This article lists notable

unsolved problems List of unsolved problems may refer to several notable conjectures or open problems in various academic fields: Natural sciences, engineering and medicine * Unsolved problems in astronomy * Unsolved problems in biology * Unsolved problems in c ...

biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...

General biology

Evolution and origins of life

Origin of life In biology, abiogenesis (from a- 'not' + Greek bios 'life' + genesis 'origin') or the origin of life is the natural process by which life has arisen from non-living matter, such as simple organic compounds. The prevailing scientific hypothes ...

. Exactly how, where, and when did life on

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

originate? Which, if any, of the many hypotheses is correct? What were the metabolic pathways used by the earliest life forms? * Origins of viruses. Exactly how and when did different groups of viruses originate? *

Development Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking, development phase, including finance and budgeting *Development (music), the process thematic material is reshaped * Photograph ...

and

evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

of brain. How and why did the brain evolve? What are the

molecular A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...

determinants of individual brain development? *Origin of Eukaryotes (

Symbiogenesis Symbiogenesis (endosymbiotic theory, or serial endosymbiotic theory,) is the leading evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms. The theory holds that mitochondria, plastids such as chloroplasts, and possi ...

). How and why did cells combine to form the eukaryotic cell? Did one or more random events lead to the first eukaryotic cells, or can the formation of eukaryotic cells be explained by physical and biological principles? How did the mitochondria's mitosis cycle come in sync with its host cell? Did the mitochondria or the nucleus develop first in eukaryotes? *

Last Universal Common Ancestor The last universal common ancestor (LUCA) is the most recent population from which all organisms now living on Earth share common descent—the most recent common ancestor of all current life on Earth. This includes all cellular organisms; t ...

. What were the characteristics of the Last Universal Common Ancestor of Archaea, Bacteria, and Eukaryotes? Did Archaea and Eukaryotes evolve out of the domain Bacteria or to a clade basal to it? Do Archaea and Eukaryotes share a later or earlier common ancestor to Bacteria?

Biochemistry and cell biology

*What do all the unknown proteins do? Almost two decades since the first eukaryotes were sequenced, the "biological role" of around 20% of proteins are still unknown. Many of these proteins are conserved across most eukaryotic species and some are conserved in bacteria, indicating a role fundamental for life. *Determinants of

cell size Cell growth refers to an increase in the total mass of a cell, including both cytoplasmic, nuclear and organelle volume. Cell growth occurs when the overall rate of cellular biosynthesis (production of biomolecules or anabolism) is greater than ...

. How do cells determine what size to grow to before dividing? *

Golgi apparatus The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic cells. Part of the endomembrane system in the cytoplasm, it packages proteins into membrane-bound vesicles ins ...

. In

cell theory In biology, cell theory is a scientific theory first formulated in the mid-nineteenth century, that living organisms are made up of Cell (biology), cells, that they are the basic structural/organizational unit of all organisms, and that all cell ...

, what is the exact transport mechanism by which proteins travel through the

? *

Mechanism of action In pharmacology, the term mechanism of action (MOA) refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect. A mechanism of action usually includes mention of the specific molecular targe ...

of drugs. The mechanisms of action of many drugs including

lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid el ...

thalidomide Thalidomide, sold under the brand names Contergan and Thalomid among others, is a medication used to treat a number of cancers (including multiple myeloma), graft-versus-host disease, and a number of skin conditions including complications of ...

and

ketamine Ketamine is a dissociative anesthetic used medically for induction and maintenance of anesthesia. It is also used as a recreational drug. It is one of the safest anesthetics, as, in contrast with opiates, ether, and propofol, it suppresses ne ...

are not completely understood. *

Protein folding Protein folding is the physical process by which a protein chain is translated to its native three-dimensional structure, typically a "folded" conformation by which the protein becomes biologically functional. Via an expeditious and reproduci ...

. What is the folding code? What is the folding mechanism? Can we predict the native structure of a protein from its amino acid sequence? Is it possible to predict the secondary, tertiary and quaternary structure of a

polypeptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A p ...

sequence based solely on the sequence and environmental information? Inverse protein-folding problem: Is it possible to design a polypeptide sequence which will adopt a given structure under certain environmental conditions? This was achieved for several small globular proteins in 2008. In 2020, it was announced that Google's

AlphaFold AlphaFold is an artificial intelligence (AI) program developed by DeepMind, a subsidiary of Alphabet, which performs predictions of protein structure. The program is designed as a deep learning system. AlphaFold AI software has had two major ve ...

