Nelson Text Review Questions   : Chapter 3

1. The modern view of evolution is based on scientific evidence which combines both genetic information and the theory of natural selection. It implies a change over time. Earlier beliefs were based on opinion and nonscientific evidence. This earlier view held that living things had been “fixed” since the beginning, and were unchangeable.

2. The variety (adaptation) of beak types displayed by the islands’ finch species made the greatest impression on Darwin.

3. Survival of the fittest means that individuals with traits best suited for and environment are better able to compete, survive, and reproduce. Adaptation is the basis through which natural selection can occur, with those individuals that are best adapted to particular environments becoming the most successful reproducers. The direction of evolution is determined by the adaptation.

4. Lamarck offered and explanation for the mechanism of evolution – that species change over time, and that the environment is a factor n that change. He showed that evolution is adaptive and that the diversity of life is the result of adaptation (see pages 91- 93).

5. Buffon’s theory indicated that the creation of a species did not occur in a single place at a single time and that a species was not created in a perfect state. Later he wondered if certain species might develop from a common ancestor. Darwin accepted Buffon’s ideas and went on to provide an explanation for the manner in which species change over time.

6. Structural, physiological, and biochemical are the three types of adaptation.

7. The moths adapted a color (pigmentation) change from light-colored to predominantly dark-colored (melanic) forms in response to the environmental changes caused by the industrial fumes of the mid-1800s.

Applying the Concepts

1. The study of genetics has shown that acquired characteristics cannot be passed on to offspring, so Lamarck’s ideas have been proven incorrect.

2. a) Lamarck would have suggested that the zebra wanted to avoid the annoying bite of the tsetse fly and developed the striped to do this.

1. b) Darwin or Wallace would have suggested that some zebras were striped more than others. Tsetse flies bit those that had few stripes, or had pale stripes. These zebras got the parasite and died, and the striped zebras, which were bitten less frequently, reproduced and passed the stripes to their offspring.

1. c) Answers can vary.

3. Human activities can affect evolution by isolating populations of organisms in different areas. Small organisms are less likely to cross roads to find a mate, so the road can become an effective barrier. Bridges can bring two isolated populations together, stopping their speciation.

4. Lamarck had recognized the impact of environmental factors on the course of evolution. He recognized that the mechanism for evolution was natural selection through adaptation. This became the basis for Darwin’s theory of evolution.

5. The traditional and widely accepted model for the rate of evolutionary change holds that change occurs slowly or gradually within populations of organisms. The peppered moth case (and others mentioned in the test) demonstrated that certain changes (e.g., coloration in moths) can take place rapidly.

• Some populations (e.g., mosquitoes exposed to insecticides) show wide fluctuations in number, indicating the loss (or gain) of tremendous numbers of individuals, but the species continues (although it may evolve in the process).

• The loss of individuals may reduce the gene pool and modify the population, but the species continues.

• The life span of individuals is trivial in comparison to the “life span” of species. Hence, specific individuals contribute very little to the survival of the species. On the other hand, if the species does not survive, there will of course be no more individuals.

7. Adaptation to environment is a very complex process and very difficult to study in the natural environment. It is impossible, for example, to devise and experiment to show the effect on a caribou population of another ice age. Adaptation also takes a very long time, and may not be suitable for direct study (e.g., even an adaptation taking hundreds of years would be difficult to study directly). Carefully constructed computer models mimic the response of organisms in the “real world,” and allow scientists to run simulations that show, in minutes, the effects of environmental changes that might take years of real time. They can also vary different aspects of the environment and look at their effects on populations. Supercomputers allow such models to contain far more complexity and to be more realistic. Examples will be various.
8. Answers will vary, and might include some of the following:

• Roads can be a barrier to some species, and their construction can subdivide populations. Each smaller population may experience slightly different selection pressures, and it may contain a slightly different gene pool than the original, continuous, population.

• Hydroelectric dams cause extensive flooding and disruption of natural populations, creating new sets of selection pressures which can affect the direction and rate of evolution. Some major projects have even been stopped because they would cause the extinction of a specific organism found only in the area that would be disrupted by the dam.

• The building of navigable waterways connecting previously unconnected (or poorly connected) bodies of water allows the spread of species beyond previous limits, and alters community composition and selection pressures (e.g., the lamprey entering the Great Lakes).

