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Are male or female animals larger?. Note taking tips. Create your own short hand Write down what makes sense to you. Review. Turn to a partner and tell them 3 big ideas you learned last class!. Natural Selection. Inference 1: Fight for survival
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Note taking tips • Create your own short hand • Write down what makes sense to you
Review Turn to a partner and tell them 3 big ideas you learned last class!
Natural Selection Inference 1: Fight for survival Only a few organisms can survive therefore they must compete for resources. Inference 2: Not everyone makes it Some traits or characteristics increase an organism chances of survival. Survival is not random. Inference 3: Time to adapt Since individuals with specific traits survive and pass on those traits the population evolves.
Vocabulary Fitness: the ability of an individual to survive and reproduce. Adaptation: any inherited characteristic that increases an organisms chance of survival.
Natural Selection Stories A population of hummingbirds lives in the jungle. Some of the hummingbirds are born with slightly longer tongues. Hummingbirds with longer tongues can reach the nectar of more flowers. More hummingbirds with long tongues survive and reproduce. After a few generations most of the hummingbirds have long tongues. Find all 3 inferences Which hummingbird type has higher fitness? What is the adaptation in this story?
Your stories • Find all 3 inferences: underline them • Which type of organism has higher fitness? Circle it • What is the adaptation in this story? Draw a box around it • Was their adaptation more helpful for survival? Or reproduction?
Learning Objectives • Explain sexual selection and give an example of an adaptation • Explain how the allele frequencies of a population reveal whether evolution is occurring • List the three types of natural selection and differentiate between them
Jigsaw! Your mission is to become an expert on an article. • Read the article, highlight important parts • Talk about the article in your “expert” group and analyze it • Share your new knowledge with your group
Is Evolution Relevant? 1) What is the adaptation? 2) How does it affect fitness? 3) What is the pressure causing the population to evolve? 4) How does this affect us? Can we learn from it? 5) Is there anything we should/can be doing in response to this evolution?
Evolution Is it the adaptive trait the result of mutation? Or variation from sexual reproduction?
Let’s Talk About Sex What makes an organism female? Male?
Defining Male and Female • Physical characteristics? • Chromosomes? • Plants? • Bacteria?
The Unfair Advantage • Egg cells are large and use energy • Sperm cells are small and use little energy
The Unfair Advantage • How many babies can a female deer have in a year? • A male deer?
Sexual Selection Since females mate less often they “want” higher fitness mates. Males compete to mate with females.
Sexual Selection https://www.youtube.com/watch?v=YTR21os8gTA
Sexual Selection http://www.youtube.com/watch?v=oS6FLueFs_s
Extrinsic vs Intrinsic Value How much is a polar bear worth?
Fitness Is about survival but also reproduction. Can you think of some examples of adaptations that would increase reproductive success?
Genetics Organisms have a genotype: a genetic code or blueprint.
Genetics This genotype is expressed in our phenotype: our physical traits, behaviour, etc.
Genetics Our genotype is recorded in our DNA. This DNA is organized into chromosomes.
Genetics The sections of DNA that code for specific things are called genes. Think of your genotype as a huge library, the shelves filled with books are chromosomes, and each book is a gene.
Genetics Some genes are larger than others, and some are linked or act together to code for complex traits. Basically some are books in a series and others stand alone.
Genetics Different forms or types of a gene are called alleles. You can think of them as books in the same genre, but by different authors: like Harry Potter and Twilight.
Genetics Can you think of a characteristic that might be coded for by one gene? Many genes?
Genetics Very few traits are single-gene traits. Most traits are polygenic: controlled by multiple genes.
Genetics All humans have the SAME genes. But…..they can have different alleles. 2 different versions of the gene for eye colour: Brown eye allele Blue eye allele
Genetics What are some other alleles? In humans? Other organisms?
Genetics Where do different form of alleles come from?
Gene Pool All the genes of a population including the different alleles.
Evolution Evolution: any change in the relative frequency of alleles in a population. What does that mean?
Frequency 9 cats 1 dog What is the relative frequency of cats in the population? Dogs?
Blue and Brown eyes What is the frequency of blue (and green) eyes in this class? What is the frequency of brown eyes?
Sickle Cell Anemia Caused by a mutation in a gene. Creates a new form of that gene: allele
Evolution Individuals that survive and reproduce pass their alleles on to the next generation. If all the individuals with an allele die what happens?
Evolution Evolution acts on phenotypes causing genotypes to change. e.g. Black rabbits get eaten, the frequency of the black allele decreases.
Evolution Go back to your story! What allele(s) are increasing in frequency? Which allele(s) are decreasing in frequency?
Single-gene Traits and Evolution Single-gene traits are one allele or the other. Populations can evolve from mostly being type A, to mostly Being type B.
Example Can you think of any examples?
Polygenic Traits and Evolution Polygenic traits produce a normal distribution (bell curve) of types. Natural selection acts on this distribution and alters it.