, a neural network based on

DeepMind DeepMind Technologies is a British artificial intelligence subsidiary of Alphabet Inc. and research laboratory founded in 2010. DeepMind was List of mergers and acquisitions by Google, acquired by Google in 2014 and became a wholly owned subsid ...

artificial intelligence, is capable of predicting a protein's final shape based solely on its amino-acid chain with an accuracy of around 90% on a test sample of proteins used by the team. *

Enzyme kinetics Enzyme kinetics is the study of the rates of enzyme-catalysed chemical reactions. In enzyme kinetics, the reaction rate is measured and the effects of varying the conditions of the reaction are investigated. Studying an enzyme's kinetics in th ...

: Why do some

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

s exhibit faster-than-diffusion kinetics? *

RNA Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...

folding problem: Is it possible to accurately predict the secondary, tertiary and quaternary structure of a polyribonucleic acid sequence based on its sequence and environment? *

Protein design Protein design is the rational design of new protein molecules to design novel activity, behavior, or purpose, and to advance basic understanding of protein function. Proteins can be designed from scratch (''de novo'' design) or by making calcula ...

: Is it possible to design highly active enzymes ''de novo'' for any desired reaction? *

Biosynthesis Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. ...

: Can desired molecules, natural products or otherwise, be produced in high yield through biosynthetic pathway manipulation? *What is the mechanism of allosteric transitions of proteins? The concerted and

sequential model The sequential model (also known as the KNF model) is a theory that describes cooperativity of protein subunits. Koshland, D.E., Némethy, G. and Filmer, D. (1966) Comparison of experimental binding data and theoretical models in proteins containi ...

s have been hypothesised but neither has been verified. *What are the endogenous

ligands In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electro ...

orphan receptor In biochemistry, an orphan receptor is a protein that has a similar structure to other identified receptors but whose endogenous ligand has not yet been identified. If a ligand for an orphan receptor is later discovered, the receptor is referred t ...

s? *What substance is endothelium-derived hyperpolarizing factor?

Other

*Why does

biological aging Senescence () or biological aging is the gradual deterioration of functional characteristics in living organisms. The word ''senescence'' can refer to either cellular senescence or to senescence of the whole organism. Organismal senescence inv ...

occur? There are a number of hypotheses as to why senescence occurs including those that it is programmed by gene expression changes and that it is the accumulative damage of biological processes, but these lack explanatory power. * *How do organs grow to the correct shape and size? How are the final shape and size of organs so reliably formed? These processes are in part controlled by the

Hippo signaling pathway The Hippo signaling pathway, also known as the Salvador-Warts-Hippo (SWH) pathway, is a signaling pathway that controls organ size in animals through the regulation of cell proliferation and apoptosis. The pathway takes its name from one of its k ...

. *Can developing biological systems tell the time? To an extent, this appears to be the case, as shown by the

CLOCK A clock or a timepiece is a device used to measure and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month and the ...

gene. * Star jelly. A complete explanation about its origins is still lacking. * Forest rings. The origin of forest rings is not known, despite several mechanisms for their creation having been proposed. Such hypotheses include radially growing fungus, buried

kimberlite pipes Volcanic pipes or volcanic conduits are subterranean geological structures formed by the violent, supersonic eruption of deep-origin volcanoes. They are considered to be a type of ''diatreme''. Volcanic pipes are composed of a deep, narrow cone o ...

, trapped gas pockets, and meteorite impact craters.

Human biology

Handedness In human biology, handedness is an individual's preferential use of one hand, known as the dominant hand, due to it being stronger, faster or more Fine motor skill, dextrous. The other hand, comparatively often the weaker, less dextrous or sim ...

: It is unclear how handedness develops, what purpose it serves, why right-handedness is far more common, and why left-handedness exists. *

Laughter Laughter is a pleasant physical reaction and emotion consisting usually of rhythmical, often audible contractions of the diaphragm and other parts of the respiratory system. It is a response to certain external or internal stimuli. Laughter ...

: While it is generally accepted that laughing evolved as a form of social communication, the exact neurobiological process that leads humans to laugh is not well understood. *

Yawning A yawn is a reflex lasting 4-7 seconds, and is characterized by a long inspiratory phase with gradual mouth gaping, followed by a brief climax (or acme) with muscle stretching, and a rapid expiratory phase with muscle relaxation. For fish an ...

