Biodiversity

http://vimeo.com/19451460

Estimates of the number of species that inhabit our planet run as high as 10 million! That means 10 million different kinds of organisms. That number certainly suggests a lot of variety. That is what diversity means--variety. When we say "biodiversity," we refer to the variety of life.

It is interesting to try to imagine how so many forms of life came about. If we also think about extinct forms, it becomes truly mind boggling.

We don't want to confuse abundance with diversity. Abundance means there are many of something. If there are thousands of geese in a flock but there is only one species of goose, then we say the geese are abundant, but there is no diversity.

Diversity is a measure of how many different species live in an ecosystem. Some biologists go a step farther and define biodiversity as the number of rare species which inhabit an ecosystem.

Certain ecosystems create great diversity. A classic example is the tropical rain forest, which has an extremely high level of biodiversity. There are many species in the rain forest that do not exist in other places.

Of course, we want to give a name to every living thing. We will look at classification systems that name species in a systematic and orderly way.

How Do Scientists Classify Organisms?

Biologists place the organisms into groups based on characteristics. These can be embryological, biochemical or structural. Groupings suggest a degree of relatedness and often an evolutionary trend. The branch of Biology that classifies organisms in groups is called taxonomy. To date scientists have classified approximately 1.5 million organisms and conservative estimates suggest that there is over 8.5 million species yet to be discovered.

One of the first taxonomists was Aristotle. His classification system placed all organisms into one of two groups. He determined which group they belonged based on where in the environment they lived and structural similarities among them.

The classification system at the right was Aristotle’s first attempt at classification. This method is still used in primary grades to begin a conversation about living things.

The classification system of today

Includes three Domains and six Kingdoms. Its original designer lived over 300 years ago, Carolus Linnaeus was a Swedish botanist who used physical

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characteristics to identify different organisms and organize them into groups. The original system has undergone some changes over the years but his main structure remains intact.

Log on to a computer or device to learn more about the key factors that separate the three domains. Record those key factors in the space provided

Key factors distinguishing Archea, Bacteria and Eukarya

http://cms.inonu.edu.tr/panel/uploads/5/898/tree-of-life.swf

Kingdom Archea

http://www.youtube.com/watch?v=N-EYTtxsL8g&list=EC9F64F28702C824B5&safe=active

Kingdom Bacteria

http://www.youtube.com/watch?v=6p9e0oolbmE&safe=active

Also called Eubacteria, Prokaryotae, or Monera. All members of this kingdom are unicellular prokaryotes. You may

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remember that prokaryotic cells lack a nuclear membrane and other membrane-bound organelles. However, do not allow this simplistic design detract from their significance and contribution to life.

Bacteria Cell walls composed of a substance derived from amino acids and sugars; may secrete a capsule made of a polysaccharide material. In pathogenic bacteria, the capsule may be protected against the defenses of the host. Cells may be spherical (cocci), rod-shaped (bacilli), or coiled (spirilla).

Cyanobacteria are specifically adapted for photosynthesis; use water as a hydrogen source. Chlorophyll and associated enzymes organized along layers of membranes in cytoplasm. Some can fix nitrogen.

Ecological Role

Decomposers; some chemosynthetic autotrophs; important in recycling nitrogen and other elements. A few are photosynthetic

Most bacteria must absorb nutrients from other sources some like the blue-green algae contain chlorophyll and are photosynthetic.

Kingdom Protista http://www.youtube.com/watch?v=-zsdYOgTbOk&safe=active

http://vimeo.com/53375158

Most of the members of this kingdom are unicellular however, some are colonial and multicellular. All are eukaryotic and show cell level of organization. Protista can be autotrophic, heterotrophic or parasitic. Some are motile where others are sessile and rely their environment to provide the necessities of life for them.

Protists that exhibit "animal-like" behavior are called protozoa. Amoeba, Paramecium are typical examples for this kingdom.

Members that are “plant-like” contain chlorophyll and undergo photosynthesis are called algae. Euglena, Clamydamonis, Spirogyra are representative examples.

Kingdom Fungi molds, yeasts, mushrooms, rusts and smuts

http://www.youtube.com/watch?v=dj9m7Oc36wM&safe=active

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Feed as parasites on other living things or act as decomposers of dead matter. Composed of thin filaments that penetrate the food sourceThey secrete digestive enzymes onto dead or decaying matter and use external digestion. Some are unicellular but most are multicellular. All are eukaryotic and have a cell wall (different than that of plants).

Rhrizopus sp. mushrooms

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MONERANS, PROTISTS and , FUNGI

1. Complete the following chart stating four kingdom characteristics for: (6 marks)

Monerana Protista Fungi

1.

2.

3.

4.

2. Give specific examples of members for each of the five Kingdoms. (5 marks)

a. List four types of monerans. _______________________, ________________,

_______________________, and _____________________

b. Give three examples of protists. ____________________, ________________,

and ______________________.

c. List three examples of fungi. _____________________, __________________,

and ______________________.

3. Differentiate between: (8 marks)

Prokaryotes and eukaryotes - _______________________________________

_______________________________________________________________autotroph and heterotroph - _________________________________________

_______________________________________________________________

_______________________________________________________________

saprophyte (saprobe) and parasite - __________________________________

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_______________________________________________________________

4. Answer the following: (10 marks)

a What is a pathogen and which kingdoms contain pathogenic organisms? ________________________________________________________________

________________________________________________________________

________________________________________________________________

b. Name the two major divisions of Protista and give the reason they are grouped this way.

_______________________________________________________________

_______________________________________________________________

b. Compare the feeding methods of paramecium and euglena.

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

c. Give two similarities and two differences between kingdom Fungi and kingdom Plantae.

_______________________________________________________________

d. Why are viruses not classified as a separate kingdom of life?

_______________________________________________________________

_______________________________________________________________

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Kingdom Plantae mosses, liverworts, ferns, and seed plants

Members of this kingdom show tissue level organization. They have specialized groups of cells that carry out a specific function stems, roots and leaves and vascular tissue which transports nutrients and products of photosynthesis. All members are sessile or non-moving. Most members contain chlorophyll and can carry on photosynthesis. They are classified as autotrophic.

All cells are eukaryotic and contain a cell wall composed of cellulose. Plants are able to live in a wide variety of habitats including both aquatic and terrestrial.

