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Teacher's Notes Subject: Biology Lesson: Evolution: variation and natural selection Topic: Environmental and inherited causes of variation Grades: 7-9 In order for evolution to occur, there has to be variation. Variation within a species increases the chance that some members of the species will survive changes in the environment. Depending on environmental conditions, inherited characteristics may be advantageous, detrimental, or neutral to the survival of the individual. Natural selection occurs when factors in the environment select for or against certain variations. Lesson Objectives By the end of this lesson, students: understand why variation is important to the survival of a species identify examples of discrete and continuous variation distinguish inherited and environmental causes of variation Lesson Notes Prior Knowledge: species population genes Major lesson points: Discrete and continuous variation Genetic and environmental causes of variation The role of variation in evolution The lesson concludes with an assessment of the students learning of the lesson concepts and objectives. Terms and Definitions Write your response, and then pull tabs for answers. Question 1: Why is variation important to the process of natural selection and evolution? Variation defines the differences among individuals of a species. It allows some individuals in a species to survive while others perish. Question 2: Why is variation important for species survival? Nature chooses the best suited variation and allows the characteristic to continue in the gene pool. Question 3: What does it mean to be ‘fit’ in terms of natural selection? Fitness: the most ‘fit’ individual has the highest number of surviving offspring. Types of Variation: Discrete and Continuous Sort the types of variation. Discrete variation means an individual either has the trait or they don’t. Discrete variations are caused by genetic changes and are controlled by a single gene or a small number of genes. Continuous variations are measured on a continuum, come in a range of forms, and are controlled by a combination of many genes. The environment can have a significant influence on continuous variations, but little effect on discrete variations. Types of Variation: Inherited and Environmental Touch blue text to reveal information. Inherited Variation An individual’s genes determine the inherited characteristics. Environmental Variation Differences in the environment lead to variation. Without the proper environment (nutrition, sun, water), the genetic instructions can’t overcome the environmental influence. Eye color, skin color and hair color are inherited traits. Hydrangeas grow pink flowers in alkaline soil and blue in acidic soil. Two trees with the same genes can grow to different heights, depending Even identical twins don’t turn out identical. on environmental factors such sunlight, water and nutrition. Environmental influences always cause variation. The environment can influence inherited traits. Variation is necessary for survival. Touch image multiple times to reveal information about the evolution of the peppered moth. What is the role of variation in species development? Move a set of birds to each island. Touch the clock to start time. Drag each new bird to the island you believe it evolved on. Why should we care about variation today? Touch the numbers to reveal. 1 A mutation causes an individual in a strain of bacteria to be resistant to antibiotics. With the normal bacteria dead, the resistant bacteria multiply and become more common. 3 Antibiotics kill most of the normal bacteria. 2 The resistant strain takes over. The antibiotic is no longer effective. 4 1 Multiple Choice Height is a _______ and _______ characteristic. A non-heritable, continuous B heritable, continuous C non-heritable, discrete D heritable, discrete Review Put the tiles in order. 1) 2) 3) 4) 5) Characteristic is more common Mutation becomes part of the (mutation). Individual born with afavorable favorable characteristic Offspring with characteristic in future generations. pool and species evolves. Individual survives and reproduces. have a highgene rate of survival. Answer 1) Individual born with a favorable characteristic (mutation). 2) 3) Individual survives and reproduces. 4) Offspring with favorable characteristic have a high rate of survival. 5) Characteristic is more common in future generations. Mutation becomes part of the gene pool and species evolves. 2 Multiple Choice Blood type is a _______ and ______ variation. A non-heritable, continuous B heritable, continuous C non-heritable, discrete D heritable, discrete 3 Multiple Choice The most ‘fit’ moths ________. A are peppered B are black C are white D blend with the environment 4 Multiple Choice Which is an example of an environmental variation? A eye color B earlobe attachment C hydrangea flower color D hair color 5 Multiple Choice Select all that apply. Choose the example(s) of continuous variation. A tongue rolling B foot length C eye color D height 6 Multiple Choice Variations in weight are ______. A completely due to genetics B completely due to the environment C heritable with environmental influences D environmental with heritable influences 7 Multiple Choice Having an attached earlobe is a ______ and ______ characteristic. A non-heritable, continuous B heritable, continuous C non-heritable, discrete D heritable, discrete 8 Multiple Choice Variations can be ______. A neutral B helpful C harmful D all of the above Why did the finch’s beak shape change over time? Use pen to write answer. Different food was available on each island. Birds with beaks the right shape to get the food survived. Over time, the differences in beak shape became more distinct until they became different species. Why should we be concerned about variations in bacteria? Use pen to write answer. The ‘fittest’ bacteria survive, requiring us to continue to develop new antibiotics and leaving us defenseless against them.