Most biology textbooks, journal articles, lab protocols and conference talks are written in English, so biology students and researchers meet English terms from the first semester onward. This glossary explains the core vocabulary of the field, from cells, DNA and enzymes to evolution, ecology, plants, animals, microbes and everyday lab techniques, with Turkish equivalents and examples taken from lectures, labs and research papers. It also points out the plurals, pronunciations and false friends that often trip up Turkish speakers.
100 terms
10 topics
56 core terms
201 example sentences
Read, understand, keep going
No account needed. Read the meaning, see where the term is used, then study the examples. Click any word in the lesson for help. You can also select a word and press Alt + Enter.
Cells and Levels of Organization
cell
noun
Meaning
The smallest unit of life that can survive on its own. Every living thing is made of one or more cells, and each cell is surrounded by a membrane.
Where you use it
The most basic word in biology. It appears in compounds such as cell biology, cell division, cell culture and cell line. Organisms are unicellular (one cell) or multicellular (many cells). The adjective is cellular.
Examples
Mature red blood cells in mammals have no nucleus.
We counted the cells under the microscope before seeding the plates.
Any individual living thing, such as a bacterium, a mushroom, a tree or a human, that can grow, reproduce and respond to its environment.
Where you use it
A neutral scientific word for 'living thing'. It appears in phrases like living organism, multicellular organism, model organism and genetically modified organism (GMO). Use it when you do not want to say plant, animal or microbe specifically.
Examples
Yeast is a single-celled organism that is easy to grow in the lab.
All the organisms in this pond ultimately depend on algae, which form the base of the food chain.
The large structure in a eukaryotic cell that holds most of its DNA and controls the cell's activities. It is surrounded by a double membrane called the nuclear envelope.
Where you use it
The plural is nuclei (/ˈnuːkliaɪ/). The adjective nuclear appears in nuclear DNA, nuclear envelope and nuclear pore. Prokaryotes such as bacteria have no nucleus; their DNA lies in a region called the nucleoid.
Examples
The nucleus was stained blue with DAPI.
Most cells have a single nucleus, but skeletal muscle fibers contain hundreds of nuclei.
Usage note
In chemistry and physics, nucleus means the center of an atom. Turkish uses 'çekirdek' for both, so the context tells you which one is meant.
Common phrases
cell nucleus · nuclear envelope · nuclear DNA · stain the nucleus
The thin, flexible layer that surrounds every cell and controls what enters and leaves it. It is built mainly from a double layer of phospholipids with proteins set into it.
Where you use it
Also called the plasma membrane, especially in cell biology and biochemistry. It is described as selectively permeable, and textbooks explain its structure with the fluid mosaic model. Do not confuse it with the cell wall, which lies outside the membrane in plants, fungi and bacteria.
Examples
Oxygen and carbon dioxide cross the cell membrane by simple diffusion.
The detergent in the lysis buffer breaks open the cell membrane.
Common phrases
plasma membrane · selectively permeable membrane · membrane protein · cross the membrane · phospholipid bilayer
An organelle that releases energy from food molecules and stores it as ATP through aerobic respiration. It has two membranes and its own small set of DNA.
Where you use it
Almost always used in the plural, mitochondria. School biology calls it 'the powerhouse of the cell'. Researchers talk about mitochondrial DNA (mtDNA), mitochondrial function and mitochondrial disease. In humans, mtDNA is inherited from the mother.
Examples
Muscle cells contain large numbers of mitochondria because they need a lot of ATP.
The drug damaged the inner membrane of the mitochondrion.
Usage note
Singular mitochondrion, plural mitochondria. Saying 'a mitochondria' is a common mistake.
Common phrases
mitochondrial DNA · inner mitochondrial membrane · mitochondrial function · mitochondrial disease
Everything inside the cell membrane apart from the nucleus: a jelly-like fluid called the cytosol together with the organelles suspended in it.
Where you use it
Used when describing where a process happens: glycolysis takes place in the cytoplasm, while transcription in eukaryotes happens in the nucleus. Researchers use the more precise word cytosol for the fluid alone. The adjective is cytoplasmic.
Examples
In bacteria, the DNA lies in the cytoplasm rather than inside a nucleus.
The fluorescent protein spread through the cytoplasm but did not enter the nucleus.
Common phrases
in the cytoplasm · cytoplasmic protein · cytoplasmic streaming · cytosol
A small structure inside a cell that has a specific job, such as the nucleus, mitochondria or chloroplasts. Most organelles are surrounded by their own membrane.
Where you use it
Literally 'little organ'. Textbooks separate membrane-bound organelles, found only in eukaryotes, from structures such as ribosomes that have no membrane. Other examples are the endoplasmic reticulum (ER), the Golgi apparatus, lysosomes and vacuoles.
Examples
Prokaryotic cells lack membrane-bound organelles.
We used a dye that stains only one organelle, the endoplasmic reticulum.
A single-celled organism whose cell has no nucleus and no membrane-bound organelles. Bacteria and archaea are prokaryotes.
Where you use it
The adjective prokaryotic is more common than the noun: prokaryotic cell, prokaryotic genome. Prokaryotic DNA is usually one circular chromosome, often with small extra rings called plasmids. Older texts sometimes spell it procaryote.
Examples
Unlike eukaryotes, prokaryotes divide by binary fission.
Prokaryotic ribosomes are smaller than eukaryotic ones, which is why some antibiotics can target them.
Usage note
From Greek, roughly 'before the nucleus'. A simple memory aid: pro- means no nucleus, eu- means a true nucleus.
An organism whose cells have a true nucleus and membrane-bound organelles. Animals, plants, fungi and protists are all eukaryotes.
Where you use it
As with prokaryote, the adjective eukaryotic is used more often: eukaryotic cell, eukaryotic gene expression. Eukaryotic cells are usually much larger and more complex than prokaryotic cells.
Examples
Yeast is often used as a simple model of eukaryotic cells.
Early eukaryotes probably gained mitochondria by engulfing an ancient bacterium.
A small structure made of RNA and protein that builds proteins by reading the instructions in messenger RNA. Ribosomes are found in all cells.
Where you use it
Ribosomes float freely in the cytoplasm or are attached to the rough endoplasmic reticulum. Each has a large and a small subunit. Prokaryotic ribosomes (70S) are smaller than eukaryotic ones (80S), a difference some antibiotics exploit.
Examples
During translation, the ribosome moves along the mRNA one codon at a time.
Rough ER looks rough because it is covered with ribosomes.
A strong, rigid layer outside the cell membrane that supports and protects the cell. Plants, fungi and most bacteria have cell walls, but animal cells do not.
Where you use it
The material differs between groups: cellulose in plants, chitin in fungi and peptidoglycan in bacteria. The cell wall stops plant cells from bursting in water and keeps them firm (turgid). Penicillin works by blocking bacterial cell wall synthesis.
Examples
The cell wall gives plant cells their regular, box-like shape under the microscope.
Gram-positive bacteria have a thick peptidoglycan cell wall.
A type of cell division in which one cell produces two daughter cells with the same number of chromosomes and the same genetic information as the parent cell.
Where you use it
Used for growth, repair and asexual reproduction. Its phases are prophase, metaphase, anaphase and telophase (remembered as PMAT), usually followed by cytokinesis. The adjective is mitotic: mitotic phase, mitotic spindle.
Examples
Skin cells are constantly replaced by mitosis.
