The Theory of Evolution The idea of Everchanging

The Theory of Evolution The idea of Ever-changing organisms on the Earth

The Puzzle of Life’s Diversity How did all organisms come to exist and rely on one another for their survival? Evolution: The process by which modern organisms have descended from ancient organisms. Theory: A well studied idea, not 100% proof.

Voyage of the Beagle This was the ship that carried Charles Darwin is the father of the Theory of Evolution by Natural Selection This ship took him to various places on Earth, many that were never seen before by humans He collected specimens from the different islands he sailed to and studied them

Darwin’s journey

Darwin noticed a few things… 1) Many plants and animals seemed very well suited to whatever environment they inhabited. 2) Animals/plants had several ways to reproduce and survive. 3) Some organisms that seemed well suited for an environment on one continent did not live in the same environment on another continent 4) Fossils that Darwin found were similar to organisms that were still alive. Some looked completely different from anything he had ever seen. Why had species disappeared?

Patterns of Diversity Darwin found that organisms were all well suited for their environments because of the traits that they had Example: Animals that lived in the tropics looked much different than those in the arctic region There are patterns to the different forms animals have

The Galapagos Island Small chain of Islands in Pacific ocean, each one is very different Darwin found that each island had different varieties of species Tortoises on each island had different shells. This occurred because the animals adapted to the unique climates on each island

Galapagos Tortoises

Ideas That Shaped Darwin’s thinking Most scientists from Darwin’s time believed the earth to be unchanged from the start of time. He found fossils that showed differences over the years. He challenged the ideas that life is created and then ends, but never changes. He provided many samples and specimens to back up his claims in the book “The Origin of the Species”

An Ancient and Changing Earth The earth is over 4 billion years old It has gone through dramatic changes: warm periods, Ice ages, depletion of oxygen Organisms must adapt to these changes in order to survive, a key idea of evolution.

Lamarck’s Ideas Along with Darwin, another scientist named Lamarck also recognized the changing of species over time. He felt animals only lived where they could survive, unless they were forced to adapt. Very incomplete ideas

Lamarck’s Theory of Use and Disuse Organisms passed on traits either by using or not using them. The more important a trait was, the more it was used, this led to that trait getting passed on. So, if I lost my left arm in a car accident, then all of my kids would have 1 arm.

Inheritance of Acquired Traits Lamarck thought acquired traits could be inherited If an animal changed while alive, this would get passed on. If I gained 200 pounds my children will all be obese too, we know that’s not true!

Evaluation of Lamarck’s Ideas: WRONG!!!! We do not inherit acquired traits nor pass traits on by use and disuse Important first step in the ideas of Evolutionary theory

Origin of the Species Book Darwin published, although he waited almost 25 years to do it 1859 published the work, it instantly became one of the most controversial works ever Discussed natural selection, adaptations and inheritance

Natural Selection “Survival of the fittest” Animals that are strong and have good traits will often survive and pass those traits on to other generations. As the world changes, organisms must adapt or they become extinct. Sometimes traits that have allowed animals to thrive for thousands of years can cause extinction if the environment changes The key to evolution of organisms

Adaptations Inherited characteristic that increases an organism’s chance of survival. Examples: Camouflage, webbed feet, wings, etc. How did these adaptations show up? Genetic Mutations!!! These mutations turned out to be beneficial and therefore, the organism that had them survived to reproduce and pass that trait on!

Darwin’s Theory of Evolution By Natural Selection Based on 4 postulates 1) There is variation in a population (Caused by mutations) 2) More organisms are born than survive to reproduce. 3) Those organisms that survive have an advantage over those that do not survive. 4) Some of those advantages (adaptations)are heritable (can be passed on)

Evolution in Action Evolution

Pollinators can cause Flowers to Evolve

Flower Evolution

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Evidence that Supports Darwin 1) Age of the Earth – 4. 5 billion years old 2) Fossil Record 3) Geographic Distribution of Living Species 4) Homologous Structures 5) Comparative Embryology 6) Genetics 7) Molecular Biology

1) Age of the Earth – Approximately 4. 5 billion years old - That is DEFINITELY enough time for evolution to occur 2) Fossil Record- although it is incomplete, it still offered Darwin the opportunity to note that countless species had come into being, lived for a time, then vanished. By comparing the rocks and fossils found in them, scientists could document the fact that life has changed over time

3) Geographic Distribution of Living Species Land masses such as Hawaii, Australia, and New Zealand had very distinct plant and animal life because they were separated by thousands of miles of ocean from all other land masses Australia had 100 s of different species of marsupials (Koalas, Kangaroos, etc. ) but very few placental mammals like dogs, cats, etc.

