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Evolution Of Menopause
There are various theories on the origin and process of the evolution of menopause. These attempt to suggest evolutionary benefits to the human species stemming from the cessation of women's reproductive capability before the end of their natural lifespan and can be categorized as adaptive and non-adaptive. Few other animals have a menopause; humans are joined by just four species in which females live substantially longer than their ability to reproduce, all cetaceans ( beluga whales, narwhals, orcas and short-finned pilot whales). Non-adaptive hypotheses The high cost of female investment in offspring may lead to physiological deteriorations that amplify susceptibility to becoming infertile. This hypothesis suggests the reproductive lifespan in humans has been optimized, but it has proven more difficult in females and thus their reproductive span is shorter. If this hypothesis were true, however, age at menopause should be negatively correlated with the amount of energy expended ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Menopause
Menopause, also known as the climacteric, is the time when Menstruation, menstrual periods permanently stop, marking the end of the Human reproduction, reproductive stage for the female human. It typically occurs between the ages of 45 and 55, although the exact timing can vary. Menopause is usually a natural change related to a decrease in circulating blood estrogen levels. It can occur earlier in those who smoke tobacco. Other causes include surgery that removes both ovaries, some types of chemotherapy, or anything that leads to a decrease in hormone levels. At the physiological level, menopause happens because of a decrease in the ovaries' production of the hormones estrogen and progesterone. While typically not needed, measuring hormone levels in the blood or urine can confirm a diagnosis. Menopause is the opposite of menarche, the time when periods start. In the years before menopause, a woman's periods typically become irregular, which means that periods may be longer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mountain Gorilla
The mountain gorilla (''Gorilla beringei beringei'') is one of the two subspecies of the eastern gorilla. It is listed as endangered by the IUCN . There are two populations: One is found in the Virunga Mountains, Virunga volcanic mountains of Central Africa, Central/East Africa, within three National Parks: Mgahinga Gorilla National Park, Mgahinga, in southwest Uganda; Volcanoes National Park, Volcanoes, in northwest Rwanda; and Virunga National Park, Virunga, in the eastern Democratic Republic of Congo (DRC). The other population is found in Uganda's Bwindi Impenetrable National Park. Some primatologists speculate the Bwindi population is a separate subspecies, though no description has been finalized. The latest population count, released in 2019, revealed there to be approximately 1060 mountain gorillas in the wild. Evolution, taxonomy, and classification Mountain gorillas are descendants of ancestral monkeys and apes found in Africa and Arabia during the start of the Oligo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Patriarch Hypothesis
The patriarch hypothesis is a hypothesis that explains the occurrence of menopause in human females and how a long post-fertile period (up to one third of a female's life-span) could confer an evolutionary advantage. It is an alternative theory to the grandmother hypothesis which tends to ignore male benefits of continued spermatogenesis and their roles in assistance. The patriarch hypothesis incorporates these neglected areas. It suggests selection pressure on male longevity extended the female lifespan; whose adjustment of life history has been constrained by the size of the ovaries – resulting in human females surviving beyond the age at which they can reproduce. With an extension of the post-reproductive female life stage, they could enhance their inclusive fitness by giving kin assistance. This way, with no choice in the timing of fertility termination, females are optimising an essentially bad situation. Frank Marlowe first put forward the patriarch hypothesis. He postul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disposable Soma Theory Of Aging
In biogerontology, the disposable soma theory of aging states that organisms age due to an evolutionary trade-off between growth, reproduction, and DNA repair maintenance. Formulated by British biologist Thomas Kirkwood, the disposable soma theory explains that an organism only has a limited amount of resources that it can allocate to its various cellular processes. Therefore, a greater investment in growth and reproduction would result in reduced investment in DNA repair maintenance, leading to increased cellular damage, shortened telomeres, accumulation of mutations, compromised stem cells, and ultimately, senescence. Although many models, both animal and human, have appeared to support this theory, parts of it are still controversial. Specifically, while the evolutionary trade-off between growth and aging has been well established, the relationship between reproduction and aging is still without scientific consensus, and the cellular mechanisms largely undiscovered. Bac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coefficient Of Relationship
The coefficient of relationship is a measure of the degree of consanguinity (or biological relationship) between two individuals. The term coefficient of relationship was defined by Sewall Wright in 1922, and was derived from his definition of the coefficient of inbreeding of 1921. The measure is most commonly used in genetics and genealogy. A coefficient of inbreeding can be calculated for an individual, and is typically one-half the coefficient of relationship between the parents. In general, the higher the level of inbreeding the closer the coefficient of relationship between the parents approaches a value of 1, expressed as a percentage, and approaches a value of 0 for individuals with arbitrarily remote common ancestors. Coefficient of relationship The coefficient of relationship r between two people B and C is obtained by a summation of coefficients calculated for every line by which they are connected to their identical ancestors point, common ancestors. Each such line ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inclusive Fitness