Kingdom Animalia (We will examine this kingdom in greater depth later)

The kingdom with the largest number of species. Organisms are multicellular eukaryotic (without cell walls) and most show organ level of specialization at the least complex end of the spectrum and system level organization at the most complex end.

Nutrients are obtained from the environment so they are heterotrophs.

Members are grouped as invertebrates (organisms without backbones) and vertebrates (organisms with backbones)

For your notes please complete this chart.

Number of CellsUni/multicellular energy Cell type examples

archaebacteria

eubacteria

protista

fungi

plantae

animalia

Taxonomy – the science of classifying organisms

Why do we need a system to classify and name organisms?

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Here are some common names:

spider monkey sea monkey sea horse

gray wolf firefly crayfish

mud puppy horned toad ringworm

black bear jellyfish spiny anteater

These names can vary by region and can also be misleading. Is a sea horse really a horse?

Naming Organisms: Organisms have common & scientific name -all organisms have only 1 scientific name-usually Latin or Greek-developed by Carolus Linnaeus

This two-word naming system is called…..

Binomial Nomenclature

-written in italics (or underlined)-1st word is Capitalized –Genus-2nd word is lowercase —species

Examples: Felis concolor, Ursus arctos, Homo sapiens, Panthera leo , Panthera tigris. These can also be abbreviated as (P. tigris or P. leo)

Linneaus also devised the system we use to organize animals. This system uses large groups divided into subgroups (like the way you organize folders on your computer) This hierarchical arrangement allows us to show relatedness between different orgnanisms.

Kingdom – Phylum — Class — Order — Family — Genus — Species

Human Lion Tiger Pintail Duck

Kingdom Animalia Animalia Animalia Animalia

Phylum/Division Chordata Chordata Chordata Chordata

Class Mammalia Mammalia Mammalia Aves

Order Primate Carnivora Carnivora Anseriformes

Family Homindae Felidae Felidae Anatidae

Genus Homo Panthera Panthera Anas

Species sapiens leo tigris acuta

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Each organism has a group and subgroups. The organisms with the most similar groups will be most closely related. Note that both the lion and the tiger are in the same genus, but are considered to be separate species.

There are currently 6 kingdoms – organisms are placed into the kingdoms based on the number and type of cells they have, and their nutritional needs.

Organizing Diversity

A phylogenetic tree, also called Dendrogram, is a diagram showing the evolutionary interrelations of a group of organisms derived from a common ancestral form. The ancestor is in the tree “trunk”; organisms that have arisen from it are placed at the ends of tree “branches.” The distance of one group from the other groups indicates the degree of relationship; i.e., closely related groups are located on branches close to one another. Phylogenetic trees, although speculative, provide a convenient method for studying phylogenetic relationships.

Hey is something missing? Where are the viruses? Research why viruses have been left out of the 6 kingdom classification system and write your answer in the space below.

Using a Biological (Dichotomous) Key

Many scientists regularly use classification manuals to identify organisms. Usually this involves the use of a dichotomous key. The key is constructed so that a series of choices must be made, and each choice leads to a new branch of the key. If choices are made accurately, the end result is the name of the organism being identified.

Here is an example of a dichotomous key used to identify: A rock, a bicycle, a tin can, a dandelion, a paramecium, an oak tree, a pine tree, an ant, mouse, deer and a robin.

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Dichotomous Key Assignment on Sharks, Hand in

One theory of how it all began

So now we are a little bit more acquainted with the many different forms of life on our planet but the question still remains regarding how life first began and how we are able to have the level of diversity given that all life began with a common ancestor.

Here is one theory according to the Urey Miller experiment.

https://www.youtube.com/watch?v=_2xly_5Ei3U

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In the space below summarize the experiment including the components of the Earth’s early atmosphere and how it lead to the production of the simplest molecules of life.

https://www.youtube.com/watch?v=6GNUlZhE_jE

Evolutionary Theory

EvolutionThe modern theory of evolution by natural selection has four main concepts:

characteristics of living things differ between individuals of the same species many differences are the result of heritable, genetic differences in individuals some differences affect how well an organism is adapted to its environment some differences in how well an organism is adapted are expressed in the number of

offspring successfully raised to pass on their genes

Evolution is change in the genetic makeup of a population over many generations. The result is noticeable changes in the traits of individuals when compared over time. The process does not mean that individual organisms change; it refers to changes that happen in a population that are gradual and take a long time.

When we look at humans we are aware that we share many common characteristics, but also that no two humans are exactly alike. There are obvious differences between individuals. There are also subtle differences that we may not notice. This variation is the expression of the genotypes of individuals. We are not as aware of it, but all species display this kind of variation in their populations. It is understandable then, that if some of these differences result in survival advantages for the individual, then over time a population can change.

Natural selection can be thought of as the collective conditions in the environment that favour certain characteristics over others in a way that results in the successful reproduction of these "selected" individuals. If these traits have a genetic basis, the offspring are more likely to also display the trait. Natural selection can only work at the phenotype level, not on genes directly. Acquired characteristics may provide a survival advantage but they do not contribute to evolution. Only inherited traits contribute to evolution. Mutations to somatic cells also do not contribute to biological evolution.

Let's use a situation that we might be more familiar with. Most people know that plants and animals are selectively bred to produce individuals with desirable traits. Breeds of dogs, cats, and farm animals are common examples. We can think of selective breeding as "artificial selection." The breeder decides which individuals will be allowed to reproduce, and artificially selects certain individuals. The selected individuals pass their genes on to their offspring which will eventually breed true, creating more individuals that display the trait.

In the natural world, chance conditions exist that allow certain individuals to reproduce and others not to reproduce. Because it happens in the natural world, we call it natural selection. We say that certain individuals are "selected" to reproduce. Those who do not reproduce do not pass on their characteristics.

We have already looked at organic evolution. Organic evolution is biological evolution. 11

Geologic evolution refers to the changes that happen to the earth itself. Over the geologic history of the earth, continents drifted apart. Mountain ranges were formed and eroded away. Volcanoes formed islands in the middle of the oceans. Glaciers scoured the earth, leaving depressions that later became lakes. Asteroids collided with the earth, forming enormous craters. Some of these changes are imperceptible to our senses given our short human life spans. Other changes are sudden and dramatic.

