Adaptation,Variation and Natural Selection

Adaptations and Survival An adaptation is a structure, behavior or physiological process These help an organism to survive and reproduce in particular environment Example: camouflage Camoflauge is genetice the genes for camoflauge were more prevalent therefore that species survived

How do These Adaptations Develop? They are a result of a gradual change of characteristics over time A variation that helps an individual in a population is likely to be passed on from survivor to survivor Some variations help and some do not, not all variations become adaptations!

Variation Within a Species

Let’s Look at Our Variations! / 20 Question: Are there measureable differences in sizes among individuals of a species? As a class, each measure your thumb and your middle finger Take the class data and graph this information Use a data table and a graph that best suits the data gathered Conclude what you see with this data

How does variation within a species occur? Biological Species A group of reproductively compatible populations How does variation within a species occur?

Genetics Organisms that reproduce sexually have a blueprint from both parents Through this reproduction, particular traits are passed on to the new organisms

Mutations Mutations are genetic changes that happen in DNA Occur from mistakes that happen when DNA is being copied For example: Your DNA has about 175 mutations compared to your parents. Sometimes you notice mutation, other times it has no effect

How it Occurs Evolution observed at the molecular scale

Examples of Genetic Mutations Down Syndrome: a genetic disorder caused by the presence of all or part of an extra 21st chromosome Often Down syndrome is associated with some impairment of cognitive ability and physical growth as well as facial appearance

Klinefelter's syndrome: Affected males have an extra X sex chromosome Klinefelter's syndrome: Affected males have an extra X sex chromosome. The principal effect is abnormal testes development and reduced fertility.

Sickle Cell Anemia: A genetic disorder passed on when BOTH parents have the trait or are carriers for the trait The blood no longer flows easily through the body. Many times the blood starts to clot in the veins and arteries – not allowing regular blood flow to the organs in the body!

Benefits of Mutation Sometimes a mutation allows for a trait that has benefits especially in a changing environment – it will select which organisms will survive A population will change in its ability to survive as the abiotic conditions around it will select those suitable to survive in the environment Mutations may provide a new selective advantage A Housefly with resistance to DDT A California ground squirrel that has a factor in their blood that helps them combat rattlesnake venom when bitten

Natural Selection Depends on reproductive success Operates on a population, NOT on an individual Dynamic between genetic change and the changing environment Environment exerts Selective Pressure: environmental conditions that select for certain individuals and select against others Natural Selection can take time or can happen quickly eg: Bacteria vs. Finches

Charles Darwin (1809-1882) Sailed around the world 1831-1836

2. What did Darwin’s Travels reveal The diversity of living species was far greater than anyone had previously known!! These observations led him to develop the theory of evolution!!

3.How did tortoises and birds differ among the islands of the Galapagos? Each island had its own type of tortoises and birds that were clearly different from other islands

Galapagos Turtles

8. Darwin finally published his ideas in 1859 Other naturalists were developing the same theory that Darwin did. Even though he was afraid of the Church’s reaction to his book he wanted to get credit for his work.

9. Artificial Selection nature provides variation, humans select variations that are useful. Example - a farmer breeds only his best livestock

10. Natural Selection The traits that help an organism survive in a particular environment are “selected” in natural selection

11. Natural Selection and Species Fitness Overtime, natural selection results in changes in the inherited characteristics of a population. These changes increase a species fitness (survival rate)

Descent with Modification Each living species has descended with changes from other species over time

Summary of Darwin’s Theory 1. Organisms differ; variation is inherited 2. Organisms produce more offspring than survive 3. Organisms compete for resources 4. Organisms with advantages survive to pass those advantages to their children 5. Species alive today are descended with modifications from common ancestors

13. Evidence of Evolution Fossil Record Geographic Distribution of Living Species Homologous Body structures Similarities in Embryology

Evidence of Evolution Fossil Record provides evidence that living things have evolved Fossils show the history of life on earth and how different groups of organisms have changed over time

What to do? Complete the Thought Lab 4.1 – omit procedure Complete the Though Lab 4.2 Complete Section 4.1 Review Q’s 1-9