Lesson 4 (#2): Common Ancestry and Evidence of Evolution

all LIVING organisms share 3 features

1. DNA and RNA are carrier of genetic info through transcription, translation, and replication. All living organisms do replication and protein synthesis using the same processes.

2. Major features do the genetic code / triplet code that corresponds to one amino acid (start codon, stop codon) are shared by all modern living systems.

3. Metabolic pathwaysto produce ATP are similar across organisms, highlighting a common evolutionary origin.

Three lines of evidence supporting common ancestry for all eukaryotes

1. Membrane bounded organelles

2. Linear chromosomes ( vs circular chromosomes in prokaryotes)

3. genes that contain introns (non-coding piece of DNA)

Mitochandria and Chloroplast structural similarities

• Double membrane

• contains circular genomes (setof genes similar to prokaryotes)

• contains ribosomes

• Endosymbiotic theory - suggests that mitochondria and chloroplasts originated from free-living prokaryotes that were engulfed by ancestral eukaryotic cells, leading to a mutually beneficial relationship.

Linear chromosomes

• contained in all eukaryotes

• histone proteins - collection of protein that DNA wraps around to condense into chromatids vs not found in prokaryotes

• Telomeres - non coding parts at end of chromosomes

• larger genomes (more complex) vs smaller in prokaryotes

• located in the nucleus vs prokaryotic DNA located in cytoplasm in prokaryotes

Introns

• found in all eukaryotic cells

• and are non-coding sequences of DNA that are removed during RNA processing prior to protein synthesis

• Exons are coding sections

How do all populations of organism evolve?

• experience changes in their allelic frequencies over time through difference mechanisms

• Changes in allelic frequency can also be called genomic changes → genome is an entire set of information in the DNA

Main Categories of Mechanisms of Evolution

Environmental Disruptions

• (genetic drift, gene flow) (random) → natural selection (continuours) which changes gene frequencies within a population

Changes in DNA (random)

• Gene Mutations (random) + chromosomal mutation

Cell Division

• Sexual reproduction increases gamete diversity

• crossing over + independent assortment

Continuous change in the fossil record

• evidence of continued evolution

• preservation/impression of an organism in the past

• arranged in the strata layers in the order they were deposited

• new fossils found indicates changes in environment as new selective pressures can result in changes in the freq of certain adaptations within a pop

Scientists wants to know:

• time period of fossil

• the organism found in the layer

• what living reference does it look like?

Resistance contribution to evolution

• resistance to dif chemicals has resulted in species’ evolution through natural selection

• mutations can result in resistance to environmental pressures, driving adaptive changes in populations over time. This occurs as organisms with advantageous mutations survive and reproduce, passing those traits to the next generation

• ongoing process * resistance to antibiotics

Pathogens contribution to evolution of other populations

• anything that makes you sick (eg. bacteria) are pathogens

• cause emergent diseases

• presence can change phenotypes selected for and against in the host pop

• co-evolution between pathogens and hosts occurs, where changes in one species influence the evolution of the other

• Pathogen genomes experience high mutation rates

• chemically compatible with host

• hosts may develop resistance or adaptations in response to the ongoing threat posed by pathogens