1 Natural Selection: A Mechanism of ChangeTheory of Evolution Natural Selection: A Mechanism of Change

2 What are we learning today?Benchmarks Learning Objectives SC.912.L – Describe the conditions required for natural selection, including: overproduction of offspring, inherited variation, and the struggle to survive, which result in differential reproductive success. I will describe the process of natural selection using the 4 principles of Darwin’s theory of evolution by natural selection. I will describe how mutations and genetic recombination increases inherited genetic variation of offspring. I will relate the concepts of adaptation and fitness to the theory of natural selection. These are the middle school benchmarks that are considered “fair game” for the assessment of today’s Biology benchmark SC.912.L Explore the scientific theory of evolution by recognizing and explaining ways in which genetic variation and environmental factors contribute to evolution by natural selection and diversity of organisms. Explore the scientific theory of evolution by relating how the inability of a species to adapt within a changing environment may contribute to the extinction of that species. Understand and explain that every organism requires a set of instructions that specifies its traits, that this hereditary information (DNA) contains genes located in the chromosomes of each cell, and that heredity is the passage of these instructions from one generation to another. Compare and contrast the general processes of sexual reproduction requiring meiosis and asexual reproduction requiring mitosis. Describe and investigate various limiting factors in the local ecosystem and their impact on native populations, including food, water, shelter, space, disease, parasitism, predation, and nesting sites. Explain that scientific knowledge is the result of a great deal of debate and confirmation within the science community. Explain that scientific knowledge is durable because it is open to change as new evidence is encountered. Identify an instance from the history of science in which scientific knowledge has changed when new evidence or new interpretations are encountered.

3 Answer these questions on the back of the small paperDo Now Answer these questions on the back of the small paper How do the mice in Fig. 1 display inherited variation? What characteristic of the mice is an adaptation that increases their fitness? How is Fig. 2 an example of survival of the fittest? How is the population of mice different in Fig. 3 from Fig. 1? Explain what process could account for this change in the mice population.

4 EVOLUTION BY NATURAL SELECTIONWhat is evolution? What type of organisms are subject to evolution? What’s the time required for evolutionary changes? What’s the evidence that scientists rely on to explain the evolutionary process?

5 How did Charles Darwin develop his theory?From 1831 to 1836, Darwin made a voyage around the world in which he collected and studied thousands of plant and animal specimens. During his travels, Darwin made numerous observations and collected evidence that led him to propose a hypothesis about the way life changes over time. In the development of his theory, Darwin did not just take his own observations and ideas into account. In fact, it took him 20 years to put together data from many sources and to account for the ideas of several other scientists of his time. SC.912.N.1.3 Recognize that the strength or usefulness of a scientific claim is evaluated through scientific argumentation, which depends on critical and logical thinking, and the active consideration of alternative scientific explanations to explain the data presented….. Stress to the students that Darwin was influenced by many other scientists of his time. These 3 scientists are just a sampling. Georges Cuvier – gave convincing evidence that organisms from the past differed greatly from living species, based on his observation of fossils from different rock layers. Charles Lyell - shared Cuvier’s ideas but also believed that geologic process that shaped the Earth in the past still continue today. Thomas Malthus – suggested that if the human population continued to grow unchecked, sooner or later there would be insufficient food and living space for everyone.

6 What is natural selection?Individuals with characteristics that are not well suited to their environment either die or leave few offspring, while individuals that are better suited to their environment survive and reproduce most successfully. I’m one smart quacker… Glad I’m more fit Use the silly duck example to emphasize the idea of fitness as having advantageous characteristics. Ask the students to identify the duckling which is most fit for its environment (in the context of the picture).

7 What are the four principles of Darwin’s theory?THIS IS THE MAIN IDEA OF TODAY”S LESSON!

9 What are the four principles of Darwin’s theory?2. Inherited Variation: Individual organisms within the population differ. Most of this variation is determined by genetic inheritance (recombination during meiosis: crossing over and independent assortment), but sometimes it is the result of genetic mutations.

10 What are the four principles of Darwin’s theory?3. Struggle for Existence: Because so many offspring are produced, many will die due to a lack of resources, predation, disease, or other unfavorable conditions. Have students analyze the pictures. Ask them to explain the struggle for existence that is evident in each. The slowest or weakest lions will succumb to hunger before fast or strong ones. Competition for limited (food) resources leaves some members of the group, probably the smallest or least agile, hungry.

11 What are the four principles of Darwin’s theory?4. Differential Reproduction: Individuals best suited to their environment survive and reproduce most successfully. Therefore these organisms pass their advantageous traits to their offspring (higher fitness) while offspring with disadvantageous traits die, produce fewer offspring or never reach sexual maturity (low fitness).

12 How does evolution by natural selection work?Darwin proposed that over long periods, natural selection produces organisms that have different structures, establish different niches, or occupy different habitats. As a result, species today look different from their ancestors. Each living species has descended, with changes, from other species over time by a principle he referred as descent with modification. Whale ancestor, homo erectus.