• Pumping of wasted water from ships’ bilges has been implicated in the introduction the zebra mussel to the Great Lakes, introducing a new and fast-growing grazer to the community, with implications both for existing species and for our use of the waterways.

9. High reproductive capacity is normally linked with high egg number and short development time (e.g., many species of fish and insects). Where there are many young, there will be many different combinations of parental genes, increasing the chance that there will be some combinations that are better able to withstand a particular selection pressure. Such populations can also respond more rapidly to sudden pressures. (Compare the response of humans, which have a nine-month gestation period and approximately 20 years between generations, with the response of flies, which may have only days between successive generations.)

Critical-Thinking Questions

1. Answers will vary. When humans are domesticating animals and plants, they choose traits that they (the humans) want to propagate. They do not allow “nature to take its course.” For example, animals many thousands of miles apart can parent an offspring by artificial insemination; this would not occur naturally.

2. answers should recognize that, in the Galapagos, similar populations of organisms invaded a series of islands on which there were different selection pressures. It is almost the type of situation a researcher might set up if she were interested in evolution in natural situations, and if she had hundreds (perhaps thousands) of years to observe the results. Answers should include the idea of isolation one island population from populations on other islands and /or the mainland.

3. If a Lamarckian explanation of evolution were to be endorsed, then evolutionary changes in an organism would be interpreted as meeting the needs of the individual organism.

4. Answers will vary, but may be evaluated in relation to the literature used to research them.

Chapter Three: Mechanisms of Change

Some notes to stimulate your appetite to think about the mechanisms of change and how to prepare for chapter three quiz.
In chapter two, we are introduced to evidence regarding showing change with time. The premise is this, from direct and indirect evidence; there are observations that show a change with time. This process of change with time can be shown in adaptations in populations of organisms. We have noted that this process can be shown using concepts such as speciation and isolation mechanisms. Basically, keep one species away from another and allow mating only to occur within this population, the chances are that a unique species will evolve. In chapter three, we begin to hypothesize about the mechanism that causes this change.

Historical note:

Though some philosophers have suggested that we learn nothing from observing history, the case is not the same for observing fossils. We begin with the notion that all species are fixed. No that does not mean neutered but that all species were put on the earth at a specific time and in a specific place. From a western philosophical point of view, those folks that were busy classifying nature never challenged this idea. Biologists were in fact part of a field of inquiry known as natural history and sometimes grouped with natural philosophers. For many years, “Naturalists” were quite content to just identify and classify and to create some universal means to classify all living things. Then the inquiry into how things worked began. The scientific method created a method of thinking to examine the world. Forces such as gravity and energy became the field of inquiry for scientists. From this inquiry came “laws” and interpretations of chemical and physical forces. As naturalist began to observe more history of organisms upon the earth, the inquiry began to follow the same pattern of questioning. What was going on? Why did organisms become extinct? Why were animals different? Were there unknown forces within nature, like the forces of gravity and Newtonian physics?

So lets look into the text to answer the following:

Who started asking questions about the fixity of species and how could this questioning affect how people perceived fossils?

Once a question is asked, more will follow.

So who proposed the idea of adaptations, the law of use and disuse?

Why do you suppose he used a term such as “law”?

Let’s make a few observations such as”: a heron has long legs, some insects are resistant to insecticides,and some organisms have thick skin or fur.

How could we explain these adaptations from Lamarck and Darwin’s point of view?

Now lets get logical and examine some of the ideas proposed by both Lamarck and Darwin.

Here are some statements, can you identify ones that Darwin would support or Lamarck would support?

Which Statements can be used with the other to create an argument?

Many types of variations exist within a species
Members of a species tend to increase in a geometric ration from generation to generation (example 2:4:8:16: 32)
Some variations have more survival value than others
Organisms in a population reproduce, but the population tends to remain constant
There is a struggle for survival
Organisms are able to adapt to their environment when they inherit variations that have been developed by their parents through use and disuse of certain organs
How would Darwin use some of these statements to support his mechanism of change?

With both Darwin and Lamarck, we have a key problem to consider: Does the environment affect how an organism evolves, or does the organism have a means to adapt to the environment?

One of the key issues is the notion of choice. If we accept the idea that the environment is selecting species, then does the notion of “free will” and “choice” have a place in human thought?

