Evolution and the History of Life Part 1 Mr. Tsigaridis Evolution and the History of Life Part 1

Change Over Time Differences Among Organisms Do Species Change Over Time Evidence of Evolution: The Fossil Record Fossils Reading the Fossil Record Gaps in the Fossil Record Vestigial Structures Case Study: Evolution of the Whale Evidence of Evolution: Comparing Organisms Comparing Skeletal Structures Comparing DNA from Different Species Comparing Embryonic Structures

Changes Over Time Differences between species relate to adaptations. Adaptations – a hereditary characteristic (attribute) that helps an organism survive and reproduce in its environment. Physical adaptations are heredity. Which means that the organism has no choice about the characteristics. Emotional, cultural, and behavioral adaptations are choices that humans can make.

= + It’s all about Species Horses and Donkeys are separate species What is a Species? A population of organisms that can mate with one another produces fertile offspring. Example: Horses, Donkeys, and Mules Breeding a male donkey to a female horse results in a mule; Breeding a male horse to a female donkey produces a hinny = + Sterile Mule Horses and Donkeys are separate species

Do Species Change Over Time The Earth is very old – 4.6 Billion Years The Earth was formed approx. 4.6 bya The oldest rock is 3.5 Billion years Fossil evidence suggests that species have changed over time because younger fossils are different, yet similar to older fossils.

Evolution Evolution is the process by which populations of organisms acquire and pass on unique traits from generation to generation, affecting the overall makeup of the population and potentially leading to new species.

4. selection (natural and “artificial”) Four distinct mechanisms generate evolution (change in allelic frequency in populations over time): 1. mutation 2. gene flow 3. genetic drift 4. selection (natural and “artificial”)

Gene flow = movement of alleles from one population to another, which may change the allele frequencies Gene flow can happen in several ways; in reality, usually a combination of them individuals leave a population, taking their alleles with them individuals join a population, introducing new alleles (or more copies of ones already present) individuals in the population mate with outsiders, but the offspring stay in the population this introduces new alleles (or additional copies of ones already present), because half of the offspring's alleles are from the outsider http://bruceowen.com/introbiological/20104s08.htm

Gene flow essentially moves alleles between populations this tends to make neighboring populations similar to each other because they exchange alleles and individuals in each have ancestors from the other gene flow can take a mutation in one population and spread it throughout the world

Gene Flow the more migration or interbreeding occurs between two population, the more rapidly they become similar gene flow is important because it explains how a species like humans can be essentially the same all around the world

Genetic Drift Genetic drift = change in allele frequencies due to chance how it works in any random process, like flipping a coin, we can predict the odds of any given outcome, but we can't predict which specific outcome will occur in any given case Genetic Drift has a greater effect on smaller populations than larger populations.

In large populations, drift will not have much effect just as when you flip a coin 1000 times, you expect to get fairly close to 500 heads but the smaller the population, the more this random sampling error will change allele frequencies every generation just as when you flip a coin only 4 times, you are not surprised at all to get 75% heads, or even 100% heads

Geologic Time Notations ya – Years Ago mya – Million of years ago bya – Billion years ago Precambrian Paleozoic ERA Mesozoic ERA Cenozoic ERA

Era word roots Geologist use the clues in some of these words. For example: zoic refers to animal life paleo means ancient meso means middle, ceno means recent. So the relative order of the three youngest eras, first Paleoozoic, then Mesozoic, then Cenoozoic, is straightforward.

Evidence of Evolution: The Fossil Record Fossils Reading the Fossil Record Gaps in the Fossil Record Vestigial Structures

Fossils Are found in the earth’s crust – the very uppermost part of the earth that is exposed to the surface or lying immediately below the oceans.

The Best Crust for Fossils Sedimentary Rocks are the best crust for fossil formations; Example: The Grand Canyon. Strata = Layers of sediment so its called sedimentary rock

Rocks contain clues to the Earth’s past.

