evolution - bainbridge island school district · ocean creating an “organic soup” or ......

Evolution

Why not invoke the supernatural

(god or gods) to explain how we

got here?

• The task of science is to make use of nature’s

redundancy to describe the world simply.

• We can use only empirical data.

• Everything else is outside the realm of

science.

• We can’t use the methods of science to

confirm or reject the supernatural. (Science is

falsifiable; the supernatural is not.)

The National Association of Biology Teachers affirms that teaching biology must be in a standards-based instructional framework, upholding scientific integrity and the right to teach accurate and current science without penalty of political or religious influences on content. Experimentation, logical analysis, and evidence-based revision, based on detectable and measurable data, are procedures that clearly differentiate and separate science from other ways of knowing. Explanations or ways of knowing that invoke metaphysical, non-naturalistic or supernatural events are outside the scope of science and not part of a valid science curriculum.

Submitted by the NABT Board of Directors April 8, 2008.

Theories of Evolution

*Heraclitus:

543 – 477 BC

“Evolution might involve conflict and a struggle for survival.”

*Lamark: 1809

Inheritance of Acquired Characteristics

1. Organisms try to improve themselves and become more and more Advanced

2. The effort to improve causes the most used body structures to develop, while unused structures waste away (Principle of Use vs. Disuse)

3. Once a structure is modified, it is inherited by the organism’s offspring (Inheritance of Acquired Characteristics)

Weismann

Weismann performed an experiment that disproved Lamarck's hypothesis. Weismann cut off the tails of mice for hundreds of generations. No inherited change in tail length ever occurred.

*Phenotype changed

*Genotype did not change

Darwin 1831 1. There is Variation in populations

2. Some variations are favorable allowing you to live longer and reproduce more

3. Differential Reproduction: More offspring are produced each generation than can survive

4. Natural Selection: Those that survive and reproduce are those with favorable variations

5. Gradualism: Over enormous spans of time, small changes accumulate, and population change

Darwin

Was different because he came up with a MECHANISM that was TESTABLE:

The theory of evolution BY MEANS OF NATURAL SELECTION

Unlike many theories, his has not yet been disproven. Amazing!

Darwin Supporters 1. Darwin Awards 2. Moth & Finch experiments 3. Fossil evidence 4. Gradualism: geological processes are slow 5. Malthus-too many humans, not enough

resources=competition * Malthus was Darwin's good friend who

was an economist and they discussed the idea of competition for resources and it's effect on species.

6. Wallace-same idea as Darwin’s: * Evolution by natural selection. Wallace was the first to publish this theory, but Darwin had 20 years of research to back it up.

Early Earth

4.6 billion years old

Originally chaotic:

Volcanoes

• Produced gases

– N2, CO2, H2O, CO, CH4

– No O2; O in CO2, H2O, CO, CH4

» Know because rocks aren’t oxidized

• Extreme temperature variations

Lightening & UV Light

• Energy sources

How did the first organic

chemicals form?

• Oparin and Haldane hypothesized that

organic chemicals were made from the

gases of the early atmosphere and the

energy from lightening, UV light, and

radioactivity from the Earth’s core.

• These organic molecules accumulated in the

ocean creating an “organic soup” or

“primordial soup.”

Miller - Urey Experiment

Stanley Miller

Results of more recent, refined

Miller – Urey experiments

• 13 of 20 amino acids

• All bases of DNA and RNA

• Ribose

ALSO: found amino acids in

meteorites and

formaldehyde in the tail of

Haley’s comet.

Life may have originated in

undersea vents

Biological Evolution

• Organic compounds had to come together to

form complex molecules.

– Clay could have attracted, held, and catalyzed

the reactions between them.

• Molecules have to self-replicate

– Some RNA can, AND they work as enzymes

• May have been original molecule of life.

Biological Evolution, cont’

• Membranes have to form:

– Put amino acids and fat in water, fat will surround amino acids in spheres similar to cells.

• Split when they get too big.

