EVOLUTION Chapter 5
5.4.1 Define evolution • The process of cumulative change in the heritable characteristics of a population. • Cumulative: building over time • Heritable: passed from parent to offspring • Interbreeding individuals of the same species • If we accept not only that species can evolve, but also that new species arise by evolution from pre-existing ones, then the whole of life can be seen as unified by its common origins.
Old Theories of Evolution • Jean Lamarck(early 1800’s) proposed: “The inheritance of acquired characteristics” • He proposed that by using or not using its body parts, an individual tends todevelopcertaincharacteristics, which itpasseson to itsoffspring.
“The Inheritance of Acquired Characteristics” • Example: 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. • Problems: no evidence • No intermediate species found • Body builders don’t pass on big muscles
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 and that 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. • Wrote in 1859: “On the Origin of Species by Means of Natural Selection”
5.4.2 • Outline the evidence provided by the fossil record, selective breeding of domesticated animals and homologous structures • Fossil Record: Predictions about evolutionary history of lines of descent are reinforced when new fossils are found • One conclusion that can be drawn from observing fossils is that life on Earth is constantly changing
5.4.2 • Outline the evidence provided by the fossil record, selective breeding of domesticated animals and homologous structures • Artificial Selection: breeding animals for specific unique combinations of characteristics which did not exist before • Breeders and farmers choose which animals will reproduce * This is not the driving force of evolution in natural ecosystems
5.4.2 • Outline the evidence provided by the fossil record, selective breeding of domesticated animals and homologous structures. • Homologous Structures: structures similar in form and function found in different species • Evidence of a common ancestor
5-fingered organisms: shape and number of bones may vary but the general format is the same
5.4.3 • Populations tend to produce more offspring than the environment can support.
5.4.4 • Explain that the consequence of potential overproduction of offspring is a struggle for survival. • Any environment has a carrying capacity for a certain population. If the population grows beyond it, only certain individuals will survive. They will struggle and if they have ‘winning’ traits that translate survival (strong beaks, camouflage, aggressiveness), then those traits will flourish (if they are heritable).
5.4.5 • Members of a species show variation. • There are multiple alleles and combinations of alleles in each individual
5.4.6 • Explain how sexual reproduction promotes variation in a species. • Mutations in DNA: sometimes mutations can produce an advantageous characteristic • Sexual reproduction: • Meiosis: gametes are unique because chromosomes assort independently (Metaphase I) and alleles get segregated from each other during Anaphase I. • Fertilization: it’ random which sperm fertilizes the egg
5.4.7 • Explain how natural selection leads to evolution. • Natural selection: • Differential success in reproduction • Connection between environment and variation in individuals • Adaptation of a population to its environment
5.4.7 • Explain how natural selection leads to evolution. • Each species produces more offspring than can survive • These offspring compete with one another for the limited resources available to them • Organisms in every population vary • The offspring with the most favorable traits or variations are the most likely to survive and produce more offspring (survival of the fittest). • This unequal ability to survive & reproduce leads to a gradual change in the characteristics of a population
5.4.8 • Explain two examples of evolution in response to environmental change (one must be antibiotic resistance in bacteria). • Antibiotic resistance: Bacteria are killed by antibiotics, except the ‘lucky’ few that are mutants with a resistance gene. These mutants will survive, and be more successful because the antibiotics don’t work against them. • 2 possible sources of genetic change that results in resistance: • Mutations • Plasmid transfer
5.4.8 • Explain two examples of evolution in response to environmental change (one must be antibiotic resistance in bacteria). • Peppered moth: Moths in England were light colored (to match the trees) until the Industrial Revolution and all its nasty sooty pollution which darkened the trees. As a result, moths that were light colored were more likely to be eaten and darker ones survived. The traits in the population changed.
5.4.8 • Two MORE examples of evolution in response to environmental change. • Galapagos Finches: The beak traits (size, length) have CHANGED over the course of each breeding season depending on the environment. • Pesticide resistance: Kind of like antibiotic resistance. Certain mutant insects aren’t affected by chemicals (like DDT), and survive to dominate the population.