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Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in carbohydrate molecules, such as sugars and starches, which are synthesized from carbon dioxide and water – hence the name photosynthesis, from the Greek phōs, "light", and synthesis, "putting together". Most plants, algae, and cyanobacteria perform photosynthesis; such organisms are called photoautotrophs. Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies most of the energy necessary for life on Earth.
Euglena is a genus of single cell flagellate eukaryotes. It is the best known and most widely studied member of the class Euglenoidea, a diverse group containing some 54 genera and at least 200 species. Species of Euglena are found in fresh water and salt water. They are often abundant in quiet inland waters where they may bloom in numbers sufficient to color the surface of ponds and ditches green (E. viridis) or red (E. sanguinea).
A taxis is the movement of an organism in response to a stimulus such as light or the presence of food. Taxes are innate behavioural responses. A taxis differs from a tropism in that in the case of taxis, the organism has motility and demonstrates guided movement towards or away from the stimulus source. It is sometimes distinguished from a kinesis, a non-directional change in activity in response to a stimulus.
Heliotropism, a form of tropism, is the diurnal or seasonal motion of plant parts in response to the direction of the Sun.
Phototrophs are organisms that carry out photon capture to produce complex organic compounds and acquire energy. They use the energy from light to carry out various cellular metabolic processes. It is a common misconception that phototrophs are obligatorily photosynthetic. Many, but not all, phototrophs often photosynthesize: they anabolically convert carbon dioxide into organic material to be utilized structurally, functionally, or as a source for later catabolic processes. All phototrophs either use electron transport chains or direct proton pumping to establish an electrochemical gradient which is utilized by ATP synthase, to provide the molecular energy currency for the cell. Phototrophs can be either autotrophs or heterotrophs. If their electron and hydrogen donors are inorganic compounds they can be also called lithotrophs, and so, some photoautotrophs are also called photolithoautotrophs. Examples of phototroph organisms are Rhodobacter capsulatus, Chromatium, and Chlorobium.
A bioindicator is any species or group of species whose function, population, or status can reveal the qualitative status of the environment. The most common indicator species are animals. For example, copepods and other small water crustaceans that are present in many water bodies can be monitored for changes that may indicate a problem within their ecosystem. Bioindicators can tell us about the cumulative effects of different pollutants in the ecosystem and about how long a problem may have been present, which physical and chemical testing cannot.
The photosynthetic efficiency is the fraction of light energy converted into chemical energy during photosynthesis in green plants and algae. Photosynthesis can be described by the simplified chemical reaction
Kinesis, like a taxis or tropism, is a movement or activity of a cell or an organism in response to a stimulus.
Photoprotection is the biochemical process that helps organisms cope with molecular damage caused by sunlight. Plants and other oxygenic phototrophs have developed a suite of photoprotective mechanisms to prevent photoinhibition and oxidative stress caused by excess or fluctuating light conditions. Humans and other animals have also developed photoprotective mechanisms to avoid UV photodamage to the skin, prevent DNA damage, and minimize the downstream effects of oxidative stress.
Marine larval ecology is the study of the factors influencing dispersing larvae, which many marine invertebrates and fishes have. Marine animals with a larva typically release many larvae into the water column, where the larvae develop before metamorphosing into adults.
The eyespot apparatus is a photoreceptive organelle found in the flagellate or (motile) cells of green algae and other unicellular photosynthetic organisms such as euglenids. It allows the cells to sense light direction and intensity and respond to it, prompting the organism to either swim towards the light, or away from it. A related response occurs when cells are briefly exposed to high light intensity, causing the cell to stop, briefly swim backwards, then change swimming direction. Eyespot-mediated light perception helps the cells in finding an environment with optimal light conditions for photosynthesis. Eyespots are the simplest and most common "eyes" found in nature, composed of photoreceptors and areas of bright orange-red red pigment granules. Signals relayed from the eyespot photoreceptors result in alteration of the beating pattern of the flagella, generating a phototactic response.
Bacterial motility is the ability of bacteria to move independently using metabolic energy. Most motility mechanisms which evolved among bacteria also evolved in parallel among the archaea. Most rod-shaped bacteria can move using their own power, which allows colonization of new environments and discovery of new resources for survival. Bacterial movement depends not only on the characteristics of the medium, but also on the use of different appendages to propel. Swarming and swimming movements are both powered by rotating flagella. Whereas swarming is a multicellular 2D movement over a surface and requires the presence of surfactants, swimming is movement of individual cells in liquid environments.
