User:Biostudent01/Developmental plasticity
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Mechanisms
During development, the central nervous system acquires information via endogenous or exogenous factors as well as learning experiences. In acquiring and storing such information, the plastic nature of the central nervous system allows for the adaptation of existing neural connections in order to accommodate new information and experiences, resulting in developmental plasticity. According to Turrigiano (2012), this form of plasticity that occurs during development is the result of three predominant mechanisms: synaptic and homeostatic plasticity, and learning. When brain areas are impaired, remaining circuits can reorganize to compensate for lost functions. Additionally, adult neuroplasticity allows for continuous learning and memory formation. Factors such as age, environment, and experience influence the extent of plasticity, with enriched environments enhancing cognitive function. These changes are driven by mechanisms like synaptic plasticity, which strengthens or weakens synapses based on activity, homeostatic plasticity, which maintains neural stability, and learning-induced plasticity, which adapts neural circuits in response to new experiences.
Phenotypic plasticity
Phenotypic plasticity is the ability of an organism to change its physical traits, behavior, or physiology in response to environmental conditions. This adaptability allows a single genotype to produce different phenotypes depending on the environment, helping organisms survive and reproduce in varying or changing habitats. For example, some plants can grow taller in low-light conditions to reach sunlight, while certain animals may change their coloration with the seasons for better camouflage. Phenotypic plasticity plays a crucial role in evolution and ecological interactions.
= Reaction norms =
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The norm of reaction, or reaction norm, is a pattern of phenotypic plasticity that describes how a single genotype can produce an array of different phenotypes in response to different environmental conditions. Furthermore, a reaction norm can be a graphical representation of organismal variation in phenotype in response to numerous environmental circumstances. The graphical representation of reaction norms is commonly parabolic in shape, which represents the variation in plasticity across a population. Additionally, reaction norms allow organisms to evaluate the need for various phenotypes in response to the magnitude of the environmental signal.
= Polyphenisms - (Alexis Lopez) =
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Polyphenism refers to the ability of a single genotype to produce a variety of phenotypes. In contrast to reaction norms, which produce a continuous range of phenotypes, polyphenisms allow a distinct phenotype to arise from altering environmental conditions.{{Cite journal |last1=Simpson |first1=Stephen J. |last2=Sword |first2=Gregory A. |last3=Lo |first3=Nathan |date=2011-09-27 |title=Polyphenism in Insects |url=https://linkinghub.elsevier.com/retrieve/pii/S0960982211006518 |journal=Current Biology |language=English |volume=21 |issue=18 |pages=R738–R749 |doi=10.1016/j.cub.2011.06.006 |issn=0960-9822 |pmid=21959164|bibcode=2011CBio...21.R738S }} Polyphenisms occur in a wide range of organisms, including both vertebrates and invertebrates.{{Cite book |last=Gilbert |first=Scott F. |title=Ecological developmental biology: the environmental regulation of development, health, and evolution |last2=Epel |first2=David |date=2015 |publisher=Sinauer Associates, Inc. Publishers |isbn=978-1-60535-344-9 |edition=Second edition |location=Sunderland, Massachusetts, U.S.A |oclc=905089531}} A specific example of a polyphenism can be seen in the Florida carpenter ant, Camponotus floridanus. For a developing ant embryo, a multitude of environmental signals–such as the temperature surrounding the developing embryo, or the nutrition and chemicals provided to the larvae–can ultimately determine the adult ant's morphology and placement within the caste system.{{Cite journal |last1=Yang |first1=Chih-Hsiang |last2=Andrew Pospisilik |first2=John |date=2019-02-26 |title=Polyphenism – A Window Into Gene-Environment Interactions and Phenotypic Plasticity |journal=Frontiers in Genetics |language=English |volume=10 |page=132 |doi=10.3389/fgene.2019.00132 |doi-access=free |issn=1664-8021 |pmc=6399471 |pmid=30863426}} For Florida carpenter ants, the end phenotype and behavior are determined by the morphology; developing ants can become minor workers, major workers, or queen ants. An example of the anatomical differences seen in this species of ant is the presence or absence of wings and the size differences between male ants. Although the polyphenism of the ants has been documented, research is still needed to determine the molecular mechanisms for the induction of each unique phenotype. Another example of a polyphenism is temperature-dependent sex determinatio
== Seasonal Polypheniesm ==
Seasonal polypheniesm occurs when a species offspring can posses two or more different phenotypes depending on the season in which they are produced {{Cite journal |last1=Kingsolver |first1=Joel G. |last2=Wiernasz |first2=Diane C. |date=1991 |title=Seasonal Polyphenism in Wing-Melanin Pattern and Thermoregulatory Adaptation in Pieris Butterflies |url=https://www.jstor.org/stable/2462402 |journal=The American Naturalist |volume=137 |issue=6 |pages=816–830 |bibcode=1991ANat..137..816K |doi=10.1086/285195 |issn=0003-0147 |jstor=2462402}}. This can be most commonly observed in varying insect species. Polypheniesm can be due to environmental variations, such as temperature, or changes in sunlight exposure, called photoperiod.