Landforms and bodies of water affect weather and climate. Large-scale changes in ocean currents and landforms can affect global climate. Climactic changes directly affect organisms adapted to specific conditions. Habitats change and food supplies dwindle or become more abundant.

We can speculate on the ways in which geologic evolution changed environments. Relatively sudden changes on a global scale caused mass extinctions. Slower changes resulted in selection pressure that caused the evolution of species. Isolation of populations from each other contributed to the formation of new species.

We can see then that biological evolution is tied up with geologic evolution. These changes are still going on today. In fact, some scientists speculate that we as a species have had and continue to have a significant effect on Earth's climate and on plant and animal populations worldwide.

What evidence do we have that evolution has occurred?

Fossils: Evidence from the Past

Strong evidence for a changing Earth began with a careful examination of fossils. Near the end of the 15th century, Leonardo da Vinci pondered the numerous seashells he found high in the Tuscany mountains, hundreds of kilometers from any sea. He became convinced that these very old shell deposits had been formed in an ancient ocean and concluded that Earth’s surface had changed dramatically over time. By the late 17th century, geologists had begun to map locations where exposed layers of rock contained distinctive and remarkable fossils that were considered to be evidence of prehistoric life. In 1669, Nicholas Steno’s detailed an impressive analysis of fossils clearly indicating that they were mineralized remains of living organisms. A fossil is defined as any trace or remains of an organism that has been preserved by natural processes. The most recognizable fossils are such hard body parts as shells, bones, and teeth.

Type of fossil Formation Example

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Petrification(permineralized fossils)

Dissolved minerals precipitate from a solution in the space occupied by an organism’s remains

Petrified forest (Roosevelt National Park)

Molds and Casts

A dead organism sinks into the muddy or sandy bottom of a lake or ocean. The organism becomes buried, and its remains start to decayThe mud or sand hardens and hold the shape of the organism. The hollow created by the organism is called a mold. Sometimes the mold becomes filled with minerals which harden into rock. The hardened minerals form a cast.

Chocolate Easter Eggs

Imprints Impressions made in mud or clay may remain and harden into rock. footprints

Preserved Fossils

Amber, hard yellow, transparent material formed by the hardening of resin, a sticky substance produced by trees. Micro-remains often become trapped and embedded in the resin, which then hardens into amber

Insects, pollen

The hard mineral parts of animals, such as bones and shells do not decay due to specific conditions located in such places as permafrost, tar pits and peat bogs.

Fossil bones, Wooly Mammoth, Dinosaurs

Formation of FossilsFossils are commonly formed when the bodies of organisms become trapped in sediments, which become compressed into strata, or layers, and eventually harden into sedimentary rock. An organism may leave an impression in hardened material, or, if the rate of decomposition is very slow, the organism’s cells may be replaced by minerals, resulting in a permineralized or petrified fossil. On rare occasions, when conditions prevent most decomposition, organisms may be preserved nearly intact; such as fossils found in tar pits, volcanic ash, peat bogs, permafrost, or hardened tree sap. The ideal conditions for fossilization are rare. After an organisms dies, its soft parts usually are consumed or decompose quickly. Consequently, organisms that have hard shells or bones and lived in or near aquatic environments are much more likely to become fossilized then soft bodied and land-dwelling organisms. The most abundant are microfossils, microscopic remains such as those of pollen and calcareous phytoplankton. Regardless of the size of species, fossils offer unique opportunities to observe evidence of past life directly.

Why Study Fossils?The study of fossils has led to the development of the fossil record, a sort of historical timeline which outlines and provides support for the theory of organic evolution on Earth. Today’s fossil record comprises more than 250 000 identified species, a number thought to be only a tiny fraction of all species that have lived on Earth. Less than 1% of species in the fossil record are living today.

Calculating the Age of Fossils

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The age of fossils is determined by one of two means relative dating and absolute dating. Relative dating is used to determine the chronological age of a fossil based upon its position in the rock strata. This is most apparent in sedimentary rock. Streams flowing into a body of water carry fine rock particles called sediments. Bodies of dead organisms that settle to the bottom may become fossils embedded in the sediments. The oldest fossils will be in the lowest layers, the youngest fossils in the upper layers.

Absolute Dating is a method that estimates the actual age of a fossil through the use of radioactive decay, the release of subatomic particles from the nucleus of an atom, which results in the change of a radioactive parent isotope into a daughter isotope which results in a change in the proton number and the subsequent formation of a different element.

The rate at which a radioactive isotope decays is fixed and unchangeable. The time required for half of the atoms of an isotope to decay is called its half-life. For example, the half-life of carbon-14, which occurs in all organisms, is 5730 years. If a fossil contains carbon-14 as a parent isotope and was formed 5730 years ago, only half of the original amount of C-14 would be left in the fossil. The other half would have changed to the C-14 daughter isotope nitrogen-14. Because carbon is found in all living things it can be used to determine the age of organic materials directly. However, the relatively short half-life of C-14 makes it unreliable for testing objects more than 100 000 years old. The chart below outlines other radioisotopes used in radioactive dating.

Parent Isotope Daughter Isotope Half-life (years) Effective dating range (years)

14C (carbon 14 ) 14N (nitrogen 14) 5730 100 -100 000235U (uranium 235) 207Pb (lead 207) 713 million 10 million – 4.6 billion

40K (potassium 40)40Ar (argon 40) and40Ca (calcium 40) 1.3 billion 100 000 – 4.6 billion

Questions

1. Suggest a reason why Leonardo da Vinci found fossils of aquatic life high on the top of the Tuscan mountains.

2. In what materials might fossil remains be found besides sediments? Explain why such finds are rare?

3. Relative dating is most effective within a small geographical area. Suggest a reason why this is so.

4. Using the axis below sketch the decay of parent isotopes and the formation of daughter isotopes over time.

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5. A fossil skull of Homo neanderthalensis, is discovered in northern Europe and is tested using carbon-14 dating. Paleontologists are curious about whether the Neanderthal was living at the same time as members of H. sapiens, who are thought to have been living in the same area of northern Europe 45 000 years ago. Measurements suggest that, of the original amount of carbon-14 isotope present in the skull when the Neanderthal died, only 1.56% remains in the fossil fragment. Prove whether or not H. sapiens and Neanderthals lived at the same time.

