Word Wednesday: Geologic Time Part 1

As a paleontologist, I frequently refer to the geologic time scale. It might seem overwhelming, but it actually does a pretty thorough job of breaking down the geologic history of the planet. To keep things simple, we’re not going to worry about anything before the beginning of life on Earth. Geologic time is like a set of nesting dolls, with many smaller divisions fitting into larger divisions. The largest commonly used unit of geologic time is the eon. Most life on Earth has lived during the Phanerozoic.

Phanerozoic

Phanerozoic breaks down into phaner and –zoicPhanero comes from the Greek word phaneros‘ which means visible and zoic comes from the Greek word ‘zoion‘ which means animal or life. In other words, the Phanerozoic eon has visible life. It started about 541 million years ago and continues to the present day. The suffix ‘zoic‘ is going to show up a lot in the geologic time scale.

The next largest division is the era. Since the start of the Phanerozoic, there have been 3 eras: the Paleozoic, the Mesozoic, and the Cenozoic.

The geologic time scale

Paleozoic

We have already come across both parts of Paleozoicpaleo and –zoic. It should therefore come as no surprise that Paleozoic means ‘ancient life’. It started 541 million years ago and ended 252.2 million years ago.

Mesozoic

Mesozoic breaks down into meso and –zoicMeso comes from the Greek word ‘mesos‘ which means middle and we already know that zoic means life. Therefore, the Mesozoic means ‘middle life’. It started 252.2 million years ago and ended 66 million years ago with the extinction of the dinosaurs.

Cenozoic

Cenozoic breaks down into ceno and -zoicCeno comes from the Greek word ‘kainos‘ which means recent. It started 66 million years ago and continues to the present day. The Cenozoic includes everything since the extinction of dinosaurs, most significantly the rise of the mammals. It is the smallest era, but scientists commonly break it down into the most parts.

Next week, I’ll talk about the two smaller divisions of geologic time: the period and the epoch.

University of California Museum of Paleontology Geologic Time Scale

Geological Society of America Geologic Time Scale

Jurassic Park v. Indiana Jones

I’ve wanted to be a paleontologist since I was a little kid. In fact, I can’t remember ever wanting to do anything else. I was that kid that actually enjoyed going to natural history museums. Spring was my favorite season because you could find the skeletons of animals that had died during the winter in the woods. My family even had a colony of dermestid beetles!

At an early age, I realized that path was more difficult than I thought. In first grade, my class made ‘About Me’ books which included things like our phone number, how many siblings we had and what we wanted to be when we grew up. Since I was only 7 years old, I had to ask my teacher how to spell ‘paleontologist’. A few years later I looked back at that little book and realized that instead of telling me how to spell ‘paleontologist’, my teacher spelled ‘archeologist’, probably assuming that I was mistaken. Therein lies the problem.

When I tell people that I am a paleontologist, frequently their reaction is “Oh, like Indiana Jones?”. No, I am not like Indiana Jones. Similarly, when I tell people that I spent two summers working at the Mammoth Site they say “So you’re an archeologist?”. No, I’m not an archeologist. Sometimes when I say that I am a paleontologist, people correct me and say “You mean an archeologist”. No, I’m not an archeologist. I must admit, I do get a bit annoyed when people mistake paleontology for archeology, as I’m sure an archeologist would be if someone asked if they studied dinosaurs.

I have nothing against archeology. I minored in biological anthropology (which is different from archeology) and took a few archeology courses as an undergrad. I don’t even have anything against Indiana Jones (enough people have already written about Indiana Jones’ archeological shortcomings).

‘Archeology’ has come to refer to at least 3 (depending on where you draw your lines) different disciplines: archeology, paleoanthropology, and paleontology. However, each of these fields has different goals and methods. Archeology is the study of past humans and their cultures based on what they leave behind.  Typically, archeology is seen as a social or soft science and deals with a shorter time scale than the other two disciplines. It is limited by material culture: if people don’t leave things behind, there is nothing to study. However, archeology is a complex field. There are forensic archeologists and archeologists who focus on food or even hairstyles.

Paleoanthropology, sometimes known as biological anthropology, can be seen as a middle ground between archeology and paleontology. It also focuses on human history, but it relies on fossil evidence instead of artifacts. Paleoanthropologists study the evolutionary history of humans as well as our nearest living relatives, the primates. It is also complex: some paleoanthropologists focus on biomechanics and how we became bipedal, some study how those changes impacted pregnancy, and others study the genetic link to other species such as Neanderthals and Denisovans. Archeology and biological anthropology are two of the four fields of anthropology: biological anthropology, sociocultural anthropology, linguistic anthropology and archeology.