4) Homologous Structures Different animals have similar bone structures in their bodies. They may look totally different, but they are very similar. Is this also proof that many animals evolved from a few simple animals long ago? Look at these examples:

Homologous Arm Bones

5) Comparative Embryology All things are extremely similar when they are embryos Could this be a leftover trait because many things evolved from similar organisms? An interesting question theory of evolution brings up. Take a look at these examples:

Embryos

Embryos

6) Genetics and 7) Microbiology Genetics – what we know about how traits are inherited supports Darwin’s ideas. Molecular Biology- looking at amino acid sequences of proteins or DNA sequences show that closely related species have almost identical DNA. What percent of their genes match yours? Another human? A chimpanzee? A mouse? A fruit fly? Yeast? A weed (thale grass)? 100% - all humans have the same genes, but some of these genes contain sequence differences that make each person unique 98% - chimpanzees are the closest living species to humans 92% - all mammals are quite similar genetically 44% - studies of fruit flies have shown how shared genes govern the growth and structure of both insects and mammals. 26% - Yeasts are single-celled organisms, but they have many housekeeping genes that are the same as the genes in humans, such as those that enable energy to be derived from the breakdown of sugars. 18% - Plants have many metabolic differences from humans. For example, the use sunlight to convert carbon dioxide gas to sugars. But they also have similarities in their housekeeping genes.

Phylogenetic Trees show animals have evolved over a long period of time. The further away a branch is, the less similar their genetics are.

Population Growth In 1798 Thomas Malthus said “the world is heading for a population crisis” Darwin believed there is a reason for death and imperfections: to keep population numbers in check If not, he believes that any species, especially humans, can take up too much food, space and other resources. The human population of the world has doubled in the last 20 years.

Evolution To sum up theory of evolution: The world is a constantly changing place All organisms must adapt to change or become extinct Natural selection or “survival of the fittest” is the mechanism for change in evolution. We are still seeing examples of evolutionary change today: resistant bacteria

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Population Genetics Genetic variation is studied in populations A gene pool refers to all of the genes, including the different alleles, that exist in a population. The frequency of an allele is the number of times that the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur. Usually shown as a percentage.

Frequency

Genetic Drift Natural selection has its effect on the frequency of alleles in a population. Some of these changes in allele frequency, however, can happen randomly. This kind of random change in allele frequency is called, genetic drift. Example: A small group of beetles may colonize a new habitat. This group of beetles may carry alleles in a different relative frequency than the one they came from. Therefore, the new population will be genetically different from the original. This is known as the founder effect.

Are there any conditions where evolution would not occur? Hardy Weinberg Principle – states that allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change. Situation in which allele frequencies remain the same is called genetic equilibrium.

FIVE CONDITIONS ARE REQUIRED TO MAINTAIN GENETIC EQUILIBRIUM FROM GENERATION TO GENERATION: Random Mating-must have equal opportunity to reproduce Large Population – less chance of genetic drift to affect a population No movement into or out of the population – no new genes can be added or taken away No mutations - genes mutate from one form into another, new alleles may be introduced into a population No natural selection – all genotypes have an equal chance to survive and reproduce

How do changes in allele frequencies lead to new species? Species- group of organisms that breed with one another and produce fertile offspring In order for a new species to arise (speciation), something needs to happen… They have to be reproductively isolated… 1) Behaviorally 2) Geographically 3) Temporally

Behavioral Isolation Two populations are capable of interbreeding but have differences in courtship rituals or reproductive strategies that involve behavior Ex: Different mating calls between the eastern and western meadowlark Eastern Western

Geographic Isolation Populations are separated by geographic barriers such as rivers, mountains, or bodies of water Example: Abert and Kaibab Squirrels

Temporal Isolation Occurs when two or more species reproduce at different times. For example, three similar species of orchid all live in the same rainforest, but they release their pollen at different times. Because they release their pollen on different days, they cannot pollinate one another.

Speciation in Darwin’s Finches Founder’s arrived Geographic isolation – on different islands Changes in the gene pool – depended on the food source Reproductive isolation- Mates choose specific traits so the different birds would not reproduce with each other Ecological competition-Competed for resources Continued evolution- over a long time this process kept occuring (14 species of Galapagos Finches exist)