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2. biology

How to Integrate STRANGE BIOLOGY Topics into Your Biology Curriculum
The world of biology is not as completely known or understood as we learned in middle school. For nearly every
‘rule’ in biology (mammals are warm-blooded) there is at least one exception (Naked Mole-Rat) and entire
ecosystems that were once inconceivable to “learned” scientists have been discovered within the last 30 years
(hydrothermal vent ecosystems). More than that, whatever ANY form of life is capable of (eg - limb regeneration)
scientists may find a human use for the processes. Einstein once said “Imagination is more important than
knowledge.” Today’s students could become the scientists of tomorrow who find a way to engineer cryptobiosis for
space flight or echolocation for the blind. Let’s teach them the foundations, the exceptions and get out of their way.
TOPICS LIST
INTRODUCTION: In the world of biology, truth really is stranger than fiction
Topic 1: The Scientific Method – This ain’t your daddy’s theory!
UNIT I –LIFE IN BOILING W ATER
How do organisms survive in temperatures above boiling? If they can live in boiling water then why do they die at
room temperature?!
Topic 2: The Chemistry of Life
Topic 3: The Cell Membrane
Topic 4: Proteins are Machines - Enzymes
Topic 5: Bacterial Structure
Topic 6: Strange Biology - A description of how hyperthermophiles thrive in temperatures that would destroy
99% of earth’s life. Interestingly, these hyperthermophiles also REQUIRE high temperatures for survival and will
die if brought to room temperature.
UNIT II – KIDNAPPED BY ALIENS
In the classic movie “Alien”, an extraterrestrial life form incubates her embryos inside of humans. When they are
ready to be born, they burst out and kill the hapless victim. There are such things among us that, unable to bear
their own young, use humans to reproduce their kind even though it injures or kills the hapless human hosts.
Topic 7: DNA and RNA
Topic 8: Gene Expression and Regulation
Topic 9: Biotechnology
Topic 10 Strange Biology - A description of the viral infection of cells. Like the creatures in ‘Alien”, viruses
abduct the energy and cellular machinery of animal (or bacterial or plant) cells to reproduce more viruses often
killing those cells as the progeny burst free to infect more cells. In another parallel with the film, our immune
system will kill infected cells rather than allow the viral incubation to be completed.
UNIT III – W HAT IF SUNBATHING MADE YOU FAT? - Elysia chlorotica
Unlike animals, plants do not ‘eat’. They use water, CO2 and sunlight to manufacture sugars and ultimately all of
their organic molecules. If we could do this, a lunch break would mean sitting outside on a lovely day and
sunbathing too much could make you fat!
Topic 11: Eukaryotic Cell Structure
Topic 12: Photosynthesis – Energy from the Sun
Topic 13: Biology of Plants and Algae
Topic 14: Strange Biology- The Sea Slug Elysia chlorotica steals algal chloroplasts and houses them in their own
cells. They turn themselves into animal-plant chimeras that do not need to eat as long as they get sunlight!! Even
stranger, they can keep the captive chloroplasts alive for many months.
UNIT IV – TRUE MUMMIES - Tardigrades
Tardigrades (‘water bears’) are animals that can enter a state (cryptobiosis) indistinguishable from death for
decades and re-animate with a single drop of water!
Topic 15: Water is Life
Topic 16: Osmosis and diffusion
Topic 17: Taxonomy of Life
Tydell
Introductory Biology: Lessons from Strange Biology
Topic 18: Strange Biology- As the environment begins to dehydrate the tardigrade, it begins to make large
amounts of a special sugar, a disaccharide called trehalose. By water substitution and vitrification, trehalose
puts every protein and cell membrane into a state of suspended animation, a real-life mummy. A single drop of
water dissolves the trehalose and life begins again as if nothing has happened!
UNIT V – A LIFE IN THE DESERT WITHOUT EVER HAVING A SIP OF W ATER
The Kangaroo Rat (Dipodomys californicus) is not just adorable, although it lives in the desert it can easily live its
entire adult life without ever taking a sip of water! How does it do it?
Topic 19: The Respiratory and Renal Systems
Topic 20: Energy Metabolism – Aerobic respiration
Topic 21: Strange Biology- Increased efficiency and special behaviors allow the kidneys, skin and lungs of
these desert rodents to conserve body water in the arid desert climate. Of the water they lose, just 10% is
replaced by moisture in the seeds they eat and 90% is replaced by water released by carbohydrate metabolism.
UNIT VI – THE DUCKBILL PLATYPUS HAS A SIXTH SENSE, BECAUSE AN EGG-LAYING MAMMAL WASN’T W EIRD ENOUGH!
The platypus is a small warm-blooded animal that lives in Tasmania and eastern Australia. It is odd in a myriad of
ways. The platypus has the bill of duck, feet like an otter, the tail of a beaver and a venomous spur. It lays eggs
but nurses the hatchlings. Most STRANGELY, the duckbill platypus hunts in murky waters with its eyes, ears and
nose closed. It has been proven that it finds its prey, small crustaceans, through a true “SIXTH SENSE”. What is it?
