Evidence for Evolution and the Theories of Evolution that are based on this evidence

What is Evolution? Evolution – process of biological change by which populations of organisms change over time and become different than their ancestors.

Origins of Evolutionary Theory Scientific beliefs prior to the 1700’s: Earth was only 6000 yrs old and had not changed since its creation Each species appeared individually on Earth Species could not go extinct

What is a Species? A group of organisms that are similar enough to reproduce and have fertile offspring (fertile – able to have babies)

Origins of Evolutionary Theory 1700s -a time of great advances in intellectual thought and discoveries By the 1800’s earlier ideas had been replaced -The idea that organisms change or evolve was more accepted. Although the idea of evolution was more accepted, the actual mechanism or method was unknown

Several people became famous historical figures due to their theories on how evolution occurs

Jean Baptiste LaMarck 1809 Inheritance of Acquired Traits Theory Organisms inherit the traits that their parents developed or acquire during their lifetime a.k.a “Use it or Lose it” Theory

Lamarkian Theory of Evolution Example Giraffe’s stretch their necks when the reach high for leaves. Over time their neck grows longer. The parent’s stretched neck gets passed down to young.

Lamarkian Theory If I wear braces to straighten my teeth then my children will have straight teeth A man breaks his nose – his kids get bent nose

Importance of Lamarkian Theory Though his ideas were discredited, they were important in stimulating scientific discussion about the mechanisms (methods) of evolution.

Charles Darwin Age 22 takes a position as naturalist about the HMS Beagle on a 5 year mapping expedition of South America and the Pacific Islands Collects hundreds of specimens and made extremely detailed observations of the natural world.

Voyage of the Beagle

Galapagos Islands

Darwin’s Observed Trait variations Observed a variations in traits among similar species Variations allowed them to adapt to their specific surroundings Ex. Finches bills adapted to different food types

Darwin’s Observations – Fossil Evidence

Darwin’s Observation – Geologic change

Darwin’s Conclusions Earth is older than 6000 years Present day life descended from older forms of life Evolution Occurs BUT HOW???????

Darwin proposed the Theory of Natural Selection as the Mechanism for Evolution Video

4 Main Principles of the Theory of Natural Selection Overproduction of offspring Variation in traits Nature “selects” the variations that provide greatest chance for survival - Adaptations Descent with Modification – Darwin’s term for evolution –organisms share a common ancestor but descendants change over time

1.Overproduction Organisms have more offspring than the environment’s carrying capacity can support – causes struggle for survival

2. Variation Individuals within a population show variation in their traits. Variations are due to inheritance and genetic mutations

Offspring may inherit the trait variations from their parents.

3. Adaptation A particular trait form may be adaptive or not Adaptation – a physical, physiological or behavioral trait that increases an organism’s ability to survive in its particular environment.

Nature “selects” organisms with traits best adapted to survival Nature “chooses” those organisms with traits that are best adapted to survival. Video Those organisms will likely: *Live the longest *Produce more offspring with the inherited trait

Nature selects the traits that are most adaptive for survival Nature DOES NOT make new traits – genetic recombination in meiosis and mutations are the source of new traits.

“Survival of the Fittest” Which is more “FIT” to Survive? Fitness – measure of the ability to survive and produce more offspring than others in the population

Fitness is relative Fitness depends on the environment in which the organism lives. The fittest genotype during an ice age will not necessarily be the fittest genotype when its over. Individual is not necessarily the strongest, fastest, or biggest.

4. Descent with modifications Survivors have traits that are better suited to surviving and passing down their traits to their particular environment. They pass these adaptive traits to offspring. Individuals not as well suited to environment die off and their genetic information is lost to the population. **Over time a change in gene frequency occurs as nature “selects” those that give rise to the most adaptive phenotypes ”.

As nature “selects” those traits that are the most adaptive for survival a change in the population’s gene frequency occurs. Gene frequency is a measure of how many individuals in the population have a particular gene Over time this causes a change in the population and thus evolution has occurred.

Types of Selection Artificial Selection – Process of breeding species to select for desired traits. (a.k.a Selective breeding)

In Artificial/Selective Breeding humans are the selective agent

Natural Selection In nature, traits are selected when they provide a survival advantage in the environment at a specific time Nature is the selective agent. Peppered moths

Selection can lead to speciation - over generations and time, new species will evolve from older forms to forms better adapted to the current environmental conditions.

Creation of new Traits Natural Selection favors phenotypes/physical traits that improve an organisms chance of survival in a specific environment Natural Selection does NOT make new traits or new genes New traits come from genes that are made through mutations and crossing over in meiosis

Natural Selection in Action Why should you take take all your antibiotic medicine even though you feel better???

