May 11, 2017 Aims: SWBAT explain how survival of the fittest and natural selection have contributed to the continuation, extinction, and adaptation of species. Agenda 1. Do Now 2. Class Notes 3. Guided Practice 4. Independent Practice 5. Practicing our AIMS: E.4-Adaptations How will you help our class earn all of our S.T.R.I.V.E. Points? 1
Aim Check: 2
SCIENCE 8 Adaptation E.4 Name: Date: Homeroom: Evolution OBJECTIVES: By the end of class, students will be able to SWBAT explain how survival of t he fittest and nat ural selection have contributed to the continuation, extinction, and adaptation of species. DO NOW 1. In order for a species to continue on into the next generation it must be able to. A. eat B. find a shelter C. reproduce D. make friends 2. Lamarck s inheritance of acquired characteristics means that A. traits an organism develops during its own lifetime are determined by nature. B. traits an organism develops during its own lifetime are not passed on to offspring. C. traits an organism develops during its own lifetime are passed on to offspring. D. traits an organism develops during its own lifetime are determined by evolution. 3. Any variation that can help an organism survive in its environment is called a(n): A. Adaptation B. Characteristic C. Competition D. Homologous structure 3
SPEAK LIKE A SCIENTIST CLASS NOTES ADAPTATION: EVOLUTION: NATURAL SELECTION: (Surv iv al of the Fittest ) ENVIRONMENTAL CHANGE A population of giraffes feeds on leaves of small bushes on the ground and short trees. Suddenly, their environment changes! After a drought, all of the bushes on the ground die. The giraffes are left with only taller trees to eat from. Though some giraffes have necks that can reach those leaves, others do not. Think like a scientist: Predict how this environmental change will affect the evolution of this population. Does a changing environment increase or decrease the chance of natural selection happening? 4
COMPETITION A population of birds uses their beaks to dig into the soil and find worms to eat. The birds have a variety of beak sizes, but since there was always an abundant supply of worms all of the birds were able to feed. One spring the worm population decreased dramatically due to a disease and the birds had to compete over the worms. The birds with the longest beaks were able to dig deepest into the soil and find enough worms to survive. Think like a scientist: Predict how the increase in competition will affect the evolution of this population. Does competition increase or decrease the chance that natural selection will occur? 5
VARIATION In the previous two examples, the populations of giraffes and birds had inherent variation- the giraffes had different sized necks and the birds had different types of beaks. Think like a scientist: What would have happened if all of the giraffes had identical short necks? What would have happened if the birds all had identical small beaks? Would the populations have evolved? VS. I 6
ASEXUAL ADAPTATIONS All of the examples that we have discussed so far have to do with species that reproduce sexually. Organisms that reproduces asexually: Think like a scientist: Do you think it is possible for organisms that reproduce asexually to evolve? Explain. A strand of bacteria called Escherichia coli is able to asexual reproduce every 20 minutes and is a single celled organism. This means every 20 minutes the bacteria is able to divide. In order for a species of bacteria to produce a new generation it only takes a couple hours. If there are mutations during DNA replication will it be passed onto future generations? If it is possible what would most likely evolve faster: a species of animal or a species of bacteria? 7
GUIDED PRACTICE 1. Circle all of the processes below that can result in variation in a population. Mitosis Meiosis Sexual Reproduction Cloning Asexual Reproduction Mutation 2. A farmer often sprays a certain kind of insecticide, a chemical that kills insects, on his plants to prevent locust bugs from eating all of his corn crops. One day there was a random change in the sequence of DNA in a locust egg cell. When the egg cell hatched, the locust was resistant to the insecticide (it would not be killed by it). Since that locust could survive and reproduce, natural selection occurred until the entire population evolved to become resistant. A. Identify the variation that existed in the insect population B. Identify the process that created this variation INDEPENDENT PRACTICE Directions: Read and annot ate t he article below. Then answer t he quest ions that follow. Cross-Dressing Salmon The common salmon (Salmo salar) is a fish found in the waters of North America. Most salmon varieties are born in fresh-water streams and migrate to the ocean as adults. These adults return to the same river they were born in when it is time to reproduce known as spawning. Like many other complex animals, salmon reproduce through sexual reproduction. However, unlike mammals (and other land animals), salmon utilize the process of external fertilization. Female salmon will prepare a special nest in a river bed and will lay thousands of unfertilized eggs into it. A male will then spray his sperm over the nest to fertilize the eggs. Males compete for this opportunity and the larger and more aggressive a male is, the more likely it is that he will get to fertilize a female s eggs since he will be able to fiercely chase away any other males who try to get near a female s nest. Figure 1: The Life-Cycle of Salmon However, scientists have noticed that not all male salm on are large and aggressive. A small number have a special adaptation that gives them characteristics usually found in female salmon (known as female mimicry). 8