Topic 22: Action Potentials in Excitable Cells
Topic 23: The Nervous System and the 5 Human Senses
Topic 24: Sensation is not Perception
Topic 25: Strange Biology- The sixth sense of the platypus is the ability to perceive electricity. Their duckbill
holds receptors that are very sensitive to motion (like our sense of touch) are paired with special receptors able
to perceive tiny currents of electricity that are made by the tiny muscles of their crustacean prey. There is
preliminary evidence that animals like elk and cattle are able to sense the magnetic fields of the planet.
UNIT VII – LIMB REGENERATION
Salamanders can re-grow amputated limbs. These new limbs are so perfect that they it is not possible to tell which
was once amputated. Could humans do this? Maybe.
Topic 26: The Musculoskeletal System
Topic 27: Developmental Biology
Topic 28: Strange Biology- A description of the way a salamander re-grows its leg. There is active research
into the hormones and proteins needed to allow human medicine to replicate this phenomenon in humans.
UNIT VIII – DEATH BY FISH - Electrophorus electricus
The electric eel (Electrophorus electricus) generates killing charges of electricity that are powerful enough to kill a
human as easily as you or I might lift a box. How!?!
Topic 29: Muscle Cell and the Action Potential
Topic 30: The Cardiovascular System
Topic 31: Strange Biology- The electroplaques of Electrophorus electricus are a subtle modification of the
Purkinje Fibers of the human heart. Here’s how they do it!
UNIT IX – YOU ARE ONLY 10% YOU! W HAT IS THE OTHER 90%? - Euprymna scalopes
If we were take all of the cells of your body and divide them into “human” and “not human”, we would find that there
are 10 times as many non-human cells sitting in your skin as human ones! The rest are mostly bacteria but they
are not simply tolerated by your human cells. It turns not that you can only be healthy if millions of bacteria are
present from the time of your birth!
Topic 32: The Digestive System
Topic 33: The Immune System
Topic 34: Strange Biology- There is a symbiotic relationship between the Hawaiian Bobtail Squid, Euprymna
scalopes, and a bacterial organism. The squid cultivates a pure population of Vibrio fischerii in a special organ.
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Tydell
Introductory Biology: Lessons from Strange Biology
If the squid never finds the bacteria, it cannot develop normally. Mammals that are raised in the absence of any
bacteria never develop a normal digestive system. Modern life seems to have made a world that is ‘too clean’
for our optimum health leading to epidemic levels of asthma and autoimmune disease.
UNIT X – GENDER CHANGE AT 30. JUST WHEN YOU START TO UNDERSTAND THE OPPOSITE SEX, YOU BECOME IT!
There are animals that are all born male and only some individuals become female later in life.
Topic 35: The Endocrine System
Topic 36: The Reproductive System
Topic 37: Strange Biology- Clownfish (like the cartoon character Nemo) are all born male. Amphiprion percula
live the early part of their lives as juvenile males, unable to reproduce. If the second biggest fish dies, the next
largest fish in the colony will “go through puberty” and become the reproductive male. If the largest fish is lost, the
nd
reproductive male (2 biggest) will change genders to become the reproductive female.
UNIT XI – VAMPIRES EXIST– Desmodus rotundus!!
Vampire bats are mammals that have true powered flight. They can echolocate, have the ability to ‘see’ infrared
radiation and have saliva that has a topical anesthetic and anticoagulant in it! How did this happen?!?
Topic 38: Patterns of Inheritance
Topic 39: Principals of Evolution
Topic 40: Strange Biology- The Tarsier and Aye-Aye are lovely hypothetical starting points for a thought
experiment asking the students to ‘make a bat’ in a stepwise fashion consistent with the rules of Darwinian
thought.
UNIT XII – W HAT IF MAMMALS LIVED LIKE BEES IN A HIVE? SOME DO! - Heterocephalus glaber
The Naked Mole-Rat, is neither a mole nor a rat but it is naked. Their skin is unable to perceive pain and they are
cold-blooded! Their teeth close OUTside of their lips and they have special adaptations for living in a low oxygen
environment. Strangest of all, their society is organized in a truly eusocial fashion, like bees or ants!
Topic 41: Animal Behavior
Topic 42: Population Growth and Regulation
Topic 43: Strange Biology- The Naked Mole-Rat Queens shove their subordinates around in shows of
dominance. This social behavior influences hormonal production by the worker NMR, shutting down its ability to
reproduce. Talk about “Mean Girls”!
UNIT XIII – SUNLIGHT IS OPTIONAL - Desulforudis audaxviator
There are ecosystems (like the black smokers) that exist independent of sunlight or photosynthesis.
Topic 44: What is an ecosystem?
Topic 45: Earth’s major ecosystems
Topic 46: Strange Biology- The Bacteria and Archaea that survive in the toxic brew around hydrothermal vents
on the ocean floor never receive a single photon of sunlight. They manufacture organic molecules by harvesting
energy when they break the chemical bonds of the toxic compounds in the water. These extremophiles form the
first trophic level of a most unusual food chain! Desulforudis audaxviator is even more extreme!
