Organisms that live in the tundra have developed unique adaptations that aid in their survival. Ursus maritimus has a variety of adaptations which enable it to survive in the tundra. It is the largest terrestrial carnivore, but it is also an excellent swimmer that spends much of its time in and near the water hunting its favorite food. It has large paws with small bumps to provide traction as it walks across the ice. Its fur is helpful as camouflage during the winter months, but not as helpful during the summer. Which organism has the adaptations described that enable it to survive in the tundra?

A. harp seal
B. arctic fox
C. polar bear
D. Kodiak bear

Option A-

notable structure = fused rings

Answer:

acid form

Explanation:

Answer: The correct answer is- Endocytosis.

Endocytosis can be described as a process in which cell engulfs large molecules from the environment by fusing them with its cell membrane (plasma membrane).

Cell membrane is a selectively permeable, hydrophobic membrane. Large polar molecules ( such as proteins and hormones) can not pass through it by means of simple diffusion.

Cell performs endocytosis for taking in such large molecules.

In this process, plasma membrane first forms a pocket around the target molecule ( such as protein) through invagination and once it completely surrounds the molecule, it is pinched off in the cytoplasm in a form of food vacuole ( phagosome in case of solid particles).

Thus, Endocytosis is the right answer.

Answer: The correct answer is D) DNA is in a nucleus in eukaryotes.

Prokaryotes are those organisms that lack a well defined nucleus and membrane bound subcellular organelles (like endoplasmic reticulum, golgi complex, mitochondria). The genetic material lies in the cytoplasm of the cell in these organisms.

Example - Bacteria like E.coli.

On the other hand, eukaryotes are those organisms that contain a well defined nucleus that possesses the genetic material (DNA). These organisms also contain membrane bound subcellular organelles.

Example - Plants and animals.

The DNA (Deoxyribose nucleic acid) of the eukaryotes is different from that of prokaryotic DNA based on their nuclear structure, a number of a chromosome, their binding protein, and selective permeability.

Further Explanation:

The difference between prokaryotic cells and Eukaryotic cells are listed in Table 1 attached below:

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Answer Details:

Grade: High School

Subjects: Biology

Topic: Structure of DNA

Keywords:

Eukaryotes, prokaryotes, chromosome, protein, cytoskeleton, membrane, histone, permeability, nucleus, condense, DNA, tetramers

The circulatory system is composed of blood vessels that take blood apart from and towards the heart. Arteries move blood aside from the heart and veins bring blood back to the heart. The circulatory system offers oxygen, nutrients, and hormones to cells, and eliminates decay products, like carbon dioxide.

Final answer:

In a DNA molecule, purines are bonded with pyrimidines. Adenine (A) bonds with Thymine (T), and Guanine (G) bonds with Cytosine (C).

Explanation:

In a DNA molecule, purines are bonded with pyrimidines. This means that Adenine (A), a purine, will always bond with Thymine (T), a pyrimidine. Similarly, Guanine (G), another purine, will always bond with Cytosine (C), a pyrimidine. The base pairs (A-T and G-C) are held together by hydrogen bonding, creating the double-stranded helical structure of DNA.

Answer:

Option (B)

Explanation:

When the initially occurring aquatic organisms such as the blue-green algae started to use the solar energy in order to convert the water molecules and carbon dioxide and converting them into organic compounds as well as the molecular oxygen (O₂). This is known as the photosynthesis process that produced a significant amount of oxygen in the atmosphere. These oxygen molecules, as absorbs the UV radiations emitted from the sun, it breaks the oxygen molecules and forms a single atom of oxygen. These atoms then again is added to the molecular oxygen and forms the ozone (O₃) molecule.

This is how the ozone layer has formed about 2 billion years ago.

Thus, the ozone layer did not form during the Cenozoic era.

Hence, the correct answer is option (B).

fossil,nuclear,geothermal

The correct order of arrangement of energy resources from highest to lowest usage world wide is fossil fuels, nuclear energy and geothermal energy.

