mscheller's blog

Mammalian teeth come in many different forms and differ from the teeth of reptiles in that mammals have evolved heterodonty which is the condition of having specialised teeth for different functions. Reptiles have uniform teeth that do not differ in form or function, the condition known as homodonty. Mammalian teeth fall into four different categories, each with different form and function. At the front of the mouth are incisors, behind which is a pair of canines which may or may not be present, followed by premolars and molars. Apart from canine teeth of which there is always only one or none on each side, the number of each tooth type varies by species. Us humans have in total (usually) 32 teeth, of which eight are incisors, four are canines, and eight premolars and molars. 

Traditionally, the methods used to test a mother’s growing fetus for abnormalities are highly invasive and pose a serious risk to the developing child. Due to advances in genetics in recent years, newer far less invasive procedures are now available to expecting mothers that offer equally valid, and in some cases, possibly more reliable results without the need to put the child at risk. Non-invasive prenatal screening involves taking a simple blood sample from a mother who is at least 10 weeks along in her gestation period. The blood is centrifuged to separate the blood plasma from the denser red blood cells, and what's left is a solution containing just cell-free DNA (cfDNA) fragments from both the fetus and the mother. The majority of the cfDNA will be from the mother, but for reliable results in this test, a percentage of just 4% fetal DNA is adequate. The analysis is done by looking at the proportions of fragments found from each of the child’s 23 chromosomes and looking for higher or lower than expected proportions of certain chromosomal fragments that could indicate a trisomy or chromosomal deletion. For example, finding a higher proportion of cell-free DNA (cfDNA) fragments from chromosome 21 of the fetus suggests the child is at a higher risk of being born with Down Syndrome. All this has only recently become possible thanks to advances in the speed and efficiency at which genetic sequencing can be performed. The samples of multiple patients may be sequenced at once leading to a much faster and cost-efficient way of analyzing DNA.

In 1869 Thomas Huxley proposed the theory that birds descended from dinosaurs. For a long time, however, the idea was widely unaccepted and it wasn't until the discovery of many specimens of feathered theropod dinosaurs such as Archaeopteryx and other like it which lived in the late Jurassic and thereafter that pushed the idea into the spotlight and allowed it to gain traction and support. The idea is now widely accepted and new fossil finds are providing insight into how small flightless feathered raptors became the incredibly diverse array of birds that share the Earth with us today.

As early as the mid-1800’s the theory that birds had descended from dinosaurs had been proposed but was widely unaccepted for some time. It was the discovery of feathered theropod dinosaurs like Archaeopteryx that pushed the idea into the spotlight and allowed it to gain traction. Now the idea is widely accepted and new fossil finds are providing insight into how small flightless feathered raptors became the incredibly diverse array of birds that share the Earth with us.

The family Canidae contains all species of living and extinct quadrupedal carnivores resembling the domestic dog. This includes domestic dogs themselves, coyotes, wolves, foxes, dingoes and many others. Some interbreeding can occur between coyotes and dogs, as well as dogs and wolves and wolves and coyotes. The offspring of these pairings are fully viable and usually fertile, begging the question are these three varieties of canines really separate species. The wolf, Canis Lupis, is the largest of these three species and has overlapping ranges with the coyote, Canis latrans. These ranges also unsurprisingly overlap with human settlement, meaning there is the potential for both of these species to interbreed with a person pet dog or a stray domestic dog, the species Canis familiaris. What separates these three as different species is their tendency under ideal circumstances to avoid breeding with members of the other species. Although interbreeding is possible, in a proper habitat with adequate resources and fertile mates available it will not occur. These rare hybrids only occur when there is a shortage of healthy and viable mates of the same species.

Inside of a small plastic container is a single beige larva about one centimeter in length. Its body is a mixture of light beige and darker shades of brown interspersed through out with a distinct brown line running the length of the back of its abdomen. At the front the body narrows to from what appear to be a small pair of mandibles. The rear of the larva is much wider and flatter than the head and has two dark brown spots that look remarkably like a pair of eyes. The animals body is broken into individual segments, 12 in total, each of which is defined by a ring around the animal.

Within the small clear plastic container is a single light beige grub. The animal is approximately one cm in length and has a darker brown stripe running down the length of its back. At the front end the body narrows and forms a set of small black mandibles. The rear end of the animals body is wider and flatter than the front. On the rear of the abdomen are two small dark brown spots. These spots likely function as false eyes and allow grubs to sometimes evade predation due to a would be predator mistakenly attacks the rear of the animal and leaves the head intact. In total the organism is composed of 12 individual body segments. The creature is most likely the larval stage of some form of insect, the identity of which is currently unknown. Some behavioral features include a sensitivity to light. Upon shining a bright flashlight in its face the animal immediately recoiled and faced the opposite direction. When the container is shaken the grub appears to shorten its body as much as possible and contract all its body segments making itself more rigid.