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It also deals with airborne and terrestrial organisms that depend directly upon bodies of salt water for food and other... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/biological-development" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/mendel-resources/3-133/images/shared/default3.png?v=3.133.36" class="default col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/biological-development" class="font-weight-bold font-16 lh-sm">biological development</a> <div class="font-serif mt-10 font-14"> Biological development, the progressive changes in size, shape, and function during the life of an organism by which its genetic potentials (genotype) are translated into functioning mature systems (phenotype).... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/taxonomy" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/78/103778-050-D797CF4F/Animals-groups-organisms-succession-general-particular.jpg?w=400&h=225&c=crop" alt="animal taxonomy" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/taxonomy" class="font-weight-bold font-16 lh-sm">taxonomy</a> <div class="font-serif mt-10 font-14"> Taxonomy, in a broad sense the science of classification, but more strictly the classification of living and extinct organisms鈥攊.e., biological classification. The term is derived from the Greek taxis... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/genetics" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/44/155244-050-4460310B/Strands-human-chromosomes.jpg?w=400&h=225&c=crop" alt="chromosome" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/genetics" class="font-weight-bold font-16 lh-sm">genetics</a> <div class="font-serif mt-10 font-14"> Genetics, study of heredity in general and of genes in particular. Genetics forms one of the central pillars of biology and overlaps with many other areas, such as agriculture, medicine, and biotechnology.... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/animal/chordate" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/93/141293-050-5C513B91/X-ray-fish-chordate-backbone.jpg?w=400&h=225&c=crop" alt="Chordate" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/animal/chordate" class="font-weight-bold font-16 lh-sm">chordate</a> <div class="font-serif mt-10 font-14"> Chordate, any member of the phylum Chordata, which includes the vertebrates (subphylum Vertebrata), the most highly evolved animals, as well as two other subphyla鈥攖he tunicates (subphylum Tunicata) and... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/topic/animal-social-behaviour" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/83/100583-050-9BD2D1AC/Herd-gnu-Tanzania-Serengeti-National-Park.jpg?w=400&h=225&c=crop" alt="Serengeti National Park, Tanzania: herd of gnu (wildebeests)" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/topic/animal-social-behaviour" class="font-weight-bold font-16 lh-sm">animal social behaviour</a> <div class="font-serif mt-10 font-14"> Animal social behaviour, the suite of interactions that occur between two or more individual animals, usually of the same species, when they form simple aggregations, cooperate in sexual or parental behaviour,... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/animal/animal" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/94/494-050-A674AD3A/Fallow-deer-dama-dama.jpg?w=400&h=225&c=crop" alt="fallow deer (Dama dama)" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/animal/animal" class="font-weight-bold font-16 lh-sm">animal</a> <div class="font-serif mt-10 font-14"> Animal, (kingdom Animalia), any of a group of multicellular eukaryotic organisms (i.e., as distinct from bacteria, their deoxyribonucleic acid, or DNA, is contained in a membrane-bound nucleus). They are... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/life" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/02/99702-050-A1BB8B94/African-elephants-Botswana.jpg?w=400&h=225&c=crop" alt="African elephants" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/life" class="font-weight-bold font-16 lh-sm">life</a> <div class="font-serif mt-10 font-14"> Life, living matter and, as such, matter that shows certain attributes that include responsiveness, growth, metabolism, energy transformation, and reproduction. Although a noun, as with other defined entities,... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/microbiology" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/26/123226-050-0DFE8193/bacteria-Photomicrograph-Streptococcus-pyogenes-scarlet-fever.jpg?w=400&h=225&c=crop" alt="Streptococcus pyogenes" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/microbiology" class="font-weight-bold font-16 lh-sm">microbiology</a> <div class="font-serif mt-10 font-14"> Microbiology, study of microorganisms, or microbes, a diverse group of generally minute simple life-forms that include bacteria, archaea, algae, fungi, protozoa, and viruses. The field is concerned with... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/zoology" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/64/92764-050-9FF66A9E/wildebeests-edge-water-Kenya-Masai-Mara.jpg?w=400&h=225&c=crop" alt="blue wildebeests" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/zoology" class="font-weight-bold font-16 lh-sm">zoology</a> <div class="font-serif mt-10 font-14"> Zoology, branch of biology that studies the members of the animal kingdom and animal life in general. It includes both the inquiry into individual animals and their constituent parts, even to the molecular... