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Home , Disruptive selection, Divergent evolution

This week (June 8th – 12th) we are reviewing .

1. Review the lecture on evolution

2. Watch the evidence of evolution video:

https://www.khanacademy.org/science/high-school-biology/hs-evolution/hs- evidence-of-evolution/v/evidence-for-evolution

3. Watch the Types of video

https://youtu.be/64JUJdZdDQo

4. Complete the Evolution Review Activity

5. Complete the Natural Selection Reading and Questions

I am grading you based on the rubric below. If you get below a 70% I will allow you to redo the assignment.

Evidence of

Evolution & the Week 5 Remote Learning Mechanisms of Biodiversity Natural Selection The total variety of all the organisms in the biosphere= Biodiversity

Where did all these different organisms come from?

How are they related? Some organisms in a population are less likely to survive. Over time, natural selection results in changes in the inherited characteristics of a population. WHAT IS DARWIN’S THEORY? These changes increase a species’ in its environment.

Any inherited characteristic Ability of an individual to that increases an organism’s survive and reproduce in its chance of survival= specific environment= FITNESS WHAT IS DARWIN’S THEORY?

STRUGGLE FOR EXISTENCE: means that members of each species must compete for food, space, and other resources.

SURVIVAL OF THE FITTEST: organisms which are better adapted to the environment will survive and reproduce, passing on their genes.

DESCENT WITH MODIFICATION: suggests that each species has decended, with changes, from other species over time. • This idea suggests that all living species are related to each other, and that all species, living and extinct,share a common ancestor. Humans select for choose useful traits in Artificial Selection organisms (ex: dog )

Fossils are same age as rock they are found in, Fossil Record tell a story

Closely related species living in different habitats have specialized traits (finches) Geographic Distribution Distantly related species living in similar habitats have similar traits (whale/shark) Evidence of Homologous Structures Limbs that look different but are made by the Evolution same bones Early stages of development in organisms Embryology have similar structures

Similarities in DNA and suggest DNA relatedness

Seeing natural variation in populations (ex: See Natural Selection Occur peppered moth)

Large scale evolutionary patterns and processes that occur over long periods of time =

1. Mass • At several times in Earth’s history large numbers of species became extinct at the same time, leads to bursts in evolution 2. (Divergent Evolution) • When a single species or small group of species has evolved through natural selection into diverse forms that live in different ways (Galapagos finches) 3. • Unrelated organisms come to resemble each other from living in similar environments (Sharks & Whales) 4. • Two species evolve in response to changes in each other over time (bee & flower) 5. • Pattern of a long stable period interrupted by a brief period of more rapid change Sample Population Frequency of

for allele for brown fur black fur 48% heterozygous black

16% homozygous black 36% homozygous The relative frequency is the number of brown times that an allele occurs in the gene pool compared to the occurrence of other alleles in the gene pool. RELATIVE FREQUENCY is often expressed as a EX: In this population percentage. Dominant B allele (black) = 40% Recessive b allele (brown) = 60% Natural selection on single-gene frequencies can lead to changes in allele frequencies and thus to EVOLUTON

• EX: A population of normally brown lizards. produce new color choices. If red lizards are more visible to predators, they might be less likely to survive. Black lizards absorb more heat to warm up faster on cold days so they can move faster to get food and avoid predators. The allele for black may increase in frequency. In a small population this random change in based on chance is called . Genetic drift can occur when a small group of individuals colonizes a new habitat. Individuals may carry alleles in different relative frequencies than in the larger population. The population they “found” will be different from the parent population. . . not through natural selection but by chance A situation in which allele frequencies change as a result of the migration of a small subgroup of the population =

FOUNDER EFFECT Individuals at both ends of Individuals at one end of the Individuals at the middle of the curve have higher fitness curve have higher fitness than the curve have higher fitness than individuals in middle. individuals in middle or at other than individuals at either end. end.

