### Science Essentials

Science allows us to understand our natural world and how it impacts us. Throughout human existence, we’ve built up an increasingly complex understanding of our natural world. Science is this collective knowledge and the continual pursuit of building on it. We still have many questions to answer and much to learn. Since the scientific revolution began in the $16^\text{th}$ century, we’ve seen rapid, unprecedented progress. Over centuries, we’ve acquired an unbelievable amount of information through observation and empirical experimentation. In this quiz, we'll explore in more detail how we organize the vast quantities of knowledge we have acquired and why this organization is both incredibly useful and necessary.

# Organization of Knowledge

Before we explore the ways in which we organize information in science, let’s explore categorization more broadly. Categorization is inborn. As human beings, we have been wired to organize. Everything in our lives has a label. Some things are "food," while others are not. There are "living things" and "nonliving things." The level of specificity of these labels may vary, but to find something in your physical world without a label would be an oddity.

You may have created some of these labels yourself. You may have decided when you were a child that you did not like clowns, and now they belong in the category of “scary things.” Other labels have been presented to us through our education and experiences. We have learned to label some individuals as doctors and others as firemen. Some people are athletes, and others are presidents.

These labels can be conscious, but some are unconscious too. We find ourselves accessing our internal label databases constantly. You know that a poodle is a dog, that “k” is a letter, and that cushion you sat on is a seat.

# Organization of Knowledge

It seems this tendency to label is not limited to our kind, or even our closest relatives, for even spiders must decide what is prey and what isn’t. In this way, categorization has a unique beauty as a common thread that is shared amongst trillions of living organisms. Why might living things share this tendency to categorize?

# Organization of Knowledge

Categorization is not just important for survival. Organization of knowledge and ideas is fundamental to the development of our understanding of the universe. Categorization enables us to organize and build on our knowledge, as it provides a method of simplifying ideas so that we can identify patterns and relationships.

While our interpretation of the universe is saturated with labels, hierarchies, tables, and models that help us organize our knowledge, it’s important to recognize that all simplifications of information have limitations. This is true both inside and outside of science. Stock market models help to assess risk, but savvy traders know that they can’t rely on models to accurately predict gains and losses every time. Weather forecasting relies on atmospheric modeling to predict general trends in the weather, but forecasts do not always align with actual weather patterns.

Models are essential tools in helping us understand systems and phenomena, but as scientists, we must recognize that they provide us with useful generalizations and not absolute truths.

# Organization of Knowledge

Let’s take a look at an example of categorization and modeling in science that demonstrates how modeling, despite its limitations, can help us better understand the world around us.

Taxonomy, which translates from Ancient Greek as “arrangement method,” is a tool for categorizing living organisms into groups (or taxa) based on shared genetic traits and common ancestry. Organisms grouped higher up in the hierarchy share very broad traits, while organisms grouped together farther down the hierarchy are more closely related (they share more genetic traits). Historically, we have classified living organisms into these taxa (in order of increasing specificity): domain, kingdom, phylum, class, order, family, genus, species.

Humans and mushrooms are in the same domain. What do humans and mushrooms have in common?

# Organization of Knowledge

After domain, organisms are grouped by kingdom. In the $18^\text{th}$ century, all living things fell into one of two kingdoms: plant or animal. But with the advent of microscopes, scientists developed more nuanced classifications, including “single-celled” vs. “multicellular” and even more specifically “cells with nuclei” (or eukaryotes) vs. “cells without nuclei” (or prokaryotes). Which kingdom is represented in this figure?

Note: Some classifications have more recently rejected the term “kingdom” after detailed genetic research revealing that organisms previously grouped by kingdom are not, in fact, all descendants of a common ancestor.

# Organization of Knowledge

According to the figure, which of the following organisms are most closely related to humans?

# Organization of Knowledge

Taxonomy can be incredibly useful. An organism’s taxonomic classification paints a unique picture of its biology, characteristics, evolutionary history, and genetics. For example, based on its taxonomic classification we know that the Sumatran orangutan (Pongo abelii) has no tail, can use its hands to gather food, and has a gestation period of $8$-$9$ months resulting (usually) in a single offspring that takes years to develop. We know these things simply from the Sumatran orangutan's taxonomic classification, and yet these are just a handful of things that taxonomy can reveal. Without taxonomic references, it would be significantly harder for scientists to characterize orangutans and understand how they compare to other organisms.

In short, taxonomy is a system for organizing our knowledge of living organisms in order to identify relationships and make inferences.

# Organization of Knowledge

Since the adoption of our current system of taxonomic classification in $1735,$ more than $1.9$ million species have been described. As new species are discovered, new categories such as clades, subspecies, and tribes are added.

One of the most interesting recent discoveries occurred in $2017$ when the first "new" species of great ape (our family, hominidae) was classified since $1929.$ From its name (Pongo tapanuliensis), we can see that this species belongs to the same genus (Pongo) as the Sumatran orangutan. In fact, they both live on the island of Sumatra. However, Pongo tapanuliensis (Tapanuli orangutan) was considered the same species as Pongo abelii until recent analysis of the Tapanuli’s skeleton and DNA proved otherwise.

How might the introduction of new species impact taxonomy?

# Organization of Knowledge

Taxa are defined collectively by organisms within them. Therefore, it's impossible for the system to be unaffected by new additions. The constant modification of taxonomy frequently undermines and changes pre-existing definitions of taxa, making it difficult for scientists to understand the relationships between different living things… which is the entire purpose of taxonomy!

Physiological evidence has revealed the wings of bats and birds to be very differentIn the past, one might’ve assumed that bats and birds are closely related as both have wings. However, in actuality, bats are more closely related to humans! Both humans and bats belong to the class Mammalia. Until recently, taxonomic classification was based solely on traits we could observe, such as an animal’s physiology. We were able to deduce, by examining the physiology of wings (as well as dozens of other traits), that bats are very distantly related to birds.

Nowadays, we would be able to rather quickly realize that bats are much more closely related to humans by looking at our genetic sequences. Taxa are rapidly changing to better reflect all the new information genetic analysis has provided. As with all models, taxonomy is ever-evolving and imperfect, but it still provides a useful approximation to help us understand the relationships between living organisms. DNA sequence comparison of hemoglobin

# Organization of Knowledge

Our brief exploration of taxonomy in this quiz has highlighted some of the benefits and limitations of organizational systems. Scientists use organization as a tool to arrange components into systems, and parts into patterns. In this course, we too will use various helpful organizational systems, such as scientific models. Throughout your journey as a scientific scholar, you will encounter such organizations of ideas. It is important to recognize these simplifications and consider their limitations. As you build your understanding of the universe, you will find that knowledge categorization and simplification will help you access information quickly and identify important relationships and patterns.

“All models are wrong, but some are useful.” - George E. P. Box, statistician

The organization of the knowledge we’ve acquired via the scientific process has helped us advance our understanding of the universe. As you continue in this course you'll explore some of that knowledge.

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# Organization of Knowledge

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