Evidence for Evolution 1.Fossils 2.Comparative Anatomy 1. Homologous structures 2. Analogous structures 3. Vestigial structures 3. Cell Structure 4. Embryology 5. DNA/ Molecular Comparison

Fossil Record – Indicates Common ancestory

Comparative Anatomy 1. Homologous structures * Same structure ; Different functions (homo=same) * Suggests the species may be related/ have common ancestor. Ex. Bats wing, human arm, and whale flipper bones. )

Comparative Anatomy 2. Analogous structures * Different structure Same function * May have developed due to living in similar conditions/ having same environmental pressures. * Does NOT suggest the species are closely related Ex. Bird wing and Dragonfly wing

Comparative Anatomy 3. Vestigial structures – those that no longer serve a present day useful function but still develop Ex. Human appendix, tailbone (coccyx)

Cytological Comparisons (Cell structure and function) ex. Eukaryotic vs. prokaryotic cells (nucleus) (no nucleus) **There are many similarities among even the most different of cells Protein synthesis same process in all cells All cells have membranes madeof same basic phospholipids Endosymbiotic Theory

Comparative Embryology Comparative embryology – examination of differences and similarities in embryo development Similar structures during development indicate shared common ancestor. Ex. Gill slits – ocean dwelling ancestor? ex. Comparison of bird, fish and early human embryos

Biochemical /Molecular Comparisons Comparisons of molecules within species and between species indicates common ancestors and relationships. DNA comparison - Strongest evidence to support evolution theory. Human and Chimpanzee DNA more than 99% identical. Humans and Gorillas and Baboons 95-97% Human and Mice 80% identical DNA. Ex. Cytochrome C, Humans differ from: Monkeys - 1 amino acid Pigs – 10 amino acids. Fish – 21 amino acids

Molecular Comparisons

Phylogeny – study of determining common ancestry between species Phylogenetic Tree of Life – suggests relationships and common ancestry between species

Sources of Variation 1. Mutation Change in the genetic code due to a spontaneous change or an outside mutagen Beneficial if they result in a useful adaptation 2. Genetic Recombination Processes of meiosis and sexual reproduction results in new combinations of alleles in the offspring

Genetic Variation in a Population Greater genetic variation increases the chance some individuals will survive changing conditions A population’s gene pool – the combined alleles of all individuals in population Allele frequency – how common the allele is Ex. Achondroplasia 1:100,000 Americans Brown hair 1:3 Americans

Causes of Evolution other than Natural Selection Genetic Drift * Bottleneck Effect * Founder Effect

Genetic Drift Another mechanism or cause of evolution Random event (natural disaster, human caused disturbance) causes change in allele frequency Does not favor adaptations like natural selection does Reduces genetic variety

Genetic Drift – Bottleneck Effect Bottleneck effect – destructive event leaves few individuals, with a reduced gene pool, to carry on the population The survivors may not have the most adaptive genes Ex. Overhunting Typhoon/Fire/natural disaster

Founder Effect Founder effect – when just a few individuals create the foundation for a new population – small gene pool ex. Amish Often results from migration, seed dispersal by birds

Founder Effect a few individuals from a population start a new population with a differenct allele frequency than what existed in the original population

Watch “ Mechanisms of Evolution” Uploaded to Google Classroom – this shows the many different events, in addition to natural selection, that can result in evolution.

Patterns of Evolution Divergent Evolution (Adaptive Radiation) Convergent Evolution Coevolution

Divergent Evolution Organisms share a common ancestor but evolved differently to adapt to new environments (Adaptive Radiation). Same internal structure.

Divergent Evolution Common ancestor gives rise to new species. Evolve due to adapting to different environments

Convergent Evolution Evolution produces species that are similar in appearance and behavior due to adapting to similar environments. No common ancestor Species have the same outer appearance but their internal structures are different. Ex.a shark and dolphin have similar body structures and live in similar environment, but they are not related

Convergent Evolution

Coevolution A change in the genetic composition of one species (or group) in response to a genetic change in another – results in an intimate connection between species Darwin’s Moth – developed a tongue that fits the flower perfectly; The moth eats and the flower is pollinated

Coevolution – results in adaptations that increase the interdependency between organisms

Evolution is a fact – species do change over time!! Natural Selection is a scientifically supported theory that explains this fact. Decades of experimental and observational evidence support Darwin’s theory of Evolution by Natural Selection

Video#1 What is Evolution? Video#2 Evidence for Evolution Video#3 What is Natural Selection