: It is yet to be established what the biological or social purpose of yawning is. *Heritable components of

homosexuality Homosexuality is romantic attraction, sexual attraction, or sexual behavior between members of the same sex or gender. As a sexual orientation, homosexuality is "an enduring pattern of emotional, romantic, and/or sexual attractions" to peop ...

: How to reconcile evolution with the heritable components of human homosexuality? Homosexuality is prevalent across human societies, past and present, and is currently responsible for reduced fecundity. These facts constitute an evolutionary puzzle. *Decline in male sperm counts: It is unclear what is causing the steady decline of sperm counts worldwide since the twentieth century. *Decline in average human body temperature since the 19th century: Medical data suggests that the average body temperature has declined 0.6 °C since the 19th century. The cause is unclear although it has been suggested that it has some relation with reduced inflammation from reduced exposure to microorganisms. *Why are there

blood types Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the ci ...

? It is unclear what the origin and purpose of having blood types is. It is thought that O blood may be an adaptation to malaria and that different blood types respond to different diseases but this hypothesis has yet to be proven. Why did these antigens develop in the first place? What accounts for the differences in blood type? How ancient are the differences in blood types? What accounts for the large number of rare non ABO blood types? What role do blood types have in fighting disease? * Photic sneeze effect: What causes the photic sneeze effect? Why is it so common yet not universal? *

Human sex pheromones No study has led to the isolation of true human sex pheromones, though various researchers have investigated the possibility of their existence. Sex pheromones are chemical ( olfactory) signals, pheromones, released by an organism to attract an ind ...

: There is contradictory evidence on the existence of human pheromones. Do they actually exist, and if so, how do they affect behavior? *Existence of the Grafenberg spot (G-spot): Does the G-spot actually exist? If so is it present in all women? What exactly is it?

Neuroscience and cognition

Neurophysiology

Cognition and psychology

Non-human biology

Ecology, evolution, and paleontology

Unsolved problems relating to the interactions between organisms and their distribution in the environment include: *

Paradox of the plankton In aquatic biology, the paradox of the plankton describes the situation in which a limited range of resources supports an unexpectedly wide range of plankton species, apparently flouting the competitive exclusion principle which holds that whe ...

. The high

diversity Diversity, diversify, or diverse may refer to: Business *Diversity (business), the inclusion of people of different identities (ethnicity, gender, age) in the workforce *Diversity marketing, marketing communication targeting diverse customers * ...

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. Ph ...

seems to violate the

competitive exclusion principle In ecology, the competitive exclusion principle, sometimes referred to as Gause's law, is a proposition that two species which compete for the same limited resource cannot coexist at constant population values. When one species has even the sligh ...

. *

Cambrian explosion The Cambrian explosion, Cambrian radiation, Cambrian diversification, or the Biological Big Bang refers to an interval of time approximately in the Cambrian Period when practically all major animal phyla started appearing in the fossil recor ...

. What is the cause of the apparent rapid diversification of multicellular animal life around the beginning of the

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

, resulting in the emergence of almost all modern animal phyla? * * Darwin's abominable mystery of

botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek w ...

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...

s. What is the exact evolutionary history of

flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...

s and what is the cause of the apparently sudden appearance of nearly modern flowers in the fossil record? *Adult form of

Facetotecta Facetotecta is a poorly known subclass of thecostracan crustaceans. The adult forms have never been recognised, and the group is known only from its larvae, the "y- nauplius" and "y-cyprid" larvae. They are mostly found in the north Atlantic Ocea ...

. The adult form of this animal has never been encountered in the water, and it remains a mystery what it grows into. *Origin of

snake Snakes are elongated, Limbless vertebrate, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Ma ...

s. Did snakes evolve from burrowing lizards or aquatic lizards? There is evidence for both hypotheses. *Origin of

turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...

s. Did turtles evolve from

anapsid An anapsid is an amniote whose skull lacks one or more skull openings (fenestra, or fossae) near the temples. Traditionally, the Anapsida are the most primitive subclass of amniotes, the ancestral stock from which Synapsida and Diapsida evolve ...

s or

diapsid Diapsids ("two arches") are a clade of sauropsids, distinguished from more primitive eureptiles by the presence of two holes, known as temporal fenestrae, in each side of their skulls. The group first appeared about three hundred million years ago ...

s? There is evidence for both hypotheses. *

Ediacaran biota The Ediacaran (; formerly Vendian) biota is a Taxonomy (biology), taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period (). These were composed of enigmatic tubular and frond-sh ...