File:Bicyclus anynana egg 4.JPG
A study conducted in 2010 sought to examine the heterogeneity of the butterfly species Bicyclus anynana{{Cite journal |last1=Oostra |first1=Vicencio |last2=de Jong |first2=Maaike A. |last3=Invergo |first3=Brandon M. |last4=Kesbeke |first4=Fanja |last5=Wende |first5=Franziska |last6=Brakefield |first6=Paul M. |last7=Zwaan |first7=Bas J. |date=2011-03-07 |title=Translating environmental gradients into discontinuous reaction norms via hormone signalling in a polyphenic butterfly |journal=Proceedings. Biological Sciences |volume=278 |issue=1706 |pages=789–797 |doi=10.1098/rspb.2010.1560 |issn=1471-2954 |pmc=3030849 |pmid=20826484}}. The study hypothesized the polyphenism observed during seasonal changes was due to temperature during development and mediated by ecdysteriod hormones. Insects have two major classes of hormones, ecdysteriods and juvenile hormones (JHs). 2000 larvae were allowed to grow to adulthood with 400 larvae per temperature treatment. Immediately following hatching the larvae were places in five different climate controlled chambers at 19°C, 21°C, 23°C, 25°C and 27°C (± 0.5°C). The lowest temperatures represent dry season conditions while the higher temperatures represent wet season conditions. Phenotypic characteristics were measured with specific specifications including the distance between the first and fifth eyespot and the radius of the fifth eyespot. Hormone levels were measured at 11 points during the first 55% of pupal development. The results showed that some phenotypic characteristics were directly proportional to temperature conditions while other characteristics showed discontinuous changes at different temperatures.
File:Gerridae carrying other Gerridae on back in Hatta River - 2.jpg
A separate study conducted in 2022 sought to explore the polyphenism observed in water strider wings, Gerris buenoi, as it relates to photoperiod{{Cite journal |last1=Gudmunds |first1=Erik |last2=Narayanan |first2=Shrinath |last3=Lachivier |first3=Elise |last4=Duchemin |first4=Marion |last5=Khila |first5=Abderrahman |last6=Husby |first6=Arild |date=2022-04-27 |title=Photoperiod controls wing polyphenism in a water strider independently of insulin receptor signalling |journal=Proceedings. Biological Sciences |volume=289 |issue=1973 |pages=20212764 |doi=10.1098/rspb.2021.2764 |issn=1471-2954 |pmc=9043737 |pmid=35473377}}. Wing polymorphism is seen in many species of insect, including the above mentioned Bicyclus anynana. Water striders are semi-aquatic insects that may display long wings, short wings, or an absence of wings entirely. Dependent on the species of water strider, these differences may be monomorphic or examples of seasonal or genetic polyphenism. Eggs were collected from a population of G. buenoi with varying wing lengths, obtained from a pond in Toronto, Ontario. Short wings were defined as forewings that did not stretch beyond the abdomen while long wings were defined as wings stretching to at least the sixth abdominal segment. The eggs and nymphs were exposed to different ratios of light and darkness. They were able to conclude that photoperiod is the strongest cue for wing determination in G. buenoi concluding specifics polypheniesm is due to environmental factors.
