See more detail of each watercolor on my Instagram feed @opuntiavisual October 2019

They are members of the order Cladocera, and are one of the several small aquatic crustaceans commonly called water fleas because their swimming style resembles the movements of fleas. They live in fresh water lakes and ponds. They are used to test climate change aspects as ultraviolet radiation that damages the zooplankton.

A flagellated parasitic microorganism. It colonizes the small intestine. Giardia trophozoites absorb their nutrients from the lumen of the small intestine, and are anaerobes.

From the Greek -to change. One of the most common amoebas in the world, Amoeba proteus changes its shape and color as it explores (and engulfs) its environment. They move by extending pseudopods ("false feet") and then oozing into them. The first illustrated resembling amoebas goes back 1755 by August Johann Rösel von Rosenhof.

A genus of unicellular ciliates, commonly studied as a representative of the ciliate group. The earliest known illustration of a Paramecium was published anonymously in Philosophical Transactions of the Royal Society, in 1703.

A genus of single cell flagellate eukaryotes. Most species of Euglena have photosynthesizing chloroplasts within the body of the cell, which enable them to feed by autotrophy, like plants. However, they can also take nourishment heterotrophically, like animals.

A is a polyphyletic genus of chlorophyte green algae in the family Volvocaceae. It forms spherical colonies of up to 50,000 cells. They live in a variety of freshwater habitats, and were first reported by Antonie van Leeuwenhoek in 1700. Volvox diverged from unicellular ancestors approximately 200 million years ago.

It usually reproduces by forming dry chains of spores (or conidia) from brush-shaped conidiophores. It is the source of several β-lactam antibiotics, most significantly penicillin.

Commonly known as comb jellies. It comprises a phylum of invertebrate animals that live in marine waters worldwide. The best-known ctenophores are those that occur near-shore. Such species are typically planktonic, transparent and unpigmented, and most swim by synchronous beating of the eight rows of comb plates.

A Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium.

The first complete DNA sequence of an E. coli genome (laboratory strain K-12 derivative MG1655) was published in 1997.

It has a contractile tail and a complex baseplate. Six long-tail fibers are attached to the upper part of the baseplate and six short-tail fibers are folded under the baseplate before infection. It infects Escherichia coli

A group of extinct marine arachnomorph arthropods. The trilobites were among the most successful of all early animals, existing in oceans for almost 300 million years. They flourished throughout the lower Paleozoic era

A phylum of water-dwelling eight-legged segmented micro-animals. Tardigrades are among the most resilient animals known, with individual species able to survive extreme conditions—such as exposure to extreme temperatures, extreme pressures (both high and low), air deprivation, radiation, dehydration, and starvation—that would quickly kill most other known forms of life.

Plant cells are eukaryotic cells present in green plants, photosynthetic eukaryotes of the kingdom Plantae. The cell was first discovered and named by Robert Hooke in 1665. He remarked that it looked strangely similar to cellula or small rooms which monks inhabited, thus deriving the name. However what Hooke actually saw was the dead cell walls of plant cells (cork) as it appeared under the microscope.

They are the basic unit of the nervous system. Here depicted a simplified version of a multipolar neuron. A typical neuron consists of a cell body (soma), dendrites, and a single axon.

A double-membrane-bound organelle found in most eukaryotic organisms. It generates most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy. A mitochondrion is thus termed the powerhouse of the cell. The term "mitochondria" was coined by Carl Benda in 1898.

All ribosomes are composed of two subunits, both of which are built from RNA and protein. Bacterial ribosomes, for example of Escherichia coli, contain a small subunit (SSU) composed of one 16S Ribosomal RNA (rRNA) and 21 Ribosomal proteins (r-proteins) and a large subunit (LSU) containing 5S and 23S rRNAs and 33 r-proteins.

In 2000, structural biologists Venkatraman Ramakrishnan, Thomas A. Steitz and Ada E. Yonath made the first structures of ribosomal subunits available in the PDB, and in 2009, they each received a Nobel Prize for this work.

