Be sure that you read through our Unit 7 online lecture this unit on Evolution as well as your text book readings. Open the Unit 7 Experiment Answer Sheet and work through the first two exercises.

Evolutionary Change and Natural Selection – Introduction

Evolution is descent with modification and includes small-scale evolutionary change (microevolution) as measured by changes in gene frequency in a population from one generation to the next and large-scale evolutionary (macroevolution) change as evidenced by speciation events. Several mechanisms contribute to evolutionary change, such as natural selection, a process in which individuals with certain beneficial traits are more likely to survive and reproduce. Natural selection is also responsible for the loss of lethal or detrimental traits from a population. It is important to keep in mind that evolution does not act on individuals; it acts on populations. Natural selection, however, does act on individuals within a population and can result in evolutionary change of that population over time.

Populations do not always change due to Natural Selection, since there are several conditions that must be met in order for Natural selection to occur:

Individuals within a population must vary; they do all exhibit identical traits.
Some traits are “better” than others or “worse” than others.
The traits that vary are heritable and not simply acquired.
The “better” individuals have more success reproducing and produce more offspring.
IF these conditions are met, then in successive generations, more offspring will exhibit the beneficial trait (or conversely, a detrimental trait will be lost).

Recall that DNA contains sequences that code for particular proteins or traits, these sequences are called genes. The alternate forms of genes are called alleles and these alleles exist in pairs because chromosomes exist in pairs. A dominant allele is one that masks another (recessive) allele; dominant does NOT mean a given allele is more frequent or necessarily better. A recessive allele is one that requires two copies to be expressed. Evolutionary biologists are interested in the frequency of alleles within a population and how they change over time (= microevolution).

Be sure that you read through our Unit 7 online lecture this unit on Evolution as well as your text book readings. Open the Unit 7 Experiment Answer Sheet and work through the first two exercises.

Mechanisms of Evolutionary Change – Introduction

There are other mechanisms besides Natural Selection that can lead to evolutionary change. These include:

Genetic drift (random changes in the gene pool)
Mutations
Gene flow (e.g., immigration and emigration)
Nonrandom mating (e.g., inbreeding, sexual selection, assortative mating)
Be sure to review our online lecture on Evolution and pp 260-264 in your book before starting this exercise. You will be using the following website for this exercise. Be sure you are able to open it and use it:

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So far we have established that the action potential and epsp’s and ipsp’s are caused by opening channels for ions in the neuron’s membrane. Voltage changes in the membrane open voltage-dependent channels to trigger an action potential, and neurotransmitters from an axon bind to receptor molecules in a dendrite or cell body to open ligand-gated channels to trigger an epsp or ipsp. Ligand is another name for transmitter, and for action potentials and epsp’s the channels are gates for sodium ions.

There’s one more complication: Ionotropic, or ligand-gated, receptors operate more simply than metabotropic, or g-protein-coupled, receptors.

Imagine you are a transmitter molecule that wants to open a door for ions to enter into a house. If your hand fits the doorknob (receptor), the door opens and ions can enter. That’s how an ionotropic receptor works. Metabotropic receptors are a variation on the ligand-gated theme. After the transmitter binds to a receptor, a mechanism is set in motion inside the neuron to open a channel for ions at another place nearby. When the transmitter binds with a metabotropic receptor it’s as if you, the transmitter, had to ring a doorbell rather than grasping a doorknob. That sets in motion a mechanism inside to bring someone to open the door, which is located to one side of the doorbell, so the ions can troop in. Now for drugs.

Drug Actions

Drugs may influence synapses as neurotransmitter agonists or antagonists. Drugs may act as agonists to facilitate the synthesis of transmitter or block its reuptake so that more transmitter is available. Or they may block the synthesis and release of transmitters as antagonists.

Drugs may also act on receptors for transmitters by stimulating (agonist) or blocking (antagonist) them. Drug actions are often specific to the receptors for a particular transmitter.

Drug actions on the brain have effects on behavior. Unfortunately we can’t predict a behavioral effect of, say, a receptor blocker unless we know the brain system on which the drug is acting. When we have some idea of the site of action, we can sometimes make predictions, such as that cocaine, amphetamine, and methylphenidate will have similar effects despite differences in their actions. However, it’s a good idea to keep in mind the principle that all drugs have multiple effects. Although we classify drugs by their main effects—as stimulants, hallucinogens, and so on—we must not forget their “side” effects, which could be lethal.

Dose-Response Curves

So far I hope you will agree that drugs act at synapses to produce most of their effects on behavior. However, a physician will not prescribe a drug on the basis of the amount that will reach synapses in the basal ganglia or hypothalamus. Instead, the dose is based on the concentration of the drug (in milligrams per kilogram of body weight) and the body weight of the patient (in kilograms). How gross.

