Today is Thursday,September 3rd, 2015

Pre-Class:Who’s your daddy, evolution?

Tell your neighbor something about him. Also, get a smallish piece of a paper towel

for you/your neighbor.

Turn in:-Root Words

-Guided Reading (Ch. 22)

In This Lesson:Unit 1

Evolution Concepts

(Lesson 1 of 3)

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Today’s Agenda

• How to make sense of the whole of biology.• Charles “Chuck D.” Darwin• Other important figures in evolution.

• Where is this in my book?– Chapter 22.

By the end of the lesson…

• You should be able to describe the broad view of evolution.

• You should be able to identify three forms of selection.

• You should be able to cite evidence supporting evolution.

• You should know what it means to be evolutionarily “fit.”

Disclaimer 1: Your Challenge

• This evolution unit is going to be considerably more rigorous than our last mini-unit.

• You face the following challenges:– A LOT of vocabulary.– Being comfortable enough with the material to be

able to link concepts together on a test.• Good habits:– “Talking out” the concepts.– Teaching someone the concepts.– Meeting with me for extra help.

Disclaimer 2: Belief versus Fact

• I am an evidence-based teacher.• Evolution has a lot of evidence behind it, to

say the least.• Therefore I am teaching evolution.• Period: .

First Up: Challenge Questions

• “Challenge Questions,” for those who have not been in my biology classes before, are my way of testing your knowledge of the topics we are going to cover before we do so.

• This has zero effect on your grades.• Guessing will likely be necessary.– Don’t be afraid to do so!

Next Up:A Compact Evolution Summary (Part 1)

• There are simply not enough resources in the environment to support every individual organism.

• Specific sets of environmental conditions put often-intense pressure on organisms to survive:– Competition with other species/individuals– Limited resources– Predation

• Any trait that makes an individual more likely to survive and reproduce is an enormous advantage.

Next Up:A Compact Evolution Summary (Part 2)

• How does this advantage arise? Through genetic mutation.

• If the mutation can be passed down, it’s considered heritable.

• Because the mutation confers an advantage, it’s known as an adaptation.

• Heritable adaptations then spread through the population, increasing in frequency until potentially giving rise to an entirely new species.

• Thus, the Darwinian line: Descent with modification.

Note

• Please make sure you fully understand that last slide. You’re gonna need it.

• Questions?

19th Century Perspective

• By the time Darwin started making his observations, biology had come a long way in terms of its understanding of how species change over time.– Sort of.

• First, the spontaneous generation concept had been disproven at long last, partially due to the Redi experiment, which we will now label just for extra practice.

Labeling the Experiment

• Francisco Redi was one of the first to prove that maggots don’t come from rotting meat.

• He used three jars: one open, one covered with netting, and one sealed.

• Into each he placed bits of meat and let it rot.• His hypothesis was that maggots come from

flies.– Notice that this is a testable hypothesis.

Labeling the Experiment• What’s his control?• What’s his independent variable?• What’s his dependent variable?• What are the constants?

http://faculty.sdmiramar.edu/dtrubovitz/micro/history/Redi.html

Jar 1: Jar 2: Jar 3:Flies No flies No flies

Answers• Control– Meat in the open jar (Jar 1).

• Independent Variable– Jar coverings.

• Dependent Variable– Maggots/flies.

• Constants– Same jars, same meat, same location.

Da Scientistz

• After Redi, the accepted thinking by most was that creationism was the answer.– All species were created by a supreme being around

3000 years prior to the present.• So now, the pre-Darwinian evolution-related

scientist-people with-hyphens.– Note: We’re going to be exploring more evolution

scientists in greater detail. These are perhaps the most important of the pre-Darwin figures, however.

Georges Cuvier• Established paleontology as a field of study.• Rejected early evolution hypotheses.• Believing that the biodiversity of fossils is due

to separate creation events.

Thomas Malthus

• An economist by trade, Malthus identified that resources are limited.

• There are not enough resources to support all individuals, therefore, not all individuals will survive.

Jean-Baptiste Lamarck

• Characteristics are acquired and then passed down.

• In other words, a giraffe stretches its neck out very far, which it then passes down to offspring.

• Close…– …but close only counts in horseshoes,

hand grenades, and bad breath.• In reality, if I were to chop off my

thumbs, my kids would still have thumbs.– Acquired traits are not heritable.

The Lamarck Disclaimer

• Most textbooks portray Lamarck as a bit of a…dunce.– Ha! Acquired traits being heritable. Please.

• Turns out he was actually not really a scientist but more a philosopher.– He promoted both the now-called Lamarckian view and the

evolution view.– Even Darwin was, at one time, a supporter of the acquired traits

deal.• Most importantly, recent research in epigenetics suggests that

mutations are not entirely random.– Genes can “jump” (jumping genes) and can activate/deactivate

others in response to environmental stressors.• Lamarck, even if we label the acquired traits view as his, was

not entirely wrong.

