Super Males

March 27, 2013 at 2:05 PM (Genetics, trivia)

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Here is a very strange fact about certain fish species; they can change sex. We usually think of animals as fairly evolved creatures and when a female or male animal is born, it stays whichever sex it started as. But not certain fishes such as the members of the wrasse family or Parrotfish. They are called protogynous hermaphrodites.

If you break down the words in proto (first), gyn (female), they are fish who start out female and then change to male. The small immature wrasses are brown or cyptic (camouflage). They start life as females and lay eggs which are fertilized by the males. As the fish grow and age, they become less female and more male. They turn pretty colors and take on harem collecting behavior. They eventually become functional males that fertilize their harems.

There are many theories of evolutionary fitness that may explain why the wrasses go through this metamorphosis. I’m not sure I buy all the explanations but you may want to read for yourself here http://en.wikipedia.org/wiki/Sequential_hermaphrodites.
There may be an environmental advantage to a species doing this. If the environment is harsh and the populations are starving and not doing well, more of the fish will stay in the small female stages longer to make more eggs and improve the number of animals. Anyway, I found this story an interesting thing to learn about after we saw this fish at the Florida Aquarium in Tampa, Florida.

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Dwarf Alberta Spruce Sports

July 10, 2011 at 4:01 PM (Botany, gardening, Genetics, trees)

Most of the time when you hear the word “sport” you think of a game like soccer or baseball. In botany there are sports of another kind. Occasionally, a plant will develop a very different looking branch compared to the rest of the plant. Sometimes this branch has characteristics that make it desirable to nurserymen to propagate a new type of the plant. If they can get a cutting going and grow the whole branch out into a plant on its own roots or graft it onto a rootstock, they may have a new variety of the plant that can be propagated for commercial purposes. These sports are highly desired because of this.

An example of a sport that has become a popular garden plant is the dwarf Alberta spruce. It is a dwarf variety of a white spruce (Picea glauca). Regular white spruce can grow in the forests up to nearly 100 feet tall. With the sport, the distance between the branches is very reduced. It may only grow a couple of inches per year. A twenty-five year old regular white spruce may be about 40 feet tall and a dwarf one may stand only 5-6 feet tall. This reduced branch growth makes the little tree very tight and compact. It is a very attractive small landscape shrub and commands a good price for the grower.

The large branch winging out is a normal Alberta white spruce without the dwarfing effect.

The picture above was taken of a Dwarf Alberta Spruce growing in a cemetery where it has attained the height of over 8 feet. Since it is actually a white spruce, genetically, it has all the makings of a big tree. Only the small genetic change that occurred in the sport branch has dwarfed the plant. Plants and other creatures make mistakes sometimes in their cell division when the chromosomes split and sort and divide. It was a mistake that created the sport in the first place and after many years and cell divisions later, another mistake can undwarf it. This “big” branch coming out will soon grow and grow and begin shading out the shrub. It is a more successful form of the spruce so if the tree has a chance, it will send more nutrients and water and growth hormones to it at the expense of the dwarf part. If you want the shrub to stay dwarfed, it is important to prune out the reverted sport and keep the form dwarfed.

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A New Category

November 21, 2010 at 12:42 PM (Botany, Genetics, Tropisms)

One of my readers recently had a good idea for a new category on the blog. His idea was to explore the fascinating world of Tropisms. What are they? Tropisms are the ability to respond, usually by growing toward or away from a particular stimulus. The Latin root “tropism” means “turning.” This refers to the plant turning towards, known as positive, or turning away, known as negative. Plants and fungi have many tropisms and are fascinating.

One of the most common tropisms in plants is positive phototropism, the ability of plants to grow towards light. Everyone knows about this phenomenon but we seldom think about how and why they do it. Usually plants respond to a stimulus because it will increase their chances for reproduction. At the simplest level, a plant grows toward the light so it will get more sunshine and grow bigger and stronger and bear a more prolific cone or fruit or berry with lots more chances to make little baby plants. But how is it done, exactly?

Well, we know some ways it is done and other ways we can only guess. The first and most obvious lesson in tropisms is the classic experiment where a seed is germinated on its side and we can observe the radical (shoot) grow up and the root, grow down. This experiment is done in the dark. This is geotropism, also known as gravitropism. The words mean earth-turning and gravity-turning, respectively. It is usually called geotropism in most classes. The shoot responds by growing in the negative direction from the earth and the root grows toward the earth. The shoot is negatively geotropic and the root is positively geotropic.
This is very handy for a seed covered with soil and starts the little plant on its way to having the roots down and the shoots up.