Three Types of Selection HARDY-WEINBERG PRINCIPLE 5 CONDITIONS REQUIRED TO MAINTAIN GENETIC EQUILIBRIUM FROM GENERATION TO GENERATION

1. Must be random mating 2. Population must be large 3. No movement in or out of population 4. No Mutations 5. No natural selection : The formation of new species Happens through

Behavioral Isolation Geographic Isolation Temporal Isolation Their behavior is different enough Geography prevents them from Timing of important stages do to prevent them from mating mating not match up, preventing them • Ex: Some members of a species • Ex: a river, mountain, volcano, or from mating dance to get a mate, others sing. city divides a population, their • Ex: one group of trees sends and Overtime they will become a gene pools no longer mix, which receives pollen in May, and dancing species and a singing will lead to two separate species another group sends and receives species. over time. pollen in June. They will no longer mate with each other and will become separate species over time. Evolution Review Activity

Please review the video https://www.khanacademy.org/science/high-school- biology/hs-evolution/hs-evidence-of-evolution/v/evidence-for-evolution before completing if you haven’t already

1. Some organisms have features that have different functions, but similar structures. One example is the forelimb of humans, dogs, birds, and whales.

What term best describes the relationship between these forelimbs? a. They are homologous. b. They are embryological. c. They are analogous. d. They are vestigial.

2. How do fossils support evolution? a. The fossil record provides evidence that all organisms developed at the same time. b. Individual species disappear and reappear in the fossil record over time. c. Organisms in the fossil record are identical to living organisms. d. The fossil record provides evidence that organisms have changed over time.

3. What best describes the hind leg bones seen in the whale?

a. Vestigial structures that had a function in an ancestor b. Analogous structures to the fins of living fish c. Fossil structures from an extinct ancestor Evolution Review Activity

4. Which of the following is the best evidence that two birds belong to the same species? a. The two birds eat the same food. b. The two birds have common behaviors. c. The two birds are the same size and color. d. The two birds mate and produce fertile offspring.

5. Snakes such as boa constrictors and pythons have tiny leg bones buried in their muscles. These leg bones are vestigial structures that have little or no known function in snakes. Which best explains the presence of these vestigial structures in snakes? a. Snakes evolved from organisms with legs. b. Snakes are developing legs for walking on land. c. Snakes born with an extra set of DNA develop legs as they mature. d. Snakes have only one copy of the allele for legs in their chromosomes.

6. In Florida, mice that live on the white sands of the barrier islands tend to be lighter in color than mice that live in the vegetation on the mainland. Which of the following statements describes how mice on the barrier islands most likely evolved their light coat color through natural selection? a. The light-colored mice were easier prey for birds than the dark-colored mice. b. The light-colored mice learned to shed more of their fur than the dark-colored mice. c. The light-colored mice had a greater reproductive advantage on the barrier islands than the dark-colored mice. d. The light-colored mice migrated from the mainland to the barrier islands more recently than the dark-colored mice

7. A scientist is trying to determine how closely related two species of plants are. Which of the following would be most useful for the scientist to compare? a. the root depths of the plants b. the leaf structures of the plants c. the genetic sequences of the plants d. the nutrient requirements of the plants

Evolution Review Activity

8. The illustrations below show the embryos of a fish, a reptile, and a bird at the same stage of development.

Which of the following can be concluded from the illustrations? a. All the embryos grow at the same rate. b. All the embryos will develop identical structures. c. All the organisms share a recent common ancestor. d. All the organisms will be the same relative size as adults.

9. Which of the following provides the weakest scientific evidence that two species have a common ancestor? a. comparing fossils b. comparing food sources c. comparing genetic information d. comparing homologous structures

10. The larvae of the common sulphur butterfly can be light green or bright yellow. Birds prey on the larvae, which are found on the green leaves of alfalfa plants. Based on the theory of natural selection, which of the following would scientists expect to observe in populations of common sulphur butterfly larvae? a. All the green larvae develop yellow stripes before metamorphosis. b. All the yellow larvae and none of the green larvae are eaten by birds. c. The percentage of green larvae in the population is much greater than the percentage of yellow larvae. d. The percentages of green larvae and yellow larvae in the population remain equal for many generations.

