What is the name for the average time needed for half the nuclei in a sample of a radioactive substance to undergo radioactive decay?
A. half-life
B. half-year
C. half-death
D. half-month

Invertebrates are animals that do not have a backbone or vertebral column, while non-vertebrate chordates are animals that possess a notochord at some stage of their development, but lack a vertebral column.

Chordates are a group of animals that are characterized by the presence of a notochord, a dorsal nerve cord, pharyngeal slits, at some point in their life cycle.

The notochord is a flexible rod-like structure that provides support to the body and serves as an attachment point for muscles.

The main characteristics that distinguish invertebrates from non-vertebrate chordates are:

Backbone: Invertebrates lack a backbone, while non-vertebrate chordates possess a notochord.

Complexity: Invertebrates are generally simpler in body plan and organization than non-vertebrate chordates.

Size: Invertebrates can range in size from microscopic to very large, while non-vertebrate chordates are typically small.

Diversity: Invertebrates are a very diverse group of animals, comprising the vast majority of animal species on Earth, while non-vertebrate chordates are relatively rare and include only a few species.

Symmetry: Invertebrates can exhibit a wide range of body symmetry, while non-vertebrate chordates typically exhibit bilateral symmetry.

Thus, these are the characteristics that distinguish invertebrates from non vertebrates chordates.

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The correct answer is the flow of water through the body of a sponge.  

The sponges are multi-cellular species in which the organ systems like the nervous system, digestive system, circulatory system, and others are absent. They possess a specific feeding system in which they maintain the continuous flow of water through their bodies. This water movement helps them to attain oxygen and food and remove waste.  

The movement of water all through the body of the sponge is unidirectional in nature, it gets inside the body of sponge via ostia, and exit through the osculum. With the external pumping of water, the cells found in the walls filter out the food present in the water.  

Answer:

Option C, image 3

Explanation:

Hydrogen bonds are weak electrostatic bond that exist between hydrogen and an electronegative atom.

In order to have hydrogen bonding, the hydrogen must be bonded to an electronegative atom.

Generally molecules having hydrogen bonded to electrogegative atom, N, O and F show hydrogen bonding.

Hydrogen bonds may exist within a molecule or between two separate molecules.

Difference in electronegativity of hydrogen and electronegative atom develops dipole which responsible for electrostatic attraction.

In image 1 and 2, hydrogen bonding is shown between two oxygen atoms, which is not correct.

In image 4, hydogen bonding is shown between two hydrogen atoms, which is also not correct.

Hence, the correct option is image 3

Animal cells obtain nutrients and energy by consuming other organisms. The complex macromolecules from these organisms are then converted into simpler molecules through digestion and absorption. These simple molecules, along with ATP derived from the harvested energy, are then used to carry out cellular functions.

All living organisms need nutrients to survive. Animals, unlike plants, obtain their nutrients and energy by consuming other organisms. The food eaten by animals typically consists of proteins, fats, and complex carbohydrates. However, in order for animal cells to function, these macromolecules must be converted into simple molecules, such as amino acids, lipid molecules, nucleotides, and simple sugars.

This conversion process is a multi-step one that involves both digestion and absorption. In the digestion process, the food particles are broken down into smaller components by both physical, such as chewing, and chemical means. Following digestion, these broken down components are then absorbed by the body during the absorption process.

Additionally, all organisms must harvest energy from their environment and convert int into ATP (adenosine triphosphate), the main energy currency in cells, in order to carry out various cellular functions.

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Answer:

           Carbon atom is responsible for this huge diversity of organic molecules.

Explanation:

Diversity of Structures:

                                    The diversity of organic compounds originate due to following properties of Carbon atoms.

                  i) Catenation: It is the unique property of carbon atoms of self linkage. This property allows carbon atoms to form a long chains.

                   ii) Multiple Bonds: Also, the carbon atoms can form multiple bonds along with single bonds. Therefore, those organic comounds in which double or triple bonds are present are known as unsaturated compounds while, that containing single bonds are termed as saturated hydrocarbons.

                  iii) Isomerism: This is very important property of organic compounds in which more than one structure can appear for a same molecular formula. Hence, resulting in increasing the number of compounds for a single molecular formula.

Carbon is the element responsible for the diversity of organic compounds in living organisms.

The element responsible for the huge diversity of molecules in living organisms is carbon. Carbon is unique in its ability to form covalent bonds with other atoms, including itself, allowing for the formation of long chains and complex molecular structures.

Carbon's ability to form multiple bonds and its flexibility in bonding with different elements gives it the versatility to form a wide range of organic compounds with unique structures and properties.

For example, carbon can form single, double, or triple bonds with other carbon atoms, resulting in the formation of different types of hydrocarbons such as alkanes, alkenes, and alkynes.

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Answer:

Answer: the answer is A Explanation:

Competition could be considered a limiting factor within an ecosystem because as the populations grow, they will compete for shelter and available resources. Also, as populations become denser, the risk of disease increases.   The competition can be considered as a limiting factor within an ecosystem because there is a limited supply of resources that can be used and consumed.

Answer:

The correct answer is hominids.

