Although estrogen is primarily produced by ovaries, it is also produced by the adrenal glands and in fat tissue. loss of the normal amount of fat lowers the level of estrogen so that the menstrual cycle and ovulation stops. female olympic athletes who train severely often shut off their cycles. what would be a reasonable evolutionary cause of this shutdown?
Final answer:
The shutdown of the menstrual cycle and ovulation in female athletes with low body fat and estrogen levels is an evolved adaptation to prevent pregnancy during times of physical stress or low energy reserves, as a way to conserve energy and ensure the mother has sufficient resources for a successful pregnancy.
Explanation:
The evolutionary cause of the shutdown of the menstrual cycle and ovulation in female Olympic athletes who train severely and experience a significant loss of body fat can be understood as a protective mechanism. The body requires a considerable amount of resources to maintain a pregnancy, and during periods of extreme physical stress or when energy reserves are low, it may not be advantageous for reproduction to occur.
If the body senses that it is not in an optimal state for supporting a pregnancy due to low levels of estrogen and fat tissue, it may shut down the reproductive cycle to conserve energy and prevent a pregnancy that could be risky for both the mother and potential offspring.
This response is likely an evolved adaptation to increase overall reproductive success by ensuring that pregnancy occurs only during times when the mother has sufficient resources to support both herself and the developing fetus.
Molecules tend to move from an area of high concentration to an area of low concentration in a process known as
What is the specific function of the structure labeled f?basic motor reflex pathways.what is the specific function of the structure labeled f?basic motor reflex pathways.determination of muscle tension increasing tension of the surrounding muscle increasing tension of the antagonistic muscle determination of muscle length?
Motor reflex pathways, the structure labeled f, regulates reflex reactions to stimuli like physical contact, maintaining muscle length, and adjusting muscle tension according to these sensory inputs.
Explanation:The specific function of the structure labeled f, the basic motor reflex pathways, refers to the mechanism that allows for reflex actions to occur. This includes the motor neuron pathway linking the sensory fibers in the spinal cord to the muscle. When a stimulus prompts a reflex action, such as a muscle stretch, the motor neuron of the muscle communicates this stimuli, triggering a response. For instance, when your knee is struck with a rubber hammer during a physical exam, the stretch reflex activates a muscle spindle receptor, causing the direct contraction of your muscles. Essentially, these pathways help to maintain muscle length and regulate muscle tension.
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Compared with people who do not have schizophrenia, synaptic pruning occurs __________ in people who do have the disorder.
What could be an additional trial to determine the effect of salt on plant growth
Which method will most accurately determine the diversity of an ecosystem?
The correct answer is D. Mangrove tree crab.
In the given food chain of a mangrove community, green algae are producers, fish is primary consumer as they feed on green algae, mangrove tree crab is secondary consumer feeding on fish, mangrove water snake is tertiary consumer which feeds of mangrove tree crabs and finally American crocodile is top consumer which feeds on snakes. In this food relationship, if the number of mangrove water snake increase, the population of mangrove tree crab will decrease as crab would be eaten by more snakes. But in the long the decrease mangrove tree crab, the population of mangrove water snake will also decrease in want of food.
Is an intentional burn that removes fuel and oxygen from an advancing fire?
An example of natural selection is the tail of a male peacock. The females of the species choose mates based on the colors of the males’ tail feathers. If females begin using different criteria than feather color when they choose mates, what would most likely happen to the tails of peacocks over time?
increased variation in tail feather color because the selection pressure has been relieved
increased variation in tail feather color because the peacocks try different ways to impress the females
decreased variation in tail feather color because no form of the trait is advantageous
decreased variation in tail feather color because the only reason for variation was selection pressure
The Sun is
A.
the same size as all the other stars.
B.
the largest star in the universe.
C.
a very small star.
D.
a medium-sized star.
Answer:
The answer is d)a medium-sized star
Explanation:
The Sun is the star that is closest to Earth and although its size is 100 times larger than Earth, it is a medium-sized star when compared to other stars. Thanks to the Sun, life on Earth is possible. The Sun exerts a great force of gravitational attraction on all the planets, which causes them to revolve around it.
Poisonous substances produced by some microorganisms are called
Microorganisms produce poisonous substances known as toxins. These include endotoxins and exotoxins, which are involved in the pathogen's ability to invade and damage body tissues. Remarkable examples are the mycotoxins produced by molds and the potent toxins produced by Bacillus anthracis.
Explanation:Poisonous substances produced by certain microorganisms are referred to as toxins. These toxins can be categorized further into endotoxins and exotoxins. They facilitate the ability of the pathogen to invade and cause damage to the host body, a characteristic called toxigenicity.
For instance, molds, a type of fungi, produce poisonous substances called mycotoxins. In bacterial microorganisms, some produce virulent factors to evade the immune system, including the M protein found in the fimbriae of certain Streptococcus species or the protective mycolic acid coat produced by Mycobacterium tuberculosis.