Evolution Review Activity

11. Thousands of years ago, the jaws and teeth of jaguars were more varied in size than they are today. During a period of climate change about 11,000 years ago, jaguars faced a shortage of food. There were fewer mammals to eat, so the jaguars had to eat shelled reptiles. The jaguars with the largest jaws and teeth could most easily eat the shelled reptiles. Which of the following statements best explains why large jaws and teeth are common characteristics in jaguars today? a. Jaguars with the smallest jaws and teeth died out completely. b. Jaguars with the smallest jaws and teeth were not ever able to mate. c. Jaguars with the largest jaws and teeth survived and reproduced more successfully than other jaguars. d. Jaguars with the largest jaws and teeth strengthened them by using them more frequently than other jaguars.

12. The XIAP is involved in the immune response of many organisms. The table below includes the amino acid sequences of one section of XIAP in humans and four other organisms.

Each letter in the sequences represents a particular amino acid. For example, G represents glycine and D represents aspartic acid. Based on the amino acid sequences in the table, which two organisms have an XIAP gene sequence most similar to that of humans? a. organisms 1 and 2 b. organisms 1 and 4 c. organisms 2 and 3 d. organisms 3 and 4

Evolution Review Activity

13. Fossil evidence shows that ancient aquatic reptiles called ichthyosaurs looked very similar to modern dolphins. However, ichthyosaurs and dolphins are not closely related animals. Which of the following statements best explains the similar appearance of ichthyosaurs and dolphins? a. Dolphins reproduce using gametes, and so did ichthyosaurs. b. Dolphins are eukaryotic organisms, and so were ichthyosaurs. c. Dolphins have the same number of chromosomes that ichthyosaurs had d. Dolphins are adapted to the same types of environments that ichthyosaurs lived in

14. Millions of years ago, seawater flooded part of the Mississippi River Valley. Scientists have concluded that chorus frogs were affected by the flooding. The flooded areas formed geographic barriers between chorus frog populations for millions of years. Which of the following most likely occurred as a result of the seawater flooding? a. The frogs lost the tadpole stage of their life cycle. b. Isolated populations of frogs became separate species. c. The frogs’ eggs were fertilized by sperm of marine species. d. Frog populations were protected from all the predators in their areas

Evolution Review Activity

OPEN RESPONSE 15. The lizard Gallotia galloti on four of the Canary Islands, as shown on the map below. Each island has its own population of lizards, numbered 1 to 4 on the map.

Scientists have sequenced and compared DNA from lizards in each population. The cladogram below shows one hypothesis regarding how the lizard populations are related.

Please Answer each of the parts below. Label your answer A, B, & C

A. The DNA sequences of individuals from population 3 are probably most similar to the DNA sequences of individuals from which other population (1, 2, or 4)? Explain your answer.

Scientists also sometimes analyze behaviors when investigating relatedness among organisms.

B. Besides DNA and behavior, identify one type of evidence scientists could have used to investigate relatedness among the four lizard populations.

Evolution Review Activity

Scientists predict that, much like the finches on the Galápagos Islands, the four populations of Gallotia galloti will become separate species over time.

C. Describe the roles of both the environment and geographic isolation in the lizards’ becoming different species.

What is Natural Selection?

Types of Natural Selection Video https://youtu.be/64JUJdZdDQo

Key Points:

• Natural selection can cause (change in allele frequencies), with fitness-increasing alleles becoming more common in the population. • Fitness is a measure of (how many offspring an organism leaves in the next generation, relative to others in the group). • Natural selection can act on traits determined by alternative alleles of a single gene, or on polygenic traits (traits determined by many genes). • Natural selection on traits determined by multiple genes may take the form of , , or disruptive selection. Introduction: We've already met a few different mechanisms of evolution. Genetic drift, migration, ...the list goes on. All of these mechanisms can make a population evolve, or change in its genetic makeup over generations. But there's one mechanism of evolution that's a bit more famous than the others, and that's natural selection. What makes natural selection so special? Out of all the mechanisms of evolution, it's the only one that can consistently make populations adapted, or better-suited for their environment, over time.

