Natural Selection A mechanism of microevolution Reference Understanding

Natural Selection A mechanism of microevolution Reference: Understanding Evolution. 2014. University of California Museum of Paleontology. 22 August 2008. http: //evolution. berkeley. edu/>.

Habit of the Mind • Applying past knowledge to new situations

Objectives • Understand how natural selection influences genetic variation. • Describe the process of natural selection as a mechanism of microevolution.

Vocabulary • Adaptation • Microevolution • Mechanism • Natural selection • Species • Population

Microevolution A change in gene frequency within a single population over time

Natural Selection Mechanism of Microevolution Definition: The process in nature by which, only the organisms best adapted to their environment tend to survive and transmit their genetic characteristics in increasing numbers to succeeding generations while those less adapted tend to be eliminated. Video: What is Natural Selection?

Natural Selection Mechanism of Microevolution • A large amount of variability exists amongst a species of animal. • Some of these differences may be related to the animal’s ability to survive. • Species that are best adapted to their environments will survive and reproduce.

Natural Selection Mechanism of Microevolution • Heredity causes offspring to resemble their parents. • This indicates that genetically well-adapted organisms will have genetically well-adapted offspring. • Traits that lead to survival of a species will be passed down, while traits that do not lead to survival of a species will eventually disappear.

Key Question to Ponder What is the relationship between an organism’s traits and its potential for survival and reproduction?

Adaptation • A feature that is common in a population because it provides some improved function. • Adaptations can take many forms: • A behavior that allows better evasion of predators • An anatomical feature that allows the organism to access a valuable new resource • Coloring that allows a greater chance of survival Top 10 Animal Adaptations Mantids

Question to Answer… • How is the use of the word "adaptation" different in everyday usage than in biology?

Natural selection - Variation There is variation in traits. For example, some beetles are green and some are brown. There is differential reproduction. Since the environment can't support unlimited population growth, not all individuals get to reproduce to their full potential. In this example, green beetles tend to get eaten by birds and survive to reproduce less often than brown beetles do. There is heredity. The surviving brown beetles have brown baby beetles because this trait has a genetic basis. End result: The more advantageous trait, brown coloration, which allows the beetle to have more offspring, becomes more common in the population. If this process continues, eventually, all individuals in the population will be brown.

Video • HHMI Natural Selection and Adaptation

Lab: Environmental Changes and Evolution Objectives: • Model how a population of organisms can change over time. • Learn how extinction can occur of a species due to environmental changes.

Lab: Environmental Changes and Evolution SURVIVING! • A niche is a combination of an organism’s needs and habitat. Extinction could possibly occur if an animal does not adapt to a change in its niche. Extinction occurs when the environment changes, and a species is no longer adapted to the environment. Extinction: the act or process of becoming extinct; a coming to an end or dying out: the extinction of a species How could an animal’s niche change? • Change could occur in a niche by introducing or eliminating predators or prey of the animal. • Competition sometimes causes species to move into new or empty niches. If two organisms occupy the same niche, there is generally competition between the two for food, shelter, and water. • An animal’s niche could change due to environmental factors.

Lab: Environmental Changes and Evolution Question: • Using beans/rice to represent populations of different species, how might the environment (size of a hole in the Styrofoam bowl) affect the “survival rate” of the species (bean/rice)? • Beans/rice that pass through the hole are considered dead. What is the … • Independent variable? • Dependent variable?

Natural Selection MISCONCEPTION: Natural selection is all powerful. • Natural selection does not produce perfection. • If your genes are "good enough, " you will get some offspring into the next generation — you do not have to be perfect. • No population or organism is perfectly adapted: people may have genes for genetic diseases, plants may not have the genes to survive a drought, and a predator may not be quite fast enough to catch her prey every time she is hungry.

Natural Selection MISCONCEPTION : Natural selection involves organisms trying to adapt. • The process does not involve effort, trying, or wanting • Natural selection results from genetic variation in a population and the fact that some of those variants may be able to leave more offspring in the next generation than other variants. • That genetic variation is generated by random mutation — a process that is unaffected by what organisms in the population want or what they are "trying" to do. • Either an individual has genes that are good enough to survive and reproduce, or it does not; it can't get the right genes by "trying. " Misconceptions about Natural Selection

Natural Selection MISCONCEPTION : Natural selection gives organisms what they need. • Natural selection has no intentions/senses; it cannot sense what a species/individual "needs. " • Natural selection acts on the genetic variation in a population • Generated by random mutation — a process that is unaffected by what organisms in the population need Misconceptions about Natural Selection

Microevolution - The Size of the Sparrow • What gene frequency has changed? • Why do you think the gene frequency has changed?

