Evolution Evolution and Diversity The Age of the Earth The Fossil Record Evidence from Living Organisms How Change Occurs

Developing a Theory of Evolution Jean Baptiste Lamarck proposed a theory of evolution and adaptation He stated that organisms respond to the environment by acquiring new traits and then passing them to subsequent generations (3 ways) Desire to Change – organisms change because they want and need to survive Use and Disuse – Size of organs decrease with less use and increase with more use Passing traits – desirable traits are passed on to offspring

According to Lamark… A giraffe would have stretched its neck to reach the leaves in a tree… …or if you cut off your finger your kids would be born without a finger.

Evolution and Diversity The Theory of Evolution is a proposed set of mechanisms that lead to changes in species over time Charles Darwin proposed the most accepted version of this theory after he wrote chronicles aboard the HMS Beagle He noted that earth contains a large, diverse number of different organisms in which to study Darwin proposed that each organism has its own behavior and phenotype to help it survive environmental conditions He called this “fitness” which is the major theme of natural selection (survival of the fittest)

Charles Darwin

Natural Selection Natural Selection- 1. Process by which individuals that are better adapted to their environment survive and reproduce more successfully than less well adapted individuals do It is also a theory to explain the mechanism for evolution.

2. Genetic Variation- within a population, individuals have different traits; occasionally new traits may appear in a population due to mutations, crossing over, random fertilization, independent assortment. 3. Struggle to Survive- individuals must compete with each other in a “struggle for existence”. Some traits improve and individual’s chance to survive while other traits reduce this chance. A trait that makes an individual successful in its environment is called an Adaptation.

4. Differential Reproduction- organisms with the best adaptations are most likely to survive and reproduce and through inheritance, the adaptations will become more frequent in the population. Populations may begin to differ as they become adapted to different environments, even if they descend from the same ancestors.

What is Fitness?

Natural Selection The theory of Natural Selection proposes that nature changes species by selecting traits Darwin sometimes used the phrase “Survival of the Fittest” to explain Natural Selection. In evolutionary terms, Fitness is a measure of an individual’s hereditary contribution to the next generation. The behaviors and characteristics that help an organism survive in its habitat and successfully reproduce.

Fitness examples: camouflage & mimicry

Camouflage

The Age of the Earth Evidence lies in stone James Hutton (1788) proposed that rain, wind, temperature, and natural disasters shaped the valleys, mountains, and rocks over extremely long periods of time Charles Lyell (1830)contributed to this by adding that current observations of volcanic eruptions and other natural disasters shows that Hutton was correct in assuming the Earth was older than originally predicted

humans evolve First placental mammals Flowering plants dominant First birds 1st dinosaurs First reptiles First seed plants First amphibians First vertebrates First invertebrates eukaryotes prokaryotes Life evolves

Rocks; The Earth’s Clocks The geologic time scale provides a measurement tool for determining the relative age of the earth Due to patterns in the rocks, it was determined that layers on top are younger than deeper layers It followed that fossils that are found in layers tend to be older the deeper you dig (relative dating) Radioactive dating The rate of radioactive decay of elements provides an accurate measurement of age (half-life) The length of time required for half of the radioactive atoms in the sample to decay

Strata or Rock Layers The layers on the top are younger than the layers on the bottom.

Plate tectonics 245 million years ago, continents were joined together in a land mass called Pangea. Fossil evidence shows this.

The Fossil Record Most fossils are found in sedimentary rock Rock created by sand and silt Some organisms die where sediment doesn’t collect quickly enough to preserve an organism or its remains. That is why there are holes in the fossil record By studying fossils of the same species of organism from different eras, we can gain visual evidence of the change over time Paleontologists study fossils to create the fossil record

Evidence from Living Organisms Embryology – the study of developing embryos Many similarities can be studied between embryos of different species This leads us to believe that a similar development has come from a common ancestor

Embryology Study of embryos and the relationships that exist between different species

Homologous – Analogous – Vestigial Structures Homologous structures – structures are similar between organisms even if they have a different function. Whale flipper and a human arm Analogous structures – two organisms that share a common function, but have different structures to achieve the result Bird wing and a butterfly wing Vestigial structures – structures an organism possesses, but no longer has a use for Human appendix, wisdom teeth, etc

Homologous Structures Structure is similar even if function is different

Analogous Structures Functions are the same between species; structures are different

Vestigial Structures Evidence shows the organ was once used, but not any longer

How change occurs

Artificial Selection Breeders and farmers use artificial selection to produce desirable/marketable offspring This is called artificial selection It is opposite of natural selection in the sense that it is not necessarily the survival of the fittest

Malthus and Lyell Thomas Malthus observed that humans were being born at a faster rate than they were dying War, famine, and disease control populations These observations provided enough curiosity for Darwin to delve deep into his theory of Natural Selection Charles Lyell showed evidence that the earth was old and had undergone many drastic changes Darwin conjectured the idea that these drastic changes favored the strong and weaned out the weaker individuals This was the groundwork for developing “Natural Selection”

Types of Evolution

Types of Evolution Speciation – species become separated by one of several ways and change over time from the original parents to fit the new niche Adaptive Radiation – One species can give rise to many different species (Darwin’s Finches) This is a form of divergent evolution Convergent Evolution – A form of evolution in which two species resemble each other after years of change Genetic Drift – Random change in the frequency of genes in a population

Speciation The formation of a new species

Adaptive Radiation One main species can give rise to several new species after being geographically separated

Convergent Evolution The separate evolution of two species that results in both species developing similar characteristics

Genetic drift The random change of allelic frequency in a population

Punctuated Equilibrium vs. Gradualism Evolution occurs much more slowly (gradually) and consistently Speciation occurs at intervals further apart Punctuated Equilibrium Evolution that occurs at more intervals and less consistently Speciation occurs more frequently

Summary Evolution is a mechanism of change It can occur gradually or in spurts Charles Darwin provided a mechanism for this change (Natural Selection) Evolution occurs within populations Convergently – different species develop similar characteristics Divergently – same species develop differently from each other due to environmental Fossil evidence shows support for speciation Many species have shown differences over time Different methods have been used to determine the age of the earth