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Evidence for Evolution: Studying Evolution by Homologyhttp://www.sumanasinc.com/webcontent/animations/content/evolution/evolution.html

Homology - Study of similar structures.Homologous structures: Structures that have a common origin but not necessarily a common function. E.g. Limbs of animals

The comparison of interspecific structures is important evidence for evolution.Human arm appears quite different from the wing of a bird or the front fin of a dolphin.Study of skeletal structures reveal numerous similarities. The different structures are modified versions of structures that occurred in a common ancestor.

Vestigial Structures: Structures with no function. They are remnants of an organism’s evolutionary past. For example: Whales propel themselves with a powerful tail. Therefore, they do not need hind limbs or the pelvis to which they would attach. The whale retains a vestigial pelvis, which lends evidence to its evolutionary past as a four- legged land dwelling mammal.

Analogous Structures: Structures found in different types of organisms that have a similar function but dissimilar structure or embryological development.For example: Bird's wing and a Bat's wing.

Lab on Homologous Structures

Studying Evolution by Embryology

Embryology- The study of the resemblance between embryos of different animals.

In the early embryological stages of development it is extremely difficult to distinguish between embryos of one species and those of another. Similar features include: Segmented muscles, gill pouches, a tubular heart which is undivided into right and left sides. However, none of these features are found in the adult forms of these organisms.

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Studying Evolution by Biochemical Similarities

Many biochemicals found in related species are similar in composition. For example hemoglobin in whales and hemoglobin in humans.

In some cases antibodies (proteins) which are manufactured in bodies of rabbits and goat can be used for immunization of humans without harmful antibody-antigen reactions.

However this all relates back to DNA and genes. The closer related two organisms are the greater the similarities in their DNA proteins.

http://www.pbs.org/wgbh/evolution/library/03/4/l_034_04.html

Other Scientists who contributed to the Theory of Evolution

Lamarck's TheoryOne of the first theories of evolution was published in the early 1800s by a French naturalist, Jean Baptiste de Lamarck. Lamarck proposed that a change in the environment causes changes in the needs of organisms living in that environment, which in turn causes changes in their behavior.

There are two main principles of Lamark’s Theory. Outline them in the space provided.

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For the following scientists relate how they added to Darwin’s growing theory

Sir Charles Lyell (1797-1875) was a British geologist.

Thomas Malthus

http://www.pbs.org/wgbh/evolution/library/02/5/quicktime/l_025_01.html

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Charles Darwin and Evolutionary theory.

Charles Darwin, was only 21 when he embarked on a round-the-world voyage on the Beagle as the ship's naturalist, and he was intrigued by the variety of life he observed during his voyage. He studied turtles, armadillos, birds, and plants. He noted the similarities and differences between 14 species of finches that existed on different islands of the Galapagos. His now classic idea was that each species, because of isolation and natural selection, had evolved from a common ancestor that existed on the mainland.

Darwin did not publish his theory of evolution immediately upon his return to England. He tested his hypotheses for many years. Others influenced Darwin's thinking, such as Thomas Malthus and Charles Lyell.

Sir Charles Lyell (1797-1875) was a British geologist. He studied geology at Oxford University and traveled on several geological expeditions in Europe and North America. In his Principles of Geology (3 volumes, 1830-33), Lyell conclusively showed that the earth was very old and had changed its form slowly, mainly from conditions such as erosion. Lyell was able to date the ages of rocks by using fossils embedded in the stone as time indicators. Charles Darwin made use of Lyell's data on fossils for his theory of evolution. Lyell himself had believed that the various species of plants and animals had remained unchanged since they were created. When confronted with Darwin's findings, he admitted "I now realize I have been looking down the wrong road." He became one of Darwin's strongest supporters.

Charles Darwin believed that natural selection was the engine driving evolution. Evolution is neither negative or positive; it is always random. Six main points of natural selection are:

1. overproduction 2. competition 3. variation 4. adaptation 5. natural selection 6. speciation

Make detailed notes with examples on Darwin’s six main points.

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Peppered Moth Simulation

Objective: Simulate changes in moth population due to pollution and predation, and observe how species can change over time.

Introduction:

Charles Darwin accumulated a tremendous collection of facts to support the theory of evolution by natural selection. One of his difficulties in demonstrating the theory, however, was the lack of an example of evolution over a short period of time, which could be observed as it was taking place in nature. Although Darwin was unaware of it, remarkable examples of evolution, which might have helped to persuade people of his theory, were in the countryside of his native England. One such example is the evolution of the peppered moth Biston betularia.

The economic changes known as the industrial revolution began in the middle of the eighteenth century. Since then, tons of soot have been deposited on the country side around industrial areas. The soot discoloured and generally darkened the surfaces of trees and rocks. In 1848, a dark-coloured moth was first recorded. Today, in some areas, 90% or more of the-peppered moths are dark in colour. More than 70 species of moth in England have undergone a change from light to dark. Similar observations have been made in other industrial nations, including the United States.

Instructions:

Click the link below to read more information on Kettlewell's study of moths. At the end, you will run two simulations for 5 minutes each, during this time you will play the part of a bluejay that eats moths.

After 5 minutes record the % of dark moths and light moths - you will need this information later.

Peppered Moth Simulation

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Data and Analysis

Answers the following questions, responses should be in complete sentences.

1. Draw a data table similar to the one shown below where data is recorded for moths after 5 minutes of running the simulation.

2. Explain how the color of the moths increases or decreases their chances of survival.

3. Explain the concept of "natural selection" using your moths as an example.

4. What would happen if there were no predators in the forest. Would the colors of the moths change over time? Defend your answer.

5. Propose a design for another experiment that tests moth phenotypes in a forest where there are no predators. The limiting factor is food availability for caterpillars (baby moths) and caterpillars with larger mouthparts are able to obtain food faster. What data would researchers take in this experiment to show how natural selection affects the moth populations.

