Most sidewalks are made out of solid concrete sections. There are spaces between the sections. What happens to the spaces during a hot day in the summer and why?

The options are :

The spaces get wider because the concrete sections shrink.

The spaces stay the same because the concrete sections does not shrink or expand.

The spaces get narrower because the concrete sections expand.

Some spaces get wider, some spaces get narrower, and some spaces stay the same because each concrete section behaves differently on a hot summer day.

The answer is

Some spaces get wider, some spaces get narrower, and some spaces stay the same because each concrete section behaves differently on a hot summer day.

Concrete surfaces react with a change in temperature by either shrinking or expanding depending on the temperature difference.

When there is an increase in temperature it expands a bit and shrinks a bit too when the temperature is decreased.

1) gene flow

- it is described as the transfer of genes from one population to another population so that frequency of gene is increased.

-a zebra migrates to join a different herd of zebras.

2) natural selection

- a mechanism of evolutionary change in which individuals with advantageous traits survive and reproduce whereas the others ( those that can not adapt) eliminate from the population.

-competition for sunlight leads to taller trees.

3) mutation

- permanent change in the nucleotide sequence of dna ( genetic material) that could have harmful or useful consequences.

-the dna of a snake changes to make its venom stronger.

4) genetic drift - it is a random phenomenon ( that occurs by chance such as fire) that results in change in the gene frequency in a small population.    

-a grassfire randomly sweeps through a population of buffalo and kills most of the animals.

explanation:

carbohydrates: (starches and sugars) composed of carbon, hydrogen, and oxygen.

lipids: (fats, oils, and waxes) are made of carbon and hydrogen atoms.

nucleic acids: contain hydrogen, oxygen, nitrogen, carbon, and phosphorus. they are polymers of nucleotides. a nucleotide has three parts, a 5-carbon sugar, a phosphate     (-po⬇️4) group, and a nitrogenous base.

proteins: made up of nitrogen, carbon, hydrogen, and oxygen. they are polymers of amino acids.