What are Fossils Fossils are the mineralized remains of animals or plants or other traces such as footprints. All of the fossils and their placement in rock formations and sedimentary layers (strata) is known as the fossil record. The study of fossils is called paleontology.

What kind of rock is this? Sedimentary Rock

Law of Superposition:Youngest on Top An undeformed sedimentary rock layer is older than the layers above it and younger than the layers below it D C B A

Law of Superposition D C B A In terms of Relative Age Rock Layer B must be younger than Rock Layer A but Rock Layer B is older than Rock Layers C and D. D C B A

Once the order of formation is known, a RELATIVE AGE can be determined for each rock layer http://pubs.usgs.gov/gip/fossils/

Gaps in the Fossil Record Occur because specific conditions are needed for fossils to form Organisms with hard body parts (skeletons) are more likely to form fossils than organisms with soft body parts. Basic to this is the organisms cannot be eaten before fossilization Find shells and bones Fossils form best without oxygen – why peat bogs and tar pits have great fossils. Burial by sediments reduce oxygen exposure. Freezing also allows fossil formation – Mammoth that Japanese scientists are trying to clone from DNA extracted from frozen Mammoth fossil. Fossils once formed must not be destroyed.

Sea shells embedded in marine rock near Santa Cruz Ammonites near Redding

Human Remains

Vestigial Structures Mammals are warm blooded vertebrates Vestigial structures are organs that have no apparent function. Examples: Human appendix – narrow tube attached to the large intestines Chimpanzee, gorilla, and orangutan appendix is functional and used to help digest tough plant material

Appendix

Whale evolution (terrestrial to aquatic in ~ 8 Myr) 8 million years total

PBS Whale Evolution One structural remnant (remaining part) of this evolutionary process are hind limb bones. These bones are called vestigial structures. http://www.pbs.org/wgbh/evolution/library/03/4/l_034_05.html

Evidence of Evolution: Comparing Organisms Comparing Skeletal Structures Comparing DNA from Different Species Comparing Embryonic Structures

Comparing Skeletal Structures Homologous Structures Having similar origins and anatomical patterns Examples – bird wings, human arms, whale flippers, bat wings, cat legs.

Homologous Structures

Analogous Structures Analogous structures do the same thing – similar function, but different anatomy. Wings (butterfly external skeleton, bat internal skeleton Analogous structures: wing of an insect, bird, bat and pterosaur

Comparing DNA from Different Species The actual molecular characteristics of DNA is measured and compared to other organisms. There are four different nucleotides in DNA (Adenine, Guanine, Cytosine, and Thymine). Gene sequencing – sections of DNA are sequenced for the order of nucleotide bases (ATCG or ATGC or ACTG, etc).

What We've Learned So Far By the Numbers: What Does the Draft Human Genome Sequence Tell Us? The human genome contains 3164.7 million chemical nucleotide bases (A, C, T, and G). The average gene consists of 3000 bases, but sizes vary greatly, with the largest known human gene being dystrophin at 2.4 million bases. The total number of genes is estimated at 30,000 — much lower than previous estimates of 80,000 to 140,000. Almost all (99.9%) nucleotide bases are exactly the same in all people. The functions are unknown for over 50% of discovered genes. The dystrophin protein plays an important structural role as part of a large complex in muscle fiber membranes.  When dystrophin is missing or non-functional, the entire complex is compromised, leading to degeneration of muscle tissue.  When the ability to regenerate the muscle is exhausted, muscle wasting occurs resulting in     Muscular dystrophy

Looking for Relatedness

Crime Solving: The COmbined DNA Index System, CODIS, blends computer and DNA technologies into a tool for fighting violent crime.

Comparing Embryonic Structures Ontogeny: Development of the Individual from conception to death. Phylogeny: Development of the Species. Vertebrate organisms (those having a backbone) have similar stages of life as an embryo

Open Court Publishing Company http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Taxonomy.html#EmbryonicDevelopment