A fossil fuel is a energy source formed by the dead remains of living organims over millions of years through the natural process. It includes the coal, petroleum and the natural gas which are the highly used energy resources all over the world. Nuclear energy is the energy generated during the fission or fusion of nuclear reactions which is used to generate electricity. It is one of the low carbon power methods to generate electricity. Geothermal energy is the thermal energy or the heat energy stored in the earth which is used to produce electricity.

Thus, fossil fuels forms the first energy resource to be highly used worldwide.

This plant response by specialized cells is called gravitropism.

Gravitropism is the growth of a plant’s organ in response to gravity. In the root cap of plants, there are specialized cells known as statocytes that contains granules known as statoliths which stimulate the production of auxin; a hormone that is important for controlling plant growth. Plants have the ability to sense gravity with the aid of these specialized cells and plant roots grow downward into the soil while stems grow in the opposite direction.

The reason is because using a longer chromosome pair would help the learner to see the pattern in the spread out

Plant cells in tissue culture change from undifferentiated mass to specialized cells, similar to animal stem cells.

When plant cells are placed in a medium for tissue culture, they undergo changes in terms of their degree of specialization. Initially, the cells form an undifferentiated mass known as callus, which is a mass of cells that have not yet specialized into specific cell types. However, over time, tiny roots, stems, and leaves start to grow from this mass as the cells differentiate and specialize into their respective cell types.

The undifferentiated plant cells in tissue culture are most similar to stem cells in animal tissues. Stem cells, like undifferentiated plant cells, have the ability to differentiate into various cell types and are capable of self-renewal. They are the foundation for growth and repair in animals, just as undifferentiated plant cells contribute to the growth and regeneration of plants.

In tissue culture, specialized plant cells de-differentiate into a less specialized, undifferentiated state known as a callus, similar to stem cells in animals.

In tissue culture, the plant cells placed in a medium change from being specialized and differentiated to a state of being undifferentiated or less specialized, forming a mass called callus. This process is akin to the meristematic cells found in plants, which are capable of continuous division and growth. The animal cells most similar to these undifferentiated plant cells are stem cells, particularly embryonic stem cells, which can also divide and differentiate into various cell types. This capacity for de-differentiation and subsequent re-specialization allows both plant tissue cultures and animal stem cells to be used for growth and regeneration of tissues.

The correct answer is A

The scientist can determine that this nucleic acid is a DNA molecule, because it contains Thymine, which does not occure in the RNA molecule. The RNA molecule contains Adenine, Guanine and Cytosine just like the DNA, but unlike the DNA it contains Uracil, not Thymine.

Secondly, the scientist can say with certainty that this DNA molecule is surrounded by a nucleus based on the structure of the nucleic acid described. Only eukaryotic cells have ladder structure. The prokaryotic cells have circular DNA and do not have any organelles, like the nucleus. Therefore, from the ladder structure of the DNA the scientist can see that the cell has a nucleus.

Aquifers are underground layers of rocks which contain water and serve as important sources of freshwater. They are located below the water table and in the saturated zone. If an aquifer becomes trapped between two impermeable layer (for example, one below and one above that overlies the aquifer), the pressure act on the aquifer and it can become a confined aquifer.

A confined aquifer is found between two impermeable layers.

Hydrogen bonds are responsible for the cohesiveness of water molecules. Cohesiveness is the tendency of molecules of a substance to stick together. In water, the molecules are held together by hydrogen bonds.

Hydrogen bonds are weak chemical bonds that form between the hydrogen atom of one water molecule and the oxygen atom of another water molecule.

The hydrogen bonds between water molecules are very weak, but they are very numerous. This means that a large number of water molecules are held together by these weak bonds, which gives water its cohesiveness.

The cohesiveness of water is a very important property that has many implications for the physical world.

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The conclusion about the effectiveness of preventive surgeries can be drawn by gathering the data from the people who experience the surgery. The data would need the observations of the patients that had the surgery.

Preventive surgeries are those surgeries in which the tissues or organs or glands are removed from the body, even if they show no signs of cancer.

Preventive surgeries are done to prevent the development of cancer in the future. These surgeries are done on people who have a high risk of developing cancer.

Thus, data gathered from those who have undergone preventive surgery can be used to derive conclusions about their efficacy. The observations made by the surgical patients would be necessary for the data.

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