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Survival of the Fittest and Natural Selection

This may be one of the most widely vocalized statements in science but also the most inappropriately applied term.

http://www.hhmi.org/biointeractive/making-fittest-natural-selection-and-adaptation

1. Watch the movie and summarize the concept of “Survival of the Fittest” as it applies in nature.

2. Give other examples and situations where this term can be applied.

3. Today health professionals are dealing with an ever increasing issue with antibiotic resistance in bacteria. Explain how this problem is a result of natural selection and survival of the fittest.

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Natural Selection can Influence Populations in Three Major ways.

Use this animation

http://wps.pearsoncustom.com/wps/media/objects/3014/3087289/Web_Tutorials/17_A02.swf0

or page 296 in our textbook, to assist you in defining each category.

Directional Selection:

Disruptive Selection:

Stabilizing Selection:

Read the Story of the Cane Toads and answer the questions in relation to the concept of Natural Selection.

Frequencies of our Genes

Population genetics describes evolution as a change in the genetic makeup of a population in successive generations. When we looked at the genetics of individuals, we described genotypes or the genetic makeup of an individual. When talking about the genetics of populations, we will use the concept of the "gene pool." The gene pool is the total of all genes possessed by all individuals in a population of a species.

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Individuals can have only two alleles of any given gene. Populations can include any number of different allelic forms of a gene. The gene pool is described in terms of the frequency of alleles of a given gene in the population. For example, given gene A and a, allele A makes up 90 percent of the total of both alleles. Allele a makes up 10 percent of the total of both alleles. We say the frequency of A and a in the gene pool of this population are 0.9 and 0.1 respectively.

We can now define evolution as a change in the genetic makeup of populations or a change in the allelic frequencies within a gene pool. Therefore, it is possible to determine what factors cause evolution by determining what factors cause changes in allelic frequencies.

If a population's allelic frequencies are constant, we say the population is in genetic equilibrium. If allelic frequencies change with time, evolution has occurred.

Hardy Weinberg Equilibrium Law

The study of allele frequencies within a population or population genetics is assisted by the Hardy-Weinberg Law which provides a method for calculating the allele frequencies in a population. From these frequencies it can be determined overtime if the population is evolving.

From previous study we are aware that all of the genes of a population of organisms compose the gene pool. Organisms that are successful at reproducing contribute most to the gene pool of that population.

The Hardy-Weinberg law examines changes in gene pools and explains how evolution can select for certain genes

The guidelines for the Hardy-Weinberg Theorem are as follows:

• The population must be very large• No mutations must occur• The population must be isolated from other populations (no immigration or emigration) no gene flow• All mating must be random

In nature these conditions do not exist

Theorem p + q =1

Where p = the frequency of the dominant allele

q = the frequency of the recessive allele

All the alleles in a population will total 100% (or 1 in this case)

Example

In pea plants tall is dominant to short

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Alleles T or t

p = T and q = t

Therefore, Homozygous tall, TT = p x p or p2

Heterozygous tall, Tt/tT = p x q / q x p or 2pq

Recessive short, tt = q x q or q2

From this information we get the formula

p2 + 2pq + q2 = 1

Example 1

If we set up a trap over a bunch of ripe bananas, we would probably catch a population of fruit flies, Drosophila. After the flies are anesthetized and counted, we might find that out of 1000 flies, we have 910 with grey bodies and 90 with black. Calculate the number of individuals who are homozygous dominant and heterozygous.

The first step in determining the allele frequencies for the body color phenotype is to determine which trait is dominant and which is recessive.

Since the bulk of the population is grey we can assume that grey is the dominant phenotype and black is recessive.

Alleles Grey

Black

How does this relate to the Hardy-Weinberg Theorem?

p2 + 2pq + q2 = 1 and p + q = 1

If the recessive phenotype in this case black ( ) is equal to q2 in the theorem.

Therefore, q2 = individuals.

If q2 =

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Therefore,

homozygous dominant p2 =

heterozygous =

To sum up p2 =

q2

2pq =

Total individuals = 1000

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Hardy Weinberg Quiz28

Genetic Drift Genetic drift is the change in allelic frequencies resulting from chance processes. Genetic drift is more likely to happen in small populations than large ones. For example, consider a population of 1 million apple trees with a frequency of r at 10%. If a severe ice storm wiped out half of the trees, leaving 500 000, it is very likely that the r allele would still be present in the population. However, suppose the initial population size of apple trees was 10 (with the same frequency of r at 10%). It is likely that the same ice storm could wipe the r allele out of the small population.

Intense natural selection or a disaster can cause a population "bottleneck," a severe reduction in population size which reduces the diversity of a population. The survivors have very little genetic variability and little chance to adapt if the environment changes. For example, by the 1890s the population of northern elephant seals was reduced to only 20 individuals by hunters. Even though the population has increased to over 30 000, there is no genetic variation in the 24 alleles sampled. A single allele has been fixed by genetic drift and the bottleneck effect. In contrast, southern elephant seals have wide genetic variation since their numbers have never been reduced by such hunting.The bottleneck effect, combined with inbreeding, is an especially serious problem for many endangered species because great reductions in their numbers have reduced their genetic variability. This makes them especially vulnerable to changes in their environments and/or diseases. The cheetah is a prime example.

Sometimes a population bottleneck or migration event can cause a "founder effect." A founder effect occurs when a few individuals, unrepresentative of the gene pool, start a new population. For example, a recessive allele in homozygous condition causes Dwarfism. In Switzerland, the condition occurs in 1 out of 1 000 individuals. Amongst the 12 000 Amish now living in Pennsylvania the condition occurs in 1 out of 14 individuals. All the Amish are descendants of 30 people who migrated from Switzerland in 1720.

http://www.sumanasinc.com/webcontent/animations/content/evolution/evolution.html

Natural Selection in Humans

http://www.hhmi.org/biointeractive/making-fittest-natural-selection-humans

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Allele Frequencies and Sickle Cell Anemia

Introduction: Allele frequency refers to how often an allele occurs in a population. Allele frequencies can change over time, depending on “selective forces” such as predation, food supply, and disease. Evolution occurs when allele frequencies change in a population.

In this activity, red and white beans are used to represent two different alleles A and a. Sickle cell anemia is a recessive trait, expressed when an individual’s genotype is “aa”. The gene pool exists in a region of Africa that is infested with malaria. Your simulation with the sickle cell gene will take place in the presence of malaria.