This means of dosing a patient works because of dose-response curves, which show the average result on a behavioral measure of different doses of each drug. The dose that is effective for half of the subjects is called the median effective dose, or ED50. The lethality of a poison is expressed by its median lethal dose, or LD50.

Please respond to either of the following:

In the comedy Arsenic and Old Lace, two elderly sisters poisoned their gentlemen roomers with elderberry wine that contained arsenic. (The wine also contained strychnine and a pinch of cyanide, but let’s ignore those.) They got no help from their nephew, played by Cary Grant; but then, he knew nothing of median effective doses or dose-response curves. Since you do, what advice could you give the elderly sisters to make sure the wine was lethal without wasting a lot of arsenic?

Videos 5 & 6 do not distinguish between a drug’s actions at a synapse and its effects on behavior. The psychoactive drugs we are concerned with have multiple effects: For example, cocaine and alcohol affect behavior in more than one way. How may a single drug produce multiple effects on behavior and the mind? (For hints, look at just the table (chart) showing how actions are linked to effects. Does a drug always have a single action, or a transmitter a single effect? Look at the Army’s concern about this when it evaluated some mind-enhancing drugs for soldiers.)
Rubrics
Participation

Question

1 of 20

Which of the following is a colonial form of green algae?

Giardia

Thiobacillus

Volvox

Paramecium

Question

2 of 20

Land was first colonized about ______ years ago.

100 million

500 million

570 million

1.7 billion

Question

3 of 20

In angiosperms, the male gametophyte develops within ______.

male cones

mycelia

filaments

anthers

Question

4 of 20

Under what abiotic conditions can monomers spontaneously form polymers?

When water evaporates from a hot surface

When ribozymes are present to catalyze the reaction

With the addition of water

By biogenesis

Question

5 of 20

Gametophytes reproduce ______.

by fission

by producing sperm and eggs

by alternation of generations

by budding

Question

6 of 20

Under ideal conditions, prokaryotes are capable of reproducing at a(n) ______ rate.

hypergeometric

exponential

infinite

arithmetic

Question

7 of 20

A pollen grain is a ______.

female gametophyte

sporophyte

type of seed

male gametophyte

Question

8 of 20

Where and when does fertilization occur in the mushroom life cycle?

Underground, as a mycelium begins to spread.

On the surface of the ground, when a spore germinates.

In a mushroom, when nuclei of a heterokaryotic cell fuse.

In a mushroom, when sperm and eggs meet.

Question

9 of 20

According to the theory of endosymbiosis, which organelles evolved from small prokaryotes that established residence within other, larger prokaryotes?

Vacuoles and lysosomes

Golgi apparatus and endoplasmic reticulum

Centrioles and ribosomes

Mitochondria and chloroplasts

Question

10 of 20

What global climatic change gave gymnosperms an advantage over ferns?

The climate becoming hotter and wetter

The climate becoming cooler and drier

Increased fluctuations in global climate

The climate becoming cooler and wetter

Question

11 of 20

Which protozoan group consists solely of parasitic forms?

Apicomplexans

Ciliates

Flagellates

Amoebas

Question

12 of 20

An explorer found a plant that had roots, stems, and leaves. It had no flowers but produced seeds. This plant sounds like a(n)

fern.

bryophyte.

angiosperm.

gymnosperm.

Question

13 of 20

Plants first moved onto land at least ______ years ago.

65 million

475 million

1.2 billion

3.5 billion

Question

14 of 20

The prokaryotic group that tends to inhabit extreme environments belongs to the ______.

kingdom Monera

kingdom Protista

domain Archaea

domain Monera

Question

15 of 20

In angiosperms, what structures house female gametophytes?

Ovules

Petals

Stigma

Sepals

Question

16 of 20

Flagellates, amoebas, apicomplexans, and ciliates are all what type of protist?

Slime molds

Protozoans

Diatoms

Dinoflagellates

Question

17 of 20

All prokaryotic and eukaryotic organisms that photosynthesize fit into which nutritional category?

Chemoautotrophs

Photoheterotrophs

Photoautotrophs

Chemoheterotrophs

Question

18 of 20

From the point of view of an angiosperm, what is the function of fruit?

It is where the male gametophyte develops.

It provides structural support for the plant.

It is a mechanism for the dispersal of seeds.

It attracts pollinators.

Question

19 of 20

Whose experiments demonstrated that, given the conditions on the primitive Earth, biological monomers could arise spontaneously?

Miller and Urey

Darwin

Watson

Margulis

Question

20 of 20

Like plants, fungi have ______; however, in plants they are composed of ______, whereas in fungi they are composed of ______.

cell walls; cellulose; chitin

cell walls; cellulose; peptidoglycan

cell membranes; phospholipids; peptidoglycan

cell membranes; cellulose; phospholipids