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 living 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 process of evolution 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 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.

Darwin’s Observations - Variation Observed a variation of traits among similar species that 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 Evolution Occurs BUT HOW???????

Darwin proposes Theory of Natural Selection as the Mechanism for Evolution Four Main Principles to Theory : Overproduction Variation Adaptations for survival are selected by nature Descent with Modificaiton

1.Overproduction Organisms have more offspring than the environment can support – not all offspring will survive

2. Variation Population – all the individuals of a species that live in a particular area. A variation of traits exists within the individuals of a population Individual differences are due to inherited or mutated genetic information

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. Those organisms will likely: *Live the longest *Produce more offspring with the inherited trait

“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

4. Descent with modifications Survivors have traits that are better suited to living in 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 this causes a change to the population and thus ________________ 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 only 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 better adapted forms.

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 Fossils Comparative Anatomy Cell Structure Embryology Molecular Comparison

Fossil Record

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) Protein synthesis same process in all cells All cells have membranes of 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

Individuals within Populations are Genetically Different

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 Stored in 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 Brown hair 1:3

Reasons for loss of variation Bottleneck effect – destructive event leaves few individuals and reduces gene pool Ex. Overhunting Ex. 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

Other causes of Evolution (other than Natural Selection) Geographic Isolation Reproductive Isolation * Temporal – organism breed at different times *

Causes of Speciation The Creation of New Species Geographic isolationGeographic isolation of populations Can lead to Reproductive isolation of population Can lead to New Species (unable to breed when together)

Geographic Isolation Members of a population may become isolated from one another by geographic boundaries like mountains, rivers or even oceans

Reproductive Isolation

Adaptive Radiation

New Species Evolve due to adapting to being in different environments

V. Evolutionary Time Frames A.Gradualism: species descend from a common ancestor gradually as the change in minor ways over a long period of time. B. Punctuated Equilibrium a newer theory developed by Stephen Jay Gould states that species remain fairly constant over long periods of time until a great change in their environment cause relatively rapid speciation.

Convergent Evolution

Divergent Evolution (Adaptive Radiation)

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