Natural Selection

Video • HHMI The Evolution of Lactose Tolerance

Fitness • Biologists use the word fitness to describe how good a particular genotype is at leaving offspring in the next generation relative to how good other genotypes are at it. • If brown beetles consistently leave more offspring than green beetles because of their color, you would say that the brown beetles had a higher fitness. The brown beetles have a greater fitness relative to the green beetles.

What about Fitness? MISCONCEPTION: The fittest organisms in a population are those that are strongest, healthiest, fastest, and/or largest. • An organism's evolutionary fitness does not indicate its health, but rather its ability to get its genes into the next generation. • The more fertile offspring an organism leaves in the next generation, the fitter it is. This doesn't always correlate with strength, speed, or size. • Example: A puny male bird with bright tail feathers might leave behind more offspring than a stronger, duller male

What about Fitness? MISCONCEPTION: Natural selection is about survival of the very fittest individuals in a population. • Though "survival of the fittest" is the catchphrase of natural selection, "survival of the fit enough" is more accurate. • In most populations, organisms with many different genetic variations survive, reproduce, and leave offspring carrying their genes in the next generation. It is not simply the one or two "best" individuals in the population that pass their genes on to the next generation.

Fitness of a Bacterial Infection? • A virulent bacteria does a lot of damage to its host, and produces a lot of offspring. • If the host's illness prevents the host from coming into contact that new hosts that the bacteria could jump to, the bacteria actually has relatively low evolutionary fitness. • In contrast, bacteria that is less virulent could infect far more hosts because the hosts are well enough to come in contact with many other potential hosts.

Lab: Moth Coloration - Natural Selection • Objective: Model how coloration (genetic variation) of a species affects survival/death. • Question: How does moth color variation (white to black) affect fitness (death count)? • Purpose: The purpose of this investigation is to discover how the color of a moth affects its survival. This investigation is important in order to understand natural selection as a mechanism of evolution.

Peppered Moths in England Video Link: Peppered Moths in England

Title: _______ Color gradient Trial 1 Death Count 2 3 4 5 6 Group Total Class Count White Barely gray Very light gray Light gray Gray Darker gray Dark gray Very dark gray Black

Artificial Selection • Farmers/breeders have been using the idea of selection to cause major changes in the features of their plants and animals over the course of decades. • Plants and animals with desirable characteristics were allowed to reproduce, causing the evolution of farm stock. • This process is called artificial selection because people (instead of nature) select which organisms get to reproduce. These common vegetables were cultivated from forms of wild mustard.

Artificial Selection People selectively breed domesticated plants and animals to produce offspring with preferred characteristics.

Artificial Selection This population of fish exhibits variation in body size. Some have genes for large size and some have genes for small size. This represents genetic variation in the population. When the population is fished, many of the largest fish are removed, so more of the small-bodied fish (and their small-bodied genes) remain.

Artificial Selection The population reproduces. Each individual passes their genes on to their offspring — however, since there are more small-bodied parents, there also more small -bodied offspring. In the next generation, the population has evolved: average body size in the population is smaller than it used to be and small-bodied genes are more common than they used to be.

Artificial Selection This downward trend in body size will continue so long as the largest fish are harvested and there is genetic variation in the population.

Video • Artificial vs. Natural Selection

Resources • • • PBS Short videos VIDEO: How Does Evolution Really Work? What is Science? Evolution in the News Video: Natural Selection (Mr. Bozeman) Video: Examples of Natural Selection (Mr. Bozeman)

Next Generation Science Standards • MS-LS 4 -4: Construct an explanation based on evidence that describes how genetic variations of traits in a population increase some individual’s probability of surviving and reproducing in a specific environment. • MS-LS 4 -6: Use mathematical representations to support explanations of how natural selection may lead to increases and decreases of specific traits in populations over time.

A Framework for K-12 Science Education LS 4. B: Natural Selection • Natural selection leads to the predominance of certain traits in a population and the suppression of others. (MS-LS 4 -4) LS 4. C: Adaptation • Adaptation by natural selection acting over generations is one important process by which species change over time in response to changes in environmental conditions. Traits that support successful survival and reproduction in the new environment become more common; those that do not become less common. Thus, the distribution of traits in a population changes. (MS-LS 4 -6)

American Association for the Advancement of Science When inherited traits are favorable to individual organisms, the proportion of individuals in a population that have those traits will tend to increase over successive generations. Students are expected to know that: • There is variation in the inherited traits of organisms of the same species, including traits that affect their ability to find food, avoid predators, and attract mates. • Some inherited traits (e. g. bacterial resistance to antibiotics, skin pigmentation in some organisms) may give individuals of a species an advantage in surviving and reproducing in their environment compared to other individuals of the same species (e. g. increased ability to find food or nesting sites, avoid predators, attract mates, resist diseases). Conversely, the individuals that do not have advantageous trait(s) are more likely to be unable to survive and reproduce. • An organism’s survival influences its reproductive success. Usually, the longer an organism lives (during its reproductive years), the more chances it has to reproduce; therefore traits that improve chances of survival (such as finding food or avoiding predators) also increase chances of success in reproduction. • Changes in environmental conditions (such as the appearance of a new predator, a slight change in temperature, or changes due to the eruption of a volcano) can change which traits are more advantageous (or less detrimental) in the new environment.

