A radioactive element is an element which is subject to spontaneous degeneration of its nucleus followed by the emission of alpha, beta and gamma particles. All elements with atomic numbers greater than 83 are radioactive.
The given phrases that describe radioactive elements are-
They have a consistent number of particles
- the particles are alpha, beta and gamma particles.
They have a half-life that determines their rate of decay.
Explanation for other options:
Not all elements occur in nature. Radioactive decay rates may not be constant as the decay happens when a radioactive substance emits a particle. It is not possible to predict exactly when a given atom of a substance will emit a particular particle. When the radioactive element release energy and particles, it decays.
A chemical reaction is a process in which one or more substances are changed into new substances.
An example of a chemical reaction is when metal rusts.
Answer: D. The succession of community is completed.
Explanation:
A succession can be define as a series of gradual changes that occur in the biotic community of the ecosystem with respect to the changes that occur in the abiotic or non-living factors with respect to time until the ecosystem attains stability.
A climax community is the community that develops in the end of the ecological succession. It is the stable community which does not require any further change to occur. With the development of the climax community the succession completes.
Answer;
-A motor protein called dynein
Cilia and flagella bend because of a motor protein called dynein.
Explanation;
-Both prokaryotic and eukaryotic cells contain structures known as cilia and flagella. These extensions from the cell surface aid in cell movement. They also help to move substances around cells and direct the flow of substances along tracts.
-Cilia and flagella are formed from specialized groupings of microtubules called basal bodies. If the protrusions are short and numerous they are termed cilia. If they are longer and less numerous they are termed flagella.
B
Plant's cuticle is an adaptation on land that prevents the evaporation of water from the plant.
Explanation:
The cuticle is made of lipid polymers impregnated with wax. A thick cuticle covers the epidermis of the leaves and prevents of some plants to prevent the loss of water from the leaves and plants via evaporation. This is especially a significant adaptation to desert plants that need to conserve water because they receive very little annual rainfall in their environment.
Learn More:
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