On the onion root tip slide, you can see cells at every stage of mitosis.
Usage note
Students often mix up mitosis and meiosis. Mitosis: two identical cells with the same chromosome number. Meiosis: four different cells with half the chromosome number.
A group of similar cells that work together to do a particular job. Organs are made of several different types of tissue.
Where you use it
Animals have four main tissue types: epithelial, connective, muscle and nervous tissue. Plants have tissues such as xylem, phloem and epidermis. The study of tissues is histology. In the lab, people talk about tissue samples, tissue sections and tissue culture.
Examples
Thin sections of the liver tissue were stained and examined under the microscope.
Cartilage is a type of connective tissue.
Usage note
In everyday English, a tissue is also a paper handkerchief. In biology it always means a group of cells.
An unspecialized cell that can divide many times and develop into one or more specialized cell types, such as muscle, nerve or blood cells.
Where you use it
The key ideas are self-renewal and differentiation. Embryonic stem cells can become almost any cell type; adult stem cells, such as those in bone marrow, are more limited. In plants, stem cells sit in meristems at the tips of roots and shoots.
Examples
Blood stem cells in the bone marrow produce red cells, white cells and platelets.
The lab is studying how stem cells differentiate into heart muscle cells.
Usage note
'Stem cell' has nothing to do with a plant stem; here 'stem' means origin. Turkish 'kök hücre' (root cell) uses a different image for the same idea.
The net movement of particles from an area where they are more concentrated to an area where they are less concentrated, without the cell using energy.
Where you use it
A form of passive transport: particles move down a concentration gradient. Facilitated diffusion uses channel or carrier proteins. Compare active transport, which moves substances against the gradient and uses ATP. The verb is diffuse.
Examples
Oxygen moves from the alveoli into the blood by diffusion.
The rate of diffusion increases with temperature.
Common phrases
simple diffusion · facilitated diffusion · rate of diffusion · concentration gradient · diffuse across
The movement of water across a selectively permeable membrane from a dilute solution into a more concentrated one, until the concentrations become more equal.
Where you use it
A special case of diffusion that involves water only. Solutions are described as hypotonic, isotonic or hypertonic. In hypotonic solutions animal cells may burst while plant cells become turgid; in hypertonic solutions plant cells undergo plasmolysis.
Examples
Red blood cells placed in pure water swell and burst because of osmosis.
The potato strips in salt water lost mass by osmosis.
Usage note
In everyday English, learning something 'by osmosis' means absorbing it gradually without effort. In biology, osmosis is always about water.
Common phrases
water moves by osmosis · osmotic pressure · hypertonic solution · hypotonic solution
A large molecule made of one or more chains of amino acids folded into a specific shape. Proteins build cell structures, speed up reactions and carry signals.
Where you use it
One of the four main groups of biological molecules, with carbohydrates, lipids and nucleic acids. Researchers talk about protein structure, protein folding, protein synthesis and protein levels. A gene encodes, or codes for, a protein.
Examples
Hemoglobin is the protein that carries oxygen in red blood cells.
The mutation changes the shape of the protein, so it can no longer bind its target.
Common phrases
protein synthesis · protein structure · protein folding · encode a protein · membrane protein
A molecule, usually a protein, that speeds up a chemical reaction in a living thing without being used up. Each enzyme acts on a specific substrate at its active site.
Where you use it
Often called a biological catalyst. Many enzyme names end in -ase: amylase, lactase, DNA polymerase. An enzyme catalyzes a reaction, binds a substrate, and can be inhibited or denatured. Every enzyme has an optimum temperature and pH.
Examples
The enzyme amylase in saliva starts breaking down starch in the mouth.
Above 60 °C the enzyme was denatured and lost its activity.
Common phrases
enzyme activity · active site · digestive enzyme · restriction enzyme · enzyme inhibitor
All the chemical reactions that take place in a living thing to keep it alive, including breaking down food for energy and building new molecules.
Where you use it
Divided into catabolism (breaking down) and anabolism (building up). Biochemists talk about metabolic pathways, metabolic rate and metabolites. The verb is metabolize: the liver metabolizes many drugs.
Examples
Small mammals have a much faster metabolism per gram of body weight than large ones.
The process by which cells break down glucose and other food molecules to release energy and store it as ATP. When oxygen is used, carbon dioxide and water are produced.
Where you use it
Has three main stages: glycolysis, the Krebs (citric acid) cycle and the electron transport chain. Aerobic respiration needs oxygen; anaerobic respiration and fermentation do not. In eukaryotes, most of it happens in mitochondria.
Examples
Cellular respiration releases the energy that was stored in glucose during photosynthesis.
In cellular respiration, oxygen acts as the final electron acceptor.
Usage note
In biology, respiration means the chemical process inside cells, not just breathing. Use 'breathing' or 'ventilation' for moving air in and out of the lungs.
Common phrases
aerobic respiration · anaerobic respiration · rate of respiration · electron transport chain
An organic molecule made of carbon, hydrogen and oxygen, such as a sugar, starch or cellulose. Carbohydrates store energy and build structures like plant cell walls.
Where you use it
Divided into monosaccharides (glucose, fructose), disaccharides (sucrose, lactose) and polysaccharides (starch, glycogen, cellulose). Sugar names usually end in -ose. Informally shortened to carbs, but not in scientific writing.
Examples
Plants store carbohydrate as starch, while animals store it as glycogen.
Cellulose is the most abundant carbohydrate on Earth.
One of the small building blocks that join in chains to make proteins. Living things use 20 common amino acids, each with a different side chain.
Where you use it
Amino acids are linked by peptide bonds to form polypeptides, and each one is coded by a three-base codon in mRNA. Essential amino acids cannot be made by the body and must come from food. They are abbreviated with three letters (Gly, Ala) or one letter (G, A).
Examples
The mutation replaces one amino acid with another at position 6 of the protein.
Humans must get nine essential amino acids from their diet.
Short for adenosine triphosphate, the molecule that cells use to store and transfer energy. Breaking off one of its phosphate groups releases energy for cell work.
Where you use it
Often called the energy currency of the cell. ATP is made in cellular respiration and photosynthesis and used for muscle contraction, active transport and building molecules. When it loses a phosphate, it becomes ADP. Said letter by letter: A-T-P.
Examples
Active transport uses ATP to move ions against their concentration gradient.
One glucose molecule yields around 30 ATP in aerobic respiration.
Common phrases
ATP production · ATP synthesis · ATP synthase · generate ATP
A fatty or oily organic molecule that does not dissolve in water, such as a fat, oil, phospholipid or steroid. Lipids store energy and form cell membranes.
Where you use it
A broad term in biochemistry; fat is only one kind of lipid. Phospholipids form the cell membrane, triglycerides store energy, and cholesterol and steroid hormones are lipids too. Lipids are described as hydrophobic (water-fearing).
Examples
Seeds such as sunflower store most of their energy as lipids.
The emulsion test uses ethanol to detect lipids in food.
To change the natural folded shape of a protein or DNA, for example with heat, extreme pH or chemicals, so that it can no longer work normally.
Where you use it
Often used in the passive or without an object: the enzyme is denatured, the protein denatures above 60 °C. In PCR, heating to about 95 °C denatures double-stranded DNA into single strands. The noun is denaturation; the reverse is renaturation.
Examples
Boiling denatures the proteins in egg white, which is why it turns solid.
The samples were heated to 95 °C to denature the DNA.