Paleontology is the odd man out in this comparison. Broadly, it is the study of prehistoric life. That could mean plants or animals, vertebrate or invertebrates, or something different entirely. It blends geology and biology to make a more complete picture. For example, I study fossil plants to determine paleoecology and paleoclimate. There has been life on Earth for billions of years, so there is a lot to study.

The moral of the story is that all three fields are complex, fascinating, and different. As I’m sure my fellow scientists would agree, if you’re not sure what we do just ask us. We love talking about our research.

Word Wednesday: Insect Orders

Insects are a fascinating part of biology, and are some of the most abundant and misunderstood organisms on Earth. Scientists who study insects are called entomologists.

Entomology (n)

Entomology breaks down easily into two parts: entom and –logyEntom comes from the Greek word ‘entomon‘ meaning insect and we already know that logy comes from the Greek word logia which means ‘the study of’. Therefore, entomology, as you probably expected, means the study of insects.

There is much dispute, but scientists recognize between 27 and 31 orders of insects. Some of these orders are more common than others, and they offer a great introduction into scientific terminology. Here are nine of the most common, and also some of my favorites!

Ephemeroptera

Ephemeroptera breaks down into ephemero and –pteraEphemero comes from the Greek word ‘ephemeros‘ meaning short-lived and ptera comes from the Greek word ‘pteron‘ meaning wing. Therefore, ephemeroptera refers to adult insects that are short-lived and winged. An example of this is the mayfly. Adult mayflies only live long enough to reproduce and don’t even have mouths!

Odonata

Odonata doesn’t need to be broken down. It comes from the Greek word ‘odontos‘ meaning tooth. This refers to the teeth on the lower jaw of these insects; however, this is not actually a good identifier as many different types of insects have toothed jaws. Odonata includes dragonflies and damselflies and is one of my favorite insect orders!

Orthoptera

Orthoptera breaks down into ortho and pteraOrtho is the Greek word for straight and ptera, like I mentioned before, means wings. Therefore, Orthoptera means straight wings. Orthoptera includes grasshoppers, locusts and crickets. Interestingly, locusts and other Orthoptera are the only insects that are considered kosher.

Phasmida

Phasmida comes from the Greek word phasma which means phantom. This refers to stick insects’ ability to blend in to their surroundings. Stick insects make good pets and many species don’t need males in order to reproduce.

Hemiptera

Hemiptera breaks down into hemi and -ptera. Hemi is a Greek word meaning half and ptera means wing. This refers to the order’s characteristic wings that are hardened at the base, leaving only half a wing. These insects are the true bugs and include cicadas, aphids and leafhoppers. Not all insects are bugs, but all bugs are insects.

Coleoptera

Coleoptera breaks down into coleo and ptera. Coleo comes from the Greek word ‘koleos’ which means sheath and ptera  means wing. Therefore, Coleoptera means sheathed wing insects, which describes beetles perfectly. Their hard shells protect their wings. In other words, ladybugs and june bugs aren’t actually bugs, they’re beetles!

Diptera

Diptera breaks down into di and pteraDi is a Greek word meaning two and ptera means wing. Ergo, Diptera describes insects with two wings: the true flies. This includes fuit flies, which are used as a model organism in genetics experiments.

Lepidoptera

Lepidoptera breaks down into lepido and pteraLepido comes from the Greek word ‘lepis‘ which means scale and ptera means wing. Lepidoptera includes moths and butterflies and the name refers to the small scales on their wings. They are also known for their proboscis, a straw-like mouth used to suck up nectar.

Hymenoptera

Hymenoptera breaks down into hymeno and ptera. Hymen is a Greek word meaning membrane and ptera means wing. Hymenoptera describes the thin, membranous wings of wasps, bees and ants, and is one of the largest insect orders.

Some insect orders have more descriptive names than others. Regardless, understanding what the names mean can make it easier to understand other words later on. To learn more about insect orders, check out the links below!

Insect Orders-Department of Entomology-Texas A&M University

Etymology Online: Entomology

Etymology Online: Coleoptera

Etymology Online: Lepidoptera

Etymology Online: Hymenoptera

To Be or Not To Be: De-extinction

There has been a lot of talk lately surrounding the concept of ‘de-extinction’, or resurrecting extinct species. However, before passing any judgement on the matter, it is important to fully understand the topic. Many people have written about it, so I’ll let you read what the experts have to say.

Stewart Brand gave a TED talk on de-extinction, and there was an entire TEDx conference: TEDxDeExtinction.

