Evolution Changes over Time
TEKS Students will analyze and evaluate B. 7 C how natural selection produces change in populations, not individuals B. 7 E/F effects of genetic mechanisms and their relationship to adaptation and the development of diversity
Darwin Awards: Chlorinating the Genepool
Definitions Evolution: change in the inheritable traits of biological populations over successive generations Inheritance: the process of genetic transmission of traits from parent to offspring
Definitions Population: A localized group of individuals that belong to the same species Species: A group of organisms that can interbreed and produce fertile offspring
Evolution the ways species change over time
Early Evolutionary Thought James Hutton Gradualism Gradual changes over time lead to the formation of new species Gould and Eldredge Punctuated Equilibrium Successful species remain unchanged, until environmental conditions cause evolution to occur in spurts Jean-Baptiste Lamark Law of Use and Disuse Organisms change the size and shape of their organs by using them or not
Early Evolutionary Thought
What is Hardy-Weinberg? Allele and gene frequencies will remain constant (at equilibrium) in the absence of other evolutionary influences Since other influences are typically present in a real population, Hardy-Weinberg represents an ideal condition (no evolution) If any of the 5 mechanisms of evolution are at play, the population is NOT at equilibrium and is therefore changing If a population is changing, it is evolving* *Evolution occurs in POPULATIONS, not INDIVIDUALS
Violating Hardy-Weinberg Causing Evolution 1. Small population (genetic drift) every change has a large impact on the total population 2. Non-random mating we pick the partner that we think is best suited (smart, pretty/handsome, nice, etc) 3. Mutations random changes in DNA 4. Gene flow migration of organisms from one population to another 5. Natural selection some organisms are better adapted to survive in their environment
Violating Hardy-Weinberg Causing Evolution
Genetic Drift The random change in the frequency of alleles in a population Usually affects smaller populations (why?) Occurs because Chromosomes are sorted randomly during meiosis (Law of Independent Assortment) OR Due to a natural disaster This can cause one allele to become more common and the other to become less common Causes loss of genetic diversity in a population
Non-random Mating Occurs when the probability that two individuals in a population will mate is not the same for all possible pairs of individuals Organisms select who they will mate with depending on who they feel has the best traits to pass to their offspring
Mutations Random changes in the DNA sequence of an organism Can be triggered by environmental factors Mutations that occur in gametes can be passed to future generations (offspring) Increases genetic variation
Gene Flow The transfer of alleles from one population to another Occurs when individuals move among populations (migration) Immigration = moving INTO a population (variation in new population increases) Emigration = EXITING a population (variation in the old population decreases)
Natural Selection (Charles Darwin) Also known as survival of the fittest Organisms that are best adapted for their environment are most likely to survive to reproduce and pass their adaptations to their offspring
Natural Selection (Charles Darwin)
Natural Selection (Charles Darwin) Caused by changes in the environment Can only act upon traits that are already present in the population. Can EITHER increase OR decrease variations in the population Increase caused by disruptive selection Decrease caused by stabilizing selection
Types of Natural Selection Stabilizing Removes organisms with extreme forms of a trait Most common form of selection Favors the average value (ex: human birth weights) Decreases variation
Types of Natural Selection Directional Favors one of the extreme forms of a trait Shifts populations towards the beneficial trait Ex: peppered moths
Types of Natural Selection Directional Example: Peppered Moths Before the industrial revolution, peppered moths were mostly light colored, which allowed them to blend in the light color of the bark found on most trees Pollution from the industrial revolution turned the tree bark a dark color (due to soot), which led to the decline in lightcolored moths and the increase in darkcolored moths
Types of Natural Selection Disruptive Removes individuals with the average form of a trait Creates two populations, each with one of the extreme forms of a trait Increases variation
Speciation (divergent evolution) The process by which some members of a sexually reproducing population change so much that they can no longer produce offspring that can mate with members of the original population I.E.: the development of a new species This can occur before fertilization (pre-zygotic isolation) or after fertilization (post-zygotic isolation)