. How should Ediacaran biota be classified? Even what kingdom they belong to is unclear. Why were they so decisively displaced by Cambrian biota?

Ethology

Unsolved problems relating to the behaviour of animals include: * Homing. A satisfactory explanation for the neurobiological mechanisms that allow homing in animals has yet to be found. *

Flocking (behavior) Flocking is the behaviour exhibited when a group of birds, called a flock, are foraging or in flight. Computer simulations and mathematical models that have been developed to emulate the flocking behaviours of birds can also generally be applie ...

. How flocks of birds and bats coordinate their movements so quickly is not fully understood. Nor is the purpose of large flocks like those of starlings which seem to invite predators rather than protect them. *

Butterfly migration Many populations of Lepidoptera ( butterflies or moths) migrate, sometimes long distances, to and from areas which are only suitable for part of the year. Lepidopterans migrate on all continents except Antarctica, including from or within sub ...

. How do the descendants of

monarch butterfly The monarch butterfly or simply monarch (''Danaus plexippus'') is a milkweed butterfly (subfamily Danainae) in the family Nymphalidae. Other common names, depending on region, include milkweed, common tiger, wanderer, and black-veined brown. It ...

all over Canada and the US eventually, after migrating for several generations, manage to return to a few relatively small overwintering spots? *

Blue whale The blue whale (''Balaenoptera musculus'') is a marine mammal and a baleen whale. Reaching a maximum confirmed length of and weighing up to , it is the largest animal known to have ever existed. The blue whale's long and slender body can ...

. There is not much data on the sexuality of the blue whale. * Gall-inducing insects. At least seven groups of insects, in six orders, have independently evolved the gall-inducing habit. Several adaptation hypotheses have been proposed, but it is largely unknown why this habit evolved and how gall-inducing insects induce gall formation in plants; chemical, mechanical, and viral triggers have been discussed.

Non-human organs and biomolecules

Unsolved problems relating to the structure and function of non-human organs, processes and biomolecules include: *

Korarchaeota In taxonomy, the Korarchaeota are a phylum of the Archaea. The name is derived from the Greek noun koros or kore, meaning ''young man'' or ''young woman,'' and the Greek adjective archaios which means ''ancient.'' They are also known as Xenarchae ...

(archaea). The metabolic processes of this phylum of archaea are so far unclear. *

Glycogen body A glycogen body is an oval structure in the spinal cord of birds that is made of specialized cells that contain large amounts of glycogen. Housed within the synsacrum, the function of this structure is not known, but it does not seem to be rela ...

. The function of this structure in the spinal cord of birds is not known. *

Arthropod head problem The (pan)arthropod head problem is a long-standing zoological dispute concerning the segmental composition of the heads of the various arthropod groups, and how they are evolutionarily related to each other. While the dispute has historically ...

. A long-standing zoological dispute concerning the segmental composition of the heads of the various arthropod groups, and how they are evolutionarily related to each other. *Ovaries of

basking shark The basking shark (''Cetorhinus maximus'') is the second-largest living shark and fish, after the whale shark, and one of three plankton-eating shark species, along with the whale shark and megamouth shark. Adults typically reach in length. ...

s. Only the right ovary in female basking sharks appears to function. The reason is unknown. *Brightly colored bird eggs. It is unknown what evolutionary process would lead birds to having brightly colored eggs given the increased visibility to predators. *

Stegosaur Stegosauria is a group of herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere, predominantly in what is now North America, Europe, ...

osteoderms/scutes. There is a long-standing debate over whether the primary function of the osteoderms/scutes of stegosaurs is protection from predators, sexual display, species recognition, thermoregulation, or other functions.

Artificial life

Unsolved problems in

artificial life Artificial life (often abbreviated ALife or A-Life) is a field of study wherein researchers examine systems related to natural life, its processes, and its evolution, through the use of simulations with computer models, robotics, and biochemistry ...

include: *How does life arise from the nonliving? *What are the potentials and limits of living systems? *How is life related to mind, machines, and culture?

References

{{DEFAULTSORT:List Of Unsolved Problems In Biology

Unsolved problems List of unsolved problems may refer to several notable conjectures or open problems in various academic fields: Natural sciences, engineering and medicine * Unsolved problems in astronomy * Unsolved problems in biology * Unsolved problems in c ...

Biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...