How does the plant detect the gravity? No one knows. We can guess that the plant hormone auxin is somehow associated with starch molecules that settle on the downward side of the plant. Strictly speaking the starch molecule theory has been disproven but some mechanism tells the auxin hormone to go to the bottom side of the plant. We do know that auxins have opposite effects on the plant parts. The shoots respond by growing away from the auxin heading the new shoot upward away from gravity.

The auxin hormone, on the other hand, makes roots grow towards itself. Down the root tip goes, down into the soil where it belongs, if you are a root. This is the way new plants get headed in the correct directions. This experiment is a classic botany lesson first described by Charles Darwin.

There are many other tropisms in plants and fungi involving different stimuli. I will try to do a occassional post on some of the more interesting ones.

Thank you to my reader who has started an interesting area of blogging.

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Bromeliads

February 25, 2010 at 10:17 PM (Genetics, Taxonomy)

Yesterday I blogged about taxonomy but I did not mention the reasons for it.  One of the benefits of a standardized naming system is that people all over the world can refer to the same organism regardless of the language they speak.  All scientific names are Latinized.  Latin is the language of choice because it is a dead language.  No one speaks it anymore, so it will never change or progress into different meanings.  

Bromeliads massed in a garden bed

 

The binomial system also gives relationship information to scientists about how organisms have evolved.  For example, plants in a Family have diverged back in time from all other families.  Those plants in the family have further divided and evolved different genuses.  All plants in a genus evolve into a particular species which does not usually crossbreed with other species in that Genus.  Species may go on to further specialize due to the forces of geography, time of blooming, or other factors.  The species becomes more and more fit to its environment.  

In the past, botanists used flower anatomy to classify plants into Genus, species, etc.  Now they have another tool.  In the hands of a skilled botanist, even the chromosomes can be counted and studied to shed new light on evolutionary paths.  Some recent studies have revealed surprises that have changed the classification of certain plants. 

Bromeliad

 

The Bromeliad family of plants has had a shake up recently.  It is composed of several subfamilies which we will not go into here.  One of the subfamilies is called Bromelioideae.  Some botanists were looking at the chromosome number of members of the subfamily, Genus Cryptanthus.  Most all other Bromeliads have been found to have 50 chromosomes.  Most of Cryptanthus sp.  have 50 also.  However, a few were found to have either 34 or 36 chromosomes.  This was quite a shock since chromosome number is a very stable and unchanging attribute in most organisms.  A reduction of chromosomes is called aneuploidy and usually causes death or distortion of the organism.  In this genus of Bromeliads, the chromosome number has changed and the plants pass this down to their offspring.  It is a sign that those reduced chromosome plants are evolving into a different group.  How should the botanists react in the name they call these new plants?  Should those species having reduced chromosome number be given a new Genus?  If we are using the naming system the way it is intended, they should probably be named separately.  Bromeliad flower stalks

Bromeliad flower stalks

Article about aneuploidy in Bromeliads:  http://www.bioone.org/doi/abs/10.1043/0363-6445-26.4.722?journalCode=sbot

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Taxonomy

February 24, 2010 at 10:21 PM (Genetics, Taxonomy)

Taxonomy

  • Kingdom Animalia
    • Phyllum Insecta
      • Class Insecta
        • Order Hymenoptera
          • Family Formicidae
            • Genus Monomorium
              • Species Monomorium minimum
                • Variety or Cultivar

 

Listed above is the taxonomic breakdown of the common ant.  You will notice that all the levels of hierarchy are single words except for the species.  We usually refer to an organism by the last two, the genus and the species.  In this case the genus is Monomorium and the species is Monomorium minimum.  Notice that the species name consists of two words.  The first is the genus the second word is called the specific epithet.  The genus is always capitalized and the specific epithet is always lower case unless you are in the Everglades National park where all the specific epithets are capitalized.  This temporarily caused Infamous to think that taxonomy had changed the rules on her, but it turns out the National Park service just messed up a little bit.  But I digress, the two word description of organisms was developed by some other people and brought to world wide attention by the Swedish botanist, Carl Linneaus.  It is called binomial nomenclature.  After he reorganized the plants in the Netherlands into modern day families, genuses and species, the systematic naming of organisms took off worldwide.  He changed taxonomy forever by grouping species into ever more general groupings as you go up the taxonomic ladder.

