Beneficial Use of Viruses
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2015
Let us reconsider the notion of disease, pathology, harm, or damage caused by parasites. A term often used to embody this concept of harm is virulence. This term, which appears repeatedly throughout this book, is also defined differently depending on the discipline. Infectious disease biologists often consider virulence to be a measure of the likelihood that an infectious agent causes disease or even fatality. Among ecologists and evolutionary biologists, virulence is generally considered and measured differently; it is the ability of a parasite to reduce its host’s fitness. Fitness is a measure of the success of an individual in passing on its genes to future generations and is influenced by the individual’s ability to survive and to reproduce. A parasite might shorten its host’s life span and thereby affect the host’s eventual reproductive output, or the parasite might diminish its host’s reproductive output but not affect survival. If a parasite castrates or kills its host, it is considered to be especially virulent.
An Introduction to Parasitism
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2023
Let us reconsider the notion of disease, pathology, harm, or damage caused by parasites. A term often used to embody this concept of harm is virulence. This term, which appears repeatedly throughout this book, is also defined differently depending on the discipline. Infectious disease biologists often consider virulence to be a measure of the likelihood that an infectious agent causes disease or even fatality. Among ecologists and evolutionary biologists, virulence is generally considered and measured differently; it is the ability of a parasite to reduce its host’s fitness. Fitness is a measure of the success of an individual in passing on its genes to future generations and is influenced by the individual’s ability to survive and to reproduce. A parasite might shorten its host’s life span and thereby affect the host’s eventual reproductive output, or the parasite might diminish its host’s reproductive output but not affect survival. If a parasite castrates or kills its host, it is considered to be especially virulent.
Evolution, Natural Selection, and Behavior
Gail S. Anderson in Biological Influences on Criminal Behavior, 2019
Siblicide is the murder of one’s siblings. Natural selection favors traits that increase reproductive fitness, which passes these traits to the next generation. Kin selection theory predicts that relatedness should promote altruism, in that it is important to protect close relatives, such as siblings, as they carry many of the same genes that you do, so ensuring that they survive to reproduce helps you indirectly by passing on those traits to the next generation.27 This is perhaps best illustrated in a beehive, in which only one female, the queen, is fertile and all the other related females are sterile. They act as workers to raise the offspring of the queen, their mother, and in so doing, help to pass their genes on to the next generation. Siblicide therefore seems counterintuitive. However, siblings may come into conflict when competing for resources such as parental investment. This is more commonly seen in non-human animals, particularly in bird species, in which a nestling will frequently push another nestling out of the nest in order to receive more resources from the parents. Although much rarer in mammals, siblicide does occur in some species, usually when food resources are low.27 It may also have been common in our ancestral past.
Differences in the Level of Functional Fitness and Precise Hand Movements of People with and without Cognitive Disorders
Published in Experimental Aging Research, 2022
Rohan Anna, Fugiel Jarosław, Winkel Izabela, Lindner Karolina, Kołodziej Małgorzata, Sobieszczańska Malgorzata
Analysis of the obtained results show that differences in the level of fitness depend on the type of motor activities performed. In the case of functional fitness tests assessing the strength of the lower extremities, agility and aerobic capacity that are similar to daily activities, people with cognitive impairment in both gender groups do not differ from those in the control group. Functional fitness depends on many factors, both genetic and environmental, as well as lifestyle. It includes habitual, automatic activities which have been transitioned from controlled too automatic while motor learning and eventually cerebellar cortex and subcortical nuclei play crucial role in controlling precise executed movements. Explanation of the fact that functional fitness in people with cognitive dysfunctions remains on the same level as in the healthy aging ones is that this kind of activities is controlled by low-level cerebral areas.
The immediate and durable effects of yoga and physical fitness exercises on stress
Published in Journal of American College Health, 2021
Jiajin Tong, Xin Qi, Zhonghui He, Senlin Chen, Scott J. Pedersen, P. Dean Cooley, Julie Spencer-Rodgers, Shuchang He, Xiangyi Zhu
Yoga is regarded as a mind-body exercise rooted in India 4000 years ago. The term yoga means “to unite,” referring to the union of the mind, body, and spirit. It has different traditional forms (e.g., Gyan yoga, Raja yoga, and Hatha yoga20) and consists of different technical components (e.g., postures, breathing, and meditation17). Fitness refers to “the ability to perform daily tasks without fatigue” including several components: muscular endurance, muscular strength, cardiorespiratory fitness, flexibility, coordination, and speed.21 Aerobic fitness exercises have been more studied than muscular fitness related exercises for mental health intervention. Aerobic fitness exercises may include but are not limited to dancing, running, and swimming,14,15 which can improve cardiorespiratory endurance.7 It differs from yoga exercise on speed, distance, and duration. Compared to fitness exercise, yoga exercise is performed at a slower pace, moves in smaller distance, and often lasts for a longer duration.
Precopulatory Sexual Cannibalism and Other Accidents: Evolution, Material Trans Theory, and Natural Law
Published in Studies in Gender and Sexuality, 2018
Initial studies by Newman and Elgar (1991) interpreted the female’s actions along Dawkinsian lines. They developed what they called the adaptive foraging hypothesis, which suggested that adult females reap a net profit from pre-copulatory sexual cannibalism in the long run. The nutrient surplus is so valuable that their long-term reproductive fitness is enhanced. They inevitably produce more offspring, outcompete other females, and their genetic configuration prevails. This would have made Dawkins happy. But a counterproposal advanced by Arnqvist and Henriksson (1997), the aggressive spillover hypothesis, took a different tack. Arnqvist and Henriksson proposed that precopulatory sexual cannibalism, rather than an adaptive mechanism that increased reproductive fitness, was actually a by-product of a “voracity syndrome” that presented in some juvenile female spiders. This “hyperactive prey-detection device,” if you will, was a frequently recurring accident that prompted the female spiders to perceive even potential mates as food sources.
Related Knowledge Centers
- Allele
- Gene Pool
- Kin Selection
- Phenotype
- Population Genetics
- Sexual Reproduction
- Genotype
- Reproductive Success
- Expected Value
- Physical Fitness