Question

review questions 1. the number of chromosomes in the body cell of an organism is called its ______. 2. is the species chromosome number of all organisms the same? ______ 3. what happens to animals born with a change in species number?

Explanation:

Question 1

The number of chromosomes in a body cell (somatic cell) of an organism is referred to as its diploid number (or sometimes just the chromosome number for that species in somatic cells). For example, in humans, the diploid number of chromosomes in body cells is 46 (23 pairs). This is a fundamental concept in biology, specifically in the subfield of genetics (within Biology) that deals with chromosome structure and number in different organisms.

The species chromosome number (the number of chromosomes in the somatic cells of a species) is not the same for all organisms. Different species have different chromosome numbers. For instance, humans have 46 chromosomes in their somatic cells, dogs have 78, fruit flies (Drosophila melanogaster) have 8, and ferns can have hundreds of chromosomes. This variation is a result of evolutionary processes and differences in genome organization among species.

When animals are born with a change in the species chromosome number (a condition called aneuploidy, if it's a change in the number of individual chromosomes, or polyploidy, if it's a change in the number of chromosome sets), several outcomes can occur:

• Aneuploidy (e.g., trisomy, monosomy): Often leads to developmental abnormalities or disorders. For example, in humans, Down syndrome is caused by trisomy 21 (an extra copy of chromosome 21). Many aneuploid conditions are lethal during embryonic development, resulting in miscarriage. If the animal survives, it may have physical, cognitive, or physiological impairments.
• Polyploidy: In animals, polyploidy (having more than two sets of chromosomes, like triploidy, tetraploidy) is less common than in plants and is usually associated with developmental problems or infertility. However, some lower animals (e.g., certain fish, amphibians) can tolerate polyploidy and may even have evolutionary advantages in some cases, but in most higher animals, polyploidy is detrimental.

In general, a change in the species chromosome number disrupts the normal genetic balance, which is critical for proper development and function. This disruption can lead to reduced viability, developmental defects, or changes in the organism’s phenotype (physical and behavioral traits).

Answer:

The number of chromosomes in the body cell of an organism is called its diploid number (or "chromosome number" in the context of somatic cells).

Question 2