Pathogens such as Bacillus anthracis, responsible for anthrax, release potent toxins causing severe symptoms like edema, hypoxia, necrosis and eventually can lead to patient's death if untreated properly.
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Severe edema in pregnant women may be a symptom of what health condition?
HIV acts by attaching to receptors on the surfaces of T-cells that aid other lymphocytes in fighting infection. Once HIV is inside a cell, its RNA is reverse-transcribed and its product DNA is integrated into the host cell. It then directs the production of new virus particles. As time goes on the number of T-cells A) increases. B) decreases. C) stays the same. D) is unpredictable.
Answer:
B) decreases.
Explanation:
The HIV virus acts within the cells of the immune system, responsible for the body's defense. After entering the cell, HIV begins to act and integrate into the genetic code of the infected cell. The cells most affected by the virus are called T-CD4, which are used by HIV to make copies of itself.
Each time this cell, when infected, divides, it produces a copy of its genetic code and, at the same time, a copy of the virus's genetic code.
Infected by the virus, the cells of the immune system begin to function less efficiently until, over time, the body's ability to fight common diseases diminishes and is subject to the onset of opportunistic diseases.
Many farmers in less densely populated areas, such as amazonia, practice _______________, also known as shifting cultivation or swidden agriculture where an area is cleared and then burned for the vegetative remains to release nutrients back into the soil.
The major source of imbalance in the carbon cycle is the result of
A) human activities.
B) changes in Earth's orbit.
C) increased volcanic activity.
D) changes in weather patterns.
The spoon is too hot after sitting in the hot soup. is this an example of conduction, convection, or radiation? why?
What does your circulatory system have in common with your nervous system
Answer:
Both systems are run throughout the entire body.
Explanation:
the fittest organisms in an environment survive and reproduce what is the name for this process
Final answer:
The process by which the fittest organisms in an environment survive and reproduce is called natural selection, which is central to the theory of evolution. It's not just the fittest but those with relative fitness to their environment who may survive and reproduce, resulting in their traits becoming more common in the population.
Explanation:
The name for the process where the fittest organisms in an environment survive and reproduce is known as natural selection. This is a fundamental concept of biology and a critical mechanism of evolution. Natural selection, also referred to colloquially as survival of the fittest, occurs when individuals with favorable traits are more likely to survive environmental changes and therefore reproduce more prolifically than those without such traits, leading to these advantageous traits becoming more common in the population over time.
It is a common misconception that only the very fittest organisms survive and reproduce. In reality, fitness is relative to the specific environmental conditions and includes a diverse range of traits, some individuals who may not seem as fit can still survive and reproduce. This variation in success is influenced by many factors, such as food availability, predator presence, and mating preferences.
Charles Darwin termed the phrase 'fitness' to describe an organism's ability to survive and reproduce. His observations and those of Alfred Russel Wallace lead to the establishment of the theory of evolution by natural selection, where nature selects the variations most useful for survival in given conditions. An example of this is the giant tortoises of the Galapagos Islands, where tortoises with longer necks were more apt to survive during droughts because they could reach more food.
Two pea plants, hybrid for a single trait, produce 60 pea plants. approximately how many of the pea plants are expected to exhibit the recessive trait. 15. a student crossed wrinkled-seeded (rr) pea plants with round-seeded (rr) pea plants. only round seeds were produced in the resulting plants. this illustrates the principle of.'
The genotype of the round pea parent plant cannot be determined from the provided data, but if it's heterozygous, the probability that all three progeny will have round peas is 12.5%.
Explanation:In pea plants, round peas (R) are dominant to wrinkled peas (r). When performing a test cross between a pea plant with wrinkled peas (genotype rr) and a plant of unknown genotype that has round peas (potentially genotype RR or Rr), and you obtain offspring plants that all have round peas, you cannot conclusively determine the genotype of the round pea parent plant based solely on this outcome. However, if we assume that the round pea parent plant is heterozygous (genotype Rr), the probability of all offspring displaying round peas can be calculated.
Considering Mendelian inheritance, a heterozygous round pea plant (Rr) crossed with a homozygous recessive wrinkled pea plant (rr) would result in a 1:1 ratio of round to wrinkled peas among the progeny. To find the probability that all three progeny are round peas, we would calculate it as (1/2) x (1/2) x (1/2) because each offspring has a 50% chance of inheriting the dominant round pea allele. Therefore, the probability would be 1/8 or 12.5%.
Approximately 15 out of 60 hybrid pea plants are expected to exhibit the recessive trait.
The cross demonstrates the principle of dominance, where the dominant allele masks the recessive allele.
In pea plants, round seeds (R) are dominant to wrinkled seeds (r). When two hybrid plants (Rr) are crossed, the possible offspring genotypes are:
25% RR (homozygous dominant, round)50% Rr (heterozygous, round)25% rr (homozygous recessive, wrinkled)Therefore, out of 60 offspring, approximately 25% will display the recessive trait, which amounts to 15 plants (0.25 * 60 = 15).