Usage note
Denature does not mean 'destroy'. The peptide bonds of the chain usually stay intact; only the 3D shape is lost.
Common phrases
denatured protein · heat-denatured · denaturing conditions · denaturation step
Short for deoxyribonucleic acid, the molecule that stores genetic information in every cell and in many viruses. It is made of two strands twisted into a double helix.
Where you use it
Always said letter by letter (D-N-A) and almost never written in full. Common phrases: DNA sequence, DNA extraction, DNA sample, DNA damage. In the lab, people extract, amplify, sequence and purify DNA.
Examples
We extracted DNA from the leaf samples and checked its quality on a gel.
UV light can damage DNA and cause mutations.
Usage note
Turkish labs say 'DNA izolasyonu'. English papers use both 'DNA isolation' and 'DNA extraction', but 'extraction' is more common in protocols and kit names.
Common phrases
DNA sequence · extract DNA · DNA sample · DNA damage · double-stranded DNA
A section of DNA that carries the instructions for making a particular protein or functional RNA. Genes are the basic units of heredity passed from parents to offspring.
Where you use it
Used in genetics, molecular biology and medicine. Genes are expressed, switched on or off, mutated, cloned or knocked out. Gene names are usually written in italics, while the protein a gene encodes is not.
Examples
This gene is expressed only in the roots of the plant.
Mutations in a single gene can cause cystic fibrosis.
Usage note
'Gene' and 'genus' look alike but mean different things: a genus is a group of closely related species, as in the genus Homo.
Common phrases
gene expression · gene mutation · target gene · gene function · knock out a gene
A long, tightly packed structure of DNA and proteins that carries many genes. Human body cells normally have 46 chromosomes, arranged in 23 pairs.
Where you use it
Used in genetics, cytology and medicine. Key phrases: sex chromosomes (X and Y), homologous chromosomes, chromosome number and chromosomal abnormality. Chromosomes become visible under a light microscope when the cell divides.
Examples
Down syndrome is caused by an extra copy of chromosome 21.
During meiosis, homologous chromosomes pair up and exchange segments.
Common phrases
sex chromosome · homologous chromosomes · chromosome number · X chromosome · chromosomal abnormality
A characteristic of an organism, such as eye color, flower shape or blood type. Some traits are inherited through genes, while others are shaped by the environment.
Where you use it
A key word in genetics and evolution. People talk about inherited traits, dominant and recessive traits, and traits that are passed on to offspring. In formal writing, 'trait' is preferred to 'feature' or 'property' for a biological characteristic.
Examples
Mendel studied seven traits in pea plants, including seed shape and flower color.
Antibiotic resistance is a trait that can spread quickly through a bacterial population.
Common phrases
inherited trait · dominant trait · recessive trait · pass on a trait · physical trait
A permanent change in the DNA sequence of a gene or chromosome. It can be harmful, neutral or occasionally useful, and it is a source of genetic variation.
Where you use it
Common types include point mutations, deletions, insertions and frameshift mutations. Mutations occur or arise, or are caused by mutagens such as UV light and certain chemicals. The verb is mutate, and an organism that carries a mutation is a mutant.
Examples
A single point mutation in the hemoglobin gene causes sickle cell anemia.
We screened the plant lines for mutations that affect flowering time.
Common phrases
point mutation · genetic mutation · harmful mutation · carry a mutation · mutation rate
A type of cell division that produces four cells, each with half the usual number of chromosomes. It makes the sex cells (gametes) and creates genetic variety.
Where you use it
Has two rounds of division, meiosis I and meiosis II. Variation comes from crossing over between homologous chromosomes and from independent assortment. Pronounced my-OH-sis. The adjective is meiotic.
Examples
Meiosis in humans produces gametes with 23 chromosomes instead of 46.
Crossing over during meiosis is one reason why brothers and sisters look different.
Common phrases
meiosis I · meiosis II · undergo meiosis · crossing over · meiotic division
One of the different versions of the same gene. For example, a gene for flower color may have one allele for purple flowers and another for white.
Where you use it
Most animals and plants carry two alleles of each gene, one from each parent. Alleles are written with letters: a capital for dominant (P), lowercase for recessive (p). Common phrases: dominant allele, recessive allele, allele frequency.
Examples
A pea plant with one purple allele and one white allele has purple flowers.
The frequency of this allele has increased in the population over 20 generations.
Usage note
Pronounced uh-LEEL (/əˈliːl/), with the stress on the second syllable.
Common phrases
dominant allele · recessive allele · allele frequency · carry an allele · mutant allele
The genetic makeup of an organism, especially the pair of alleles it carries for a particular gene, such as PP, Pp or pp.
Where you use it
Paired with phenotype: the genotype is what the genes say, the phenotype is what you can observe. A genotype can be homozygous (two identical alleles) or heterozygous (two different alleles). As a verb, to genotype means to test an organism's DNA.
Examples
A cross between two Pp plants gives a 1:2:1 genotype ratio.
All the mice were genotyped by PCR before the experiment.
Common phrases
genotype ratio · homozygous genotype · heterozygous genotype · genotype frequency
The observable characteristics of an organism, such as height, color or blood type, which result from its genotype together with the environment.
Where you use it
Used in genetics, breeding and medicine. Researchers describe a mutant phenotype, a wild-type phenotype and phenotypic differences. Two organisms can share a phenotype but have different genotypes: PP and Pp pea plants both have purple flowers.
Examples
The knockout mice showed no obvious phenotype until they were exposed to cold.
Identical twins share a genotype, but their phenotypes can differ slightly because of the environment.
Describing an allele whose effect shows in the organism even when only one copy is present. It hides the effect of a recessive allele.
Where you use it
Used in phrases like dominant allele, dominant trait and autosomal dominant disorder. Dominant alleles are written with capital letters. In ecology, a dominant species is the most common or influential species in a community.
Examples
Purple flower color is dominant over white in Mendel's peas.
Huntington's disease is caused by a dominant allele, so one copy is enough to cause it.
Usage note
Dominant does not mean more common. Some dominant alleles are rare, and some recessive ones are very common in a population.
Common phrases
dominant allele · dominant trait · dominant over · autosomal dominant · dominant species
Describing an allele whose effect shows only when an organism has two copies of it. With only one copy, its effect is hidden by a dominant allele.
Where you use it
Recessive alleles are written in lowercase (p). A person with one recessive allele for a disease is called a carrier. Common phrases: recessive allele, recessive trait, autosomal recessive and X-linked recessive.
Examples
Cystic fibrosis is a recessive condition, so a child must inherit the allele from both parents.
White flowers appeared again in the second generation because the recessive allele had been hidden.
To receive genes, and the traits they control, from your parents. A trait that is inherited is passed from one generation to the next.
Where you use it
Usually 'inherit something from someone': she inherited the allele from her mother. The noun is inheritance and the adjectives are inherited and heritable. The opposite idea is acquired traits, which develop during life and are not passed on through genes.
Examples
Each child inherits half of its chromosomes from the mother and half from the father.
Mitochondrial DNA is inherited only through the mother's line.
Usage note
In everyday English, 'inherit' also means receiving money or property after someone dies. In biology it always refers to genes.
Common phrases
inherit a trait · inherit from · inherited disease · pattern of inheritance · inherited mutation
Short for ribonucleic acid, a usually single-stranded molecule that carries genetic information from DNA and helps build proteins. It contains uracil instead of thymine.