Thinking they are females, the larger dominant males do not pay attention to these so-called cross-dressing salmon, who are able to sneak close to the nest and release some of their sperm as well. Once their deception is revealed, they are chased away by the larger males, but not before they have had the chance to fertilize a small number of eggs in the nest (usually around 10%). Shortly after competing this process both parents die, and the eggs are left to develop on their own. Because their parents are not around to protect them, out of the millions of salmon eggs laid each year only 0.3% will survive to become spawning adults themselves. 1. Identify the variation that exists within the population of male salmon and explain how this variation may have arisen within the salmon population. 2. Male salmon with the female-mimicry trait are neither large nor aggressive, and would lose a fight with a more dominant male salmon. Does this mean the cross-dressing salmon are not fit? Why or why not? 3. What would happen to the frequency of small, un-aggressive male salmon in the salmon population if none could disguise themselves as females? Explain your answer in terms of fitness, adaptation, competition, natural selection, and evolution. 9
Directions: Answer each multiple choice question by circling the best answer and defend your answer in the textbox that is below. 4. A species that lacks the variation necessary to adapt to a changing environment is more likely to A. develop many mutated cells B. become extinct over time C. begin to reproduce sexually D. develop resistance to diseases 5. If an ecosystem is changed through a natural disaster, organisms will have the best chance of survival if A. their environment has few abiotic factors B. the organisms are large C. the population size is small D. their species exhibits genetic variation 6. In an environment that undergoes frequent change, species that reproduce sexually may have an advantage over species that reproduce asexually because the sexually reproducing species produce A. more offspring in each generation B. identical offspring C. offspring with more variety D. new species of offspring in each generation 10
7. Due to a mutation, a kangaroo living in a population in Australia is born with increased leg strength. This trait allows the kangaroo to escape predators more easily than the other kangaroos in the population. It is able to successfully pass on this adaptation and many more kangaroos with this trait are born. Explain how evolutionary change might occur in this population of kangaroos over time. In your answer be sure to include the concepts of -Variation - Natural Selection 8. A population of bats feeds on flying insects. Some of these bats have a gene that results in much stronger flight muscles than those of the other bats in the area. Explain how this occurrence could lead to evolutionary change within this species of bat. In your answer, be sure to include the concepts of - Variation - Competition - Natural Selection 11
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Science 8 Name: SKILL SNAPSHOT Date: E.4: Adaptations Homeroom: Quick Notes: Directions: Support your selection by jotting down your reasoning. Like A Scholar? Yes No Redo? Yes No Question 1. When the adaptive characteristics of a species are inadequate to allow survival, that species is likely to Reasoning A. mate with other species B. form a fossil C. produce a beneficial mutation D. become extinct 2. The sexual reproduction is important to evolution because these processes A. decrease variation and help maintain a stable population B. increase variation that enables species to adapt to change C. decrease the chances of producing offspring that are adapted to the environment D. increase the ability of all the offspring to adapt to the environment 3. The graph shows the percent of variation for a given trait in four different populations of the same species. The populations inhabit similar environments. In which population will the greatest number of individuals most likely survive if a significant environmental change related to this trait occurs? A. 1 B. 2 C. 3 D. 4 13
Question 4. Which statement is most closely related to the modern theory of evolution? Reasoning A. Characteristics that are acquired during life are passed on to offspring by sexual reproduction B. Evolution is the result of mutations and recombination only C. Organisms best adapted to a changed environment are more likely to reproduce and pass their genes to offspring D. Asexual reproduction increases the survival of species Refer to the reading in the independent practice when answering the following question. 5. An ecologist discovers a small group of aggressive male salmon who are able to distinguish between true females and males mimicking females. When they sense a male nearby, they quickly fight him off before he can approach the nest. How might this affect the salmon population after many generations? CONCEPT CONNECTION 6. Scientists recently discovered a species of cuttlefish with similar female-mimicking males. They want to determine whether the cuttlefish are evolutionarily related to salmon. Identify one piece of evidence they could look for to determine whether cuttlefish and salmon are related. 14