Materials: 75 white beans (represent A)25 red beans (represent a)5 cups (labelled AA, Aa, aa, Non-surviving Alleles, Gene Pool)1 coin to toss

Hypothesis/Prediction:

1. What do you think will happen to the frequencies of the A and a alleles as a result of the presence of malaria? (Will the frequency of A increase or decrease? a?) Formulate a hypothesis and corresponding prediction. Be sure to explain your reasoning.

Procedure:

1. Together with your lab partner, obtain five containers, labelled as follows: AA, Aa, aa, Non-surviving Alleles, Gene Pool

2. Place the 75 white and 25 red beans in the Gene Pool container and mix the beans up.3. Simulate fertilization by PICKING OUT two beans WITHOUT LOOKING.4. For every two beans that are chosen from the gene pool, another person will FLIP A COIN

to determine whether that individual is infected with malaria.5. Using the table below, the coin flipper tells the bean picker in which containers to put the

beans.

Genotype Phenotype Malaria (Heads) Not infected (Tails)

A A(White-White).

No sickle cell disease. Malaria susceptibility.

Die: place in Non-surviving

Live: place in AA

A a(White/Red).

No sickle cell disease. Malaria resistance.

Live: place in Aa Live: place in Aa

a a(Red/Red)

Sickle cell disease. Die: place in Non-surviving

Live for a brief time: place in aa

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6. Repeat steps 3-5 until all the beans in the Gene Pool are used up.7. Record the results in the F1 CUP TALLY table on the data sheet.8. At the end of the round, COUNT the number of individual white beans (A alleles) and red

beans (a alleles) in the containers labelled AA and Aa. These individuals survive to reproduce. RECORD those numbers in the F1 TOTAL SURVIVING ALLELES table. Put them in the gene pool afterwards.

9. Because aa individuals do not survive to reproduce, move all beans from the aa allele's container into the Non-surviving alleles container. STOP TO COUNT!!!

10.Repeat the procedure for the F2 generation. Record your results in the F2 CUP TALLY table and F2 TOTAL SURVIVING ALLELES table.

F1 CUP TALLY:

Cup Tally

AA

Aa

aa

Non-surviving

F1 TOTAL SURVIVING ALLELES:

Number of A (WHITE) alleles surviving (Count out of AA and Aa containers)

Number of a (RED) allele surviving (Count out of Aa container)

***Put the survivors in the gene pool and create the next generation!

F2 CUP TALLY:

Cup Tally

AA

Aa

aa

Non-surviving

F2 TOTAL SURVIVING ALLELES:

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Number of A (WHITE) alleles surviving (Count out of AA and Aa containers)

Number of a (RED) allele surviving (Count out of Aa container)

Analysis Questions:

1. What do the white and red beans represent in this simulation?

2. What does the coin represent?

3. What does "allele frequency" mean?

4. What are the "selective forces" in this simulation (the forces changing the allele frequencies)?

5. What was the general trend you observed for Allele A over the generations (did it increase or decrease)? What was the general trend for Allele a over time? Was your hypothesis supported?

6. Do you anticipate that the trends in question 5 will continue for many generations? Why or why not?

7. Since few people with sickle cell anemia (aa) are likely to survive to have children of their own, why hasn’t the mutant allele (a) been eliminated? (Hint: what is the benefit of keeping it in the population?)

8. Why is the frequency of the sickle cell allele so much lower in the United States than in Africa?

9. Scientists are working on a vaccine against malaria. What impact might the vaccine have in the long run on the frequency of the sickle cell allele in Africa? (Would it increase or decrease? Why?)

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Section Review

1. What is meant by the term gene pool?

2. How would you determine the allele frequencies in a gene pool?

3. How does population size affect the likelihood of changes in allele frequencies by chance alone?

4. What is genetic drift? Give an example.

5. Can significant changes in allele frequencies (evolution) occur as a result of genetic drift?

6. If you measured the allele frequencies of a gene and found large differences from the proportions predicted by the Hardy-Weinberg principle, would that prove that natural selection is occurring in the population you are studying?

7a) Describe three ways in which natural selection can affect a population over time.

b) Which way(s) is/are likely to occur in a stable environment?

c) Which way(s) is/are likely to occur in a rapidly changing environment?

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Sickle Cell Anemia: A Profile for Genetic Screening

Sickle-cell anemia is caused by a defective gene that produces an abnormal form of hemoglobin which distorts the normal biconcave disc shape of red blood cells producing those that resemble a type of crescent-shaped cutting blade used in agriculture called a sickle. The sickled shape makes it difficult for these cells to pass through tiny blood vessels, resulting in intensely painful blockages that prevent vital oxygen and nutrients in the blood from reaching organs and tissues, impairing their function. As a result, sickle-cell patients are also vulnerable to a number of infections. When the blood flow to the brain is affected, sickle-cell patients may experience brain damage, such as stroke. Sickle cells also break apart more readily than healthy red blood cells, leading to a deficiency of red blood cells, known as anemia.

Sickle-cell anemia is an autosomal recessive genetic trait—that is, a child with the disease must inherit one copy of the defective hemoglobin gene from each parent. Many people carry one hemoglobin S gene with no significant health problems as the heterozygous condition expresses codominantly. Certain ethnic populations have more people who are carriers of the sickle-cell trait. The hemoglobin S gene is particularly common in western Africa and people of western African ancestry. In these gene pools the allelic frequency of hemoglobin S can reach 40% whereas in North America it is estimated at approximately 4% with 8 to 12 percent of all African Americans carry the sickle-cell gene. Sickle-cell anemia is also more common in people from Mediterranean countries, the Middle East, and India, or people whose ancestors came from these regions. Researchers believe that the hemoglobin S gene is particularly common in these populations because carriers of the sickle-cell gene are less susceptible to malaria, once one of the leading causes of illness and death in these geographical regions. Carrying the sickle-cell gene makes individuals more likely to survive bouts with malaria than non-carriers, making them more likely to reproduce and pass the sickle-cell gene to their offspring.

For parents who are both carriers of Sickle-cell anemia prenatal screening is often used to determine if the fetus has inherited two copies of the defective gene. Parents are then able to make an informed choice about whether or not to terminate the pregnancy.