Where you use it
The main types are messenger RNA (mRNA), transfer RNA (tRNA) and ribosomal RNA (rRNA). Some viruses use RNA instead of DNA as their genetic material. Lab phrases: RNA extraction, RNA sequencing (RNA-seq), RNA degradation.
Examples
RNA degrades quickly, so we keep the samples at −80 °C.
During transcription, a strand of messenger RNA is copied from the DNA template.
The basic building block of DNA and RNA, made of a sugar, a phosphate group and a nitrogen-containing base such as adenine (A), thymine (T), guanine (G) or cytosine (C).
Where you use it
In DNA, A pairs with T and G pairs with C; in RNA, uracil (U) replaces thymine. People talk about nucleotide sequences, single-nucleotide polymorphisms (SNPs) and nucleotide substitutions. A DNA strand is a chain of nucleotides.
Examples
A change in a single nucleotide can alter the amino acid that a codon codes for.
The process by which the information in a gene is used to make a product, usually a protein. It includes transcription of DNA into RNA and translation of RNA into protein.
Where you use it
Researchers measure, compare and regulate gene expression. Genes can be upregulated (expressed more) or downregulated (expressed less). Every cell in the body has the same genes, but different cell types express different ones.
Examples
We used qPCR to measure gene expression in treated and untreated cells.
Light switches on the expression of several genes involved in photosynthesis.
The first step of gene expression, in which the DNA sequence of a gene is copied into a matching strand of RNA by the enzyme RNA polymerase.
Where you use it
In eukaryotes it takes place in the nucleus; in prokaryotes, in the cytoplasm. Proteins called transcription factors switch it on or off. The verb is transcribe: a gene is transcribed into mRNA.
Examples
Transcription begins when RNA polymerase binds to the promoter.
This drug blocks transcription, so no new mRNA is made.
Usage note
In everyday English, a transcription is a written copy of speech. In biology, it means copying DNA into RNA.
Common phrases
transcription factor · start of transcription · RNA polymerase · transcribed into mRNA
The step of gene expression in which a ribosome reads the codons in messenger RNA and joins the matching amino acids together to build a protein.
Where you use it
Follows transcription. Transfer RNA (tRNA) molecules bring amino acids to the ribosome. Translation starts at a start codon (AUG) and ends at a stop codon. The verb is translate: the mRNA is translated into protein.
Examples
Many antibiotics stop bacterial growth by blocking translation.
In bacteria, translation can begin before transcription is finished.
Common phrases
start codon · stop codon · translated into protein · translation initiation
The complete set of genetic material in an organism or cell, including all of its genes and the DNA between them.
Where you use it
Researchers sequence, assemble and annotate genomes. The human genome has about 3 billion base pairs and roughly 20,000 protein-coding genes. The field is called genomics, and the adjective is genomic, as in genomic DNA.
Examples
The first draft of the human genome was published in 2001.
We sequenced the genome of a new bacterial strain isolated from hot springs.
Common phrases
human genome · genome sequencing · whole genome · genome size · genomic DNA
A group of similar organisms that can breed with each other and produce fertile offspring. It is the basic unit used to classify living things.
Where you use it
The same form is used for singular and plural: one species, two species. Scientific names have two parts, genus and species, as in Homo sapiens. Ecologists talk about native, endangered, invasive and keystone species.
Examples
More than 30 species of orchid grow wild in this valley.
Lions and tigers are different species, although they can produce hybrids in captivity.
Usage note
'Specie' is not the singular of species; it is a different word meaning coins. Always write 'a species'.
Common phrases
endangered species · native species · new species · species diversity · closely related species
The change in the inherited traits of populations over many generations. It explains how all living species descend from earlier forms of life.
Where you use it
Central to all of biology. The verb is evolve (species evolve, a trait evolves) and the adjective is evolutionary: evolutionary biology, evolutionary history. In science, evolution is a well-supported theory; 'theory' here does not mean a guess.
Examples
Darwin's ideas on evolution were published in 1859 in On the Origin of Species.
The evolution of antibiotic resistance in bacteria can be observed within a few years.
Common phrases
theory of evolution · evolutionary biology · human evolution · convergent evolution · evolve over time
The process by which individuals with traits better suited to their environment survive and reproduce more, so those traits become more common over generations.
Where you use it
The main mechanism of evolution described by Charles Darwin and Alfred Russel Wallace. Natural selection acts on, favors or selects against a trait. Compare artificial selection, in which humans choose which plants or animals breed.
Examples
Natural selection favored darker moths when soot covered the tree trunks.
Students often confuse natural selection with the idea that animals change because they need to.
Common phrases
process of natural selection · favored by natural selection · selective pressure · artificial selection
A feature that helps an organism survive and reproduce in its environment, such as a camel's wide feet; also the evolutionary process that produces such features.
Where you use it
Adaptations can be structural (body shape), physiological (body chemistry) or behavioral (migration). The verb is adapt: a species adapts to its environment over many generations. In everyday speech, adapt also means an individual adjusting during its lifetime.
Examples
Thick fur and a layer of fat are adaptations to life in the Arctic.
Cacti show many adaptations to dry habitats, including spines instead of leaves.
Common phrases
adaptation to · structural adaptation · behavioral adaptation · adapt to the environment
The science of naming, describing and classifying organisms into groups based on their shared characteristics and evolutionary relationships.
Where you use it
The main ranks, from broadest to narrowest, are domain, kingdom, phylum, class, order, family, genus and species. A scientist in this field is a taxonomist. Carl Linnaeus introduced the two-part naming system (binomial nomenclature) still used today.
Examples
The taxonomy of this group was revised after DNA studies revealed unexpected relationships.
She is a taxonomist who has described more than 40 new beetle species.
An earlier species from which two or more later species have descended. The more recently two species shared a common ancestor, the more closely related they are.
Where you use it
A key idea in evolution and phylogenetics. Scientists speak of the most recent common ancestor (MRCA) and say that species share or descend from a common ancestor. On a phylogenetic tree, each branching point represents a common ancestor.
Examples
Humans and chimpanzees share a common ancestor that lived several million years ago.
Birds and crocodiles have a more recent common ancestor than birds and lizards do.
Usage note
Humans did not evolve from chimpanzees; both evolved from a common ancestor. This is a frequent misunderstanding.
Common phrases
share a common ancestor · most recent common ancestor · descend from a common ancestor · last universal common ancestor
The preserved remains or traces of an organism that lived long ago, such as bones, shells, leaf prints or footprints, usually found in sedimentary rock.
Where you use it
The fossil record is the history of life as shown by fossils. Scientists who study fossils are paleontologists. Fossils are dated, excavated and described. A transitional fossil, such as Archaeopteryx, shows features of two different groups.
Examples
The oldest known animal fossils are more than 500 million years old.
Archaeopteryx is a famous transitional fossil with features of both dinosaurs and birds.
A branching diagram that shows the evolutionary relationships among species or genes, based on how recently they shared a common ancestor.
Where you use it
Built from DNA sequences, protein sequences or physical traits. The tips are species, the branching points (nodes) are common ancestors, and a clade is an ancestor with all its descendants. It is also called an evolutionary tree; the field is phylogenetics.
Examples
We built a phylogenetic tree from the 16S rRNA sequences of the isolates.
On the phylogenetic tree, whales group with hippos, not with fish.