= Environmental cues - Mary Mantooth =
Peppered Moths [edit]
Since we are speaking of cues, the adult peppered moth's melanism is primarily a genetic adaptation driven by natural selection which is applied through environmental cues. The question is why?
During the Industrial Revolution, air pollution caused a change in the moth population, with an increase in dark-colored moths due to industrial melanism. The caterpillars of the peppered moth have demonstrated the ability to change their coloration to match the color of the twigs they rest on. This is a prime example of phenotypic plasticity, where an organism's phenotype (observable characteristics) changes in response to environmental cues. This color change is a gradual process, allowing the larvae to blend in with their surroundings, providing camouflage against predators. The primary environmental cue that causes the larval color change, is visual information, gathered through the skin of the larvae. The larvae respond to the color and luminance of the twigs they are on. Studies have shown that even when blindfolded, the caterpillars can still sense and react to the color of their environment, indicating that they possess extraocular photoreception (light sensing through their skin). This shows that the light wavelengths that are being reflected off of the twigs, is the environmental cue causing the color change. This color plasticity is crucial for the larvae's survival. By matching their background, they significantly reduce their risk of being detected and eaten by avian predators. In essence, the peppered moth larvae demonstrate a remarkable ability to adapt their appearance to their immediate environment, showcasing the power of phenotypic plasticity in enhancing survival.
== Limb Morphology [edit] ==
Research has shown that Anolis lizard (anole) limb morphology can be influenced by the environment during development. Specifically, studies have demonstrated that the length of their hind limbs can vary depending on the substrate they experience as hatchlings. For example, Anolis lizards raised on broad surfaces tend to develop relatively longer hind limbs, while those raised on narrow surfaces develop relatively shorter hind limbs. This adaptation is thought to be related to their ability to move efficiently in their respective environments. This is a great example of developmental plasticity, because the environment experienced during the early stages of life, effects the physical development of the animal.
Ecological relevance [edit]
This developmental plasticity is ecologically relevant because it allows Anolis lizards to fine-tune their locomotor abilities to match their specific habitat. This can enhance their survival and reproductive success. This is especially important when considering the vast amount of different microhabitats that Anolis lizards occupy. It's important to note that while Anolis lizards exhibit developmental plasticity in some traits, research also highlights that the extent of this plasticity can vary. Also, research indicates that while plasticity is present, it does not fully explain all of the morphological differences observed in Anolis lizards. Evolutionary adaptation, through genetic changes, also plays a large role. In all, Anolis lizards demonstrate developmental plasticity, particularly in their limb morphology, allowing them to adapt to different environmental conditions during their early development.
== Plants [edit] ==
File:Environmental_cues_in_plants.png
In one study, the mechanisms of signaling certain triggers and responses in plants is studied. These networks function in providing the plants with a sort of cushion to environmental changes. Just like animals, plants know when or when not to do produce flowers or fruit based on environmental changes. Since plants are immobile, they have to develop these systems of recognizing certain cues in order to provide a response that works in relation to their fitness and even more so their survival. Plants have a certain sensitivity about them, and this is exactly why it is needed. This study describes how canalization is the driving property of the developing genetic plasticity in plants. It also discusses how the vernalization2 gene mediates the epigenetic regulation of vernalization in one species known as Arabidopsis. Vernalization is a process performed due to the environmental cues letting the plant organism know that flowering is near. As fluctuations in temperature and light can impact the health of the plant, the organism confers with its intricate network of a buffer to produce the best response in terms of survival and flourishment. An organism's sensitivity to light during development could be useful in predicting what phenotype may be the most beneficial in the future based on the foliage of the mature organism.
References