For Sickle-cell anemia the exact nucleotide sequence of the mutant gene is known. It is a single point mutation where the sequence GAG is changed to GTG. For prenatal diagnosis, two DNA oligonucleotides (short sequences of DNA ~ 20bp) are synthesized -one corresponding to the normal gene sequence in the region of the mutation and the other corresponding to the mutated sequence.

The individual’s DNA is exposed to the restriction endonuclease Hpa1. The normal fragment length of the target sequence for hemoglobin is 7600 bp but due to that single amino acid change the mutant sequence releases a fragment of 12000 bp.

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Analysis:

1. Given the information regarding fragment size for hemoglobin A and hemoglobin S fill the appropriate bands represented by restriction analysis with Hpa1 in the following electrophoresis gel.

2. What is the amino acid substitution that occurs in the mutant gene?

3a. How does the allelic frequency of the hemoglobin S gene change from populations in Africa compared to that of North America?

b. What factors of evolutionary theory lead to this change? Explain.

c. What is the source of the selection pressure for the sickle cell gene that prevents it from being removed from the human gene pool?

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Adaptations

Any organism is a complex of adaptations designed to carry out life functions. An adaptation is a genetically controlled characteristic that increases an organism's fitness. Fitness in evolutionary biology refers to an individual's likely genetic contribution to the next generation. An adaptation is a characteristic that improves an organism's chances of perpetuating its genes, usually by leaving offspring.

Adaptations do not increase the organism's chances for survival. An adaptation that improves the likelihood of producing descendants will likely also increase the likelihood of pre-reproductive survival but not post-reproductive survival. In many species, adults die soon after reproducing.

Adaptations can be structural, physiological, or behavioral. They may be genetically simple or complex. They may involve single cells or whole organs and organ systems.

Structural Adaptations As the name suggests, structural adaptations are characteristics of body form including skeleton, size, shape, number of limbs, body covering, and so on. Many plants have structural adaptations designed to attract pollinators, and many plants and animals have structural adaptations that are protective in purpose. For example, some plants have thorns to reduce the likelihood of being eaten, and others have fruits to increase the likelihood of being eaten and having their seed distributed. Some animals use warning or camouflage colouration for protection. For example, poisonous or stinging animals are often brightly coloured. Other animals blend in with their surroundings, and yet others are not poisonous but mimic the colouration of those that are. Still others mimic twigs, leaves, and so on.

All of these adaptations are responses to selection pressures that make individuals possessing the right adaptations more likely to pass on their genes.

Physiological Adaptation Physiological adaptations are not as obvious as structural adaptations, as physiological adaptations deal with the individual's physiology. For example, many arthropods secrete chemicals of one kind or another. Some are to ward off predators, others are for building materials, and others are to attract mates. Some insects secrete a chemical called a pheromone that affects behaviour. It is used primarily to attract the opposite sex for reproduction. Spiders produce silk for webs. Squids (mollusks) produce an ink to distract predators while they escape. Snakes produce a chemical called venom that is specialized in immobilizing their prey. Even plants secrete chemicals called toxins. Although different from venom, the purpose of toxins is to keep pests away.

Behavioural Adaptation Combinations of structural and physiological adaptations usually make possible the behaviours of organisms. For example, hunting behaviour results from colouration, strength and speed, or stealth to catch food. Avoiding being eaten can be the result of the right colour pattern and keeping to the right background, or being able to run faster than a predator.

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Migration and the daily and seasonal activity of plants and animals are all the result of the interplay between all forms of adaptations.

Certain plants and animals have evolved to live together in symbiotic relationships. In mutual relationships (mutualism) both organisms benefit from the partnership. Organisms that clean others is a classic example of mutualism.

Populations and Species How can a single population split and give rise to two or more different descendent populations? When speaking of sexually reproducing organisms, a population is a group of individuals that interbreed and share a common gene pool.

It is useful to introduce a new term--deme. A deme is a small, local population such as all the deer mice or all the maple trees in a woodlot. No two members of a deme are exactly alike, but they resemble each other more closely than members of other demes. This is because individuals in a deme are more closely related genetically, because matings occur more frequently within a deme than between members of different demes. Also, members of the same deme are exposed to similar environmental influences, and therefore similar selection pressures.

Demes are not permanent units of population. In the woodlot example, neighbouring lots can grow together or a single woodlot can be divided. Two demes can fuse into one or one can be split into two or more.

Units of population that are longer lasting, larger, and more distinct are species. The modern view of a species is a genetically distinctive group of populations within which effective gene flow occurs or can occur. Regardless of outward appearance, anatomical or behavioural differences, distinct species are reproductively isolated. Populations may resemble each other but if there can be no gene flow, then they are different species. Conversely, populations may appear quite different, but if they can interbreed, then they are the same species.

Subspecies and race are terms that are often used interchangeably. These are situations where there is an abrupt, genetically controlled difference from one part of a species range to another. When this occurs, they are said to be different subspecies but they can still interbreed. Examples of subspecies include fish in different rivers or water beetles in different ponds.

Geographic Isolation Our discussion of speciation is primarily concerned with divergent speciation which attempts to describe how a single population gives rise to two or more descendent populations which grow increasingly different as they evolve.

As we have seen, by definition, different species are unable to interbreed. How is it that two populations that initially share a common gene pool come to have completely separate gene pools? How does the possibility of effective gene flow between two sets of populations disappear? How do barriers to the exchange of genes arise?

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Most biologists agree that the most probable factor in starting speciation is geographic isolation. As long as all the populations of a species are in some form of contact, there will be gene flow. There may be considerable variation in characteristics in populations corresponding to variations in the geographical distribution or range of a species, but gene flow can still occur.

If, however, a geographic barrier is established that splits a set of populations in a way that there is no further contact, then there is no possibility to exchange genes and evolution will continue independently in the separated populations. Given enough time, the separate population sets will become quite different but they could still interbreed if they came into contact. At this point these populations are still the same species. Eventually there will be sufficient differences in their gene pools so that if members of these populations should come into contact, they would be unable to reproduce. At that point they have become separate species.

Several factors cause geographically separated populations to diverge. Some examples of geographic barriers are mountain ranges, prairies, and canyons. If we look into the past, glaciers and oceans have been significant barriers. A geographical barrier is unlikely to divide a set of populations neatly in half. More likely, the fringes of the range will be separated from the rest of the population. The result is that the separated population already has different gene frequencies from that the parent population. The so-called "founder effect" is apparent when a relatively small population is separated from the rest of the population and as a result of genetic drift evolution follows a different path.