A type of blood cell that is made in the bone marrow and found in the blood. Erythrocytes contain a protein called hemoglobin, which carries oxygen from the lungs to all parts of the body. In 1959, by use of X-ray crystallography, Dr. Max Perutz was able to unravel the structure of hemoglobin, the red blood cell protein that carries oxygen.

A muscular organ that pumps blood through the blood vessels of the circulatory system. In humans, the heart is divided into four chambers: upper left and right atria and lower left and right ventricles.

Primary organs of the respiratory system. The trachea conducts inhaled air into the lungs through its tubular branches, called bronchi. The bronchi then divide into smaller and smaller branches (bronchioles), finally becoming microscopic.

The bronchioles eventually end in clusters of microscopic air sacs called alveoli. In the alveoli, oxygen from the air is absorbed into the blood.

They are two bean-shaped organs, each about the size of a fist. They are located just below the rib cage, one on each side of your spine.

Healthy kidneys filter about a half cup of blood every minute, removing wastes and extra water to make urine. The nephron is the structural and functional unit of the kidney. Each human adult kidney contains around 1 million nephrons, while a mouse kidney contains only about 12,500 nephrons.

The central organ of the nervous system.

The intestines are a long, continuous tube were most absorption of nutrients and water happens. It includes the small intestine and large intestine. The small intestine (small bowel) is about 20 feet long and about an inch in diameter. The large intestine (colon or large bowel) is about 5 feet long and about 3 inches in diameter. The human intestinal microbiome is among the most complex of the body sites: it includes 500–1000 species and several million genes.

Deoxyribonucleic acid carries the genetic information of all organisms. My favorite experiments in history are the Hershey-Chase experiment that demonstrated that DNA carried the genetic material of phage T2 and Photo 51: X-ray diffraction image by Rosalind Franklin.

A piston-driven air displacement pipette that handles volumes of liquid in the microliter scale. They are the everyday lab tool of most biochemists and biologists.

The microscope was still largely a novelty until the 1660s and 1670s when naturalists in Italy, the Netherlands and England began using them to study biology. Italian scientist Marcello Malpighi, called the father of histology by some historians of biology, began his analysis of biological structures with the lungs. Robert Hooke's Micrographia had a huge impact, largely because of its impressive illustrations. A significant contribution came from Antonie van Leeuwenhoek who achieved up to 300 times magnification using a simple single lens microscope.

Red flying fox. A species of megabat native to Australia. With a weight of 300-600 grams is the smallest flying fox in mainland Australia.

The wild ancestor of maize, was domesticated around 9000 years ago in southern Mexico. Cobs about 25 mm long were found in caves near Puebla. Teosinte plants typically have many long branches, each bearing multiple small ears along their length and tassels at their tip.

A monotypic gymnosperm genus, comprising solely the distinctive Welwitschia mirabilis, endemic to the Namib desert within Namibia and Angola. The age of individual plants is difficult to assess, but many plants may be over 1000 years old. Some individuals may be more than 2000 years old.

The Venus flytrap possesses an active trapping mechanism to capture insects with one of the most rapid movements in the plant kingdom. Trap closure consists of three distinctive phases: a silent phase with no observable movement; an accelerated movement of the lobes; and the relaxation of the lobes in their closed state, resulting in a new equilibrium. This small plant consists of five to seven leaves with each leaf divided into two parts: the upper leaf and the lower leaf. The upper leaf has a pair of trapezoidal lobes held together by a blade (midrib). The center of each lobe contains three sensitive trigger hairs and a red anthocynanin pigment that attracts insects.

They are mainly large trees with a massive erect stem, reaching a height of 5–80 metres (16–262 ft). The horizontal, spreading branches grow in whorls and are covered with leathery or needle-like leaves. These columnar trees are living fossils, dating back to early in the Mesozoic age. Fossil records show that the genus also formerly occurred in the northern hemisphere until the end of the Cretaceous period.

Ginkgo biloba, also known as the maidenhair tree, is the only living species in the division Ginkgophyta, all others being extinct. It is found in fossils dating back 270 million years.