Chapter 30 The Theory of Evolution

Chapter 30 The Theory of Evolution http://www.pbs.org/wgbh/nova/odyssey/debate/ http://www.nationalgeographic.com/features/outpost/ http://www.discovery.com/news/features/humanorig

Evolution A process of change through time

Theory of Evolution 1. Suggests that existing forms of life on earth have evolved from earlier forms over long periods of time 2. Evolution accounts for the differences in structures, function, and behavior among life forms as well as changes that occur in populations over many generations

(I) Evidence of Evolution Observations supporting the theory of organic evolution can be made through the study of: 1. Geologic record 2. Comparative Cytology, Biochemistry, Anatomy, and Embryology

(A) Geologic Record 1. Earth is between 4.5 to 5 billion years old (age was determined by radioactive dating of rocks) 2. Fossils- are the remains of traces of organisms that no longer exist. Fossils have been preserved in ice, sedimentary rock, amber, and tar

Archaeopteryx

Tyrranosaurus rex

3. Other fossils have been formed from petrification, a process by which the tissues are gradually replaced by minerals that produce a stone replica of the original material 4. Imprints, casts, and molds of organisms or parts of organisms are frequently found in sedimentary rock 5. In undisturbed layers (strata) of sedimentary rock, the lower strata contain old fossils while the upper strata contain younger fossils

(B) Comparative Anatomy 1. Evidence supports that similarities of basic structures exist between different organisms 2. Homologous structures are anatomical parts found in different organisms in origin and structure 3. The presence of such homologous structures suggest that these organisms have evolved from a common ancestor

(B) Comparative Anatomy Homo sapiens Paranthropus boisei

(C) Comparative Embryology Although certain adult organisms may be different from each other, a comparison of the earl stages of their embryonic development may show similarities that suggest a common ancestor

(D) Comparative Cytology 1. All living things are made up of cells 2. Cell organelles including the cell membrane, ribosome's, and mitochondria are structurally and functionally similar in most organisms

Mitochondrion DNA and can replicate

(E) Comparative Biochemistry All living things contain similar biochemical compounds Examples would include: structure and function of DNA, RNA, and proteins (including enzymes) are similar in all organisms

(II) Theories of Evolution 1. Attempts to explain the similarities and differences among species 2. Adaptations- are a major component to these theories. Adaptations are features which make a species better suited to live and reproduce in its environment

(A) Jean Baptiste Lamark

(A) Lamark The evolutionary theory of Jean-Baptiste Lamark was based on the principle of: 1. Use and Disuse 2. Inheritance of acquired traits

Principle of Use and Disuse For an organism, new structures appeared in the course of evolution because they were needed. Structures that were present and were used became better developed and increased in size; structures that were not used decreased in size and eventually disappeared Ex: muscles of an athlete vs. appendix

Inheritance of Acquired Traits Useful characteristics acquired by an individual during its lifetime can be transmitted to its offspring These acquired traits results in species that are better adapted to their environment Ex: a giraffe s neck became longer as a result of stretching to reach higher branches. This acquired trait was then passed down to the offspring

Inheritance of Acquired Traits Arnold s kids wouldn t be pumped

(B) Weisman 1. August Weisman did not agree with Lamark s theory of acquired traits 2. In a series of experiments, Weisman removed the tails of mice 3. The mating of these tailless mice produced offspring with tails of normal length 4. Weisman removed the tails of these mice and allowed them to mate 5. Again, offspring were produced with tails of normal length 6. The acquired condition of taillessness was not inherited

) Darwin s Ship the HMS Beagle

(C) Darwin Charles Darwin devised a theory of evolution based on variation and natural selection as seen in the Galapagos islands. Included in hid theory were five main ideas: 1. Overpopulation 2. Competition 3. Survival of the Fittest 4. Reproduction 5. Speciation

Overpopulation Within a population, there are more offspring produced in each generation than can possibly survive

Competition Natural resources; like food, water, and space available to a population is limited Because there are many organisms with similar nutritional requirements, there must be competition between them for the resources needed to survive

Survival of the Fittest Variations among members of a population make some of them better adapted to the environment than others It is generally the bestadapted individuals that will survive The environment is the agent of natural selection determining which species will survive

Reproduction Individuals that survive and then reproduce transmit these variations to their offspring

Speciation The development of a new species occurs as variations or adaptations accumulate in a population over many generations Ex: caveman present man

Speciation El Chupacabra

Speciation What is El Chupacabra? El Chupacabra - Means "the goat sucker" in Spanish. Named because of the way it sucked all the blood from Puerto Rican goats, the Chupacabra has been leaving fear in its tracks for many years now.