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/molecular-biology" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/80/81980-050-52913D4F/structure-cholera-enterotoxin-X-ray-protein-crystallography-image.jpg?w=400&h=225&c=crop" alt="X-ray protein crystallography in molecular biology" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/molecular-biology" class="font-weight-bold font-16 lh-sm">molecular biology</a> <div class="font-serif mt-10 font-14"> Molecular biology, field of science concerned with studying the chemical structures and processes of biological phenomena that involve the basic units of life, molecules. The field of molecular biology... </div> </div> </div> </div> </div> </div> <div class="adm my-30"></div> <div class="subcategories"> <h2 class="h4 mt-40 mb-30 font-weight-bold">Biology Subcategories</h2> <div class="grid gy-30 mb-30"> <div class="col-100 col-sm-33 col-md-25"> <a href="/browse/Archaea-Bacteria"> <img loading="lazy" src="https://cdn.britannica.com/56/21056-004-0441EB6F/Francois-Jacob-1965.jpg?w=400&h=225&c=crop" alt="Fran莽ois Jacob, 1965." class="col-100 mb-20" /> </a> <a href="/browse/Archaea-Bacteria" class="font-weight-bold font-16">Archaea & Bacteria</a> <div class="font-serif mt-10 line-clamp clamp-3">Even if you can't see them, that doesn't mean they're not there! Prokaryotes are one good example of why you can't always trust the naked eye to show you everything that's going on around you. Prokaryotes are single-celled organisms that can't be seen without the use of a microscope. Prokaryotic organisms fall into one of two groups: bacteria and archaea. Despite bacteria鈥檚 bad reputation as the cause of diseases in humans, animals, or plants, most bacteria are harmless, and they function as beneficial ecological agents. Archaea, too, fulfill important ecological roles in cold and temperate ecosystems. Without archaea and bacteria, our lives would be much more difficult: soil would not be fertile, and our ability to prepare certain foods, chemicals, and antibiotics would be hindered, among other difficulties.</div> <div class="label mt-20">Articles</div> <ul class="list-unstyled"> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/biography/Ferdinand-Cohn">Ferdinand Cohn</a> <div class="font-serif">German botanist</div> </li> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/biography/Frances-Arnold">Frances Arnold</a> <div class="font-serif">American chemical engineer</div> </li> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/biography/Antonie-van-Leeuwenhoek">Antonie van Leeuwenhoek</a> <div class="font-serif">Dutch scientist</div> </li> </ul> </div> <div class="col-100 col-sm-33 col-md-25"> <a href="/browse/Branches-Biology"> <img loading="lazy" src="https://cdn.britannica.com/78/103778-050-D797CF4F/Animals-groups-organisms-succession-general-particular.jpg?w=400&h=225&c=crop" alt="animal taxonomy" class="col-100 mb-20" /> </a> <a href="/browse/Branches-Biology" class="font-weight-bold font-16">Branches of Biology</a> <div class="font-serif mt-10 line-clamp clamp-3">The field of biology is subdivided into separate branches for convenience of study, though all the subdivisions share basic principles. Biology encompasses fields such as botany, genetics, marine biology, microbiology, molecular biology, and much more. </div> <div class="label mt-20">Articles</div> <ul class="list-unstyled"> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/science/community-ecology">community ecology</a> <div class="font-serif"></div> </li> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/science/botany">botany</a> <div class="font-serif"></div> </li> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/biography/Louis-Pasteur">Louis Pasteur</a> <div class="font-serif">French chemist and microbiologist</div> </li> </ul> </div> <div class="col-100 col-sm-33 col-md-25"> <a href="/browse/Cells-Organs-Tissues"> <img loading="lazy" src="https://cdn.britannica.com/14/93314-004-F9954BFA/vertebrate-skeletons.jpg?w=400&h=225&c=crop" alt="vertebrate: skeleton" class="col-100 mb-20" /> </a> <a href="/browse/Cells-Organs-Tissues" class="font-weight-bold font-16">Cells, Organs & Tissues</a> <div class="font-serif mt-10 line-clamp clamp-3">Even if you feel you have nothing in common with a stinkbug or a ficus, you're guaranteed to share one crucial aspect of life with these beings: you are all made up of cells, the fundamental molecules of life, of which all living things are composed. As an individual unit, the cell is capable of metabolizing its own nutrients, synthesizing many types of molecules, providing its own energy, and replicating itself. In a multicellular organism, cooperative assemblies of similar cells form tissues, and a cooperation between tissues in turn forms organs, which carry out the functions necessary to sustain the life of an organism.</div> <div class="label mt-20">Articles</div> <ul class="list-unstyled"> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/science/skeleton">skeleton</a> <div class="font-serif"></div> </li> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/science/human-respiratory-system">human respiratory system</a> <div class="font-serif">physiology</div> </li> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/science/human-digestive-system">human digestive system</a> <div class="font-serif"></div> </li> </ul> </div> <div class="col-100 col-sm-33 col-md-25"> <a href="/browse/Evolution-Heredity-Genetics"> <img loading="lazy" src="https://cdn.britannica.com/mendel/resources/encyclopedia-placeholder.jpg?w=400&h=225&c=crop" alt="subcategory placeholder" class="col-100 mb-15" /> </a> <a href="/browse/Evolution-Heredity-Genetics" class="font-weight-bold font-16">Evolution, Heredity & Genetics</a> <div class="font-serif mt-10 line-clamp clamp-3">Earth has housed a vast variety of plants, animals, and other living things throughout the history of its existence, and many living things have changed in discernible ways over the years. The theory of evolution, one of the fundamental keystones of modern biological theory, examines the way in which such changes unfold. Heredity describes the biological processes by which certain characteristics are transmitted from parents to their offspring. Genetics studies heredity in general and genes in particular.