Alex Dainis has a great video on the topic at Bite Sci-zed.

The Brain Scoop has two videos on de-extinction: Part I and Part II.

Hannah Waters has an interesting take on the topic, and so does Carl Zimmer.

The editors at Scientific American feel very strongly about de-extinction.

Extinct Passenger Pigeon (Ectopistes migratorius) at Cincinnati Zoo by Ltshears

Regardless of your stance on de-extinction, it raises a lot of questions. Do humans have a moral obligation to resurrect species that died out under our watch or by our hand? Should we instead be focusing on species that are endangered in hopes of saving them from a similar fate? Also, should we be focusing our efforts on ‘warm fuzzy’ big name creatures, such as mammoths and tasmanian tigers, or smaller animals, such as reptiles and amphibians? Should we try to resurrect plants and invertebrates as well? Where is the line?

De-extinction does raise some valid points. It is a good idea to preserve the DNA from living species, particularly endangered species, to ensure genetic diversity. It is much easier to get people excited about resurrecting extinct species than protecting living species that are dying out. All in all, de-extinction is in its infancy and scientists are still debating its ethical and ecological impacts. It is vital to understand how such a dramatic idea could impact the world we live in. The Earth is a living, changing planet and its ecosystems are continuously changing. And remember: science is a powerful tool, so use it wisely.

Word Wednesday: Plants

In honor of the nice spring weather, let’s talk about plants!

botany (n)

This is another word that doesn’t need to be broken down. Botany comes from the Greek word ‘botane‘ which means plant or grass. In other words, botany is the study of plants. Like other scientific studies, modifying prefixes can be added to botany to be more specific. For example, I am a paleobotanist, meaning I study ancient plants.

Plants are often taken for granted. Because plants don’t move around, many people find them boring. Plants are an essential part of most environments. They provide food for other organisms and take in carbon dioxide and release oxygen into the atmosphere during photosynthesis.

Dill (Anethum graveolens) by Walter J. Pilsak, Waldsassen

photosynthesis (n)

Photosynthesis breaks down into two parts: photo and –synthesisPhoto is a Greek word meaning light and synthesis is a Greek word meaning put together or combine. Ergo, photosynthesis means to combine light. This makes sense, because during photosynthesis plants use light to make energy.

To learn more about the etymology of botany and photosynthesis, check out the links below!

Online Etymology Dictionary: Botany

Online Etymology Dictionary: Photosynthesis

Salamanders: Amazons and Thieves

The summer after my sophomore year of college, I spent a semester at the University of Michigan Biological Station (UMBS). While I was there I took an ecology field class, which was one of the most memorable classes that I have ever taken. My teacher was very passionate about a lot of topics (house cats, lawns, dunes), but one subject that caught my attention was unisexual salamanders.

It is common knowledge that vertebrate organisms reproduce sexually; in other words, it takes a male and a female of a species to produce offspring and those offspring are a genetic mix of both parents. However, that is not always true. In fact, there are about 90 different lineages of unisexual vertebrates. There are three primary methods of unisexual reproduction in vertebrates: parthenogenesis, hybridogenesis, and gynogenesis. Parthenogenesis, simply put, is cloning. Barring any random mutations, the offspring are genetically identical to the mother. Hybridogenesis is ‘hemi-clonal’, or half clonal. The mother passes on her genes clonally to the offspring, but the genetic material of a father is also passed on. The father’s genetic material is later discarded and only the mother’s genome continues to be passed on. Finally, gynogenesis is neither asexual nor sexual reproduction. Organisms that use gynogenesis require sperm to trigger cellular division in the egg, but the egg is not fertilized and the father’s genetic material is only incorporated about a quarter of the time. Unlike parthenogenesis, gynogenetic genomes are very flexible and will mix and change. Unisexual salamanders use a unique method of gynogenesis called ‘kleptogenesis’, meaning that female unisexual salamanders will steal the spermatophore (sperm packet) of male salamanders of the same genus to use in reproduction.

Blue-spotted salamander (Ambystoma laterale) by Greg Schechter

Unisexual salamanders come from the genus Ambystoma. Commonly known as ‘mole salamanders’, they are native to North America and are typically terrestrial as adults, with the notable exception of the axolotl (Ambystoma mexicanum). They live in burrows and return to water to lay their eggs. Unisexual Ambystoma salamanders live in the Great Lakes and northeastern regions of the United States and incorporate the genomes of 5 different species: the blue-spotted salamander (Ambystoma laterale), the Jefferson salamander (A. jeffersonianum), the small-mouthed salamander (A. texanum), the streamside salamander (A. barbouri), and the tiger salamander (A. tigrinum).