Common phrases
build a phylogenetic tree · phylogenetic analysis · branching point · clade
A community of living things together with the non-living parts of their environment, such as water, soil and climate, all interacting as one system.
Where you use it
Used in ecology, environmental science and the news. Living parts are called biotic factors and non-living parts abiotic factors. An ecosystem can be as large as a forest or as small as a pond.
Examples
The dam changed the whole river ecosystem downstream.
Wetlands are among the most productive ecosystems on Earth.
The natural place where a particular organism or species lives and finds the food, shelter and conditions it needs.
Where you use it
Common in ecology and conservation. Typical phrases: natural habitat, habitat loss, habitat destruction and habitat fragmentation. A habitat is the place; the role a species plays there is its niche.
Examples
Habitat loss is the biggest threat to many amphibian species.
The Mediterranean monk seal needs undisturbed sea caves as its breeding habitat.
All the members of one species that live in the same area at the same time and can breed with each other.
Where you use it
In biology, population is not limited to people. Ecologists measure population size, density and growth and study why a population increases, declines or crashes. Population genetics studies how allele frequencies change over time.
Examples
The wolf population in the park has doubled in ten years.
A simple sequence showing what eats what in an ecosystem. It starts with a producer such as a plant and passes energy from one consumer to the next.
Where you use it
A typical example: grass → grasshopper → frog → snake → hawk. The arrows show the direction of energy flow. Organisms are described as producers, primary consumers, secondary consumers and so on. Several connected food chains form a food web.
Examples
Some pesticides become more concentrated at each step up the food chain.
Phytoplankton are at the bottom of almost every marine food chain.
Common phrases
top of the food chain · bottom of the food chain · marine food chain · aquatic food chain
The variety of life in a particular place or on Earth as a whole, including the diversity of genes, species and ecosystems.
Where you use it
A short form of 'biological diversity', used in ecology, conservation and environmental policy. People talk about biodiversity loss, biodiversity hotspots and conserving biodiversity. Tropical rainforests and coral reefs have very high biodiversity.
Examples
Turkey has rich plant biodiversity, with many species found nowhere else in the world.
Draining the wetland led to a sharp loss of biodiversity.
An animal that hunts, kills and eats other animals. The animal that it hunts is called its prey.
Where you use it
Usually paired with prey: predator-prey relationships, predator-prey cycles. Top or apex predators, such as wolves and sharks, have few or no natural predators. The verb is prey on: owls prey on mice. The process is called predation.
Examples
When the number of predators falls, the prey population often grows quickly.
Wolves are the main predator of deer in this forest.
Common phrases
predator and prey · top predator · natural predator · predator-prey relationship
A network of connected food chains that shows all the feeding relationships in an ecosystem, since most organisms eat, and are eaten by, more than one species.
Where you use it
More realistic than a single food chain. Ecologists use food webs to predict what happens when one species is removed or added. Each feeding level in a web is called a trophic level.
Examples
Removing sea otters from the food web led to an explosion in sea urchin numbers.
Draw a food web for the pond using at least eight organisms.
Common phrases
complex food web · marine food web · trophic level · draw a food web
An organism, mainly a bacterium or fungus, that breaks down dead plants, animals and waste, returning nutrients to the soil and the ecosystem.
Where you use it
One of the three main roles in an ecosystem, together with producers and consumers. The process is decomposition and the verb is decompose. Without decomposers, nutrients such as nitrogen and phosphorus would stay locked in dead matter.
Examples
Fungi are the main decomposers of wood in forests.
Decomposers recycle the nutrients that plants need to grow.
Usage note
Textbooks sometimes separate decomposers (bacteria and fungi) from detritivores, animals such as earthworms that eat dead material.
A close, long-term relationship between two different species that live together. It can benefit both, benefit one without affecting the other, or harm one.
Where you use it
Biologists divide it into mutualism (both benefit), commensalism (one benefits, the other is unaffected) and parasitism (one benefits, the other is harmed). The adjective is symbiotic, and each partner is a symbiont.
Examples
A lichen is a symbiosis between a fungus and an alga or cyanobacterium.
Bacteria in the root nodules of beans live in symbiosis with the plant and fix nitrogen.
Usage note
In everyday English, symbiosis usually suggests a relationship that is good for both sides. In biology, the term also covers parasitism.
Common phrases
mutualistic symbiosis · live in symbiosis · symbiotic relationship · symbiotic bacteria
A species brought by humans, on purpose or by accident, to a region where it does not naturally live, and which spreads and harms native species or the ecosystem.
Where you use it
Also called an alien, non-native or introduced species, although not every introduced species becomes invasive. Ecologists talk about controlling, managing or eradicating invasive species. Islands and inland waters are especially vulnerable.
Examples
The silver-cheeked toadfish, an invasive species, entered the Mediterranean through the Suez Canal.
Invasive species often spread quickly because they have no natural predators in their new habitat.
Common phrases
control invasive species · invasive alien species · spread of invasive species · introduced species
The process in which plants, algae and some bacteria use light energy to make glucose from carbon dioxide and water, releasing oxygen as a by-product.
Where you use it
Takes place in chloroplasts and has two stages: the light-dependent reactions and the Calvin cycle. The verb is photosynthesize and the adjective photosynthetic, as in photosynthetic organisms. Stress falls on SYN: pho-to-SYN-the-sis.
Examples
We measured the rate of photosynthesis by counting the oxygen bubbles released by the pondweed.
Photosynthesis slows down when the stomata close on hot, dry days.
Common phrases
rate of photosynthesis · carry out photosynthesis · light-dependent reactions · photosynthetic pigment
An organelle in plant and algal cells where photosynthesis takes place. It contains the green pigment chlorophyll and has its own DNA.
Where you use it
Chloroplasts contain stacks of membranes called thylakoids (one stack is a granum) surrounded by a fluid called the stroma. Like mitochondria, they are thought to descend from bacteria that once lived inside other cells (endosymbiosis).
Examples
Leaf cells near the surface are packed with chloroplasts to capture as much light as possible.
Root cells usually have no chloroplasts because they receive no light.
The plant tissue that carries water and dissolved minerals upward from the roots to the stems and leaves. Its cells are dead when mature and form hollow tubes.
Where you use it
Paired with phloem in the vascular bundles of plants. Xylem walls are strengthened with lignin, the material that makes wood hard. Water moves up the xylem mainly because of transpiration pull. Pronounced ZY-lem (/ˈzaɪləm/).
Examples
Water moves up the xylem from the roots to the leaves.
In the cross-section, the xylem vessels were stained red.
Common phrases
xylem vessels · xylem sap · vascular bundle · transport in the xylem
The plant tissue that carries sugars and other products of photosynthesis from the leaves to other parts of the plant, such as roots, fruits and growing tips.
Where you use it
Made of living sieve tube elements and companion cells. Transport in the phloem is called translocation and can move both up and down the plant. Pronounced FLOH-em (/ˈfloʊem/): the 'oe' is two separate sounds.
Examples
Aphids feed by pushing their mouthparts into the phloem.
Removing a ring of bark cuts the phloem and stops sugars from reaching the roots.
Common phrases
phloem sap · sieve tube · companion cell · transport in the phloem
The transfer of pollen from the male part of a flower (the anther) to the female part (the stigma), which allows fertilization and seed production in flowering plants.
