Yolk sac is a structure that has a short duration in intrauterine development and is an important site for early blood cell formation.
What is the yolk sac?It is the bag that houses yolk inside and that allows the embryos of certain species to feed in the initial stages of development.
Due to this structure, the embryo receives oxygen and nutrients and can discard its waste, in the case of the human being, the yolk sac fulfills the functions of the circulatory system, until the internal circulation begins to develop.
Therefore, we can conclude that the yolk sac is a structure that has a short duration in intrauterine development and is an important site for early blood cell formation.
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conclusion for air pollution
What is the gravitational constant on earth?
______________ m/s²
Answer:
9.807 m/s²
Explanation:
Hope this helps!
Answer:
9.807 m/s²
Explanation:
What is the science dealing with the size, distribution, composition,and changes in population.
Answer:
Demography
Explanation: Demography is the study of human populations – their size, composition and distribution across space – and the process through which populations change. Births, deaths and migration are the 'big three' of demography, jointly producing population stability or change.
What sequence of bases on RNA would match, or pair with, the following DNA sequence: GCA?
The sequence of bases on RNA that would match or pair with the following DNA sequence: GCA is CGU.
What is transcription?Transcription is the process by which mRNA sequence is produced from a DNA template in the nucleus of a cell.
During transcription process, the following applies:
Adenine (A) pairs with Uracil (U)Guanine (G) pairs with Cytosine (C)This means that the mRNA sequence that will result from a template of DNA with sequence: GCA is CGU.
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Make a table summarising the main components of tobacco smoke and their effects on the human body.
Answer: Some of the components in tobacco smoke include:
Nicotine (the addictive drug that produces the effects in the brain that people are looking for)
Hydrogen cyanide.
Formaldehyde.
Lead.
Arsenic.
Ammonia.
Radioactive elements, such as polonium-210
Benzene.
Explanation: Highly damaging components of tobacco smoke include:
tar – is the word for the solid particles suspended in tobacco smoke. The particles contain chemicals, including cancer-causing substances (carcinogens). Tar is sticky and brown, and stains teeth, fingernails and lung tissue
carbon monoxide – is a poisonous gas. It is odourless and colourless and, in large doses, quickly causes death because it takes the place of oxygen in the blood. In people who smoke, the carbon monoxide in their blood makes it harder for oxygen to get to their organs and muscles
oxidizing chemicals – are highly reactive chemicals that can damage the heart muscles and blood vessels of people who smoke. They react with cholesterol, leading to the build-up of fatty material on artery walls. Their actions lead to heart disease, stroke and blood vessel disease
metals – tobacco smoke contains several metals that cause cancer, including arsenic, beryllium, cadmium, chromium, cobalt, lead and nickel
radioactive compounds – tobacco smoke contains radioactive compounds that are known to be carcinogenic.
The effects of tobacco smoke on the body include:
raised blood pressure and heart rate
constriction (tightening) of blood vessels in the skin, resulting in a drop in skin temperature
less oxygen carried by the blood during exercise
‘stickier’ blood, which is more prone to clotting
damage to the lining of the arteries, which is thought to be a contributing factor to atherosclerosis (the build-up of fatty deposits on the artery walls)
reduced blood flow to extremities (fingers and toes)
increased risk of stroke and heart attack due to blockages of the blood supply.
Answer:
nicotine.
carbon monoxide.
tar.
toxic chemicals such as benzene, arsenic and formaldehyde.
Their actions lead to heart disease, stroke and blood vessel disease. tobacco smoke contains several metals that cause cancer.
Explanation:
In rock layers, jellyfish fossils are found lower than trilobite fossils, and trilobite fossils are found lower than ammonite fossils. what can be determined from this information? trilobites existed before jellyfish and ammonites. jellyfish existed before trilobites and ammonites. ammonites existed before trilobites and jellyfish. jellyfish, trilobites, and ammonites lived together.
Trilobites were exclusively marine animals. They were first appeared at the beginning of the Cambrian Period. In the context Jellyfish existed before trilobites and ammonites.
What is method to determine fossil age?To find the age of fossil, scientists use some type of clock to determine the date it was formed.
Geologists usually use radiometric dating procedures which is based on the natural radioactive decay of some elements such as potassium and carbon, as reliable clocks to date ancient events.
In the given context, jellyfish fossils are found lower than trilobite fossils, and trilobite fossils are found lower than ammonite fossils. Which determines that jellyfish existed before trilobites and ammonites.
