Evolution and Darwin
Evolution The processes that have transformed life on earth from it s earliest forms to the vast diversity that characterizes it today - Darwin
Old Theories of Evolution Jean Baptiste Lamarck (early 1800 s) proposed: The inheritance of acquired characteristics -an individual acquires certain characteristics, which it THEN passes on to its offspring
The Inheritance of Acquired Example: Characteristics A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal s increasingly lengthened neck was passed on to its offspring.
Theories with no real basis!..
Let s Start with DNA!! DNA (genes) Mutations in DNA (genes) Changes in traits/ characteristics/ metabolism/behaviors Changes in proteins Natural selection of most favorable changes Changes within a population Evolution!!
MUTATIONS are the fundamental basis or RAW MATERIAL, for evolution (slow change over time)
What is evolution? A basic definition of evolution! evolution can be precisely defined as any change in the frequency of alleles within a gene pool from one generation to the next." - Helena Curtis and N. Sue Barnes, Biology, 5th ed. 1989 Worth Publishers, p.974
So what does the definition mean? Evolution is a change in the number of times specific genes that code for specific characteristics occur within an interbreeding population Individuals don t evolve, populations do There is no implied improvement in evolution many mutations in DNA are NOT GOOD!!
Example of a mutation that s not particularly advantageous!!
Charles Darwin Influenced by Charles Lyell who published Principles of Geology. This publication led Darwin -to realize that natural forces gradually change Earth s surface, - the forces of the past are still operating in modern times.
Charles Darwin Darwin set sail on the H.M.S. Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands) to collect plants and animals. On the Galapagos Islands, Darwin observed species that lived no where else in the world. These observations led Darwin to write a book.
Charles Darwin Wrote in 1859: On the Origin of Species by Means of Natural Selection Two main points: 1. Species were not created in their present form, but evolved from ancestral species. 2. Proposed a mechanism for evolution: NATURAL SELECTION
Darwin s finches 14 species of found on the Galapagos
Darwin s view There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.
Natural Selection Individuals with favorable traits (adaptations) are more likely to leave more offspring that are better suited for their environment. Also known as Differential Reproduction Example: English peppered moth (Biston betularia) - light and dark phases
Figure 22.12 Evolution of insecticide resistance in insect populations
Evolution by natural selection (Darwin s premises) Organisms possess heritable variations (different alleles). More individuals are born than will survive to reproduce. Some individuals are more likely to reproduce because of their heritable characteristics Those characteristics become more common in the next generation
The CONFLICT BEGINS!!!
Artificial Selection The selective breeding of domesticated plants and animals by man. Question: What s the ancestor of the domesticated dog? Answer: WOLF
Evidence of Evolution 1. Biogeography: Geographical distribution of species. 2. Fossil Record: Fossils and the order in which they appear in layers of sedimentary rock (strongest evidence).
Vertebrate wings homologous limbs analogously adapted to flight Bird Pterosaur Bat
The evolution of tetrapods??
Eastern Long Necked Turtle
Evidence of Evolution 3. Taxonomy: Classification of life forms. 4. Homologous structures: Structures that are similar because of common ancestry (comparative anatomy)
Figure 22.14 Homologous structures: anatomical signs of descent with modification
Evidence of Evolution 5. Comparative embryology: Study of structures that appear during embryonic development. 6. Molecular biology: similarities in DNA and proteins (amino acids) between species
Population A localized group of individuals belonging to the same species.
Species A group of populations whose individuals have the potential to interbreed and produce viable offspring.
Gene Pool The total collection of genes in a population at any one time.
Macroevolution The origin of taxonomic groups higher than the species level Examples: the evolutionary split of birds from reptiles The evolution of mammals
Microevolution A change in a population s gene pool over a secession of generations. Evolutionary changes in species over relatively brief periods of geological time.
Mechanisms of Microevolution Mutation: Change in an organism s DNA that creates a new allele. Non-random mating: The selection of mates other than by chance. Natural selection: Differential survival and reproduction.
Speciation The evolution of new species. 210 MYA
Allopatric Speciation Induced when the ancestral population becomes separated by a geographical barrier. Example: Grand Canyon and ground squirrels
Adaptive Radiation Emergence of numerous species from a common ancestor introduced to new and diverse environments. Example: Darwin s Finches
Interpretations of Speciation Two theories: 1. Gradualist Model (Neo-Darwinian): Slow changes in species overtime. 2. Punctuated Equilibrium: Evolution occurs in spurts of relatively rapid change.
Convergent Evolution Species from different evolutionary branches may come to resemble one another if they live in very similar environments. Example: 1. Ostrich (Africa) and Emu (Australia). 2. Sidewinder (Mojave Desert) and Horned Viper (Middle East Desert)
Coevolution Evolutionary change, in which one species act as a selective force on a second species, inducing adaptations that in turn act as selective force on the first species. Example: 1. Acacia ants and acacia trees 2. Humming birds and plants with flowers with long tubes