Variation in Populations Tennessee SPI Objective: Notes Science Tennessee SPI Objective: Analyze data on levels of variation within a population to make predictions about survival under particular environmental conditions. Essential Question 1) What is the link between genetic variations within a population, environmental conditions, and the survival rate of sub-groups within that population? Success Criteria 1) I can explain the link between genetic variations, the environment, and survival rates. 2) I can analyze data relating to survival rates and variations within a population of organisms.

Variation in Populations Variation refers to a variety or diversity of traits (different kinds) within any given population. Three causes of variation 1) Diversity of genetic traits from sexual reproduction 2) Diversity of genetic traits that result from mutations 3) Response to changing environmental conditions Variation in human populations Look around at the other students. Notice the unique traits that individuals have such as hair color, height, eye color, skin color, etc. Variation in wild populations variations occur in nature in populations of plants, animals, birds, insects, fish, bacteria etc.

Notes SPI 0807.5.2 Adaptations 1) When environmental changes occur… Science 1) When environmental changes occur… …organisms must change (adapt) by either changing their behavior or changing their body structure or both. 2) The process that drives this… … is called natural selection. 3) Changes and variations in populations result from… …sexual reproduction (over many generations) and changes in the environment. 4) Changes and variations also result from… …genetic mutations (over many generations) and changes in the environment.

Four Phases of Natural Selection Bunny Rabbits Overproduction Too many offspring are born. Phase 1 Genetic Variation in a Population Offspring are born with a variety of traits. Some offspring are better suited to survive than others. Phase 2 Genetic Variation in a Population Offspring are born with a variety of traits. Some offspring are better suited to survive than others. Struggle to Survive Offspring compete for limited resources. Many die or are eaten by predators. Phase 3 Successful Reproduction The stronger, smarter, faster offspring survive to breed with each other. Phase 4

4 Phases of Natural Selection Spiders Phase 1 Phase 2 Phase 3 Phase 4

Variation in Populations The Galapagos Islands are located in the Pacific Ocean about 600 miles west of Ecuador (see picture below). At some point in the past, a small population of Finches (birds) were blown from South American to these islands. Each island has a slightly different ecosystem, and these finches adapted accordingly. This lead to significant variation in the shapes and sizes of their beaks. South American Finch Galapagos Islands Consists of 18 larger islands and 3 smaller islands.

Variation in Populations Over time the finches developed different beak shapes and sizes in order to eat the local food (structural adaptations). Food Source Only Bugs Food Source Nuts & Bugs Food Source Only Nuts narrow-pointed beak for eating insects Moderately wide beak with a sharp point for cracking nuts and eating insects Very wide beak for only eating nuts

Finches on the Galapagos Islands Essential Question What is the link between genetic variations, the environment, and the survival rate of sub-groups in the population? Finches on the Galapagos Islands Due to the genetic diversity inherent in sexual reproduction, the population of Finches had offspring born with a variety of traits. This included different shaped beaks. Some Finches were born with larger/wider beaks. Some were born with narrow/pointed beaks. Food Sources Some islands have an abundance of seeds/nuts while other islands have an abundance on insects. Larger/stronger beaked offspring thrived on islands with seeds. Sharper/narrow beaked offspring thrived on islands with insects. On each island, Finches with the most effective beaks dominated while those with less effective beaks died out (Natural Selection)

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Note: Termination refers to the percentage of bugs that were killed Review Questions Note: Termination refers to the percentage of bugs that were killed

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