proposed that as a result of Natural selection the characteristics of organisms change The structures of organisms change, they establish different niches, and occupy different habitats Each living species has descended from another living species over time

Common Descent Darwin’s idea of descent with modification was revolutionary because it implied that there existed the principle of common descent This countered the idea that all living species have always existed on earth unchanged in their present form This principle implied that all living and extinct species were derived from a common ancestor

Divergent Evolution Divergent evolution is the process in which a population of interbreeding species accumulate differences and become anew species

Natural Selection Darwin felt that all organisms were constantly struggling to stay in existence and that only the fittest would survive He felt that fitness was the result of adaptation Adaptations are any inherited characteristic that would make an organism better suited to survive in their environment

Natural Selection Vs. Artificial Selection Darwin recognized that the selection that occurs in the wild is different than that which occurs in domesticated areas. Artificial selection occurs when there is a variation that occurs in nature and humans select for that variation Selective breeding is an example of artificial selection Can any body tell any possible current practices in farming that could be considered artificial selection?

Mechanisms for Natural Selection 1. Overpopulation 2. Variation 3. Selection 4. Adaptation

Evidence of Evolution Scientists use many different forms of evidence to establish that evolution has occurred Fossils Comparative anatomy DNA Embryology

Fossils Provide physical evidence that can be seen for millions of years Shows how organisms change over long periods time Gradualism- Evolution occurs slowly over long periods of time

Comparative Anatomy By comparing the structures of different organisms scientists are able to determine possible relationships between different species. Homologous structures-Structures that have different mature forms, but develop the same way in the embryo Analagous Structutes

Homologous Structures From looking at the structure below scientists believe that there is strong evidence that these organisms have descended from a common ancestor

Vestigial Organs These are organs that serve no useful functions These are useful for scientists studying evolution because they provide traces of where the organisms descended from Ex. In humans the appendix is classified as a vestigial organ Ex. Skinks are lizards that live in the water, but have legs that have no useful purpose.

Comparative Embryology Scientists compare the embryos of different species to show that many different organisms develop in similar ways

DNA The most recent way scientists have been researching the descent of organisms is through DNA Scientists often use mitochondrial DNA because it has little impact on the survival of an organism Maternal lineage can be traced

Progression of Evolution Scientist have two theories on how evolution progresses Gradualism- Evolution occurs slowly and gradually over long periods of time Punctuated equilibrium- Scientists use this term to describe long stable periods interrupted by brief periods of more rapid change.

Variation in Gene Pools Gene pool- consists of all the genes including the different alleles Relative frequency- the number of times an allele occurs in a gene pool

Selection These types of selection only occur in polygenic traits Directional Occurs on end or the other Stabilizing Occurs at both ends Disruptive Selects against the middle traits

Genetic Drift Genetic drift is the random change in allele frequencies that occur in small population The expression of a few recessive traits could dramatically affect the overall gene frequency Founder effect This is the change in allele frequencies as a result of the migration of a small group of organisms from a population

Speciation Speciation is the formation of new species Caused by different isolation factors Reproductive Isolation Behavioral Isolation Geographic Temporal

Reproductive Isolation This is when two organisms of different populations cannot interbreed and produce fertile offspring At this point the organisms have separate gene pools

Behavioral Isolation This occurs when two populations of organisms do not interbreed because they have different courting rituals This is seen in birds through their different songs

Geographic Isolation Geographic isolation occurs when two populations are separated by some type of geographic barrier such as a lake, mountain, or a river. Geographic isolation does not guarantee the formation of a new species. As long as the two populations can still interbreed the still belong to the same species Geographic barriers do not cause isolation for all organisms Birds can fly over rivers where rabbits cannot cross rivers

Temporal Isolation This occurs when two or more species reproduce at different times Ex. Three different species of orchids release their pollen a single day at different times during the year, as a result they never have the opportunity to fertilize each other.

Darwin’s finches Darwin observed at least six species of finches during his trip to the Galapagos Each of these different species had different niches, which made their individual characteristics best fit for their different environments

Adaptive Radiation Speciation that originates with a single ancestor and diverge into several different species

Coevolution The change of one species sparks the evolution of another species Flowers and bees Grass and horses

Darwin’s Evolution Principles 1) Overpopulation: Within a population more offspring are produced than can possibly survive 2) Competition: Because there are more organisms produced than can survive there is competition between them for food, water, space and mates 3) Survival of the fittest: Variations among the population make some individuals fitter than others!

Darwin’s Principles Continued 4) Natural Selection: Those individuals best able to survive due to certain traits pass those traits on to their offspring 5) Reproduction: Those that survive and thrive live long enough to reproduce 6) Speciation: The development of new species occurs as variations or adaptations accumulate over many generations The modern theory of evolution uses Darwin’s work and adds a few new ideas

Major Things to Remember Evolution Rates are dependent on environmental change and reproductive rates. Evolution does not happen on purposes in a specified direct, but happens purely by chance. The higher variation in a species the higher the survival rate will be

Taxonomy

Taxonomy Scientists have a highly organized way of naming and grouping similar organisms together This is called taxonomy. The system of classification created by Carolus Linnaeus has seven different levels. From the largest to smallest there is kingdom, phylum, class, order, family genus, species. - An easy way to remember the order is Kids Pick Candy Over Fancy Green Salads

Binomial nomenclature- This is a two word naming system that utilizes the genus and species of an organism. Ex. Humans are called Homo sapiens because humans are classified under the genus Homo and the species sapiens

Dichotomous key A dichotomous key is used to identify unfamiliar organisms based on physical characteristics These keys are step by step guides that lead you