The Big Picture

The Darwinian Revolution

• And then there was Charles Darwin.• Darwin spent 5 years on the HMS

Beagle as a younger, less bearded 22-year-old, which turned out to be crucial to his understanding of descent with modification, aka evolution.– All this at a time when Europe believed in a

divine creation event only a few thousand years before.

• Among other destinations were the Galapagos Islands, and having small but isolated populations and ecosystems to study was essential.

But wait!

• Turns out Darwin wasn’t the only one onto the whole evolution thing.

• Alfred Russel Wallace, also bearded, was working toward similar conclusions.

• Wallace was working in the East Indies (think Indonesia), where he discovered, among other things, the Wallace Line.

The Wallace Line• Wallace noted that on the

west side of the line, most species were “Asian-like,” (placental mammals), whereas east of the line animals were “Australian-like” (marsupials), though similar.

• The line, therefore, is a biogeographical boundary of genetic isolation.

http://1.bp.blogspot.com/-Qvvxbs1hN1c/UXqP8qTME8I/AAAAAAAABic/I0VIyTgiEl0/s1600/wallace+line.gif

Back to Wallace

• Years after Darwin started formulating his theory (but never having published it), Wallace sends Darwin a draft of his findings.

• Darwin realizes he’s going to lose credit.• Darwin publishes The Origin of Species and gets

credit.• Ernst Mayr later breaks down Darwin’s ideas

into the following observations and inferences.

Observations

1. More individuals are born for each species than survive to reproduce themselves.

2. Populations tend to remain stable except for seasonal fluctuations.

3. Environmental resources are limited (Malthus, remember?).

4. No two individuals in a species are exactly alike.5. The variation among individuals can often be

passed down.

Inferences (therefore…)

1. Individuals in a population must struggle for existence and not all will survive.

2. Survivors are not “selected” randomly. Those with traits that make them more “fit” for their environment (or reproduction) are more likely to survive.

3. The environment’s favoring of some traits leads to gradual change in a population toward the most fit form.

In other words…

Homework: Evolving Views

• To better understand the historical context behind evolution, you and your lab partner will do a short research project on a scientist.– How short? You’re preparing only one PowerPoint

slide (or similar image).• Your scientist matches the number of your lab

station.• Next class, you’ll “present” your scientist to other

students.– Not a formal presentation, FYI.

Fitness

• Included in those inferences was a mention of the word “fit,” as in, “fitness.”

• Fitness is the measure of an individual’s adaptation to its environment.– The best-adapted are the most fit.

• The most fit organisms are those that are most likely to survive and reproduce successfully.

IMPORTANT: Fitness Test

• Who’s most fit?A. The top predator in a food chain.B. A mouse that rears 11 total surviving pups.C. A 300 year old tortoise with no offspring.D. A bull elephant with superior strength.

• The correct answer is B.• Key: Fitness only has to do with surviving and

reproducing.• It has nothing to do with strength, age, et cetera.

Wait…hold on a sec.

• Here we are, halfway through our first evolution lesson, and I haven’t defined evolution.– Though you should have a pretty darn good idea

of it.• Evolution can best be described as the

development of populations over time in response to selective/environmental pressures.

Forms of Selection

• We’re all familiar with natural selection, often called “survival of the fittest.”– There’s that “fit” word again.

• The environment exerts certain selective pressures:– Competition– Limited Resources– Predation

• These pressures create enormous advantages for individuals that are even slightly better-suited for dealing with them.– Thus, the environment selects for certain traits and selects

against others.

Forms of Selection

• There’s also artificial selection and sexual selection, both of which are worth mentioning.

Artificial Selection

• Canus familiaris is the species name of all dogs, from chihuahuas to Great Danes.

• The different “breeds” have been selected by humans over time to bring out the desired traits, like having a white-tipped tail, or being the size of a horse.

• Darwin identified this in pigeon breeds, plants, and other organisms.

So what is artificial selection?

• Long definition, so I’ll break it into parts. You write what you need to in order to understand it:– Artificial selection, also known as “selective

breeding,” occurs when humans create the selective pressures…

– …by setting up crosses (mating pairs) that possess desirable traits…

– …but because humans are doing this, it’s not natural selection.

Sexual Selection• The male Indian Peafowl is known for its

dramatic train feathers:

http://upload.wikimedia.org/wikipedia/commons/8/83/Indian_Peafowl.jpg

Sexual Selection

• Here’s the thing: having a big dramatic train doesn’t help you survive better (it’s actually worse).– Less aerodynamic.– Less camouflage.– Costs resources to produce and maintain.

• However, because having a grand feather display is a “go big or go home” kind of thing, it is selected for by peahens, and therefore is an adaptation.– This same thing explains lots of ornaments in animals and

gives rise to the Sexy Sons Hypothesis, wherein the flashiest males have flashy male offspring.

So what is sexual selection?

• Sexual selection is a form of natural selection in which one sex (usually females) apply the selective pressures.

• Some last comments:– Females (typically) use ornaments as proxies for genetic quality.

• “Girl, look at that display. He must have good genes.”