Explanation:

The group, which comprises modern humans and their direct ancestors are termed as Hominidae. It is also known as great apes or Hominids. Basically, the term Hominidae is considered for only the humans and their closest relatives. However, some of the people still continue to use this term in its limited sense, rather than in the modern sense.

Answer:

This plant is probably an angiosperm and its pollination is through insects.

Explanation:

We can conclude that this plant is an angiosperm because it is a plant that produces seeds.

Angiosperms produce root, stem, leaf, flower, seed and fruit. Considering these structures, note that in relation to gymnosperms, angiosperms present two "novelties": flowers and fruits.

Flowers can be eye-catching in color and shape; They also often give off a pleasant odor and produce a sugary liquid - nectar - that feeds the bees and other insects that will be responsible for pollination. There are also flowers that do not have colorful pieces, are not fragrant and do not produce nectar.

Convection currents in Earth's mantle result from heat transfer from the core, causing mantle material to circulate in a pattern that drives tectonic plate movement. Hot mantle material rises, cools, and then sinks back, creating a continuous convective cycle.

The convection currents in Earth's mantle are movements of the mantle material caused by the internal heat from Earth's core. Think of it like a pot of water on the stove, where the heated water expands, becomes less dense, and rises, while cooler water sinks to replace it, setting up a continuous circulating pattern.

Inside Earth, heat is continuously transferred from the core to the mantle, causing mantle convection. Although the mantle is solid rock, it can flow very slowly over time. These mantle convection currents are the primary driving force behind the movement of tectonic plates. Underlying convection cells can push the plates apart at mid-ocean ridges, where new lithosphere forms, or cause them to converge, with one being subducted, at deep-sea trenches.

As the hot mantle material rises and reaches the surface, it moves horizontally, cools down, and eventually sinks back into the mantle, completing the cycle and forming a convection cell. This cycle is fundamental for many geological processes, including the formation and movement of tectonic plates.

Answer:

C (Third one)

Explanation:

Answer:

B. The world`s food supply is slowly decreasing.

Explanation:

Since human population is getting growing little by little, and the need of meat that is necessary  to feed the population, is reducing the green areas in the world to be planted by vegetable food. Also the are needed to live, work and move is reducing this areas around the world, as humankind, we have less green areas to plant our food.

Answer:

Explanation:

In general, ergonomics involves knowledge and technologies that allow a comfortable and productive adaptation between man and the place where he works. The idea is to “shape” working conditions for greater comfort, efficiency and safety.

Although there are countless ways to improve our ergonomics, we can name four very useful ways to do this. These forms are:

Answer:

Object A, by 0.5 cubic centimeter      

Explanation:

Density (d) is given by :

[tex]d=\dfrac{m}{V}[/tex]

m is the mass of an object

V is its volume

For object A:

[tex]V_1=\dfrac{m_1}{d_1}[/tex]

[tex]V_1=\dfrac{9\ g}{10\ g/cm^3}=0.9\ cm^3[/tex]...........(1)

For object B:

[tex]V_2=\dfrac{m_2}{d_2}[/tex]

[tex]V_2=\dfrac{4\ g}{10\ g/cm^3}=0.4\ cm^3[/tex]...........(2)

From equation (1) and (2) it is clear that volume of object A is greater by 0.5 cm³. So, the correct option is (b) "Object A, by 0.5 cubic centimeter".

Answer: Vaccine

Explanation:

The weakened or dead form of pathogens that evoke immune response in the body of an organism is known as vaccine. They are used to generate the immune response against pathogens.

It contains an agent that typically resembles the disease causing microorganism, it is often made weekend or used in killed form of the pathogen that generates the same immune response as like of real disease causing microorganism.

The defense mechanism of body is prepared prior to the original exposure to disease causing microorganism.

The weakened or dead form of pathogens that evoke immune response in the body of an organism is known as vaccine. They are used to generate the immune response against pathogens.

There are many types of vaccines, such as:

Thus, option "B" is correct,  vaccine they are used to generate the immune response against pathogens.

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the answer is B) The same number of dots would appear in the diagram for carbon.

Answer: The same number of dots would appear in the diagram for carbon.

Explanation:

Electron dot structure are structure in which dots are used to represent the number of valence electrons of an element in compound. These electrons dots are placed around the chemical symbol of that element.

In electron dot structure of silicon, there are four dots present around the symbol 'Si' because their are four valence electrons present in the valence shell of the silicon atom.

Also in electron dot structure of carbon, there are four dots present around the symbol 'C' because their are four valence electrons present in the valence shell of the carbon atom.

So, the number of dots  would appear in the diagram for carbon will be same.

b and d are completely wrong, leaving a or c  

a: ADP requires energy to make ATP, even though the net gain by the release of energy from ATP is > energy required to make ATP from ADP. ATP may be considered potential energy until it is actually used as an energy source  

c: ADP has 2 phosphates and to get energy from this, more energy must be put into the system to remove a phosphate than the energy released upon the removal of the phosphate.  

ATP has 3 phosphates and to get energy from this, the 3rd phosphate can be easily removed to give this energy. ADP could be considered potential energy in that it only requires the attachment of a phosphate group to make ATP.  

to me, there isn't really a clear answer for a or c  

if i had to choose, i would go with C