Quick review of natural selection: • Organisms with heritable (genetically determined) features that help them survive and reproduce in a particular environment tend to leave more offspring than their peers. • If this continues over generations, the heritable features that aid survival and reproduction will become more and more common in the population. • The population will not only evolve (change in its genetic makeup and inherited traits), but will evolve in such a way that it becomes adapted, or better-suited, to its environment. Natural selection can cause microevolution Natural selection acts on an organism’s , or observable features. Phenotype is often largely a product of (the alleles, or gene versions, the organism carries). When a phenotype produced by certain alleles helps organisms survive and reproduce better than their peers, natural selection can increase the frequency of the helpful alleles from one generation to the next – that is, it can cause microevolution. • Example: Rabbit coat color As an example, let's imagine a population of brown and white rabbits, whose coat color is determined by dominant brown (B) and recessive white (b) alleles of a single gene. If a predator such as a hawk can see white rabbits (genotype bb) more easily than brown rabbits (BB and Bb) against the backdrop of a grassy field, brown rabbits are more likely than white rabbits to survive hawk predation. Because more brown than white rabbits will survive to reproduce, the next generation will probably contain a higher frequency of B alleles.

Fitness = Reproductive Success The and favored by natural selection aren't necessarily just the ones that survive best. Instead, they're the ones with the highest overall fitness. Fitness is a measure of how well organisms survive and reproduce, with emphasis on "reproduce." Officially, fitness is defined as the number of offspring that organisms with a particular genotype or phenotype leave behind, on average, as compared to others in the population.

Survival is one important component of fitness. In order to leave any offspring at all in the next generation, an organism has to reach reproductive age. However, survival is not the only part of the fitness equation. Fitness also depends on the ability to attract a mate and the number of offspring produced per mating. An organism that survived for many years, but never successfully attracted a mate or had offspring, would have very (zero) low fitness.

Fitness depends on the environment Which traits are favored by natural selection (that is, which features make an organism more fit) depends on the environment. For example, a brown rabbit might be more fit than a white rabbit in a brownish, grassy landscape with sharp-eyed predators. However, in a light-colored landscape (such as sand dunes), white rabbits might be better than brown rabbits at avoiding predators. And if there weren't any predators, the two coat colors might be equally fit!

In many cases, a trait also involves tradeoffs. That is, it may have some positive and some negative effects on fitness. For instance, a particular coat color might make a rabbit less visible to predators, but also less attractive to potential mates. Since fitness is a function of both survival and reproduction, whether the coat color is a net "win" will depend on the relative strengths of the predation and the mate preference.

How natural selection can shift phenotype distributions There are three basic ways that natural selection can influence distribution of phenotypes for polygenic traits, traits determined by many genes, in a population. To illustrate these forms of selection, let's use an imaginary beetle population, in which beetle color is controlled by many genes and varies in a spectrum from light to dark green.

1. Stabilizing selection. In stabilizing selection, intermediate phenotypes are more fit than extreme ones. For example, medium-green beetles might be the best camouflaged, and thus survive best, on a forest floor covered by medium-green plants. Stabilizing selection tends to narrow the curve.

2. Directional selection. One extreme phenotype is more fit than all the other phenotypes. For example, if the beetle population moves into a new environment with dark soil and vegetation, the dark green beetles might be better hidden and survive better than medium or light beetles. Directional selection shifts the curve towards the favorable phenotype.

3. Disruptive selection. Both extreme phenotypes are more fit than those in the middle. For example, if the beetles move into a new environment with patches of light-green moss and dark-green shrubs, both light and dark beetles might be better hidden (and survive better) than medium-green beetles. Diversifying selection makes multiple peaks in the curve.