Speciation Bigfoot? Sasquatch?

(III) Modern Theories of Evolution The modern theory of evolution includes both Darwin s ideas of variation and natural selection and the current knowledge of the sources of variations

(A) Sources of Variations 1. Segregation and the recombination of alleles during sexual reproduction 2. Gene mutation occurs spontaneously and at random

(B) Natural Selection 1. Natural selection involves the struggle of organisms to survive and reproduce in a given environment 2. Traits which are beneficial to the survival of an organism in a particular environment tend to be retained and passed on, and therefore, increase in frequency within a population 3. Traits which have low survival value to an organism tend to diminish in frequency from generation to generation 4. If environmental conditions change, traits that have low survival value may now have a greater survival value. Therefore, traits that prove to be favorable under new environmental conditions will increase in frequency

Ex: Insects resistant to insecticides 1. Genetic make-up of some insects make them resistant to the effects of insecticides 2. Before the widespread use of insecticides, this trait was of no particular survival value 3. With the increased use of insecticides, this trait developed a very high survival value 4. Therefore, insects with resistance to insecticides survived and reproduced much more successfully than those lacking the trait 5. As a result, the frequency of insecticide resistance has increased greatly in insect populations

(C) Geographic Isolation Gene frequency- the percentage of organisms in a population that carry an allele 1. Isolation of a population increases the chances for speciation (the development of a new species) by separating a small group of organisms from the main population with its large gene pool (inheritable traits) 2. Changes in gene frequency are more likely to occur in small populations than in large ones 3. Geographic isolation of a population is caused by natural barriers like mountains, large bodies of water, and deserts

4. The evolution of an isolated population into a new species may involve the following factors: a) the gene frequency in the isolated population may have been different than the gene frequency in the main population to begin with b) different mutations occur in the isolated population and in the main population c) different environmental factors may also have exerted different selection pressures on each population (natural selection was different)

(D) Reproductive Isolation If the isolated population becomes so different from the main population that members of the two cannot interbreed and produce fertile offspring, then they have become two distinct species

(E) Time Frame for Evolution There are two different theories proposed by scientists to address the rate of evolution: 1. Gradualism- proposes that evolutionary change is slow, gradual, and continuous 2. Punctuated Equilibrium- proposes that species have long periods of stability (several million years) interrupted by geologically brief periods of significant change during which a new species may evolve

(IV) Heterotroph Hypothesis Is one proposed explanation for how life arose and evolved on primitive earth According to this hypothesis, the first life forms were heterotrophic and had to obtain their nutrients from the environment

(A) Primitive Earth Based on assumption 1. Earth was very hot consisting of inorganic substances in all states: solid, liquid, and gas 2. Many sources of energy including heat, lightning, solar radiation(x-rays and U.V. rays), and radiation from radioactive rocks 3. The atmosphere consisted of water vapor, hydrogen, methane gas, and ammonia 4. As the earth cooled, water condensed in the atmosphere and rain fell forming seas described as hot, thin soup

tanley Miller s experiment

(B) Synthesis of Organic Compounds 1. In the seas, (primordial soup) chemical bonds formed between the dissolved substances 2. Eventually, various types of organic molecules formed in the seas, including amino acids and simple sugars 3. More complex organic compounds were then formed by the interactions between the simpler molecules

(C) Nutrition 1. Some of the large. Complex molecules formed groupings or clusters called aggregates 2. These aggregates developed a surrounding membrane 3. It is believed that aggregates absorbed simple organic molecules from the environment for food 4. Therefore, they carried on a form of heterotrophic nutrition

(D) Reproduction 1. In time, as these aggregates became more complex and highly organized, they developed the ability to reproduce 2. At the point where the ability to reproduce had evolved, the aggregates were considered to be living cells

(E) Heterotroph to Autotroph 1. It is thought that these early heterotrophic life forms carried on a form of anaerobic respiration known as fermentation 2. As a result of the extended periods of fermentation, carbon dioxide was added to the atmosphere 3. Eventually, as a result of evolution, some heterotrophic forms developed the capacity to use carbon dioxide from the atmosphere to form organic compounds (food) 4. These organisms were the first autotrophs

(F) Anaerobes to Aerobes 1. Autotrophic activity (photosynthesis) added free oxygen to the atmosphere 2. Over time, the capacity to use oxygen in respiration (aerobic) evolved in both autotrophs and heterotrophs 3. Present day organisms may be heterotrophic or autotrophic; aerobic or anaerobic

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