Where you use it
It can be self-pollination (within one plant) or cross-pollination (between plants). Animals that carry pollen, such as bees, butterflies and bats, are pollinators; some plants are pollinated by wind or water. The verb is pollinate.
Examples
Many crops depend on bees for pollination.
Grasses, oaks and birches rely on wind pollination.
Usage note
Pollination is not the same as fertilization. Pollination moves the pollen; fertilization is the fusion of the male and female gametes that follows.
Of a seed or spore, to start growing and develop into a new plant or organism, usually once it has enough water, oxygen and the right temperature.
Where you use it
Used without an object (the seeds germinated) and with one (we germinated the seeds on wet filter paper). The noun is germination: germination rate, germination test. Some seeds stay dormant and need cold or light before they germinate.
Examples
Most of the seeds germinated within five days at 20 °C.
Salt stress reduced the germination rate by almost half.
Common phrases
seeds germinate · germination rate · germination test · fail to germinate
A tiny pore, mostly on the underside of a leaf, that lets carbon dioxide in and oxygen and water vapor out. Each stoma is opened and closed by two guard cells.
Where you use it
Almost always used in the plural, stomata (/ˈstoʊmətə/). Plants close their stomata in drought to save water, which also slows photosynthesis. Researchers measure stomatal density and stomatal conductance.
Examples
Most stomata are on the lower surface of the leaf, away from direct sunlight.
Each stoma is surrounded by a pair of guard cells.
Usage note
Singular stoma, plural stomata. In medicine, a stoma is a surgical opening in the body, which is a different meaning.
Common phrases
guard cells · stomatal closure · stomatal density · open stomata
The loss of water vapor from a plant, mainly through the stomata in its leaves. It pulls water up through the xylem from the roots.
Where you use it
The rate of transpiration rises with heat, wind, light and low humidity, and students measure it with a potometer. Transpiration also cools the plant. The verb is transpire, but in everyday English 'transpire' usually means 'happen' or 'become known'.
Examples
On hot, windy days the rate of transpiration increases sharply.
A large tree can lose hundreds of liters of water a day through transpiration.
The young produced by an animal or plant; its children. The same word is used for one young or for many.
Where you use it
Offspring has the same form in singular and plural. It is neutral and scientific, used for animals, plants and microbes. Common verbs: produce, raise, care for offspring. A more technical synonym is progeny.
Examples
Sea turtles produce hundreds of offspring, but very few survive to adulthood.
The offspring of the cross were all heterozygous.
Usage note
Never add -s: 'offsprings' is a mistake.
Common phrases
produce offspring · fertile offspring · number of offspring · care for offspring
The ability of an organism or cell to keep its internal conditions, such as temperature, water balance and blood sugar, stable while the outside world changes.
Where you use it
Usually works through negative feedback: a change is detected and the body responds to reverse it. Examples include sweating when hot and insulin release after a meal. The adjective is homeostatic. Stress: ho-me-o-STA-sis.
Examples
The kidneys play a central role in water homeostasis.
The network of cells, tissues and organs that protects the body from pathogens and other harmful substances, and remembers threats it has met before.
Where you use it
Has two main parts: innate immunity (fast and general) and adaptive immunity (slower, specific and with memory). Key cells include white blood cells such as B cells, T cells and macrophages. The immune system recognizes, attacks or responds to a pathogen.
Examples
Vaccines train the immune system to recognize a pathogen without causing disease.
In autoimmune diseases, the immune system attacks the body's own cells.
A chemical messenger made in one part of an organism and carried, often in the blood, to target cells elsewhere, where it changes their activity.
Where you use it
In animals, hormones are secreted by endocrine glands such as the thyroid and pancreas; insulin, adrenaline and estrogen are examples. Plants also have hormones, such as auxin and gibberellin. Hormones are secreted or released and act on target cells.
Examples
Insulin is a hormone that lowers blood glucose.
The plant hormone auxin makes shoots bend toward light.
A nerve cell that carries information as electrical and chemical signals. It has dendrites that receive signals and an axon that passes them on.
Where you use it
Neurons communicate across small gaps called synapses using neurotransmitters. The main types are sensory neurons, motor neurons and interneurons. British texts sometimes spell it neurone. The adjective is neuronal.
Examples
A motor neuron carries signals from the spinal cord to a muscle.
When a neuron fires, an electrical signal travels along its axon.
An animal with a backbone made of vertebrae, such as a fish, amphibian, reptile, bird or mammal.
Where you use it
Used as a noun and as an adjective (vertebrate species, vertebrate evolution). Animals without a backbone are invertebrates, such as insects, worms and mollusks; they make up the large majority of animal species.
Examples
Zebrafish are a popular vertebrate model for studying development.
Fish were the first vertebrates to appear in the fossil record.
Common phrases
vertebrate species · vertebrate animal · invertebrate · vertebrate model
A Y-shaped protein made by B cells of the immune system that recognizes and binds to a specific antigen, such as part of a virus, and marks it for destruction.
Where you use it
Also called an immunoglobulin (Ig), with classes such as IgG and IgM. Antibodies are also key lab tools: researchers use primary and secondary antibodies to detect proteins in Western blots, ELISA and immunostaining.
Examples
After vaccination, the body produces antibodies against the virus.
We used a primary antibody against the protein and a fluorescent secondary antibody.
Usage note
Antibody and antigen are different: the antigen is the target, and the antibody is the protein that binds to it.
Common phrases
produce antibodies · primary antibody · secondary antibody · monoclonal antibody · antibody test
A form of reproduction in which two gametes, usually from two parents, fuse to form a new individual with a unique mix of genes.
Where you use it
Contrasted with asexual reproduction, in which one parent produces genetically identical offspring, for example by budding or binary fission. Sexual reproduction involves meiosis and fertilization and increases genetic variation. Many plants and fungi can reproduce both ways.
Examples
Sexual reproduction produces offspring that differ from both parents.
Aphids switch between asexual and sexual reproduction depending on the season.
A reproductive cell, such as a sperm or egg cell, that carries half the normal number of chromosomes. Two gametes join during fertilization to form a zygote.
Where you use it
Gametes are haploid (n), while body cells are diploid (2n). In animals they are produced by meiosis. In flowering plants, the male gametes are carried in pollen. Related words: fertilization, zygote, haploid, sex cell.
Examples
Human gametes contain 23 chromosomes each.
Errors in meiosis can produce a gamete with an extra chromosome.
Common phrases
male gamete · female gamete · gamete formation · haploid gamete · fusion of gametes
Single-celled microorganisms without a nucleus that live almost everywhere, from soil and water to the human gut. Most are harmless or useful; some cause disease.
Where you use it
Bacteria is the plural; the singular is bacterium. The adjective is bacterial: bacterial infection, bacterial culture, bacterial cell wall. Bacteria are grouped by shape (cocci, bacilli) and by Gram staining (Gram-positive, Gram-negative).
Examples
These bacteria grow best at 37 °C, the temperature of the human body.
E. coli is a rod-shaped bacterium that lives in the intestine.
Usage note
'A bacteria' is a frequent mistake: say 'a bacterium' or 'these bacteria'. In Turkish, 'bakteri' covers both singular and plural.
A tiny infectious particle made of genetic material (DNA or RNA) inside a protein coat. It can only make copies of itself inside a living host cell.
Where you use it
Viruses are not made of cells and are usually not counted as living organisms. Scientists say a virus infects a cell, replicates and spreads. Viruses that infect bacteria are called bacteriophages. Antibiotics do not work against viruses.