Natural Selection Questions:

1. The graph below shows which type of natural selection?

a. Disruptive Selection b. Directional Selection c. Stabilizing Selection

2. The graph below shows which type of natural selection?

a. Disruptive Selection b. Directional Selection c. Stabilizing Selection

3. The graph below shows which type of natural selection?

a. Disruptive Selection b. Directional Selection c. Stabilizing Selection

4. Directional selection tends to eliminate...

a. Both extremes in a range of phenotypes c. intermediate phenotypes b. One extreme in a range of phenotypes d. none of the above

5. Stabilizing selection tends to eliminate...

a. Both extremes in a range of phenotypes c. intermediate phenotypes b. One extreme in a range of phenotypes d. none of the above

6. The range of phenotypes shifts toward one extreme in

a. Stabilizing selection c. directional selection b. Disruptive selection d. polygenic selection

7. Which of the following statements is true concerning Disruptive selection?

a. The mean trait is selected against c. The mean trait is selected for b. The extreme trait is selected for d. Both extreme traits are selected against

8. Biologists studied a population of lizards. They found that small lizards had trouble defending their territories and that large lizards were more likely than small or medium lizards to be preyed upon by owls. Which of the following graphs represents the most likely distribution for body size in this lizard population?

For each of the following scenarios, determine what type of selection (Disruptive, Directional, or Stabilizing) is going to take place. (Hint: I would draw the graph on a scrap piece of paper to help you out).

9. Starlings produce an average of five eggs in each clutch. If there are more than five, the parents cannot adequately feed the young. If there are fewer than five, predators may destroy the entire clutch. As a result, five eggs becomes the most common clutch size. a. Disruptive Selection b. Directional Selection c. Stabilizing Selection

10. Seed cracker birds have either large beaks or small beaks. They do not have medium sized beaks because medium sized beaks do not allow for adequate cracking of seeds. a. Disruptive Selection b. Directional Selection c. Stabilizing Selection

11. A scientist measures the circumference of acorns in a population of oak trees and discovers that the most common circumference is 2 cm. There are very few acorns with circumferences of 3 cm or circumferences of 1 cm. Only the 2 cm circumference acorns survive. a. Disruptive Selection b. Directional Selection c. Stabilizing Selection

12. A population of Madagascar hissing cockroaches lives in a woodpile. The cockroaches are eaten by lizards. Because the lizards have small heads, the lizards are unable to eat the very largest adult cockroaches, and instead prey upon small and medium sized adults. Over time, only the large headed lizards survive. a. Disruptive Selection b. Directional Selection c. Stabilizing Selection

13. Female birds that lay close to the optimum number of eggs have the most surviving offspring. Those that lay fewer or more eggs have lower relative fitness. a. Disruptive Selection b. Directional Selection c. Stabilizing Selection

14. A population of birds with various size beaks eats seeds. Small seeds can be eaten by birds with small beaks. Larger, thicker seeds can only be eaten by birds with larger, thicker beaks. During a drought, only large thick seeds exist so only the large, thick-beaked birds survive. a. Disruptive Selection b. Directional Selection c. Stabilizing Selection

15. Black rabbits (BB) and white rabbits (bb) are both able to survive because they can into the white and black rocks in their environment. However, the intermediate gray rabbits (Bb) do not survive. This results in only white and black rabbits. a. Disruptive Selection b. Directional Selection c. Stabilizing Selection

16. Small lizards have difficulty defending territories, so they end up dying out. Large lizards are more likely to be preyed upon by owls. Over time, only medium sized lizards end up surviving. a. Disruptive Selection b. Directional Selection c. Stabilizing Selection

17. Women often have complications during labor while giving birth to very large babies, whereas very small babies tend to be underdeveloped. As a result, medium sized babies are the ones that end up surviving to adulthood. a. Disruptive Selection b. Directional Selection c. Stabilizing Selection