Inclusive fitness is a conceptual framework in evolutionary biology first defined by W. D. Hamilton in 1964. It is primarily used to aid the understanding of how social traits are expected to evolve in structured populations. It involves partitioning an individual's expected fitness returns into two distinct components: direct fitness returns - the component of a focal individual’s fitness that is independent of who it interacts with socially; indirect fitness returns - the component that is dependent on who it interacts with socially. The direct component of an individual's fitness is often called its personal fitness, while an individual’s direct and indirect fitness components taken together are often called its inclusive fitness. Under an inclusive fitness framework direct fitness returns are realised through the offspring a focal individual produces independent of who it interacts with, while indirect fitness returns are realised by adding up all the effects our focal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertebrate
Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebrata with some 65,000 species, by far the largest ranked grouping in the phylum Chordata. The vertebrates include mammals, birds, amphibians, and various classes of fish and reptiles. The fish include the jawless Agnatha, and the jawed Gnathostomata. The jawed fish include both the Chondrichthyes, cartilaginous fish and the Osteichthyes, bony fish. Bony fish include the Sarcopterygii, lobe-finned fish, which gave rise to the tetrapods, the animals with four limbs. Despite their success, vertebrates still only make up less than five percent of all described animal species. The first vertebrates appeared in the Cambrian explosion some 518 million years ago. Jawed vertebrates evolved in the Ordovician, followed by bony fishes in the Devonian. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Follicular Atresia
Follicular atresia refers to the process in which a Ovarian follicle, follicle fails to develop, thus preventing it from Ovulation, ovulating and releasing an egg. It is a normal, naturally occurring progression that occurs as mammalian Ovary, ovaries age. Approximately 1% of mammalian follicles in ovaries undergo ovulation and the remaining 99% of follicles go through follicular atresia as they cycle through the growth phases. In summary, follicular atresia is a process that leads to the follicular loss and loss of oocytes, and any disturbance or loss of functionality of this process can lead to many other conditions. Background Ovary, Ovaries are the site of development and breakdown of ovarian follicles which secrete hormones and Oocyte, oocytes. Oocytes are immature eggs and are surrounded by granulosa cells and internal and external theca cells. Oocytes are then able to mature within the follicle through meiosis. In humans with ovaries, this process occurs continuously, as th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coronary Artery Disease
Coronary artery disease (CAD), also called coronary heart disease (CHD), or ischemic heart disease (IHD), is a type of cardiovascular disease, heart disease involving Ischemia, the reduction of blood flow to the cardiac muscle due to a build-up of atheromatous plaque in the Coronary arteries, arteries of the heart. It is the most common of the cardiovascular diseases. CAD can cause stable angina, unstable angina, myocardial ischemia, and myocardial infarction. A common symptom is angina, which is chest pain or discomfort that may travel into the shoulder, arm, back, neck, or jaw. Occasionally it may feel like heartburn. In stable angina, symptoms occur with exercise or emotional Psychological stress, stress, last less than a few minutes, and improve with rest. Shortness of breath may also occur and sometimes no symptoms are present. In many cases, the first sign is a Myocardial infarction, heart attack. Other complications include heart failure or an Heart arrhythmia, abnormal h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alzheimer's Disease
Alzheimer's disease (AD) is a neurodegenerative disease and the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in remembering recent events. As the disease advances, symptoms can include problems with language, disorientation (including easily getting lost), mood swings, loss of motivation, self-neglect, and behavioral issues. As a person's condition declines, they often withdraw from family and society. Gradually, bodily functions are lost, ultimately leading to death. Although the speed of progression can vary, the average life expectancy following diagnosis is three to twelve years. The causes of Alzheimer's disease remain poorly understood. There are many environmental and genetic risk factors associated with its development. The strongest genetic risk factor is from an allele of apolipoprotein E. Other risk factors include a history of head injury, clinical depression, and high blood pressure. The progression of the di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osteoarthritis
Osteoarthritis is a type of degenerative joint disease that results from breakdown of articular cartilage, joint cartilage and underlying bone. A form of arthritis, it is believed to be the fourth leading cause of disability in the world, affecting 1 in 7 adults in the United States alone. The most common symptoms are joint pain and Joint stiffness, stiffness. Usually the symptoms progress slowly over years. Other symptoms may include joint effusion, joint swelling, decreased range of motion, and, when the back is affected, weakness or numbness of the arms and legs. The most commonly involved joints are the two near the ends of the fingers and the joint at the base of the thumbs, the knee and hip joints, and the joints of the neck and lower back. The symptoms can interfere with work and normal daily activities. Unlike some other types of arthritis, only the joints, not internal organs, are affected. Possible causes include previous joint injury, abnormal joint or limb development ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osteoporosis
Osteoporosis is a systemic skeletal disorder characterized by low bone mass, micro-architectural deterioration of bone tissue leading to more porous bone, and consequent increase in Bone fracture, fracture risk. It is the most common reason for a broken bone among the Old age, elderly. Bones that commonly break include the vertebrae in the Vertebral column, spine, the bones of the forearm, the wrist, and the hip. Until a broken bone occurs there are typically no symptoms. Bones may weaken to such a degree that a break may occur with minor stress or spontaneously. After the broken bone heals, some people may have chronic pain and a decreased ability to carry out normal activities. Osteoporosis may be due to lower-than-normal peak bone mass, maximum bone mass and greater-than-normal bone loss. Bone loss increases after menopause in women due to lower levels of estrogen, and after andropause in older men due to lower levels of testosterone. Osteoporosis may also occur due to a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
