The bark of a tree is impervious to gases and water because bark cells are dead cells of the epidermis and compactly arranged without intercellular spaces. They contain a chemical called suberin in their walls that make them impervious to gases and water and it doesn't allow gases or water into the tree as bark cells are in the bark outer most layer of the tree.
<span>Answers;
1.Breeding of individuals that have genes for two different characteristics; Dihybrid cross
2.A grid system used to predict possible combinations of genes due to random fertilization; Punnet square
3 A condition in which both alleles are dominant; Codominance
4.when more than two alternatives exist for a gene; multiple alleles
5.A condition in which neither pair of alleles is dominant or recessive, so the traits blend in the phenotype ;Incomplete dominance;
Explanation;
</span>Dihybrid cross;
<span>It involves the breeding of individuals that have genes for two different characteristics. It involves the cross of individuals that are both heterozygous for two different traits. For example two different traits in a pea plant; color and shape; for color we have; Y-allele for yellow seeds and y- allele for green seeds, For Shape trait; R-allele for round seeds and r-allele for wrinkled seeds. So the dihydbrid cross would be (RrYy </span>× RrYy).
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Punnet square;
</span><span>This a grid system or a square diagram that is used to predict possible combinations of genes due to random fertilization. It is used by biologists determine the probability of an offspring having a particular genotype.
</span><span>The letters on the outside of a Punnett Square stand for the parent allele.
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Codominance;
<span>This is a condition in heterozygotes in which both members of an allelic pair are dominant and both contribute to the phenotype.
A good example of codominance is the ABO blood group; A person with blood group AB, it means that both the A allele and B allele are equally expressed.
Multiple alleles
</span><span>This is when more than two alternatives for a gene exist.
Examples of multiple allelism in human;The genes of the ABO blood group system. The human ABO system is controled by three alleles, namely; A-allele, B-allele and O-allele.
Incomplete dominance;
</span><span>This is condition in heterozygotes in which both members of an allelic pair are neither dominant nor recessive to other alleles, so the two traits blend in the phenotype of the individual.
An example; is a snapdragon flower that is pink as a result of cross-pollination between a red flower and a white flower. Which means neither the white allele or the red allele are dominant. </span>
D.
Glucose is energy, which means it breaks down when energy is consumed. When a fox consumes it's pray, a seagull glides trough the air and a duck rests on a pond, not much glucose is consumed.
Energy is used when physical effort is necessary, and running from a predator, requires a lot of energy.
Hope it helped,
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