Thus, the correct option is B.
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Answer:
B
Explanation:
Its the Answer
Which statement best describes why the author of "Water Efficiency Strategies" organized the text into two main sections? Question 2 options: To show readers that thinking about both the supply side and the demand side are important for water efficiency. To show readers that thinking about the supply side is more important than the demand side. To use one section to describe the cause and the second section to describe the effect. To follow the structure most informational texts use when organized into two main sections to show two sides of a topic.
Answer:
A
Explanation:
Took the test!
Which best describes the lower body structures of humans and chimpanzees?.
The statement that best describes the lower body structures of humans and chimpanzees is that the big toes of humans and chimpanzees are enlarged.
What is the lower body structure?The lower body structure is defined as the lower extremities of a vertebrae that is distal to the upper extremities.
The first toes of both human and chimpanzees are enlarged because they are mammals sharing a similar specie.
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sources of food stuff in animal nutrition
Answer: Animal source foods include many food items that come from an animal source such as fish, meat, milk, eggs, honey, cheese and yogurt.
Explanation:
A tautomeric shift may result in _____________ A. Transition mutations B. Induced mutations C. Any of the above D. Transversion mutations E. Frameshift mutations
Answer: C
Explanation:
Any of the above are possible
How is DNA stored in the nucleus?
Explanation:
DNA is tightly packed up to fit in the nucleus of every cell. As shown in the animation, a DNA molecule wraps around histone proteins to form tight loops called nucleosomes. These nucleosomes coil and stack together to form fibers called chromatin.
How does a fossil gets into the fossil record?
Answer:
Explanation:
For an organism to be fossilized, the remains usually need to be covered by sediment soon after death. Sediment can include the sandy seafloor, lava, and even sticky tar. Over time, minerals in the sediment seep into the remains. The remains become fossilized
Answer:
i got u
Explanation:
For an organism to be fossilized, the remains usually need to be covered by sediment soon after death. Sediment can include the sandy seafloor, lava, and even sticky tar. Over time, minerals in the sediment seep into the remains. The remains become fossilized.
An organism that is eukaryotic and photosynthetic is.
Answer:
A protist
Explanation:
Trust me.
The tough, fibrous, outermost covering of the spinal cord is the.
The moon orbiting the Earth - Non-contact
fore.
On Earth, the mass of an astronaut is 120 kg and a weight of 1200 N. What
predictions could we make about the mass and weight of the astronaut on
the Moon, where there is less gravity?
The mass of the astronaut is the same in both places. However, the weight is different due to the variation of gravity.
What is the weight?Weight is a term that refers to the force with which the Earth or another celestial body attracts a body due to the action of gravity. It is measured in Newtons.
What is the mass?Mass is a term that refers to a physical magnitude and general property of matter that expresses the inertia or resistance to the change of movement of a body. It is measured in kilograms.
How do weight and mass differ on Earth and the Moon?The weight of a body is not the same on Earth as on the Moon because the Moon is smaller and the force of gravity is less. Therefore, the weight of the astronaut will vary depending on the gravity with which he is attracted to the center.
On the other hand, the mass of the body does not vary even if the astronaut is in different places such as the Earth or the Moon, because he will always occupy the same space.
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Which statement summarizes the law of superposition?
Answer:
The top layer of rock in a rock formation is the oldest.
Explanation:
it's A
When a farmer breeds only his or her best livestock, the process involved is:.
Answer:
Selective breeding
Explanation:
Select all that apply.
Which of the following are photosynthetic autotrophs?
plants
arthropods
all bacteria
protists
some bacteria
algae
Answer:
Plants. Some Bacteria. Algae. These 3 are the photosynthetic autotrophs..
Why the others don't fit:
Athropods are hetertrophs. Not all bacteria are autotrophs. Only some protists are autotrophs.
True or false: The first division of the zygote (fertilized egg) in a flowering plant is asymmetrical.
Systemic gas exchange is the unloading of ____________ and loading of carbon dioxide.
2. Which body of water does not directly contribute water vapor into the atmosphere?
A. aquifers
C. oceans
B. rivers
D. Lakes
Answer:
a) aquifers
Explanation:
Looking at the answers choices, 3 of the answers have something in common. Oceans, rivers, and lakes all have their surfaces exposed to the atmosphere—including the direct path to the sun. This means that they evaporate the most into the atmosphere.
Aquifers are underground wells, meaning they only evaporate slightly into the atmosphere due to high levels of heat energy. However, they stay mostly underground and are not in the direct path of the sun's energy.