UNIT XIV – A VEGAN SERIAL KILLER - Pepsis thisbe
The Tarantula Hawk Wasp, Pepsis thisbe, feeds on nectar its entire adult life. Why then do they kill Tarantulas?
And why do they do it in such a spectacularly horrid way?
Topic 47: Competition for Survival
Topic 48: Predation and Parasitism
Chapter 49: Strange Biology- The Tarantula Hawk Wasp has a sting more painful than almost any other insect.
Although the adults are vegetarians, female Tarantula Hawk Wasps hunt Tarantulas in order to feed their young.
When a female Tarantula Hawk Wasp finds her prey, she paralyzes the spider with her venom and drags her
victim to a burrow where she lays a single egg on her paralyzed victim. When the wasp larva hatches, it feeds
on the living body of the spider, consuming it from least essential organs (intestines) to most (heart) before
finally killing it. The larger the Tarantula, the more likely the larva is to develop into a female wasp.
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Tydell
Introductory Biology: Lessons from Strange Biology
TOPIC 14 SUMMARY. ELYSIA CHLOROTICA
So, plants are plants and animals are animals, right? Not so fast! What should we call an animal that uses
chloroplasts inside of its cells to photosynthesize? A plantimal?
Elysia chlorotica is the scientific name for the Eastern Emerald Elysia. They are small aquatic mollusks, relatives of
the garden slug. Elysia can grow up to 2½ inches long but are usually about half that size. In the salt marshes and
shallow creeks where they live, they look quite a bit like dark green leaves with optical tentacles crawling along
the rocks under water.
Elysia chlorotica are green in color as adults because the cells that line their highly branched digestive tract are
filled with chloroplasts and these chloroplasts contain chlorophyll a and b. This should strike you as very strange
because chloroplasts that contain chlorophyll a and b were previously ONLY found in Viridoplantae, the land plants
and green algae. Did Elysia evolve from algae? That would be cool, but no. If these little mollusks were related to
algae we would find evidence in their DNA and Elysia do not have genes for making chloroplasts or for making
chlorophyll. So where do the chloroplasts come from?!? They steal the chloroplasts from the algae they eat. This
is called kleptoplasty and scientists are trying to figure out how the sea slug does it!
When Elysia chlorotica hatch from eggs, they do not contain chloroplasts and are not green. Young sea slugs feed
on green algae called Vaucheria litorea by piercing the algae cells and sucking out the contents as if they were
drinking a smoothy through a straw. Most animals that eat algae digest everything they slurp down but Elysia
(and a few of its close relatives) have a way of saving the algal chloroplasts from destruction while digesting
everything else. The cells that line their digestive tract phagocytose the chloroplasts. Originally, it was assumed
that Elysia acquired these chloroplasts only as camouflage, allowing them to hide from predators among the
green algae that is their food. The truth is even more interesting. Sunlight can shine through their slug-like
bodies hitting the chloroplasts inside and causing photosynthesis. Any glucose that the chloroplasts make can be
used by the sea slug. In the same way that a plant can ‘feed itself’ by photosynthesis, these sea slugs can nourish
themselves by ‘sunbathing.’ Ingenious!
That is not the whole story, though. Other sea slugs that can steal chloroplasts can’t keep their captured
chloroplasts alive and have to keep replacing them. Elysia chlorotica has a way to keep the chloroplasts it has
stolen alive. In Chapter 11, we learned about the Theory of Endosymbiosis. Evidence that mitochondria and
chloroplasts are the result of endosymbiosis includes the fact that these organelles contains their own DNA but
remember, they also need genes found in the cell nucleus to stay alive. When scientists examined Elysia’s nuclear
DNA they found evidence of “horizontal gene transfer.” Horizontal gene transfer is “any process in which an
organism incorporates genetic material from an organism without being the offspring of that organism.”
(Wikipedia) What researchers found in Elysia chlorotica was a gene identical to one used by Vaucheria litorea to
maintain its chloroplasts. Eureka! At some point in its evolutionary history, Elysia chlorotica has incorporated at
least one gene from its FOOD into the Elysia cell line DNA.
Horizontal gene transfer has been studied in prokaryotes like bacteria for a long time but scientists have had a
difficult time believing that it could happen in multicellular organisms, particularly animals. Now that we have
been looking for it, we have documented multiple examples of horizontal gene transfer even though we have very
little idea of HOW it could be happening. Could it happen in humans? We don’t actually know.
Now that we know that a sea slug can photosynthesize, how could scientists use this knowledge? Perhaps we
could put chloroplasts into the combs and wattles of chickens so they could make eggs with much less feed.
Could we make green cattle that make milk with half as much grain? Imagine interstellar colonists that can feed
themselves on long voyages with only UV light as food. Would it even be possible to eradicate hunger on Earth by
engineering chloroplast technology into people? What do you think?
Are you interested in growing Elysia chlorotica in your classroom?
Then check out the website http://sbe.umaine.edu/symbio/index.html
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