Examples
The virus uses the host cell's ribosomes to make its own proteins.
Flu vaccines are updated every year because influenza viruses keep changing.
Usage note
Pronounced /ˈvaɪrəs/ (VY-rus), not like the Turkish 'virüs'. The plural is viruses, never 'viri'.
A living thing too small to see without a microscope, such as a bacterium, a yeast or a single-celled alga. Viruses are often studied alongside them.
Where you use it
A formal word used in microbiology, food science and medicine. The shorter, less formal word is microbe; 'germ' is everyday language for harmful ones. The study of microorganisms is microbiology.
Examples
A single gram of soil can contain billions of microorganisms.
Pasteurization kills most of the harmful microorganisms in milk.
A microorganism or virus that causes disease in its host, such as certain bacteria, viruses, fungi or parasites.
Where you use it
Used in microbiology, medicine and plant science. People talk about human pathogens, plant pathogens and foodborne pathogens. The adjective is pathogenic, and the ability to cause disease is pathogenicity. Most microbes are non-pathogenic.
A member of the group of organisms that includes yeasts, molds and mushrooms. Fungi feed on organic material and have cell walls made of chitin.
Where you use it
The plural is fungi (/ˈfʌŋɡaɪ/ or /ˈfʌndʒaɪ/). The adjective is fungal: fungal infection, fungal spores. Fungi are not plants: they cannot photosynthesize and are more closely related to animals. Many are decomposers.
Examples
Penicillin was first discovered in a mold, which is a type of fungus.
Many fungi live in partnership with plant roots and help them take up nutrients.
A population of microorganisms or cells grown in the lab in a nutrient medium under controlled conditions. As a verb, it means to grow them in this way.
Where you use it
Common phrases: bacterial culture, cell culture, pure culture and overnight culture. The nutrient material is the culture medium (liquid broth or solid agar). In clinics, a culture identifies the microbe behind an infection, as in a blood culture.
Examples
Inoculate 5 mL of LB broth and grow the culture overnight at 37 °C.
We cultured the cells in medium containing 10% fetal bovine serum.
Common phrases
bacterial culture · cell culture · pure culture · overnight culture · culture medium
An organism or cell that a parasite, virus or other organism lives in or on, and from which it usually gets food or shelter.
Where you use it
Common phrases: host cell, host plant, host species and host range (the hosts a pathogen can infect). A pathogen infects or invades a host, and the host mounts an immune response. Some parasites need an intermediate host.
Examples
Viruses cannot replicate outside a host cell.
Snails are the intermediate host of several parasitic worms.
Common phrases
host cell · host plant · host range · intermediate host · infect a host
An instrument that uses lenses or a beam of electrons to make very small objects, such as cells and microbes, look much larger so they can be studied.
Where you use it
Students use light microscopes; research labs also use fluorescence, confocal and electron microscopes. You look at something 'under the microscope'. Key words: magnification, resolution, objective lens, eyepiece, slide and focus. The adjective is microscopic.
Examples
Place the slide on the stage and start with the lowest magnification on the microscope.
Under the electron microscope, we could clearly see the inner membrane of the mitochondria.
Common phrases
light microscope · electron microscope · under the microscope · fluorescence microscope · microscope slide
A laboratory tool used to measure and transfer exact small volumes of liquid. As a verb, it means to move liquid with this tool.
Where you use it
Most labs use adjustable micropipettes with disposable tips, with volumes set in microliters (µL). Common phrases: pipette tip, change tips, pipette up and down to mix. Glass serological and Pasteur pipettes are also used. American English also spells it pipet.
Examples
Pipette 10 µL of each sample into the wells and change the tip every time.
Calibrate your pipettes regularly, or your volumes will not be accurate.
Usage note
Stress the second syllable: pi-PETTE (/paɪˈpet/), not PI-pet.
Common phrases
pipette tip · micropipette · pipette up and down · serological pipette · Pasteur pipette
Short for polymerase chain reaction, a lab technique that makes millions of copies of a chosen piece of DNA in a few hours through repeated cycles of heating and cooling.
Where you use it
Each cycle has three steps: denaturation, annealing of primers and extension by a heat-stable DNA polymerase such as Taq. The machine is a thermal cycler. People run, set up or do a PCR; qPCR measures the amount of DNA in real time.
Examples
We set up a PCR to amplify the 500-base-pair fragment.
The PCR failed because the annealing temperature was too high.
Common phrases
run a PCR · PCR product · real-time PCR · PCR primers · thermal cycler
A lab technique that separates DNA, RNA or protein fragments by size, using an electric current to pull them through a gel.
Where you use it
DNA is negatively charged, so it moves toward the positive electrode, and smaller fragments travel farther. DNA is usually run on agarose gels and proteins on polyacrylamide (SDS-PAGE) gels. People run a gel, load the samples and compare the bands with a DNA ladder.
Examples
We checked the PCR products by agarose gel electrophoresis.
After electrophoresis, the gel was stained and photographed under UV light.
Common phrases
agarose gel · run a gel · load the gel · DNA ladder · band on the gel
A machine that spins samples at high speed so that heavier particles move to the bottom of the tube. As a verb, it means to spin samples in this machine.
Where you use it
Speed is given in rpm or, more precisely, as relative centrifugal force (× g). The solid at the bottom is the pellet and the liquid above it is the supernatant. In lab talk, you 'spin down' cells. Always balance the tubes before starting.
Examples
Centrifuge the samples at 5,000 g for 10 minutes and discard the supernatant.
The centrifuge stopped because the tubes were not balanced.
Usage note
Pronounced SEN-tri-fyooj (/ˈsentrɪfjuːdʒ/). The noun and the verb have the same form.
Common phrases
spin down · pellet · supernatant · balance the centrifuge · benchtop centrifuge
A set of working methods that stop unwanted microorganisms from contaminating cultures, samples, equipment or the person doing the work.
Where you use it
It includes disinfecting the bench, flaming the inoculating loop, working near a Bunsen burner or in a biosafety cabinet, and keeping lids closed. Related words: sterile, contamination, contaminated plate. It is also called sterile technique.
Examples
Poor aseptic technique is the most common reason for contaminated plates.
Students must practice aseptic technique before they work with live bacteria.
Common phrases
use aseptic technique · sterile conditions · risk of contamination · biosafety cabinet · inoculating loop
A shallow, round, clear dish with a lid, used to grow microorganisms or cells on a layer of agar or another culture medium.
Where you use it
Named after the German bacteriologist Julius Petri. Lab staff often just say 'plate': an agar plate, to plate out bacteria, a contaminated plate. Plates are usually incubated upside down so that condensation does not drip onto the agar.
Examples
Pour the warm agar into each petri dish and let it set.
After two days, small white colonies appeared on the petri dishes.
Usage note
Pronounced PEE-tree (/ˈpiːtri/) in American English; some British speakers say PET-ree. Because it comes from a name, it is often written with a capital P: Petri dish.
Common phrases
agar plate · pour a plate · plate out · sterile petri dish · bacterial colony
To keep samples, cultures or eggs at a controlled temperature, and sometimes humidity or gas level, for a set time so that growth or a reaction can take place.
Where you use it
Protocols say 'incubate at 37 °C for 24 hours' or 'incubate on ice'. The device is an incubator; mammalian cells are kept in a CO2 incubator. In medicine, the incubation period is the time between infection and the first symptoms.