So let’s look outside the realm of the human mind. Organisms on the planet have genetic material. This material allows organisms to display traits. This information, first shown by an inventive monk named Mendel remained unknown to both Lamarck and Darwin. While both were looking for a source of change, either within the organism or due to the environment, neither of them knew about the origin and transmission of variation.

Darwin did consider domestic animal breeding and noted how humans could artificially select traits, but he still didn’t know about the source of these traits. He did suggest that through artificial breeding of animals, humans could “select” a desirable trait. However he was still in a muddle about the origins of traits or why some organisms produced infertile young. For example, the notion of a “hybrid”…which is a product of a cross of two species and in some cases can be infertile such as a donkey and horse was a mystery to Darwin. Darwin did note the formation of species, and the multiplication of species or speciation. He suggested that this process was gradual with time. Yet the more evidence that was brought forth challenged this portion of his idea. Can you define and show examples of the idea known as “punctuated equilibrium”?

Now here is the challenge…

Darwin suggested that his observations about finches in the Galapagos islands was an example of the process of evolution and that by noting this process, the mechanism for natural selection could be illustrated

First of all…who offered the idea of a struggle for existence and natural selection to Darwin?
Now by using some of the terminology such as:

Isolation mechanisms

Speciation

Hybrid

Competition

Predators

Can you describe what occurred with the finches and why they changed with time? Remember to break up you explanation into two parts…the observations that showed a process and the concepts that explain the mechanism.

Chapter Two Notes

Big Ideas in Biology: Change with Time

What is the significance of a change with time? How do we define evolution? What are some patterns of evolution and how can we prove that a change actually occurred. How are species formed or changed with time? These are the primary questions in chapter two.

Evolution is:

• an explanation for the increase in biological diversity.

• a theory that describes how current species are descendants of species of previous generations.

• is a process by which populations show change (gradual or punctual) over several generations.

• a basic definition of evolution is a gradual change of species with time.

First of all, a change within a species of organisms can be noted by a change in structure, habitat or even behaviour. This change can be refered to as an adaption.

When is a population of organisms considered to be adapted to it’s environment?

( this is a great question to remember..)

• Even though the environment may change to a small degree, successive generations of offspring thrive.

• The most desirable adaptations are those which give an organism a advantage to survive.

A way of showing a longer duration of change with time is to examine remnants of previous generations. These remnants can be actual bones or imprints of organisms. This preserved bits of structural or imprinted information are refered to as fossils.

Ø  Fossil records provide the most direct evidence of evolution

• Most fossils are found in sandstone and limestone.
• Problems with fossils:

There are gaps in fossil records

• due to movement of the earth
• no know record of organism in that time period
• one organism eating another at one location and then depositing the remnant at another location

Some specimens are not complete organisms

The process of fossilization requires a specific type of soil

Some specimens are too soft to make a fossil

• for example a shelled organism would make a better imprint than a worm)

With the advent of genetic research and cell biology, there are now new ways to establish indirect proof of a change with time:

1. Embryology:

• Examining the stages of development of an embryo in a variety of species, there appears to be some similarities. This similarity was noted by …who said “     “. Basically, the development of an embryo shows the species phylogenic or family history.

2. Examining structures

There are three terms relative to structures that are useful for comparing species.

This table may be helpful for comparing homologous to analogous structures.

3. Physiology

4. Biochemistry

Pattern of Evolutions:

Convergence

If an organisms develops similar structures due to living in similar environments but they are separated due to being geographically isolated, this is an example of convergent evolution. Basically two distinct species show a similarity, although they are not genetically link. The term converge means to come together.

Divergence

If an organism is separated by geographic barriers, then it will not be able to reproduce with other species. This population will diverge from the original species that it was separated from.

Sources of change

The concept of speciation

The term “speciation” refers to the formation of new species. New species are formed when one population of the same species is separated from another and there is no exhange of genetic information between the two populations.

what can cause speciation?

Isolating mechanisms that may lead to speciation

( remember diagram in class about sea snails)

• geographic
• ecological
• behavioral
• morphology
• genetic

While many of these isolation mechanisms may be crossed, for example a snail may adapt from one ecological environment to another. The one barrier that cannot not be crossed in natural situations is the reproductive or genetic barrier.