13 How does evolution by natural selection work?Whale ancestor, homo erectus.

14 REVIEW: Darwin’s Natural Selection1. Overproduction of Offspring: Organisms produce more offspring than can survive. Many of the offspring do not survive to reproductive age. 2. Inherited Variation: Individual organisms within the population differ. Most of this variation is determined by genetic inheritance (recombination during meiosis: crossing over and independent assortment), but sometimes it is the result of genetic mutations. 3. Struggle for Existence: Because so many offspring are produced, many will die due to a lack of resources, predation, disease, or other unfavorable conditions. 4. Differential Reproduction: Individuals best suited to their environment survive and reproduce most successfully. Therefore these organisms pass their advantageous traits to their offspring (higher fitness) while offspring with disadvantageous traits die, produce fewer offspring or never reach sexual maturity (low fitness). Misconception: Living things can not change their characteristics according to their environment. The variation must already be present in the population so an organism can use that trait (variation) to adapt to its environment so natural selection can occur

15 Collaborative Activity: Natural Selection ScenariosObjectives: I will use the 4 principles of Darwin’s theory of natural selection to describe the process of evolution. Procedure: Work within your group quietly. You and your group members will have 8 minutes to read the scenario and use what you know about Darwin’s 4 principles of natural selection to answer the corresponding questions. You may compare and discuss your notes, but you may not copy from anyone’s paper. There are 3 stations. Set stations 1-3 up on the wall along one side of the room and another set of 1-3 along the opposite side of the room so that there is a total of 6 stations. Students should be assigned to their first station and then they will rotate only among the 3 stations on that side of the room.

16 Collaborative Activity: Natural Selection ScenariosThe ostrich is the largest living species of bird and it is native to Africa. Although it is flightless, it has the ability to run at very high speeds. Some ostriches can commonly run between mph, but many ostriches can reach speeds between 46 and 60 mph. Jackals love to eat ostrich, and they can reach speeds of up to miles per hour. A flock of ostrich will lay approximately 20 eggs but many rodents break into the eggs and eat the fetus before they hatch. Work through this example together as a whole group so that the students understand exactly what is expected of them when they get started on the gallery walk.

17 Collaborative Activity: Natural Selection ScenariosWhich ostriches is natural selection selecting AGAINST? Which ostriches is natural selection selecting FOR? Which ostrich has a higher fitness? B. Identify Darwin’s 4 principles of natural selection from the scenario you read: Overproduction of Offspring: Inherited Variation: Struggle for Existence: Differential Reproduction: Descent with Modification: Over many generations, how would you expect this population of ostriches to change? Work through this example together as a whole group so that the students understand exactly what is expected of them when they get started on the gallery walk.

18 Do Now Answer the following questions on a sheet of paperImagine a white lizard and a brown lizard sitting on a brown rock. A hawk is circling overhead hunting for its next meal. Which lizard do you think the hawk would most likely try to catch? Explain your choice. Now imagine that the same two lizards were sitting on a dune of white sand. Which lizard do you think the hawk would then most likely try to catch? Why?

19 Gizmos: Mutation and Natural SelectionPurpose Observe evolution in a fictional population of bugs. Objectives: Understand what contributes to an organism’s fitness. Explain how mutation and sexual reproduction produce variation in a population. Determine that, in general, fit individuals have a better chance of surviving and reproducing than less fit individuals (survival of the fittest). Predict how a population will evolve when its environment changes. Describe how mutation and natural selection allow a population to become adapted to its environment.

20 Standardized Assessment PracticeQuestion 1 A small, isolated population of parrots lives in a part of the jungle that does not undergo any changes for an extended period of time. Genetic drift is likely to cause this population to change in what way? The population will stop evolving. New traits will appear more frequently. Genetic diversity within the population will decrease. The population will begin to break up into separate species. Q1 – C Q2 - H

21 Standardized Assessment PracticeQuestion 2 Why does a nonspecialized animal population have a much better chance of surviving a major disturbance in its habitat than a very specialized population? It can reproduce at a faster rate. It can hibernate through a time of crisis. It can more easily adapt to different conditions. It can mutate faster than a specialized population.

22 Standardized Assessment PracticeQuestion 3 A female lobster carries hundreds of fertilized eggs attached to the underside of her abdomen. After they hatch into larvae, almost all of them are eaten by predators before they are full-grown. Why is the large number of offspring an evolutionary advantage even though most get eaten? The hatched lobster larvae are an important part of the ocean food web. The large number of offspring provides the raw material for natural selection. The large number of offspring ensures that at least one will survive and reproduce. The more that are eaten by predators, the more food there is for the surviving ones. Q3 - C

23 Standardized Assessment PracticeQuestion 4 One species of moth is normally light-colored. A mutation causes some moths to be darker, making them harder for predators to spot against the dark tree trunks on which they rest. What is most likely to occur after several generations due to natural selection? The dark moths will become a new species. There will be more dark moths than light-colored ones. There will be fewer dark moths than light-colored ones. There will be an equal number of light-colored and dark-colored moths. Q4 - 2