Why do elements within a group have similar chemical properties?

Elements in the same group have similar properties because they have the same number of valence electrons.

Explanation:

What are valence electrons?

Valence electrons are the electrons on the outermost shell. For example take the element carbon or it’s symbol C. It’s has 4 valence electrons.

How do you find valence electrons?

Several ways, but one way is to draw Lewis structures, also known as Lewis dot diagrams.

Hope this covered the basics of your question :) Though there are more thorough answers for this question.

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.

the answer would be 2, if crossing over doesn’t occur 2 out of 4 of the daughter cells will have that allele.

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