Examples
Incubate the plates at 37 °C overnight.
The enzyme and substrate were incubated together for 30 minutes before the reaction was stopped.
Common phrases
incubate at 37 °C · incubate overnight · incubation period · CO2 incubator · incubate on ice
A possible explanation or prediction that can be tested by an experiment or observation. Scientists design studies to support or reject it.
Where you use it
The plural is hypotheses (/haɪˈpɑːθəsiːz/). Researchers propose, test, support or reject a hypothesis, and a good one is testable and falsifiable. In statistics, the null hypothesis states that there is no effect or difference.
Examples
Our hypothesis is that higher temperatures will increase the growth rate of the algae.
The results did not support the original hypothesis.
Usage note
A hypothesis is not the same as a theory. In science, a theory, such as the theory of evolution, is a broad explanation backed by a large body of evidence.
Common phrases
test a hypothesis · null hypothesis · support a hypothesis · reject a hypothesis · working hypothesis
The group in an experiment that does not receive the treatment being tested, so that its results can be compared with those of the treated group.
Where you use it
Often shortened to 'the control'. Lab researchers use positive controls (expected to show the effect) and negative controls (expected to show no effect). The group that receives the treatment is the experimental or treatment group.
Examples
Plants in the control group were watered with tap water only.
Without a proper control group, we can't say that the drug caused the change.
Common phrases
compare with the control group · experimental group · negative control · positive control · untreated control
Any factor that can change in an experiment, such as temperature, light or time. Scientists change one variable and measure its effect on another.
Where you use it
The independent variable is what you change, the dependent variable is what you measure, and controlled variables are kept the same. In reports, you 'control for' a variable to rule out its effect. As an adjective, variable means changeable: variable results.
Examples
In this experiment, light intensity is the independent variable and the rate of photosynthesis is the dependent variable.
Temperature was kept constant so that it would not act as a confounding variable.
Common phrases
independent variable · dependent variable · controlled variable · confounding variable · control for a variable
Done outside a living organism, for example in a test tube, a petri dish or a cell culture. The Latin phrase literally means 'in glass'.
Where you use it
Used as an adjective (in vitro studies, an in vitro assay) and as an adverb (the cells were tested in vitro), often in italics. Results in vitro do not always predict what happens in vivo. In vitro fertilization (IVF) is a well-known example.
Examples
The compound killed cancer cells in vitro, but it has not yet been tested in animals.
We used an in vitro assay to measure enzyme activity.
Common phrases
in vitro study · in vitro assay · tested in vitro · in vitro fertilization
Done or happening inside a living organism, such as a mouse, a plant or a human. The Latin phrase means 'in the living'.
Where you use it
Used like in vitro, as an adjective (in vivo experiments) or adverb (tested in vivo), and often in italics. Researchers usually confirm in vitro findings in vivo before clinical trials. A related term, ex vivo, describes tissue taken from an organism and studied outside it.
Examples
The drug worked well in cell culture but showed no effect in vivo.
In vivo imaging allowed us to follow the tumor in the same mouse for weeks.
Common phrases
in vivo study · in vivo experiment · tested in vivo · in vivo imaging
A species that is studied in great detail because it is easy to keep and breed in the lab, so that findings can help explain biology in other organisms.
Where you use it
Classic examples are the bacterium E. coli, baker's yeast, the fruit fly Drosophila, the worm C. elegans, the plant Arabidopsis, zebrafish and the mouse. Each has a large research community, shared databases and established protocols.
Examples
Arabidopsis is the most widely used model organism in plant biology.
Fruit flies are a good model organism because they breed quickly and are cheap to keep.
Common phrases
genetic model · mouse model · animal model · model system
One of several repeats of the same measurement or experiment, done to check that the results are reliable. As a verb, it means to repeat an experiment or, for DNA and viruses, to copy itself.
Where you use it
Researchers separate biological replicates (different samples, plants or animals) from technical replicates (the same sample measured again). Papers state 'three biological replicates'. The noun is said REP-li-kit, the verb REP-li-kate. The process is replication.
Examples
Each treatment was tested in three biological replicates.
Other labs were unable to replicate the results.
DNA must replicate before the cell divides.
Common phrases
biological replicate · technical replicate · replicate an experiment · replicate the results
Ten questions from this glossary. Pick the right meaning for each term and see your score.
How to learn biology vocabulary
Learn the word parts that biology builds on: cyto- (cell), photo- (light), hydro- (water), endo-/exo- (inside/outside), -ase for enzymes (lactase, polymerase) and -ose for sugars (glucose, sucrose). Many new terms then explain themselves.
Learn processes as word families, not single words: divide and division, mutate and mutation, inherit and inheritance, evolve and evolution, germinate and germination. Lectures use the verb, papers often prefer the noun.
Read real biology texts in English every week, such as textbook chapters, journal abstracts and lab protocols. Notice how methods sections use the passive voice: 'Samples were centrifuged at 5,000 g for 10 minutes.'
Draw and label diagrams in English: a plant cell, a flower, the DNA double helix, a food web. Labelling from memory is one of the fastest ways to fix the terms in your head.
Study confusing pairs side by side and write one sentence for each: mitosis and meiosis, transcription and translation, genotype and phenotype, xylem and phloem, in vitro and in vivo.
Frequently asked questions
Which English biology terms should I learn first?
Start with the words every lecture uses: cell, organism, DNA, gene, protein, enzyme, species, evolution and ecosystem. Then learn the main cell structures, the basics of heredity (allele, dominant, recessive), the key processes (photosynthesis, cellular respiration, mitosis, meiosis) and the lab words you will hear in your first practicals (microscope, pipette, culture, control group). The first tier of this list follows that order.
Why do so many biology words have strange plurals?
Many biology terms come from Latin and Greek and keep their original plurals: bacterium/bacteria, nucleus/nuclei, fungus/fungi, mitochondrion/mitochondria, hypothesis/hypotheses, stoma/stomata. Some words do not change at all: one species, two species; one offspring, many offspring. Saying 'a bacteria' or 'a specie' is a common mistake in exams and papers, so learn the singular and plural together.
How do I write the scientific name of a species in English?
Use the two-part Latin name in italics: the genus starts with a capital letter and the species name is all lowercase, as in Homo sapiens or Escherichia coli. After the first full mention you can shorten the genus to its first letter: E. coli. If you cannot use italics, for example in handwriting, underline the name. Common names such as 'house mouse' are not italicized.
How can I pronounce biology terms correctly?
Do not read English terms the way they are said in Turkish. Meiosis is 'my-OH-sis', not 'mayoz'; allele is 'uh-LEEL'; enzyme is 'EN-zime'; species is 'SPEE-sheez'; xylem starts with a 'z' sound. Stress often falls on a different syllable than in Turkish: pho-to-SYN-the-sis, me-TAB-o-lism, hy-POTH-e-sis. Listen to recorded lectures and audio dictionaries and repeat new terms aloud.
Do Turkish biologists use the English or the Turkish terms?
Both. School textbooks and Turkish-language courses use Turkish terms such as baskın, çekinik, tozlaşma and ayrıştırıcı, while research labs often mix in English words: 'Örnekleri santrifüjledik', 'PCR kurduk', 'kültürü overnight bıraktık'. Papers, theses with English abstracts and international meetings require the English terms. Knowing both sets lets you follow a Turkish lecture and write an English paper about the same topic.