• Are selectively permeable

Oldest Fossils

• Are composed of

microorganisms

• 3.485 billion years old

• Found in stromatolites

(mats of bacteria)

Earliest Life

• Bacteria (prokaryotes)

– Heterotrophs

• Didn’t have the machinery to photosynthesize

• Absorbed organic nutrients from the primordial soup

• Anaerobic, no O2 on early Earth

– Probably a bag of RNA and that’s it

• Similar to today’s prokaryotes (Ribose, Nucleic

Acid & Phosphate Group bound by Hydrogen)

Life on Earth

3.5 BYA: first anaerobic prokaryotes, (no O2 yet), heterotrphic

3.2 BYA: chemosynthetic prokaryotes, anaerobic, autotrophic

2.8 BYA: photosynthetic prokaryotes, anaerobic, autotrophic

2.5 BYA: aerobic prokarytoes (O2!), autotrophic, heterotrophic

1.5 BYA: eukaryotes, autotrophic, heterotrophic

Earliest Eukaryotes

• Developed by endosymbiosis:

– Theory by Lynn Margulis

– Large bacteria incorporated smaller, energy

producing bacteria

– Mutualistic, symbiotic relationship formed

eukaryotes from prokaryotes

• Large bacteria get nutrients

• Small bacteria get protection

Earliest Eukaryotes

Evidence for endosymbiosis:

• Mitochondria and Chloroplasts have

– Own DNA – like today’s bacteria

– Own ribosomes – like today’s bacteria

– Double membranes (outer may have been from

vacuoles that engulfed the bacteria)

Biodiversity Increased With the

Accumulation of Oxygen

Presently Earth has about 3 million different

kinds of organisms.

For variation you need sexual reproduction.

For sexual reproduction you need a lot of

energy.

To get a lot of energy (ATP) you need aerobic

respiration.

Biodiversity Increased With the

Accumulation of Oxygen

For aerobic respiration you need oxygen.

For oxygen you need photosynthesis.

For photosynthesis you need plants.

Variation did not come about until plants had

produced significant quantities of oxygen so

that aerobic respiration could take place.

Biodiversity and Oxygen

Level of Oxygen Gas (O2)

Number of different

kinds of organisms

600 million ybp 4.6 billion

SO: # of critters = sex = energy = O2 = photosynthesis

Darwin's ideas underlying evolution

1. variation exists among individuals in a population (varying phenotypes due to varying genotypes, variations due to mutations)

2. in some environments resources may become limited and individuals must compete for the resources (survival of the fittest)

3. those individuals best adapted to their environment will survive and pass their genes on to the next generation

(this is the Theory on Natural Selection)

Adaptation: inherited trait or characteristics that increases an individual's survival in a particular environment

Empirical Evidence of Evolution

Fossil Evidence

• Study of fossils = paleontology

• Record is incomplete

– Most organisms decay

– Not all found

• NOTE: Older fossils found in deeper rock

– Not many people who hunt for them

Empirical Evidence of Evolution

Fossil Evidence

• Best finds: Intermediate forms (species to species)

– E.g., Archaeopteryx & China fossils

• Feathers and wings of birds, but teeth and tails of reptiles.

Empirical Evidence of Evolution

Homologous Structures

Empirical Evidence of Evolution

Embryology

Empirical Evidence of Evolution

Genetic Information

Origin of Species

• Individuals do not evolve, populations do.

• Evolution

– change in a population through time

– Source of changes in genes

• Mutations

• Recombination at fertilization

• Crossing over

• Independent assortment

Meiosis

Origin of Species

• Microevolution

– Change in gene frequency within an individual

population.

• Studies can help us tell what is going on in the

environment.

• Have to look at the gene pool

Hardy-Weinberg Law (useful for studying large, sexually

reproducing populations)

A population will NOT change IF

1. There is no mutation

2. Mating is completely random

3. There is no migration in or out

4. Natural selection does not occur (one

individual is not favored over another)

Hardy-Weinberg Law And How often does this happen?

NEVER – all populations evolve because

eventually the environment changes

http://zoology.okstate.edu/zoo_lrc/biol1114/tutorials/Flash/li

fe4e_15-6-OSU.swf

Microevolution Example

Natural Selection of the Peppered Moth

Microevolution Example

Kinds of Selection: based on fitness

Stabilizing Directional Disruptive

Microevolution Example

Genetic Drift in Beetles: Occurs in small populations

because the chances of coming up with the

expected results is low compared to a large

population.

