11. (i) What is a chromosome? (ii) The haploid number of chromosomes is found in the human egg and sperm - Leaving Cert Biology - Question 11 - 2008

The haploid number is half of the diploid number of chromosomes and refers to the single set of chromosomes found in gametes (egg and sperm) which are produced during meiosis.

An allele is a form of a gene or type of gene, represented as B (brown) or b (red). The dominant allele (B) prevents the expression of the recessive allele (b); therefore, brown hair is expressed when the dominant allele is present.

Séán's hair is brown.

Máire's hair is red.

Séán can produce gametes with genotypes B and b, while Máire can produce gametes with genotype b.

The possible genotypes for their children are Bb (brown hair) and bb (red hair).

The probability that one of their children may have red hair (bb) is 50%, or 1 in 2.

Evolution refers to the process of change in the genetic composition of populations over time, leading to the emergence of new organisms.

Charles Darwin is one of the scientists associated with the Theory of Natural Selection.

The Theory of Natural Selection posits that organisms with variations that are beneficial for survival will reproduce and pass on these traits to their offspring. This process of 'survival of the fittest' leads to gradual changes in the species over time.

Evidence for evolution can be found in comparative anatomy, such as the similarities in the bone structures of various species (e.g., horse limbs and human arms), which indicate common ancestry.