Cellule (biologie) Un article de Wikipédia, l'encyclopédie libre. Pour les articles homonymes, voir cellule. Cellules épithéliales en culture. L'ADN est coloré en vert, les filaments de kératine en rouge. La théorie cellulaire implique l'unité de tout le vivant : tous les êtres vivants sont composés de cellules dont la structure fondamentale est commune ainsi que l'homéostasie du milieu intérieur, milieu de composition physico-chimique régulé et propice au développement des cellules de l'espèce considérée. Dessin de « cellules » observées dans des coupes d'écorce d'arbre par Robert Hooke en 1665. Le nombre de cellules propres à un organisme humain adulte est de l'ordre de 1014. La cellule est l'unité constitutive des organismes vivants. Ici on se demande avant tout quelles sont les caractéristiques communes aux cellules, malgré leur diversité. Une petite section d'une membrane cellulaire. La cellule constitue une unité spatiale, délimitée par une membrane.
Ecology Ecology is an interdisciplinary field that includes biology and Earth science. The word "ecology" ("Ökologie") was coined in 1866 by the German scientist Ernst Haeckel (1834–1919). Ancient Greek philosophers such as Hippocrates and Aristotle laid the foundations of ecology in their studies on natural history. Modern ecology transformed into a more rigorous science in the late 19th century. Evolutionary concepts on adaptation and natural selection became cornerstones of modern ecological theory. Ecology is not synonymous with environment, environmentalism, natural history, or environmental science. Ecology is a human science as well. Integrative levels, scope, and scale of organization Hierarchical ecology System behaviors must first be arrayed into different levels of organization. O'Neill et al. (1986):76 Biodiversity Biodiversity refers to the variety of life and its processes. Noss & Carpenter (1994):5 Habitat Biodiversity of a coral reef. Niche
Anatomy Anatomy is the branch of biology concerned with the study of the structure of animals and their parts; it is also referred to as zootomy to separate it from human anatomy. In some of its facets, anatomy is related to embryology and comparative anatomy, which itself is closely related to evolutionary biology and phylogeny. Human anatomy is one of the basic essential sciences of medicine. Definition Human compared to elephant frame Anatomical chart by Vesalius, Epitome, 1543 The discipline of anatomy can be subdivided into a number of branches including gross or macroscopic anatomy and microscopic anatomy. Gross anatomy is the study of structures large enough to be seen with the naked eye, and also includes superficial anatomy or surface anatomy, the study by sight of the external body features. The term "anatomy" is commonly taken to refer to human anatomy. Animal tissues A diagram of an animal cell Unlike plant cells, animal cells have neither a cell wall nor chloroplasts.
Cell (biology) The cell (from Latin cella, meaning "small room") is the basic structural, functional and biological unit of all known living organisms. Cells are the smallest unit of life that can replicate independently, and are often called the "building blocks of life". The study of cells is called cell biology. The cell was discovered by Robert Hooke in 1665. The cell theory, first developed in 1839 by Matthias Jakob Schleiden and Theodor Schwann, states that all organisms are composed of one or more cells, that all cells come from preexisting cells, that vital functions of an organism occur within cells, and that all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells. Cells emerged on Earth at least 3.5 billion years ago. Anatomy There are two types of cells, eukaryotes, which contain a nucleus, and prokaryotes, which do not. Prokaryotic cells Eukaryotic cells Subcellular components Membrane
Cell In biology, the cell is the basic structure of organisms. All cells are made by other cells. Kinds of cells[change | edit source] There are two basic kinds of cells: prokaryotic cells and eukaryotic cells. Eukaryotes are complex cells with many organelles and other structures in the cell. Kinds of prokaryotic organisms[change | edit source] The only kinds of prokaryotic organisms alive at present are bacteria and archaea. Kinds of eukaryotic organisms[change | edit source] Unicellular[change | edit source] A paramecium Unicellular organisms are made up of one cell. Unicellular organisms live without other cells to help them. eatmoverespire (use oxygen to make sugar into energy)sense its environment All organisms must: get rid of wastereproduce (make more of itself)grow Some may: get their energy from the sun (e.g., cyanobacteria)ferment (e.g., yeasts)use anaerobic respiration (e.g. Multicellular[change | edit source] Multicellular organisms are made from many cells.