American Association for the Advancement of Science When inherited traits are favorable to individual organisms, the proportion of individuals in a population that have those traits will tend to increase over successive generations. Students are expected to know that: • Because more of the individuals with favorable inherited traits survive and reproduce than those that do not have them, and because the favorable traits are passed on to the offspring, the proportion of individuals with the favorable inherited traits increases in each subsequent generation. This process is called natural selection. • There is no guarantee that any members of a population will be able to survive and reproduce in a changed environment. Sometimes changes in environmental conditions may cause an entire population of organisms to die, or even an entire species to become extinct. • The process of natural selection does not lead to changes in the characteristics of individual organisms. It only changes the characteristics of populations (i. e. the proportion of individuals in the population having certain inherited traits) over time. • After natural selection has operated on many successive generations of a population, the descendants can be very different from their original ancestors. • Even though organisms can be very different in both appearance and behavior from their ancestors of many generations ago, they retain some of the inherited traits of those early ancestors.

Standard: 2. Life Science Prepared Graduates: Explain how biological evolution accounts for the unity and diversity of living organisms Grade Level Expectation: Seventh Grade Concepts and skills students master: 1. Individual organisms with certain traits are more likely than others to survive and have offspring in a specific environment Evidence Outcomes Students can: a. Develop, communicate, and justify an evidence-based explanation for why a given organism with specific traits will or will not survive to have offspring in a given environment (DOK 1 -3) b. Analyze and interpret data about specific adaptations to provide evidence and develop claims about differential survival and reproductive success (DOK 1 -3) c. Use information and communication technology tools to gather information from credible sources, analyze findings, and draw conclusions to create and justify an evidence-based scientific explanation (DOK 1 -2) d. Use computer simulations to model differential survival and reproductive success associated with specific traits in a given environment (DOK 1 -2) 21 st Century Skills and Readiness Competencies Inquiry Questions: 1. What is the relationship between an organism’s traits and its potential for survival and reproduction? 2. How is the use of the word “adaptation” different in everyday usage than in biology? Relevance and Application: 1. Bacteria have evolved to survive in the presence of the environmental pressure of antibiotics – giving rise to antibiotic resistance. 2. Species that can live with humans –such as rats and pigeons – are more common around towns and cities. Nature of Science: 1. Create and use sound experimental designs to collect data around survival and genetic traits. (DOK 2 -3) 2. Describe several ways in which scientists would study genetics, and suggest ways that this has contributed to our understanding of survival and populations. (DOK 1 -2)

STANDARD: 2. LIFE SCIENCE Prepared Graduates: Explain and illustrate with examples how living systems interact with the biotic and abiotic environment Grade Level Expectation: Sixth Grade Concepts and skills students master: 1. Changes in environmental conditions can affect the survival of individual organisms, populations, and entire species Evidence Outcomes 21 st Century Skills and Readiness Competencies Students can: a. Interpret and analyze data about changes in environmental conditions – such as climate change – and populations that support a claim describing why a specific population might be increasing or decreasing b. Develop, communicate, and justify an evidence-based explanation about how ecosystems interact with and impact the global environment (DOK 1 -3) c. Model equilibrium in an ecosystem, including basic inputs and outputs, to predict how a change to that ecosystem such as climate change might impact the organisms, populations, and species within it such as the removal of a top predator or introduction of a new species d. Examine, evaluate, question, and ethically use information from a variety of sources and media to investigate how environmental conditions affect the survival of individual organisms (DOK 1 -2) Inquiry Questions: 1. How do ecosystem changes affect biodiversity? 2. How does biodiversity contribute to an ecosystem’s equilibrium? Relevance and Application: 1. The development and application of technologies intended to aid some populations and ecosystems. Nature of Science: 1. Ask testable questions and make a falsifiable hypothesis about how environmental conditions affect organisms, populations, or entire species and design a method to find the answer. (DOK 2 -4) 2. Recognize and describe the ethical traditions of science: value peer review; truthful reporting of methods and outcomes; making work public; and sharing a lens of professional skepticism when reviewing the work of others. 3. Use models and technology tools to show what might happen to individuals, populations, and species as environmental conditions change. (DOK 1 -2)