Separated populations will probably have different mutations. Mutations that happen in one population may not happen in the other. Since there is no gene flow, a mutant gene arising in one group cannot spread to the other. Isolated populations will probably be exposed to different selection pressures because they inhabit different ranges with correspondingly different conditions.

View the animation http://wps.pearsoncustom.com/wps/media/objects/3014/3087289/Web_Tutorials/18_A01.swf

Allopatric speciation:

Sympatric speciation:

Explain in your own words how geographic isolation can lead to reproductive isolation.

Adaptive Radiation Adaptive radiation is an example of divergent evolution in which new species result from isolated populations evolving separately. One of the most famous examples of new species

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developing from a single isolated species is Darwin's finches of the Galapagos islands. There are 14 species of finches that are believed to have evolved from a single species. The islands are separated by ocean and the finches tend not to travel very far. Interspecies competition is minimal because the finches have adapted to exploit different environments and food sources.

Many of the Galapagos islands have more than one species of finch. This may seem to be a contradiction, but in fact it is not. These finches are not geographically isolated but they are isolated reproductively and behaviorally. It is likely that after evolving on another island, finches found their way to other islands but they were sufficiently different and remained distinct species.

Regarding adaptive radiation, open the URL and take the prequiz, watch the animation and take the post-quiz

http://kisdwebs.katyisd.org/campuses/MRHS/teacherweb/hallk/Teacher%20Documents/AP%20Biology%20Materials/Evolution/Adaptive%20Radiation/26_A01s.swf

Polyploidy Speciation that does not involve geographic isolation is called sympatric speciation (speciation as a result of geographic isolation is called allopatric speciation). An example of almost instant sympatric speciation is commonly found in plants but rarely in animals. It is called polyploidy.

Polyploidy is an increase in the number of chromosomes, usually resulting from errors in meiosis. Polyploidy can result in the offspring and the parent belonging to separate species. The polyploid individuals can breed with one another but not with their diploid relatives. For this reason, they qualify for the species definition that we are using. Many crop plants that we cultivate are polyploids, including oats, wheat, potato, cotton, coffee, tobacco, and sugarcane.

Chromosomal rearrangements, however small, might give rise to individuals or small populations that are genetically incompatible with the rest of their species. If the variation is at a competitive advantage, selection would favour further isolation and a new species can develop without geographical isolation.

Convergent Evolution and Coevolution Convergent evolution is the development of similar structures in unrelated organisms, due to living in a similar environment. For example, the wings of bats and the wings of insects are both adapted to flying, yet the wings have evolved on two distinct groups of animals. Another example is the fins of fish and the flippers of whales. Form has adapted for function. A certain similarity of design is necessary for similarity in purpose. Flying requires wings. Swimming requires fins.

Convergent evolution can be a problem when determining the relatedness of organisms. It must be determined if structures are homologous (from a common ancestor) or analogous (similar in function but of different evolutionary origins). It is always important to say in what sense to structures are considered homologous and analogous. For example, the wings of bats and birds are considered to be homologous in terms of their bone structure, but they are analogous as wings. We say that wings of bats and birds are homologous as forelimbs but analogous as

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wings. Likewise, whale flippers and seal flippers evolved independently of each other, but both evolved from front legs of land mammals. The modifications that make them act as flippers are analogous.

Coevolution involves the evolution of two organisms because they have adapted to each other's presence. An example would be the predator-prey relationship between a species of bats and moths. Some species of moths have evolved thicker, powder-like scales on their wings and this makes it difficult for bats to find these moths using echolocation. Scientists later discovered that some bats evolved different behaviour to adapt to the changing moths. The bats developed flight patterns that allowed them to use echolocation from more than one location. This allowed the bats to find the "new" moths. Other often-used examples of coevolution are the relationships between plants and the organisms that pollinate them. Plants have evolved a variety of colours and forms to entice specific animals to visit them. The plants offer pollen and nectar in exchange for transferring pollen from one plant to another of the same species. Some plants are adapted so that only certain insects or hummingbirds can reach the nectar. Certain animals are adapted to visit only certain plants for food.

http://www.hhmi.org/biointeractive/making-fittest-got-lactase-co-evolution-genes-and-culture

Evolution Questions Review

1. Describe Lamarck's theory of evolution according to his two principles. Relate this theory to the evolution of the giraffe.

2. Explain how Charles Lyell and Thomas Malthus contributed to Darwin's theory of evolution.

3. Summarize and explain the 6 main points of Darwin's theory, i.e. overproduction, competition, variation, adaptation, natural selection, and speciation.

4. What is the difference between geologic evolution and organic evolution?

5. How does relative dating (not the redneck kind) differ from absolute dating? 6. What is a fossil?

7. Name 6 types of fossils.

8. What is the relationship between a mold and a cast?

9. In what type of rock are fossils found?

10. What is the fossil record?

11. Name three different types of evidence, other than the evidence supplied by the fossil record, that support the theory of organic evolution.

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12. Define homologous structures.

13. Name two analogous structures.

14. Looking at the diagram of the development of vertebrate species, how do you know that the evolutionary relationship between humans and chickens is closer than that between humans and fish?

15. Name the components of the atmosphere thought to have been present on the primitive earth.

Adaptations and Natural Selection

16. Define the term gene pool.

17. Describe how evolution can occur as a result of genetic drift.

18. Why is genetic drift less likely to affect large population than small ones?

19. Define the term adaptation.

20. Distinguish between structural, physiological, and behavioral adaptations. Give examples of each.

21. List, describe, and give examples of the following types of speciation: Isolation (geographical and reproductive), and adaptive radiation.

22. Explain why Darwin's finches may be said to represent an example of adaptive radiation?

23. Distinguish between convergent evolution and coevolution and give examples of each.

24. Describe and give examples of evolution that are observable today.

25. Give examples of artificial and natural selection

26. Define and identify types of natural selection from graphs (disruptive, stabilizing and directional)

27. Relate the conditions a population must follow for the Hardy-Weinberg Theorem.

28. Solve Hardy-Weinberg problems

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