What is Evolution???? THEORY - It IS a THEORY that says that present-day life forms developed from earlier, distinctly different life forms - Evidence suggests that life began more than 3 billion years ago - Started as a single cell - Evolution is caused by rapid changes in the environment

Evidence Supporting Evolution 1. Fossil Record - Oldest rocks have little or no fossils - Life was small single celled bacteria - Fossils found further up in strata are generally younger and more complex then those found in deepest layers

- Fossils show how life diverged gradually from a common ancestor - Much like a bush - Some branches live, others die

- Fossils may also exist in amber, tar, and ice

2. Comparative Cytology - Most life forms have similar cell structures indicating that they are related to some degree

3. Comparative Biochemistry - Nucleic acids, their structures and functions are similar in all living things - The closer the similarities the more closely related the organisms

4. Comparative Anatomy - Homologous bones and other structures indicate that organisms diverged at some point common ancestor - Indicates they may have developed from a common ancestor

5. Comparative embryology - Early embryo’s are very similar in structure

Theories of Evolution A. Lamarck – early 1800’s - Said new organs arise as they are needed 1. Theory of Use and Disuse - Organs that are used become bigger and stronger - Those that aren’t used eventually disappear 2. Transmission of Acquired Traits - New traits can be passed on to offspring - Causes gradual change in species But was WRONG!!!!!

Weisman- Cut of tails of mice and then breed them - None of the mice were born without tails - Disproved Lamarck

Charles Darwin- 1830’s - Said populations change due to variations and natural selection - Variations that prove to be helpful enable those organisms to have a higher selection rate ( more offspring) Darwin's Major ideas include: 1. Overproduction -Within a population more offspring are born than can possibly survive and reproduce

2. Competition- Organisms must compete for finite resources - food, mate, place to live 3. Survival of the Fittest- Organisms that survive are those that are best adapted to the environment - Traits that help an organism have an adaptive value

4. Reproduction- Those animals that survive are able to reproduce 5. Speciation- After many generations adaptations are perpetuated until the organisms have evolved into a form different from the original

Problem: What is the source of Darwin’s variations? Mutations- Sudden spontaneous changes in genetic material - Mutations are rare, and mostly harmful or even lethal - In very rare cases a mutation can have beneficial results Normal Short wingsCurly wings No eyesLegs on head - In order to be passed on to offspring, mutations must take place in the sex cells - If a mutation takes place in a body cell then the individual may change, but the mutation will not go to the offspring

Chromosome Mutations Non-disjunction- Gametes have more or less chromosomes than they are supposed -results in Down’s syndrome, marfans syndrome, others

Structural Alterations of Chromosomes - Translocation- Transport part of a chromosome to a non-homologous chromosome - Addition- Gain a portion of a chromosome - Deletion- Lose a portion of a chromosome

Gene Mutations adaptive valuemutation - The adaptive value of the mutation is dependent on the nature of the mutation and the type of environment in which the organism interacts Mutagenic Agents- Increase the likelihood that a mutation will take place - radiation - chemicals

Natural Selection 1. Traits with high survival value tend to increase in frequency in a population – are passed on to offspring population - The population not the individual changes as a result of evolution 2. If environmental conditions change then the survival value of a trait can also change

Artificial Selection Selective breeding - used to obtain traits that are desired by mating animals with desired traits together

Plant artificial selection Teosinte vs. modern corn Tomato

1. Penicillin- Less effective today because bacteria which had a mutation allowing them to survive in a penicillin environment were able to multiply – those that died did not have the survival trait 2. Insecticides- Bugs that had a mutation allowing them to live in a pesticide are still around and reproducing Selecting Agents - Insecticides are not as effective anymore selected *** It is important to note that the mutation was NOT caused by the antibiotic or by the insecticide. The mutation was “selected” because it had a high survival value. - Select the organisms that are going to survive

Geographic Isolation - Changes in gene frequencies are more likely in small populations - Isolated populations may evolve into a separate species WHY? 1. Gene frequencies may be different initially 2. Different mutations occur in main population and in isolated population 3. Different environmental factors may be acting on each population - This is what happened on the Galapagos islands with the finch

How long does it take for evolution to take place? Two theories : 1. Gradualism- Evolution take place slowly and continuously - Supported by fossil records showing only slight differences over thousands or millions of years

2. Punctuated Equilibrium- Species remain stable for long periods of time with sudden bursts of rapid evolution - Also supported by fossil record -fossils record shows little changes from layer to layer then suddenly there are lots of changes

How did life begin on Earth? Heterotroph Hypothesis - Assumes that Earth started as a hot body of inorganic substances in gas, liquid, and solid states and lots of energy in the environment - Energy from the Earth caused chemical bonds to form in the “hot thin soup” of the seas - Led to formation of organic substances - sugars, amino acids, nucleotides

- Experiments have been done with chemicals and an environment similar to primitive earth - Cell like structures were formed -some of these probably “ate” other molecules - Eventually evolved with ability to reproduce - Were probably anaerobic at first - Added CO 2 to environment - Some of these evolved the ability to use CO 2 and became first autotrophs - Autotrophs added O 2 to atmosphere -aerobic organisms then evolved