Scientists think that the lineage of unisexual Ambystoma salamanders originated between 2.4-3.9 million years ago from a hybridization event of a female A. barbouri. Now, the genetic material of A. barbouri is virtually unknown within unisexual salamanders but every individual has a least one genome from A. laterale. This suggests adaptation within the lineage. Also, these salamander populations are composed solely of females, and they are sometimes referred to as ‘Amazons’ after the mythical female warriors. This is an advantage for the salamanders, because it means that every individual can give birth. However, how this happens is not fully understood. In salamanders, sex is determined differently than in humans. In humans, female is the default gender and is represented by ‘XX’, while males are ‘XY’. In salamanders, males are the default gender and are represented by ‘ZZ’, while females are ‘ZW’. Most Ambystoma salamanders are diploid, meaning that they have two sets of genes (typically one from each parent). Unisexual Ambystoma salamanders can be triploid, tetraploid or even pentaploid. During reproduction, the male genome is incorporated about 25% of the time. This could be by replacing an existing genome or by increasing the ploidy level.

The more scientists learn about alternative methods of reproduction, the better we can understand why sexual reproduction came to be so prevalent. It can also shed light on to what it means to be a species. Traditionally, a species is considered to be ‘reproductively isolated’, meaning it can only reproduce with its own species. Unisexual salamanders and other similar lineages remind us that our methods of classification are artificial constructions and do not necessarily reflect the natural world. Also, what are the advantages of unisexual reproduction? Perhaps it allows the salamanders to adapt to minute changes in the environment. Research on the topic of unisexuality in vertebrates has exploded in recent years, but we still have a lot to learn.

To learn more about unisexual salamanders, check out the links below!

Bi, Ke; James P Bogart, Jinzhong Fu (2008). “The prevalence of genome replacement in unisexual salamanders of the genus Ambystoma (Amphibia, Caudata) revealed by nuclear gene genealogy” (Open access). BMC Evolutionary Biology 8: 158.

Bi, Ke; James P Bogart (2010). “Time and time again: unisexual salamanders (genus Ambystoma) are the oldest unisexual vertebrates”. BMC Evolutionary Biology 10: 238.

Bogart, James P; Ke Bi, Jinzong Fu, Daniel W A Noble, John Niedzwiecki (2007). “Unisexual salamanders (genus Ambystoma) present a new reproductive mode for eukaryotes”. Genome / National Research Council Canada = Génome / Conseil National De Recherches Canada 50 (2): 119–136.

Mole Salamanders

The Secret to Life on Mars?

This week, scientists published research in Geochimica et Cosmochimica Acta (a bi-weekly journal co-sponsored by the Geochemical Society and the Meteoritical Society) that might help reveal the secret to life on Mars. To study Mars, scientists are primarily limited to meteorites that have fallen to Earth. Unfortunately, these meteorites have weathered and this might mask any clues from their time on the red planet. However, if scientists can show that clues to habitability date from before the meteorite’s time on Earth, they can draw conclusions as to the possibility of life on Mars.

From NASA and The Hubble Heritage Team (STScI/AURA)

The meteorite in this study, the Nakhlite Meteorite, was recovered from the Miller Range of Antarctica in 2003 and formed on Mars about one billion years ago. It weighs approximately 1.5 pounds and is the size of a tennis ball. By studying the composition of the meteorite, scientists are attempting to identify the difference between weathering that occurred on Earth and weathering that occurred on Mars. They identified water-related minerals and other chemicals signatures associated with liquid water.

This research is by no means definitive, but it serves as a jumping off point for future research. Past studies of meteorites, as well as data from the Mars Rover and satellites, have shown that there was likely liquid water on Mars in the past. However, until it is possible to return samples from a Mars mission to Earth, meteorites are scientists best option for research. Current research also suggests that the ‘habitable zone’, or the region in a solar system that can support liquid water, might be larger than previously thought. This could mean a lot for the future of astronomy.

To learn more about the possibility of life on other planets, check out the links below!

Studying meteorites may reveal Mars’ secrets of life

Stopar, J.D., Taylor, G.J., Velbel, M.A., Norman, M.D., Vicenzi, E.P., Hallis, L.J. 2013. Element abundances, patterns, and mobility in Nakhlite Miller Range 03346 and implications for aqueous alteration.Geochimica et Cosmochimica Acta 112: 208-225.

Search for E.T. Should Extend Beyond ‘Alien Earths’, Astronomer Says.