The Christmas season brings with it both real and imaginary elements. For this contest, I chose to highlight what has an objective existence or is real in some of those elements, although in some cases there will be an imaginary touch.

There is a wide variety of evergreen trees that are used as Christmas trees. The most commonly used are fir trees of the genus Abies, pines, cypresses, and spruces.

Christmas trees are often cut down before being brought into homes. Indoor pets may ingest needles, branches, or bark from trees, which contain monoterpenes and diterpenes, as well as a variety of essential oils, and some of the terpenes and essential oils have been shown to cause fetal deaths and malformations in laboratory rodents.

The Fraser fir (Abies fraseri) is one of the most sought-after Christmas tree species due to its fragrance, physical appearance, and durability.

In the representation of the birth of Jesus, the mule has been incorporated; predominantly considered sterile.

The mule is a hybrid animal produced by crossing a donkey (Equus asinus) and a mare (Equus caballus). The resulting hybrid is given the scientific name Equus asinus x caballus or Equus mulus. There is also a hybrid animal resulting from the cross between a horse (Equus caballus) and a female donkey (Equus asinus) known as a hinny. In either case, the offspring is considered sterile.

Although mules are generally considered infertile, there are reports of successful gestations.

The star of Bethlehem is also incorporated into the representation of the birth of Jesus.

Astronomical and historical evidence suggests that the star of Bethlehem was a comet visible in the year 5 BC. It has been proposed that a sequence of three astronomical events stimulated the journey of the Magi: the triple conjunction of Saturn and Jupiter in the year 7 BC; the massing of the three planets Saturn, Jupiter, and Mars in 6 BC; and, finally, the appearance in 5 BC of the “star of Bethlehem,” a comet that was initially located in Capricornus. The evidence points to Jesus being born in the period between March 9 and May 4, 5 BC. In this sense, the new date of the Nativity would construct a new chronology of the life of Christ.

The Camelidae family includes the genus Camelus (Latin word meaning camel), and although domesticated species are generally distinguished as camels with 2 humps and dromedaries with 1 hump, the reality is that both are camels. Camelus bactrianus, the two-humped camel, and Camelus dromedarius, the one-humped camel.

Illustrations almost always assume that the 3 Wise Men (three Kings, Magi) traveled to Bethlehem on camels to see Jesus, but what kind of camel would that be? Based on geographical distribution, it would be the Camelus dromedarius species.

Camels adapted to the desert have evolved physiological adaptations that reduce water loss or can tolerate significant losses. In mild climates, where green forage is available, camels may go several months without drinking water. During winter and cold seasons, camels can go months without drinking water. Under very hot conditions, they may drink water only every 8 to 10 days and lose up to 30 % of their body weight through dehydration.

The binomial name for poinsettia is Euphorbia pulcherrima. The showy red, pink, or white parts of the plant, commonly known as flowers, are modified leaves called bracts. The actual flowers are the tiny yellow structures resembling stamens.

Santa Claus uses a sleigh pulled by 9 reindeer to deliver Christmas presents. Reindeer belong to the genus Rangifer, which has only one species, Rangifer tarandus, which has several subspecies generally known as reindeer in Eurasia and caribou in North America. Their predominant geographical distribution is around the North Pole.

The species of Santa Claus' reindeer is Rangifer tarandus saintnicolas magicalus, and there are only nine of them; one of them has a genetic abnormality, which is a bright, red, glowing nose.

In male Arctic reindeer of the subspecies Rangifer tarandus tarandus, the cornea and lens do not block all ultraviolet rays, and the retina responds electrophysiologically to these wavelengths. Furthermore, in this subspecies, both rod and cone photoreceptors respond to ultraviolet rays with low-intensity stimulation, and the response to ultraviolet rays is not mediated by a specific ultraviolet photoreceptor mechanism. Ultraviolet rays are normally highly damaging to the retina, resulting in photoreceptor degeneration, but this damage appears not to occur in Arctic reindeer, suggesting that they may have evolved retinal mechanisms that protect them from extreme ultraviolet exposure.

In Santa Claus's environment, when temperatures reach or dip below freezing with minimal moisture in the air, snow crystals begin to form in the atmosphere and grow into snowflakes. If temperatures are warm enough on the ground (around 5 °C), the snow will land and begin to accumulate, but if it is warmer, it will melt.

Snow begins with a single crystal that forms when water vapor freezes and, as it falls, takes on a unique hexagonal shape. If the crystal collides with others, it grows larger until it becomes a snowflake. Under a microscope, snowflakes have the shape of stars, plates, prisms, and columns.

Snowmen are connected with Christmas.

I invite users @abneagro and @belkisa758 to participate in this contest. For information about the contest, click here.