Microevolution Example

Founder Effect

Migrate out and

found a new

population with

different gene

frequency.

Microevolution Example

Bottleneck: number of organisms is drastically

reduced for a few generation and the ones that

survive have a different gene frequency.

This population increases.

Origin of Species

• Macroevolution

– Change in species

– Source of change in species = MUTATIONS

– Inherited variations give some individuals an improved chance to survive and reproduce as the environment changes.

• NOTE: ENVIRONMENT = LIVING THINGS TOO!

– Viruses and Bacteria

– Competitors

Origin of Species

• Organisms do not intentionally change.

They cannot “will” a mutation because they

“need” it. Those with mutations that help

them survive do. Those without, die.

Origin of Species

• For new species to evolve

– Two populations become so different in their

genetic makeup that they can no longer

interbreed.

– Most common mechanism that separates

populations: geographic isolation.

Geographic Isolation

Prezygotic Isolation

Other Forms of Isolation

Gamete Isolation –

sperm not

chemically

attracted to egg or

not gain entry to

egg

Prezygotic Isolation

Other Forms of Isolation

Seasonal

Isolation –

Trees may

give off

pollen at

different

times of

year

Prezygotic Isolation

Other Forms of Isolation

Zygote

doesn’t

develop

normally,

or produces

a sterile

offspring.

Postzygotic Isolation

Back to Geographic Isolation

New environments with few competitors

allow populations to easily separate and

go their own ways. Speciation will result

– Called adaptive radiation

Evolution - Rate

• Darwin:

– gradualism

• Niles Eldridge and Stephan J. Gould:

– Punctuated Equilibrium

• Fossil evidence shows long periods of stasis

followed by rapid change

Gradualism

Punctuated

Equilibrium

Extinctions - Many

So What Do We Have

Today?

3,000,000 different types

of organisms.

“Types” means “species”

Species Concept

Two organisms are of the same species IF they

• Breed naturally

• Produce fertile offspring

“Species” is a man-made

term to help us organize

our thinking

Classification of Organisms

= Taxonomy

Now based on evolutionary

relationships (DNA) rather

than just physical

characteristics.

Physical characteristics are

important still

– About the only thing we can

see in fossils!

Classification System Kingdom, Phylum (Division for plants), Class,

Order, Family, Genus, Species

Why not common names?

Which one of these is a gopher?

Florida Washington

Classification System

Binomial nomenclature = Two-name naming

system

• Invented by Carolus Linnaeus

– Uses Latin (dead language doesn’t change)

Classification System

• Species name = genus + specific epithet

– E.g.,

• Homo sapiens (humans)

• Amphiprion percula

(clown fish)

Classifying Organisms

• Cladistics - based on evolutionary

relationships and homologous

structures

– Compare shared derived characteristics

Classifying Organisms

• Elves, Gnomes, Leprechauns, and Fairies are thought to form an evolutionary group of little people with magic powers. However, the exact relationships are unknown.

• Infer the phylogenetic pattern based on the following information.

Classifying Organisms

• Pointy ears evolved from ears that were not pointy.

• Inhabiting woods is more primitive than inhabiting other places

• Ability to find hidden treasure evolved from the lack of such ability

• Ability to fly is primitive

Classifying Organisms

• Elves: pointy ears; haunt woods; can't find treasure; can't fly

• Fairies:ears not pointy: live in woods; can't find treasure; can fly

• Gnomes: ears not pointy; live in mines and quarries; find treasure; can't fly

• Leprechauns:ears not pointy; live in woods; find treasure; can't fly

Classifying Organisms

Fairies

X X Leprechauns

X X X Gnomes

X X Elves

NOT fly Find

Treasure

NOT

woods

Pointy

Ears

Classifying Organisms Fairies Gnomes Leprechauns Elves

Not Fly

Find Treasure

Pointy Ears Not live in

woods

Have Don’t Have

Evolution Nothing in Biology Makes Sense

Except in the Light of Evolution

Theodosius Dobzhansky (1900-1975)