Principle of Dominance
Crossing wrinkled-seeded (rr) pea plants with round-seeded (RR) plants and getting only round seeds demonstrates the principle of dominance, where the dominant allele (R) masks the expression of the recessive allele (r).The principle of dominance, also known as Mendel's first law or the law of dominance, is a fundamental concept in genetics that describes the relationship between alleles of a single gene.The principle of dominance is crucial for understanding how genetic traits are inherited and expressed in organisms, providing the foundation for Mendelian genetics and subsequent developments in the field of genetics and inheritance."owls eat rats, mice, shrews, and small birds. assume that, over a period of time, an owl consumes 5,000 j of animal material. the owl loses 2,300 j in feces and owl pellets and uses 2,500 j for cellular respiration. what is the production efficiency of this owl?"
What does a fern have in common with an apple tree?
Ferns and apple trees, despite being different types of plants, share some key features. Both are vascular plants, use photosynthesis, and have a life cycle that involves alternation of generations. However, the specifics of these shared characteristics can vary.
Explanation:A fern and an apple tree share some common characteristics despite belonging to different plant groups. Both are part of the larger group of vascular plants, meaning they have specialized tissues (xylem and phloem) that conduct water, nutrients, and sugars throughout the plant. This allows them to grow larger and live in a diversity of habitats.
Another common feature is their usage of photosynthesis for energy. They both possess photosynthetic tissues, whether it's in the fronds of a fern or the leaves of an apple tree, that allow them to capture sunlight and convert it into chemical energy. This is a fundamental characteristic shared by almost all the green plants.
Finally, they also exhibit the phenomenon of alternation of generations in their life cycle, involving the shift between a diploid stage (the sporophyte) and a haploid stage (the gametophyte). It's important to note, however, that this process differs between the two: in the apple tree - a seed plant - the dominant, most visible stage is the sporophyte, whereas in a fern, although the sporophyte is also dominant, the gametophyte stage is independent and free-living.
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What is the muscular organ that holds the developing embryo?
The prokaryotic cells that built stromatolites are classified as _____.'
The prokaryotic cells that built stromatolites are classified as bacterial and archaean prokaryotic cells.
Explanation:The prokaryotic cells that built stromatolites are classified as d. bacterial and archaean prokaryotic cells. Prokaryotes are predominantly single-celled organisms of the domains Bacteria and Archaea. Stromatolites are layered rock-like structures formed by the activities of prokaryotes, specifically bacteria and archaea, that live in shallow water environments.
Lichen is a symbiotic decomposer that attachers itself to trees and slowly breaks them down. they obtain nutrients from the tree, allowing them to survive and reproduce. what type of relationship is this?
Which product of combustion contributes most to the greenhouse effect?
Why are humans important to the life cycle of malaria parasites?
Techno and electronica are performed at dancing events known as
Techno and electronica are performed at dancing events known as raves.
Explanation:Techno and electronica are performed at dancing events known as raves. Raves are high-energy gatherings where people gather to dance and enjoy electronic music. These events often feature DJs and live performances, creating an immersive and energetic atmosphere.
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What is evolution? what are the pieces of evidence scientists use to study evolution?
Answer:
Evolution is how living things change over time and how new species develop. Scientists can study fossils for evidence.
Explanation:
The eastern meadowlark and the western meadowlark are two closely related bird species. the two species avoid interbreeding because they have different mating songs. this is an example of -
The answer is behavioral isolation
_____ is a special case of explosive speciation in which new species form rapidly in response to numerous "open" ecological niches. peripatric speciation adaptive radiation allopatric speciation co-speciation sympatric speciation
Final answer:
Adaptive radiation is a form of rapid speciation where new species evolve to fill different ecological niches, often after a mass disaster or colonization event provides access to new resources.
Explanation:
Adaptive radiation is a special case of explosive speciation in which new species form rapidly in response to numerous "open" ecological niches. It involves the relatively rapid evolution from a single species to several species to fill a diversity of available ecological niches.
Examples include the cichlid fish in East Africa's lakes and Darwin's finches in the Galapagos, where a population experiences speciation following a mass disaster or colonization of a new area with diverse habitats. These events provide access to a range of unexploited resources and niches, leading to the diversification of the species.
which organ is involved in ingestion
Digestion starts in the "mouth" and continues in the stomach. The small intestine completes the digestion process.
Answer:
The mouth is the organ involved in ingestion in the digestive system.
Explanation:
Intake of food into the mouth and break down into small pieces there, is the process of the ingestion. In the ingestion process food is taken into the mouth and crushed and broken down into smaller pieces with the help of teeth. The presence of food triggers nervous reflexes to cause the salivary glands to release a fluid saliva. Saliva also softens and provides moisture to the food in the mouth to make it easier to swallow down to esophagus. It helps in digestion of starches to begin, present in food.