– Ornaments do not have to increase survival to be helpful.– In some cases, females may adjust their own investment in

their young according to the differential allocation hypothesis.• In birds, females may lay different numbers of eggs, lay eggs with more

favorable nutrient balances, or care for the young differently based on the genetic quality of the male.

Proof of Proxy

• Biologists have noticed proof that the whole “females use flashy behaviors or displays as evidence of genetic quality” thing exists.– How?

• Take the peafowl again.• Turns out, there’s a very strong correlation

between fanciest display and strongest immune system.– Pretty cool.

One last sexual selection example…

• Zebra Finches:• Males allocate

carotenoid pigment to their beaks, legs, and cheek patches to make them bright red.– Females love it.

• Give males green leg bands and suddenly they’re not so attractive.

http://www.rbgsyd.nsw.gov.au/__data/assets/image/0011/88535/Taeniopygia_guttata_Zebra_Finch_620.JPG

I know you think my beak is

attractive.

What drives selection?

• Okay, great, some traits are desirable (adaptations) and others aren’t.– This still doesn’t explain change.

• These changes are brought about by random changes in DNA – mutations.– “Random” is the keyword here.– Would I get a lot of women if I could fly? Probably.– But, that trait needs to arise by mutation, and it needs to be

heritable – I need to be able to pass it on.• As you can imagine, the work of Darwin and Mendel

combined make all of biology make sense.

Mutation and Selection in Action

• Peppered moths exist in one of two color morphs – light or dark.

• Generally, light colored moths blend in with their environment much more effectively.– At any given time, there are more light colored

moths around because the dark ones get eaten.– The environment selects for light colored moths

and against dark colored moths.• However, increased air pollution in the

Industrial Revolution temporarily darkened the bark of trees throughout Great Britain.– Suddenly, the favorable trait was to be dark

colored.

Peppered Moths

• Population numbers shifted dramatically as a result of the change in the environment, only to change again (back to favoring light colored individuals) when pollution cleared up years later.

• Importantly, no individual moth ever changed color.– Instead, evolution occurred between generations – light

colored moths briefly began to be eaten more often prior to reproduction, meaning the gene(s) for being light colored were less abundant in the population than those for being dark colored.

Other Examples

• Antibiotic and insecticide resistance are becoming major issues today.

• Not all individuals are killed, allowing those that are resistant to pass on their genes and give rise to an entire resistant population.

• Think MRSA:– Methicillin-resistant

staphylococcus aureus.

Antibiotics and Selective Pressure

• Using (and misusing) antibiotics (or even Purell) is a cause for developing resistance.– The antibiotics create INTENSE selective pressure on

bacteria, which have a relatively high mutation rate.– Any mutation on the part of the bacteria that allows for

drug resistance will lead to rapid growth of drug-resistant bacteria.

• The solution?– Use a wide array of treatments and don’t apply such

intense pressure. Use antibiotics (et cetera) as minimally as possible.

Uh…excuse me…

• You know how many diseases are hereditary?– Like, Type I Diabetes, for example?

• Exactly how might these disease-causing alleles still be in the gene pool?– Natural selection would predict that these individuals

should be at a disadvantage and the alleles slowly be “shuffled out.”

• Two possibilities for why they’re here:– Modern medicine is preventing their removal (unlikely).– They’re vestigial alleles. As in, they serve(d) a different

purpose.• Survival of the Sickest excerpts.

Evidence for Evolution

• Fossils– Unlike Cuvier’s thoughts, the fossil record (in rare areas of relative completion)

shows gradual changes through time.• Geographic Distribution:

– Fossils are distributed only in areas where related species could have lived.• Homologous Structures*:

– Similar anatomical traits exist between closely-related species.• Vestigial Structures:

– Organs that carry no apparent present function are maintained by current populations – they must have served a purpose in the past.

• Embryology– Early developmental stages look very similar in closely-related species.

• DNA– The big one – DNA is strikingly similar between closely-related species (99%

similar DNA between humans and chimpanzees & bonobos).

Homologous Structures

• Simply put, these come up all the time in bio tests.• Homologous structures are features of organisms’

phenotypes that look similar because they come from a common ancestor.– Example: A horse’s hoof and a dog’s foot have similar

bones because they share a common ancestor.• Analogous structures are features of organisms’

phenotypes that look similar but the similarity is a coincidence because they evolved separately.– Example: A bird’s wing and a bat’s wing look somewhat

similar, but each evolved independently.

Closure

• TED: Paul Andersen – The Five Fingers of Evolution

• TED: Alex Gendler – Myths and Misconceptions About Evolution

Closure: Chicken or Egg?

• So, which came first, the chicken or the egg?– You should be able to answer this now, in one of two ways.

1. Reptiles evolved before birds, and therefore were laying eggs before birds.– Since proto-reptiles are also thought to have given rise to

birds, it makes sense that birds also lay eggs.

2. Given that evolution occurs between generations, the parent of the first chicken was not a chicken.– Therefore, the egg came first.