</div> <div class="label mt-20">Articles</div> <ul class="list-unstyled"> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/science/human-genome">human genome</a> <div class="font-serif"></div> </li> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/science/human-evolution">human evolution</a> <div class="font-serif"></div> </li> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/science/evolution-scientific-theory">evolution</a> <div class="font-serif">scientific theory</div> </li> </ul> </div> <div class="col-100 col-sm-33 col-md-25"> <a href="/browse/Fungi-Protists-Viruses"> <img loading="lazy" src="https://cdn.britannica.com/mendel/resources/encyclopedia-placeholder.jpg?w=400&h=225&c=crop" alt="subcategory placeholder" class="col-100 mb-15" /> </a> <a href="/browse/Fungi-Protists-Viruses" class="font-weight-bold font-16">Fungi, Protists & Viruses</a> <div class="font-serif mt-10 line-clamp clamp-3">Fungi, protists, and viruses may not be the most cuddly of organisms, but they鈥檙e no less worth studying for it. Fungi, whose ranks include yeasts, rusts, molds, and mushrooms, are among the most widely distributed organisms on Earth. Protists such as algae and protozoans are microscopic eukaryotic organisms. Viruses are infectious agents of small size and simple composition that can multiply only in living cells of animals, plants, or bacteria.</div> <div class="label mt-20">Articles</div> <ul class="list-unstyled"> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/science/Marburg-virus">Marburgvirus</a> <div class="font-serif">virus genus</div> </li> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/biography/Ferdinand-Cohn">Ferdinand Cohn</a> <div class="font-serif">German botanist</div> </li> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/science/mushroom">mushroom</a> <div class="font-serif">fungus</div> </li> </ul> </div> <div class="col-100 col-sm-33 col-md-25"> <a href="/browse/Life-Cycle-Processes"> <img loading="lazy" src="https://cdn.britannica.com/90/9590-004-56A7C1F5/Primates-mammals-groups.jpg?w=400&h=225&c=crop" alt="primates" class="col-100 mb-20" /> </a> <a href="/browse/Life-Cycle-Processes" class="font-weight-bold font-16">Life Cycle, Processes & Properties</a> <div class="font-serif mt-10 line-clamp clamp-3">None of us are born looking exactly the way that we do today; this is because humans, like other species, undergo a series of changes as they mature and age, in accordance with their biological life cycle. This process can look very different across different species. In many simple organisms and in higher animals, the life cycle is completed within a single generation, while in most plants, the life cycle is multigenerational.</div> <div class="label mt-20">Articles</div> <ul class="list-unstyled"> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/science/paedomorphosis">paedomorphosis</a> <div class="font-serif">biology</div> </li> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/science/human-digestive-system">human digestive system</a> <div class="font-serif"></div> </li> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/science/animal-learning">animal learning</a> <div class="font-serif">zoology</div> </li> </ul> </div> <div class="col-100 col-sm-33 col-md-25"> <a href="/browse/Biologists"> <img loading="lazy" src="https://cdn.britannica.com/13/19413-050-A75D4BE2/Rachel-Carson.jpg?w=400&h=225&c=crop" alt="Rachel Carson" class="col-100 mb-20" /> </a> <a href="/browse/Biologists" class="font-weight-bold font-16">Biologists</a> <div class="font-serif mt-10 line-clamp clamp-3"></div> <div class="label mt-20">Articles</div> <ul class="list-unstyled"> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/biography/Rachel-Carson">Rachel Carson</a> <div class="font-serif">American biologist</div> </li> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/biography/Georges-Cuvier">Georges Cuvier</a> <div class="font-serif">French zoologist</div> </li> <li class="mt-20"> <a class="font-weight-bold" href="https://www.britannica.com/biography/Albert-Bruce-Sabin">Albert Bruce Sabin</a> <div class="font-serif">American physician and microbiologist</div> </li> </ul> </div> </div> </div> <DIV class="marketing-CATEGORY_PAGE_SUBSCRIPTION marketing-content" data-marketing-id="CATEGORY_PAGE_SUBSCRIPTION"><style> .student-promo-banner-wrapper { container-type: inline-size; margin-bottom: 15px; } @container (min-width: 475px) { .student-promo-banner { flex-direction: row; } .student-promo-banner-img-wrapper { margin-bottom: 0; margin-right: 10px; justify-content: flex-start; } .student-promo-banner-text-wrapper { text-align: left; margin-bottom: 0px; margin-left: 10px; } .student-promo-banner-button-wrapper { margin-right: 0; } }</style> <div class="student-promo-banner-wrapper"> <div class="student-promo-banner d-flex flex-column align-items-center bg-blue rounded p-20"> <div class="student-promo-banner-img-wrapper mb-20 mr-0 d-flex justify-content-center"> <img class="rounded" style="max-width: 100px; min-width: 80px" src="https://cdn.britannica.com/marketing/BlueThistle.webp" /> </div> <div class="student-promo-banner-text-wrapper ml-0 mb-10 text-center text-white"> <div class="h2 mb-10">Britannica Premium</div> <div class="h4 font-weight-semi-bold">Did you know you're not getting the full Britannica experience? 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