Genome editing techniques have been developed to exploit the CRISPR system of bacteria and archaea. Only the _____ component of the system is used in editing.
Answer:
Cas9
Explanation:
Genome editing techniques have been developed to exploit the CRISPR system of bacteria and archaea. Only the Cas9 component of the system is used in editing.
Csf flows into which ventricle through the interventricular foramen and out through the cerebral aqueduct?.
CSF flows from the lateral ventricles, via the interventricular foramens, and into the third ventricle, cerebral trench, and the fourth ventricle.
How does CSF flow through the ventricles?CSF flows from the lateral ventricles to the third ventricle via the foramen of Monro, it flows across the cerebral trench of Sylvius to the fourth ventricle and onto the subarachnoid space through the cracks of Magendie and Luschka.
Thus,CSF flows from the lateral ventricles, through the interventricular foramens, and into the third ventricle, cerebral trench, and the fourth ventricle.
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In addition to atp, what are the products of glycolysis?.
Generally, the changes normally associated with menopause occur because the cells in the reproductive tract are:
Answer:
The uterus no longer produces eggs [ova] which results in infertility and since the eggs are no longer produced there will no monthly blood flow [menstruation]
Mendel cross-pollinated second-generation purple-flowering hybrids.
What was the result of the second-generation cross, and why was it important?
Answer:
For the second generation, Mendel cross-pollinated two hybrids that had purple flowers. About 75 percent of the second-generation plants had purple flowers. These plants had at least one dominant factor. Twenty-five percent of the second-generation plants had white flowers.
The results of Mendel's second set of experiments led to his second law. This is the law of independent assortment. It states that factors controlling different characteristics are inherited independently of each other.
What do geologists think happened during the last ice age? A. The Siberian land bridge was covered in water B. Glaciers retreated worldwide C. A mass extinction occurred D. Sea levels dropped 300 feet
Answer:
D
Explanation:
Just got it right on my quiz :)
Geologists believe that during the last ice age, glaciers advanced and retreated worldwide, resulting in changes in sea levels and climate. So, the correct option is B.
Who are Geologists?Geologists are scientists who study the Earth, its composition, structure, processes, and history.
During the last ice age, which lasted from about 115,000 to 11,700 years ago, Earth's climate was much colder than it is today. Geologists believe that a variety of factors contributed to the ice age, including changes in Earth's orbit, atmospheric composition, and plate tectonics.
One major feature of the last ice age was the formation of massive ice sheets and glaciers, which covered much of the Northern Hemisphere. These ice sheets were up to 3 miles thick and covered Canada, Greenland, and parts of the northern United States and Europe. As a result, sea levels dropped by as much as 300 feet, exposing land bridges between continents and allowing humans and animals to migrate across them.
Another feature of the last ice age was the occurrence of periodic "ice ages within an ice age" known as stadials. During these stadials, temperatures in some regions of the world dropped by as much as 20 degrees Celsius, leading to widespread glaciation, droughts, and other environmental changes.
Overall, the last ice age was a complex and multifaceted period in Earth's history, and scientists continue to study it to better understand the mechanisms that drive climate change on our planet.
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Which action describes an experimental investigation?
• A. Measuring the temperatures at which two rock samples melt
• B. Exploring the relationship of the material in a rock sample and its
hardness
•
C. Describing the types of materials that make up one rock sample
• D. Comparing the sizes of the crystals in two rock samples
BMIT
The action that describes an experimental investigation is measuring the temperatures at which two rock samples melt (option A).
What is an experimental investigation?Experimental investigations involve a process in which a test is designed and variables are actively manipulated, controlled, and measured in an effort to gather evidence to support or refute a causal relationship.
An experiment is conducted under controlled conditions to either;
demonstrate a known truth
examine the validity of a hypothesis
determine the efficacy of something previously untried
According to this question, measuring the temperatures at which two rock samples melt shows an action taken that exemplifies an experimental investigation.
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The main function of which of these body systems is to create the movement a swimmer needs to swim across a swimming pool?.
Answer: Muscular System
Explanation:
The Muscular System creates the movement a swimmer needs to swim across a swimming pool.
Why did Charles Darwin predict that tetrapods evolved from fish?
Answer:
fish and tetrapods are both vertebrates that have a backbone with a spinal cord. fish lived before tetrapods because their fossils are in rocks over 500 million years old.
Explanation:
fish and tetrapods are both vertebrates that have a backbone with a spinal cord