Evolution Catalyst Spider monkeys use their claws to climb trees and reach food. There is not enough food for everyone. A spider monkey population has some monkeys with large claws, and other monkeys with smaller claws. What is the environmental pressure exerted on this population? What will happen to the frequency of the gene that produces large claws? Why? Write in complete sentences! Don’t talk during the Catalyst! Objectives By the end of today… SWBAT define species and describe how evolution leads to new species SWBAT analyze phylogenetic trees to determine how related two species are Agenda Catalyst Species Where do they come from? What happens if you cross a mouse and mango? Phylogenetic Trees COLLEGE LEVEL EXPLORATION! Can you handle it? Exit Question Microevolution Key Point #1: Microevolution is the change in allele frequency of a population over time. Allele frequency is the percentage that an allele is relative to other alleles for a trait. Remember that natural selection CAUSES evolution. with good mutations survive Reproduce Their offspring have that good mutation also Allele frequency of the good mutation increases in the gene pool Individuals with bad mutations die Do not reproduce Allele frequency of the bad mutation decreases in the gene Individuals And Why Are Populations Important? Natural selection occurs at the population level. Selects for (keeps around) helpful mutations in a population. Selects against (weeds out) harmful mutations in a population. Evolutionary Change Example Imagine that you go to the mountaintop this year, and sample a population of beetles. You determine that 80% of the genes in the population are for green coloration and 20% of them are for brown coloration. You go back the next year, repeat the procedure, and find a new ratio: 60% green genes to 40% brown genes. What is happening??? What is happening??? Allele frequency for the green allele is decreasing while the allele frequency for brown allele is increasing… This is EVOLUTION!!! Remember allele frequency is how often an allele occurs in a gene pool relative to other alleles for that same gene Another Example Two alleles for tree frogs: green (10%) and orange (90%) Green frogs blend in with surroundings, orange frogs don’t What happens? Orange frogs are eaten quickly Green frogs live longer, have lots of offspring, pass on the gene for being green Allele frequency of the green allele will increase (10 70%) Allele frequency of a orange allele will decrease. (90 30%) What if this process happened over and over again…? Eventually the gene pool will change - some alleles disappear entirely (0%), some become universal (100%)! If this is happening with many traits at the same time…BIG CHANGES ONE More time… Microevolution is the change in allele frequency of a population over time. PRACTICE: Spider monkeys have two alleles for tails: a prehensile tail is 30% of the population and a short tail is 70% of the population. A prehensile tail helps monkeys escape from their predators. What will natural selection do to the frequency of the alleles in this population? Butterflies can have large wings or small wings. 80% of the butterflies have large wings. What percentage of the butterflies have small wings? In twenty years, 40% of the butterflies have large wings and 60% have small wings. WHY? Objectives Key Point #2 Macroevolution happens when changes become so big that we get new species. A species is a group of organisms that can produce fertile offspring with each other. Example of different species… Dogs Cats They cannot breed, therefore, they are not the same species Well… cool. How do these new species originate? I’ve enlisted this help of a few friends for this one… Mouse mango video Speciation Key Point #3 Speciation is the process of new species forming due to reproductive isolation. Reproductive isolation means that two organisms cannot make children. Think Pair Share- Do you get it?? How does speciation relate to Mutations Adaptations Different Environments? Video: Cross a Mouse and Mango Mouse 20 20 40 Each of these has the correct number of chromosomes The number, size, and shape of chromosomes matter. The half from your mom and half from your dad have to add up to the correct pairs. Two different species’ chromosomes won’t pair up right. Mango 12 24 12 Mice and Mango 12 ?? 20 Phylogenetic Trees Key Point #4: We trace how different species formed through phylogenetic trees. Organisms grow more different as they diverge on the tree Common Ancestor: A relative of two organisms Practice Would you expect Feliofornia to look more like Canifornia or Melursus? Would you expect Pinnipedia to look more like Otariidae or Felidae? Practice Are diatoms more like green algae or gerns? Would archaebacteria have more DNA in common with Ciliates or Slime Molds? Practice What process occurred if brown algae cannot produce fertile offspring with red algae? These two organisms have a recent _____ ______. Practice What is reproductive isolation (IN YOUR OWN WORDS)? How can you tell if two organisms are part of the same species? Exit Question Describe what is necessary for a new species to be made A horse and a donkey cannot mate to produce fertile offspring— are they in the same species?