Phototaxis is a kind of taxis, or locomotory movement, that occurs when a whole organism moves towards or away from a stimulus of light. This is advantageous for phototrophic organisms as they can orient themselves most efficiently to receive light for photosynthesis. Phototaxis is called positive if the movement is in the direction of increasing light intensity and negative if the direction is opposite.
Gravitaxis is a form of taxis characterized by the directional movement of an organism in response to gravity.
Plakobranchus ocellatus is a species of sea slug, a sacoglossan, a marine opisthobranch gastropod mollusk in the family Plakobranchidae. It is found in shallow water in the Indo-Pacific region.
Discodoris boholiensis, known commonly as the Bohol discodoris, is a species of sea slug in the family Discodorididae. It gets its name from the island of Bohol in the Philippines. Discodoris boholiensis has a distinctive pattern of chocolate brown and cream-white all over its flattened body and wavy-edged mantle. It reaches a length of 12 cm (5 in).
Every organism requires energy to be active. However, to obtain energy from its outside environment, cells must not only retrieve molecules from their surroundings but also break them down. This process is known as intracellular digestion. In its broadest sense, intracellular digestion is the breakdown of substances within the cytoplasm of a cell. In detail, a phagocyte's duty is obtaining food particles and digesting it in a vacuole. For example, following phagocytosis, the ingested particle fuses with a lysosome containing hydrolytic enzymes to form a phagolysosome; the pathogens or food particles within the phagosome are then digested by the lysosome's enzymes.
A mixotroph is an organism that can use a mix of different sources of energy and carbon, instead of having a single trophic mode on the continuum from complete autotrophy at one end to heterotrophy at the other. It is estimated that mixotrophs comprise more than half of all microscopic plankton. There are two types of eukaryotic mixotrophs: those with their own chloroplasts, and those with endosymbionts—and those that acquire them through kleptoplasty or through symbiotic associations with prey or enslavement of their organelles.
Protists are the eukaryotes that cannot be classified as plants, fungi or animals. They are mostly unicellular and microscopic. Many unicellular protists, particularly protozoans, are motile and can generate movement using flagella, cilia or pseudopods. Cells which use flagella for movement are usually referred to as flagellates, cells which use cilia are usually referred to as ciliates, and cells which use pseudopods are usually referred to as amoeba or amoeboids. Other protists are not motile, and consequently have no built-in movement mechanism.
Run-and-tumble motion is a movement pattern exhibited by certain bacteria and other microscopic agents. It consists of an alternating sequence of "runs" and "tumbles": during a run, the agent propels itself in a fixed direction, and during a tumble, it remains stationary while it reorients itself in preparation for the next run.
References
- ↑ Häder, D.-P.; Lebert, M. (2001). Photomovement. Elsevier. p. 305. ISBN 978-0-08-053886-0.
- 1 2 Häder, Donat-Peter; Hemmersbach, Ruth; Lebert, Michael (2005). Gravity and the Behavior of Unicellular Organisms. Cambridge University Press. p. 115. ISBN 978-0-521-82052-3.
- ↑ Smith, Kendric C. (2013). The Science of Photobiology. Springer Science & Business Media. pp. 308–309. ISBN 978-1-4615-8061-4.
- ↑ Häder, D.-P.; Lebert, M. (2001). Photomovement. Elsevier. p. 477. ISBN 978-0-08-053886-0.
- ↑ Wolken, J.J.; Shin, E. (1958). "Photomotion in Euglena gracilis * I. Photokinesis II. Phototaxis". The Journal of Protozoology. 5 (1): 39–46. doi:10.1111/j.1550-7408.1958.tb02525.x.
- ↑ Rudman, Bill (8 July 2002). "Discodoris boholiensis from Malaysia". Sea Slug Forum. Australian Museum, Sydney. Retrieved 12 July 2020.
- ↑ Barnes, Harold (1989). Oceanography and Marine Biology. CRC Press. p. 42. ISBN 978-0-08-037718-6.
- ↑ Advances in Marine Biology. Academic Press. 1962. p. 174. ISBN 978-0-08-057924-5.