Teacher's Notes 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. Subject: Biology Lesson: Evolution: variation and natural selection Topic: Environmental and inherited causes of variation Grades: 7-9

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.

Write your response, and then pull tabs for answers. Question 1: Why is variation important to the process of natural selection and evolution? Question 2: Why is variation important for species survival? Question 3: What does it mean to be ‘fit’ in terms of natural selection? Variation defines the differences among individuals of a species. It allows some individuals in a species to survive while others perish. Nature chooses the best suited variation and allows the characteristic to continue in the gene pool. Fitness: the most ‘fit’ individual has the highest number of surviving offspring. Terms and Definitions

Types of Variation: Discrete and Continuous Sort the types of variation. The environment can have a significant influence on continuous variations, but little effect on discrete variations. Continuous variations are measured on a continuum, come in a range of forms, and are controlled by a combination of many genes. 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.

Types of Variation: Inherited and Environmental Touch blue text to reveal information. Two trees with the same genes can grow to different heights, depending on environmental factors such sunlight, water and nutrition. The environment can influence inherited traits. Inherited Variation Environmental Variation Even identical twins don’t turn out identical. Environmental influences always cause variation. Eye color, skin color and hair color are inherited traits. Hydrangeas grow pink flowers in alkaline soil and blue in acidic soil. Differences in the environment lead to variation. An individual’s genes determine the inherited characteristics. Without the proper environment (nutrition, sun, water), the genetic instructions can’t overcome the environmental influence.

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. 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. Antibiotics kill most of the normal bacteria. The resistant strain takes over. The antibiotic is no longer effective

1 Multiple Choice A non-heritable, continuous B heritable, continuous C non-heritable, discrete D heritable, discrete Height is a _______ and _______ characteristic.

Put the tiles in order. Review 1) 2) 3) 4) 5) Individual born with a favorable characteristic (mutation). Characteristic is more common in future generations. Individual survives and reproduces. Offspring with favorable characteristic have a high rate of survival. Mutation becomes part of the gene pool and species evolves.

Answer 1) 2) 3) 4) 5) Individual born with a favorable characteristic (mutation). Characteristic is more common in future generations. Mutation becomes part of the gene pool and species evolves. Offspring with favorable characteristic have a high rate of survival. Individual survives and reproduces.

2 Multiple Choice A non-heritable, continuous B heritable, continuous C non-heritable, discrete D heritable, discrete Blood type is a _______ and ______ variation.

3 Multiple Choice A are peppered B are black C are white D blend with the environment The most ‘fit’ moths ________.

4 Multiple Choice A eye color B earlobe attachment C hydrangea flower color D hair color Which is an example of an environmental variation?

5 Multiple Choice A tongue rolling B foot length C eye color D height Choose the example(s) of continuous variation. Select all that apply.

6 Multiple Choice A completely due to genetics B completely due to the environment C heritable with environmental influences D environmental with heritable influences Variations in weight are ______.

7 Multiple Choice A non-heritable, continuous B heritable, continuous C non-heritable, discrete D heritable, discrete Having an attached earlobe is a ______ and ______ characteristic.

8 Multiple Choice A neutral B helpful C harmful D all of the above Variations can be ______.

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. Use pen to write answer. Why did the finch’s beak shape change over time?

Use pen to write answer. Why should we be concerned about variations in bacteria? The ‘fittest’ bacteria survive, requiring us to continue to develop new antibiotics and leaving us defenseless against them.