Biochemistry Biochemistry is closely related to molecular biology, the study of the molecular mechanisms by which genetic information encoded in DNA is able to result in the processes of life. Depending on the exact definition of the terms used, molecular biology can be thought of as a branch of biochemistry, or biochemistry as a tool with which to investigate and study molecular biology. Much of biochemistry deals with the structures, functions and interactions of biological macromolecules, such as proteins, nucleic acids, carbohydrates and lipids, which provide the structure of cells and perform many of the functions associated with life. History It once was generally believed that life and its materials had some essential property or substance distinct from any found in non-living matter, and it was thought that only living beings could produce the molecules of life. Starting materials: the chemical elements of life Biomolecules Carbohydrates Lipids Proteins
Neuron All neurons are electrically excitable, maintaining voltage gradients across their membranes by means of metabolically driven ion pumps, which combine with ion channels embedded in the membrane to generate intracellular-versus-extracellular concentration differences of ions such as sodium, potassium, chloride, and calcium. Changes in the cross-membrane voltage can alter the function of voltage-dependent ion channels. If the voltage changes by a large enough amount, an all-or-none electrochemical pulse called an action potential is generated, which travels rapidly along the cell's axon, and activates synaptic connections with other cells when it arrives. Neurons do not undergo cell division. In most cases, neurons are generated by special types of stem cells. A type of glial cell, called astrocytes (named for being somewhat star-shaped), have also been observed to turn into neurons by virtue of the stem cell characteristic pluripotency. Overview Anatomy and histology
Vocabulary Category:Cell biology Organism Life is a characteristic distinguishing objects having signaling and self-sustaining processes from those that do not, either because such functions have ceased (death), or because they lack such functions and are classified as inanimate. Biology is science concerned with the study of life. Though life is confirmed only on the Earth, many think that extraterrestrial life is not only plausible, but probable or inevitable. Other planets and moons in the Solar System have been examined for evidence of having once supported simple life, and projects such as SETI have attempted to detect radio transmissions from possible alien civilizations. According to the panspermia hypothesis, microscopic life exists throughout the Universe, and is distributed by meteoroids, asteroids and planetoids. Early theories Materialism Herds of zebra and impala gathering on the Maasai Mara plain Democritus (460 BC) thought that the essential characteristic of life is having a soul (psyche).
Brain This article compares the properties of brains across the entire range of animal species, with the greatest attention to vertebrates. It deals with the human brain insofar as it shares the properties of other brains. The ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because much more can be said about them in a human context. The most important is brain disease and the effects of brain damage, covered in the human brain article because the most common diseases of the human brain either do not show up in other species, or else manifest themselves in different ways. Anatomy Cross section of the olfactory bulb of a rat, stained in two different ways at the same time: one stain shows neuron cell bodies, the other shows receptors for the neurotransmitterGABA. Cellular structure Neurons generate electrical signals that travel along their axons. Evolution
Cellule procariote ed eucariote In Prima Media in genere si studiano le cellule. Una prima distinzione le suddivide in procariote ed eucariote. Sfogliamo queste diapositive tratte dal libro Biologia.blu di Sadava, Heller, Orians, Purves, Hillis, edizioni Zanichelli. Proseguiamo il nostro studio utilizzando queste due brevi, ma molto ben fatte, presentazioni. Si tratta di interattivi multimediali che, dopo aver illustrato le principali caratteristiche e differenze tra i due tipi di cellule, permettono di approfondire la conoscenza delle varie componenti, semplicemente cliccando sopra ai nomi che compaiono nell’immagine. Cellula procariote Cellula eucariote Articoli che ti possono interessare Risorse interattive di matematica Questa risorsa multimediale comprende attività interattive per la matematica, strategie di apprendimento e video che illustrano come la matematica serva nella vita quotidiana.