Evolution Unit: What is Evolution?

What is The Theory of Evolution? Evolution is, a change (in the genetic composition) of a population over time. on a larger scale, the entire biological history, from the earliest life forms to the enormous diversity of organisms that live on Earth today. an explanation for the diversity of life we see today. A body of evidence that supports the idea that all living things are related and share an ancient common ancestor.

What is a Theory? A widely accepted explanation that is supported by a large body of evidence. Examples Big Bang Theory Newton's Laws of Motion Universal Law of Gravitation Kepler's Laws of Planetary Motion Law of Relativatey

Who Was Darwin? Born February 12, 1809 in England Consumed by his interest in nature. He was 22 years old when he set sail on a 5 year voyage around the world on the HMS Beagle (the voyage of the Beagle).

The Voyage of the Beagle

The Voyage of the Beagle On his journey on the Beagle, Darwin collected thousands of specimens. observed an incredible amount of diversity. observed that organisms are well suited to the environments they live in. found fossils -the preserved remains of ancient organisms. Darwin observed that some fossils look similar to modern organisms, while others look completely different!

Galapagos Islands

Darwin s Conclusions On November 24, 1859, nearly 23 years after the voyage of the Beagle, Charles Darwin published On the Origin of Species by Means of Natural Selection, an assemblage of facts about the natural world. Descent with Modification

Darwin s Conclusions Darwin made 2 main points in The Origin of Species. 1. Organisms inhabiting Earth today descended from ancestral species. a) species is defined as a group of organisms with the same anatomical characteristics that can breed and produce fertile offspring. 2. Natural selection is the mechanism for evolution.

What is Natural Selection? Natural selection is a process in which organisms with certain inherited characteristics are more likely to survive and reproduce than are individuals with other characteristics.

Survival of the Fittest!! Natural selection leads to evolutionary adaptation. an adaptation is an inherited trait that leads to an increased fitness. fitness is the ability to survive and reproduce!!!

How Does Natural Selection Work? Natural Selection can be broken down into 4 processes 1. Genetic Variation individuals in a population vary in many heritable traits. 2. Overproduction of Offspring populations of most species have the potential to produce more offspring than the environment can support.

3. Struggle for Existence - Organisms compete for resources. 4. Unequal reproductive success individuals with better suited traits will leave more offspring.

Evolution through the Process of Natural Selection As a result of natural selection, a population, a group of individuals of the same species living in the same place at the same time, changes over generations.

Examples of Natural Selection

WARM UP QUESTIONS 1. Define evolution. 2. In your own words, explain the process of natural selection. 3. In order for natural selection to work, what 4 processes must be present in a population? 4. Can an individual organism evolve? Explain your answer. 5. In any given natural population, natural selection is constantly exerting a selective pressure on individuals in that population. What changes in the population due to natural selection?

Natural Selection on Single-Gene Traits Leads to changes in allele frequency and thus to EVOLUTION!

Natural Selection on Polygenic Traits Natural selection can affect the distribution of phenotypes in three ways 1. Directional Selection 2. Stabilizing Selection 3. Disruptive Selection

Directional Selection: When individuals at one end of the curve have higher fitness than individuals in the middle or at the other end

Stabilizing Selection: When individuals at the center of the curve have higher fitness than individuals at the extremes

Disruptive Selection: When individuals at either end of the curve have higher fitness than those at the center.

WARM UP Using your knowledge of the Rock Pocket Mouse, explain how natural selection works as a mechanism of evolution. Include the following vocabulary words in your explanation: evolution, fitness, genetic mutation, population, natural selection.

EVIDENCE OF EVOLUTION Evolution leaves observable signs. We will examine three of the many lines of evidence in support of evolution: 1. the fossil record 2. comparative anatomy 1. embryology 3. molecular biology (DNA).

Fossils are The Fossil Record imprints or remains of organisms that lived in the past often found in sedimentary rocks. The fossil record is the ordered sequence of fossils as they appear in rock layers reveals the appearance of organisms in a historical sequence

The Fossil Record Paleontologists (scientists who study fossils) have discovered many transitional forms that link past and present. Transitional fossils include evidence that birds descended from one branch of dinosaurs whales descended from four-legged land mammals.

Figure 13.7-3

Transitional Fossils Evolution of Tetrapods (four-limbed creatures)

Whale Evolution

Comparative Anatomy Comparative anatomy is the comparison of body structure between different species Shows us that evolution is a remodeling process in which ancestral structures become modified as they take on new functions.

Comparative Anatomy Homologous Body Structures structures that have different mature forms and functions, but develop from the same embryonic tissue.

Analogous Structures Evolved to fulfill the same function in unrelated species, not because they were inherited from a common ancestor.

Comparative Anatomy Vestigial structures structures found in living animals that are greatly reduced in size and serve no obvious function

WARM UP Look at the image below. Explain how evolutionary biologists can conclude that the organisms below share a common ancestor.

WARM UP Examine the picture below and explain what evidence is present that supports the Theory of Evolution..

Molecular Biology (DNA) The hereditary background of an organism is documented in its DNA The (amino acids) proteins encoded by the DNA. Evolutionary relationships among species can be determined by comparing genes proteins of different organisms.

Speciation Speciation is the formation of new species. The biological species concept defines a species as A group of populations whose members have the potential to interbreed with one another in nature to produce fertile offspring. So.what must happen for a species to evolve into two or more new species??? And how does this happen?????

Speciation-Separation of Gene Pools For a species to evolve into two or more new species the gene pools of two populations must become separated. As new species evolve, populations become reproductively isolated from each other which means they can no longer interbreed and produce fertile offspring.

Reproductive Isolation As new species evolve, populations become reproductively isolated from one another. Reproductive isolation - members of two populations that cannot interbreed and produce fertile offspring.

Geographic Isolation Two or more populations separated by geographic barriers such as rivers, mountains or bodies of water.

Geographic isolation can then lead to changes in the genetic diversity of a population, which lead to physical and behavioral changes. If the physical and behavioral changes are big enough, they can lead to reproductive isolation and the formation of a new species = SPECIATION!!!!

Behavioral changes within a population can also lead to speciation!!! Meet the Eurasian Blackcap Sylvia atricapilla