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Turkey Genetics

January 12, 2010 at 9:12 PM (Genetics)

Yes, Well, continuing on with our study of wierd genetics, today we consider the Turkey.  The bird, not the country.  I know nothing about Turkish genetics, just turkey genetics.  The Beltsville Small White, specifically.

A long time ago, in a state we shall call Maryland, there were agricultural scientists called breeders.  In Beltsville, MD, some breeders developed a fowl from the turkey which had white feathers.  White is easier on the eyes when you pluck the feathers off a bird on its way to becoming Thanksgiving dinner.   The turkey breeders were massing a bunch of birds into a pen and discarding the  boy turkeys because their meat might be tough to the consumer.  When a wonderous thing happened.  Although the pen consisted of all girl turkeys, they continued to lay eggs.  (That isn’t the wonderous part)  The eggs hatched.  Girl birds lay eggs all the time, just as most females ovulate routinely.  The mystery is how the eggs turned into live turkeys if there were no boy turkeys in there?

And then here we come to the most wonderous part.  Turkeys do not need men turkeys in the short term.  Turkeys are parthenogenic.  Girl turkeys can cook up a perfectly functional baby turkey from NOTHING.  They just lay an egg and out comes a baby turkey.  However, in a cruel twist of fate, all the parthenogenic baby turkeys were boy-turkeys.

Unlike the XY sex determination system in your upper, normal animals like kitties and humans, turkeys are on the ZW system.  Girl turkeys have the genotype of ZW and can make an egg for either a girl (W) or for a boy (Z).   Double u-ness equals girl turkey.  Z-ness is boy.  So a diploid girl turkey is ZW and a diploid boy turkey is ZZ.  In turkeys, WW is a lethal gene combination.  So no parthenogenically created turkeys will ever be WW.  So that leaves ZZ which is a boy.  So turkeys can get one generation from creating fertile eggs without mating.  That generation will be composed entirely of guy turkeys.  The ladies can get away with it at first, but sooner or later, they need the guys.

All us girls are fierce and proud

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Bee’s Genetics

January 9, 2010 at 10:17 PM (Genetics, Insects)

Bee genetics

One of my favorite people is taking genetics in school now. That class can tell you some weird biology. One of my favorites is the fun facts of bee genetics and sex. Bees live in a social colony with only one queen laying eggs. The workers scatter throughout the hive taking care of it.  They fly out gathering nectar and pollen to provide for the members of the hive. Workers are aptly named because they do all the work and the queen does nothing except have babies (eggs). The queen has a full complement of chromosomes, 2X. One X comes from her mother and one X comes from her father. She has 2x and when she is ready to mate, as in all most animals, she makes eggs by meiosis which are 1X. She needs a mate to supply the other half of the chromosomes, (1X) . Where does her mate come from? Well, from the previous queen usually. When virgin queens fly out of the hive on mating flights, they are looking to mate with a boy bee called a drone. The queen only flies and mates once for her whole life. She then stores the sperm in her body and uses a little at a time as she cooks up eggs that need it. She only lives a year or two, but that is still some impressive longevity for an insect. As she uses up her stored sperm, workers are created. The egg has half the chromosomes and the sperm has the other half. The fertilized eggs grow up to become worker bees. They stay worker bees unless they are fed royal jelly as infants by the workers. So the queen and the workers are both genetically diploid organisms. Now for the males. The queen makes males when her supply of sperm gets depleted. Her eggs are 1X and if they are not fertilized by any sperm, she lays them anyway as 1X organisms. In insects, 1X, or haploid organisms occur sometimes. These are the drones or boy bees. The guys are only made of half the normal chromosone number, so when they make sperm, they do not do meiosis or reduction division, they just do gametogenesis by mitosis, or regular cell division. When the queen begins laying drones, the workers take a cue and start making a bunch of new queen cells because they know the end of the current queen is near. The new queen cells grow and hatch. New queens must fly and mate before they can lay eggs. One hive may produce numerous new queens who either fly away and make a new colony or fight with each other for dominance of the current colony. Summary: Queen=2x, make eggs by meiosis. Eggs=1x Drones=1X, make sperm by mitosis Sperm=1x Eggs 1X+sperm 1X =2X workers= BEES! Cool genetics, huh?

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