Speciation (divergent evolution) Before fertilization (Pre-zygotic isolation) - Prevents genotypes from entering the gene pool Mechanical sex organs are incompatible Temporal different breeding seasons or times of day Behavioral different mating rituals Habitat different locations Gametic sperm and egg not compatible
Speciation (divergent evolution) After fertilization (Post-zygotic isolation) offspring cannot survive and/or reproduce Sometimes two separate species are capable of mating and producing offspring, but that offspring will be sterile (unable to reproduce) Examples Tiger + Lion = Liger Horse + Donkey = Mule
Speciation (divergent evolution) Four principals that allow one species to change into multiple new species 1. Individuals in a population show differences 2. Differences are inherited (parent offspring) 3. Animals have more young than can survive on the resources of the environment 4. Some differences increase reproductive success. These differences will be inherited by offspring and become more common in the next generation
TEKS Students will analyze and evaluate B.7 A how evidence of common ancestry among groups is provided B. 7 B explanations about changes to the fossil record
Homologies Anatomical Homologous Structures: structural features with a common evolutionary origin Ex: the arm of a human, the leg of a horse, and the wing of a bird/bat
Homologies Anatomical Homologous Structures Inherited from a common ancestor Modifications due natural selection They look similar, but may have very different functions to
Homologies Vestigial Structures A body structure in a present-day organism that is no longer useful However, it was useful to an ancestor Examples: appendix, tailbone, wisdom teeth, occipitalis muscle
Homologies Molecular (biochem) Species with a more recent common ancestor have similar hemoglobin amino acid sequences The more similar two species are, the more similar their DNA (and therefore their amino acids) will be Genome Map Results Hemoglobin Comparison Species Gorilla 1 Rhesus monkey 8 Mouse 27 Chicken 45 Frog 67 Lamprey 125 Amino Acid Differences from Human Hemoglobin Protein
Homologies Genome Map
Homologies Developmental embryology The embryos of a fish, reptile, bird, AND mammal all have A notochord A dorsal hollow nerve chord A post-anal tail Pharyngeal gills This suggests evolution from a distant, common ancestor
BioGeography The study of how plants and animals are distributed on Earth Provides evidence that similar environments can lead to the evolution of similar animals, even if they are far apart
BioGeography Geographical barriers that cause physical separation indicate areas of different species ie: evidence of common ancestry exists between species that have no physical barriers between them *Physical barriers include things like mountain ranges & large bodies of water
Fossil Record A fossil is an impression, cast, original material, or track of any animal or plant that is preserved in rock after the original organic material is transformed or removed
Fossil Record For an organism to be preserved as a fossil, it must be quickly buried in sediment Layers of sediment build up over time Law of Superposition: younger layers of rock are deposited on top of older layers (therefore, the oldest rock will be at the bottom with the youngest rock at the top)
Fossil Record
Fossil Record
Endosymbiosis
Endosymbiosis Ancestors of eukaryotic cells lived together with prokaryotic cells Prokaryotic cells may have even lived inside eukaryotic cells (entering as undigested prey or internal parasites) Eventually the relationship benefitted both cell types and prokaryotes became organelles inside eukaryotic cells
Endosymbiosis Ex: mitochondria and chloroplasts Both have their own DNA, separate from the rest of the cell Both have ribosomes of their own, more similar to the ribosomes of prokaryotes than those in eukaryotes Both reproduce by binary fission, independent of the rest of the cell
Endosymbiosis
Determining Evolutionary History
Phylogenetic Tree (Cladogram) Phylogeny the evolutionary history of a species A cladogram is a branching diagram that shows the proposed phylogeny of a species
Phylogenetic Tree (Cladogram) The groups on a cladogram are called clades The places where branching occurs are called nodes The groups that are closer on a cladogram share more similarities and likely share a more recent common ancestor than groups that are farther away
Phylogenetic Tree (Cladogram)
Phylogenetic Tree (Cladogram)
Cladogram Practice http://www.isd622.org/cms/lib07/mn0100137 5/Centricity/Domain/718/Learning_Target_4.6 _Cladograms.pdf