From Mutations to New Species Speciation From Mutations to New Species Hawaiian Honeycreeper

Introduction How does a mutation in one individual, selected for by nature (natural selection), evolve into new species? Populations, not individuals, evolve!

A. Evolution of Populations If the allelic frequency in gene pool doesn’t change from one generation to the next, no evolution occurs Population is said to be in genetic equilibrium (genes are equal to previous generation) Four major factors or forces can bring about change or evolution: Mutations Genetic drift Gene flow Natural Selection

mUTAT ON MUTATION Can occur due to environmental factors or by chance Lethal mutation: organism won’t survive, change not passed down Beneficial mutation: part of population’s gene pool by process of natural selection; now considered adaptation

QUESTION: Which came first, the bigger skull or the bigger brain? ANSWER: Scientists are still debating.

2. Genetic Drift alteration of allelic frequencies (genes) by chance events such as when a smaller population of gene pool gets cut off from rest of gene pool, those few families represent a FRACTION of original alleles New population contains different proportions of alleles than initial populations, probably even certain alleles totally from the original gene pool. Caused by two things: A. bottleneck effect B. Founder effect

A. Bottleneck Effect An event in which only a few members of a population survive (natural disasters). May lead to mass extinction then rapid recovery.

Example: Pacific Northern Fur Seals and the California Sea Otters. November 9, 2018 Example: Pacific Northern Fur Seals and the California Sea Otters. Both populations of each species were reduced from tens of thousands to less than a hundred due to massive hunting for their fur – a bottleneck. Once each species became protected from hunting, populations grew, but each new population contains less diversity than their original populations.

B. Founder Effect a few individuals from a population start a new population in a new habitat with a different allele frequency than the original population.

Founder EFFECT Big lake

EX: Galapagos Islands organisms probably resulted from founder effect of genetic drift since few of each species came over from South America, and those that did are the only genes found in the “new” population Ex: few human populations such as Amish people in Lancaster, PA

THE AMISH

Amish Genetic Drift different Christian religious sect that left Europe (German-Dutch) due to persecution 30 people came to PA in 1730 to start new community, and to this day don’t associate with anyone on outside, so gene pool never increases or changes 1 individual of that founding 30 carried recessive allele for short arms and legs, extra fingers and toes Allele frequency in general American population is 1:1000; Amish 1:14!

“Founder Effect” 1:14 Amish carries allele for Ellis–van Creveld syndrome

Genetic Drift In Action NEW POPULATION BEGINNING POPULATION Red: 1 in 3 Red: 1 in 33

Gene Flow (Migration) movement of individuals’ genes in or out of a population Immigration to California – now have so many different types of genes in our gene pool

November 9, 2018 18 Diversity

November 9, 2018 4. Natural Selection New smaller population must survive and reproduce – must undergo natural selection Hard to see in humans since our intelligence often overrules nature (we take care of our “less fit” individuals)

Can see evolution occurring in bacteria Antibiotics target differences in bacteria (prokaryotes) that aren’t present in us (eukaryotes) Penicillin: weakens cell wall & makes it burst Sulfanomides: prevent folic acid formation Tetracycline: binds to ribosome preventing translation Antibiotics that used to work on bacteria now are useless (ex: tuberculosis) Bacteria have evolved resistance to them! Very fast natural selection & adaptation

Evolution of Bacteria antibiotic natural selection can significantly alter genetic equilibrium of gene pools over time can evolve into new species over time! antibiotic

B. Evolution of Species natural processes such as mutation, genetic drift, gene flow, and natural selection can change population’s gene pool over time How do these processes result in a new species?

Species: group of organisms that look alike and can interbreed to produce fertile offspring in nature

Evolution of a new species is called speciation Results when members of similar populations no longer interbreed to produce fertile offspring within natural environment Two types of isolation can prevent interbreeding: Allopatric (geographic) speciation: when physical barriers isolate populations and prevent mating Sympatric (reproductive) speciation: when reproductive habits isolation populations and prevent mating

1. Allopatric “Other Country” Speciation In nature, if the animals can’t see each other, they can’t mate Physical barriers such as lava flows or new rivers or lakes can isolate populations. This is also called geographic isolation

Speciation of Tree Frogs Banana tree? Palm tree?

Speciation of Tree Frogs Over many generations, lack of exchanging mutated genes will make each small population adapt to own environment through natural selection own gene pool develops genes become so different that each population becomes own species or become extinct

2. Sympatric “Same Country” Speciation formerly interbreeding organisms can no longer produce fertile offspring even though in same environment Two barriers: Prezygotic “before fertilization” barriers: physical mating may take place but differences in chromosomes in gametes prevent fertilization (EX: horse & donkey) Postzygotic “after fertilization” barriers: physical mating can’t take place due to differences in behavioral patterns (EX: butterfly & moth)

Prezygotic Barriers Genetic material differences don’t allow fertilization of embryo organisms CAN mate physically, but genes are so different that male gamete and female gamete don’t produce fertile offspring Ex: salamanders in California Ex: mules

Tiger Salamander Coast Salamander Slender Salamander

Ancestor was in northern California As salamander migrated south, Sierra Nevada Mountains separated populations & became isolated By the time they met up in southern California, genes were so different interbreeding was impossible

Postzygotic Barriers Behavioral patterns of mating don’t allow mating to occur organisms don’t mate due to timing differences (spring vs. fall, nocturnal vs. diurnal) ex: tree frogs

Allopatric vs. Sympatric Speciation

Process is known as polyploidy and occurs only in plants Speciation can occur due to chromosome numbers multiplying to become polyploids mutations can make a new species in the same population Process is known as polyploidy and occurs only in plants Forced Polyploidy in Flower Industry is Common

Polyploid: any species with a multiple set of chromosomes Remember, 2 sets (2 of each chromosome) is what every mature organism has which is known as 2n A polyploidy may have 3n or 4n or even 10n in some flowers!!

Mistakes during mitosis or meiosis can result in polyploidy ~Parent organism is 2n. Meiosis should split that set up and become gamete n, but nondisjunction leaves it as 2n ~Next step is to join gametes (male and female sex cells) * n + n = 2n  normal * n + 2n = 3n  sterile offspring (can’t divide number normally during meiosis or mitosis) * 2n (mistake) + 2n (mistake) = 4n  new polyploid species (fertile)

Many fruit & grain species are a result of polyploidy Strawberries (8n & 10n) Apples (3n & 4n) Seedless watermelon (3n) Banana (3n) Wheat (4n & 5n)

Hawaiian Honeycreeper Speciation Ancestor 1 2 3 4 5 6 7 Hawaiian Honeycreeper Speciation All new species evolved from one common ancestor

Does not occur if species can’t EVOLUTION Does not occur if species can’t is driven by Natural selection adapt Occurs in Which requires Which results in populations Conditions in the extinction Genetic variation environment Which lead to isolation divergence Which can result in polyploidy Due to speciation

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