Microscopes and Magnification

“I have got the power”

One of the tools that biologist use is the microscope. It function is to view a world that the normal eye cannot see. Stop for a moment and Imagine the first time some one saw moving matter under the lens. If you were that person, would you be afraid or full of wonder? This is a loaded question simply because now it is common to see magnified images of virus and bacteria in TV commercials. Perhaps the novelty is gone but the usage of the microscope remains a basic skill of any one studying biology.

Concept One:           Power

“You’ve got the power…”, nope-wrong idea, but here is the scope. Power means the ability to make something bigger. End of story. The larger the power, the smaller the object you can view. The smaller the power, then you are already looking at organisms that are relatively large. The compound microscope enlarges images through a series of lens and mirrors. By illuminating the image, a reflection of that image passes through the lens to the eye. Starting with the eye is the ocular lens. This lens is used for viewing and is the lens that is adjusted to focus on an object. The objective lens is next to the object and remains stationary while viewing. So how much bigger is the object? Well if you take the ocular lens magnification (on the side of the lens) and multiply that number times the objective lens magnification ( on the side of the lens) you have the total magnification or power that the microscope enlarges the object. Here is the catch. Magnification in this context, is how many times larger is the object your are looking at. For example, at low power on a microscope, the ocular lens is let’s say (10x). This means that the lens will make the actual object 10 times larger. The objective lens is perhaps 5X. So the actual object will now appear ( 5×10) or 50 times larger than it is in real life.

So what!

Well if we are looking at objects under the microscope, we have to realize that the tool, the microscope, is altering what is actualy occurring under the lens. All that we view is now larger than life and just to keep things interesting, all images are inverted and upside down. So if you are looking at an organism swimming to the left of your field of view, it is actually upside down and swimming the opposite way. This may be helpful to remember the next time you are trying to draw a moving organism.

So how do we draw these critters? Well let’s use the worksheet to explain…

Prior to answering questions, lets come up with a strategy to organize our work. This will make life and marking a lot easier.

How to lay out your work: (save this as a template!)

Record facts                        Do work or calculations                           Answer

here                                                    here

Write formulas

here

Problems..

Record facts                        Do work or calculations                           Answer

three lens                                                                  5 x 2                =          10   low power

2x                                                                                5 x 20             =          100 medium power

20x                                                                              5 x 200           =          1000 high power

200x

ocular=5x

Write formulas

ocular times objective = total power

Record facts                        Do work or calculations                           Answer

field of diameter = 10 mm             10 mm/ 4 =                                       2.5 mm

Write formulas

field of diameter/ # of object = actual size

Record facts                        Do work or calculations                           Answer

none                                                   use micrometer slide to measure

field of view

remember on average

low power     field diameter

Write formulas

4.

Record facts                        Do work or calculations                           Answer

high power diameter                      .45 mm / 20 seconds         =                      mm/sec

equals .45 mm                                always include units

Write formulas

field diameter (distance)

divided by time equals speed

5.

1. the source of light is actually quite good and can be focused to level of magnification, as you increase power, you need more light. The amount of light can be adjusted by using the diaphragm.
2. the organism may or may not be dead. If alive and you are using a slide with a concave depression in the slide, the critter is going to move up and down through the water. So you need to adjust focus as the critter moves. Correct answer
3. Usually the microscope remains at the same level of magnification. This may change not with time but with who is looking down the lens. Always remember to start with low power, switch to the next objective power and slowly adjust the fine tuning knob.

6.

Trick question…it depends on the type and size of cells. At low power, you would be able to see the largest field of view, so more distance. This is the obvious answer. However you may not be able to focus on small images and so you may have to move up to the next power to see these images. Don’t worry I don’t like trick questions either.

Questions

Chapter One/Two Notes:

• Big Ideas in Biology

1. Unity and Diversity
2. Changes with time
3. Structure and Function

Review:

In chapter one, we attempt to observe and define some of the attributes of life. We note that all activities of life arise from living things. Through experimentation and the invention of the microscope, we can now theorize that all living things are composed of cells. Therefore; as basic units in biology we can state that cells are the basic unit of life and that there can be as many as six different activities of life observed by all living things. We also noted that in the subcellular level, cells are composed of molecules and that these molecules help regulate and continue the activities of life. We could say that we have outlined some of the parameters of what links all living things together. Therefor exploring part of one of the big ideas in biology, which is Unity and Diversity. Put simply there are several factors, including cellular and molecular structures and activities, which link all living things based upon cellular and molecular activities.

