THEORY OF EVOLUTION Natural Selection A Mechanism of

THEORY OF EVOLUTION Natural Selection: A Mechanism of Change

WHAT ARE WE LEARNING TODAY? Benchmarks ü SC. 912. L. 15. 13 – Describe the conditions required for natural selection, including: overproduction of offspring, inherited variation, and the struggle to survive, which result in differential reproductive success. Learning Objectives ü I will describe the process of natural selection using the 4 principles of Darwin’s theory of evolution by natural selection. ü I will describe how mutations and genetic recombination increases inherited genetic variation of offspring. ü I will relate the concepts of adaptation and fitness to the

DO NOW Answer these questions on the back of the small paper 1. How do the mice in Fig. 1 display inherited variation? 2. What characteristic of the mice is an adaptation that increases their fitness? 3. How is Fig. 2 an example of survival of the fittest? 4. How is the population of mice different in Fig. 3 from Fig. 1? 5. Explain what process could account for this change in

EVOLUTION BY NATURAL SELECTION 1. What is evolution? 2. What type of organisms are subject to evolution? 3. What’s the time required for evolutionary changes? 4. What’s the evidence that scientists rely on to explain the evolutionary process?

How did Charles Darwin develop his theory? q From 1831 to 1836, Darwin made a voyage around the world in which he collected and studied thousands of plant and animal specimens. q During his travels, Darwin made numerous observations and collected evidence that led him to propose a hypothesis about the way life changes over time. q 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.

What is natural selection? q Natural selection is the differential survival and reproduction of individuals due to differences in phenotype; it is a key mechanism of evolution. q 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

What are the four principles of Darwin’s theory?

What are the four principles of Darwin’s theory? 1. Overproduction of Offspring: Organisms produce more offspring than can survive. Many of the offspring do not survive to reproductive age.

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.

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.

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).

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. q As a result, species today look different from their ancestors. q Each living species has descended, with changes, from other species over time by a principle he referred as descent with modification. q Whale (mammal in the ocean) Wolf-like organism (mammal on land)

How does evolution by natural selection work?

Adaptive Radiation: is a process in which organisms diversify rapidly into a multitude of new forms/species, particularly when a change in the environment makes new resources available, creates new challenges and opens environmental niches. Darwin’s Finches are a perfect example of adaptive radiation. Their ancestor came from the south American mainland. There were no other finches on the islands. One specie radiated into about 13 different species of finches. All due to the different food sources available on different islands

Pools with killifish but no guppies prior to transplant Experimental Pond Predator: Killifish preys mainly on small guppies transplant of Guppies to new pond Guppies: Larger at sexual maturity than those in “pike-cichlid pools” Predator: Pike-cichlid; preys mainly on large guppies Guppies: Smaller at sexual maturity than those in “killifish pools”

160 120 80 67. 5 76. 1 40 Males Females Age of guppies at maturity (days) Mass of guppies at maturity (mg) 185. 6 161. 5 200 100 85. 7 92. 3 80 60 48. 5 58. 2 Guppies from pools with pike-cichlids as predators Experimental population: 40 20 Males Control population: Females Guppies transplanted to pools with killifish as Predators (larger size and Slower maturation, older at sexual maturity) Conclusion: change in predator from Pike-cichlid (eat larger guppies so Guppies: Smaller at sexual maturity than those in “killifish pools”) to killifish (eat smaller guppies so Guppies: Larger at sexual maturity than those in “pike-cichlid pools”) resulted in different variations in the population (larger size and slower maturation) being favored. Over a relatively short time, this altered selection pressure resulted in an observable evolutionary change in the experimental population of guppies

Collaborative Activity: Natural Selection Scenarios Objectives: I will use the 4 principles of Darwin’s theory of natural selection to describe the process of evolution. Procedure: 1. Work within your group quietly. 2. 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. 3. You may compare and discuss your notes, but you may not copy from anyone’s paper.

Collaborative Activity: Natural Selection Scenarios The 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 35 -45 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 35 -40 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.

Collaborative Activity: Natural Selection Scenarios A. Which ostriches is natural selection selecting AGAINST? Which ostriches is natural selection selecting FOR? What is the environmental pressure for natural selection? Which ostrich has a higher fitness? B. Identify Darwin’s 4 principles of natural selection from the scenario you read: 1. Overproduction of Offspring: 2. Inherited Variation: 3. Struggle for Existence: 4. Differential Reproduction: C. Descent with Modification: Over many generations, how would you expect this population of ostriches to change? D. What do you think will happen to the Jackals over time?

Do Now Answer the following questions on a sheet of paper 1. Imagine 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. 2. 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?

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

Standardized Assessment Practice Question 1 Question 2 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? A. The population will stop evolving. B. New traits will appear more frequently. C. Genetic diversity within the population will decrease. D. The population will begin to break up into separate species. Why does a nonspecialized animal population have a much better chance of surviving a major disturbance in its habitat than a very specialized population? F. It can reproduce at a faster rate. G. It can hibernate through a time of crisis. H. It can more easily adapt to different conditions. I. It can mutate faster than a specialized population.

Standardized Assessment Practice Question 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? A. The hatched lobster larvae are an important part of the ocean food web. B. The large number of offspring provides the raw material for natural selection. C. The large number of offspring ensures that at least one will survive and reproduce. D. The more that are eaten by predators, the more food there is for the surviving ones.

Standardized Assessment Practice Question 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? A. The dark moths will become a new species. B. There will be more dark moths than light-colored ones. C. There will be fewer dark moths than light-colored ones. D. There will be an equal number of light-colored and dark-colored moths.

REVIEW: Darwin’s Natural Selection 1. Overproduction of Offspring: 3. Struggle for Existence: Organisms produce more offspring than can survive. Many of the offspring do not survive to reproductive age. Because so many offspring are produced, many will die due to a lack of resources, predation, disease, or other unfavorable conditions. 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. 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