In this next chapter we are going to explore, the other half of this idea, that idea of diversity.

Developing an idea:

Idea Number One: Activities of Life and Adaptation

From the previous chapter, we noted that one of the activities of life is the ability to adapt.

Adaptations put simply is the ability to respond to changes in or around an organism. These changes allow the organism to improve chances of survival. This ability can be inherited and increase an organisms chance of survival.

Idea Number Two: Levels of organization

The next question is:

“ If organism can be so similar, then how do or how did they become so different?” To explain this change we have yet another theory classified under the concept of evolution. Evolution can be thought of as the change of organism over a period of time. This is yet another big idea in biology “ Changes with time”.

Some questions to ponder:

1. If organisms change with time, how can that change be shown?

• Is the change shown similarity or diversity?
• Does the change shown directly or indirectly?

2. If organism change with time, what is the mechanism that creates that change?

Types of proof in regards to evolution

Like the cell theory, we need proof or evidence to create a theory:

For the theory of evolution we have two types of proof

1. Direct Evidence

• fossils offer direct evidence of pathway, or evolutionary history. This pathway can be considered to be a history to show origins of species and how they changed. This history can be used to explain organisms phylogenic or evolutionary history.
• fossils are created due to preserved hard parts of organisms. Fossils can either be original body parts or imprints preserved or “ petrified” with mineral matter.
• fossils can be used to show geological time scales
• fossils can be used to show two types of evolution, called divergent and convergent evolution.

• Divergent Evolution:

process where original organisms evolve into variety of distinct species. Each new population then becomes a new distinct species. Fossil histories can have gaps and so biologist have to hypothesis as to original species, which lead to a variety of species. Put simply a primitive ancestor has the potential to adapt to a variety of environments through structural changes, behavioral change or changes in reproduction. Divergent evolution often notes changes in structures of fossils to create “ family trees” for organisms.

• Convergent Evolution:

process of development of similar forms from unrelated species due to adaptation to similar environment. Best example: Marsupials in Australia. Another definition: similar forms in geographically different areas responding to similar environments.

Comparing Divergence to Convergence:

convergent evolution occurs when two dissimilar species change in response to similar environmental conditions and show development of similar characteristics.

Example: Kangaroo and the deer

similarities: in location of eyes, type of teeth, long ears and herd behavior

dissimilarity: marsupial verses placental ancestors

Divergent evolution occurs when members within a singes species change in response to a new and different environmental condition, and each population develops into dissimilar characteristics.

Example: Primate ancestral groups evolving into specific of apes

2. Indirect Evidence

Often instead of looking at fossils, biologist can look at current species and use other methods to hypothesis their family background. If we assume that adaptation is an inherited trait, then we can look at patterns of inheritance through embryological , structural, physiological or biochemical evidence.

( remember: How many and what are the types of indirect proof ?)

• Embryology:

Each organism starts off as a simple cell. If it divides into a multicellular organism the cells divide and create unique structures. An embryo is the prebirth stage of living organism. Embryology is the study of organisms in their earliest stages of development. In the 1800’s it was noted that several organisms show similarities in their embryonic development. This observation brought forth the statement and a theory of recapitulation:

“ Ontogeny recapitulates Phylogeny”

In simple terms, each organism shows their evolutionary history ( phylogeny) in its own embryonic development ( ontogeny).

• Homologous and Analogous Structures:

                     Homologous Structures:

                     Often organisms will have similar structures but these structures serve different functions. This is an example of an indirect proof of divergent evolution. Key thing to remember. Similar structure but different function.

Analogous Structures:

                     Often organisms will show structures that provide the same function but have differences in structure. Key point, similarity in function but not in structure. This can also be used as indirect proof of divergent evolution.

Vestigial Structures:

                   Sometimes creatures have structures that serve no apparent function, like hips on snakes or a human appendix. A structure with no apparent function is said to be vestigial.

• Physiological Evidence:

Physiology:

                   How organs within an organism work is the study of physiology. For example observing and learning how organisms excrete waste, would be examining a physiological phenomenon. Tissues and chemical reactions within organs can be regulated by specific