Sex chromosomes are chromosomes that determine sex in all species.
True
False
The correct answer and explanation is:
Correct Answer: False
Explanation:
Sex chromosomes do determine the sex in many species, including humans, but not in all species. Therefore, the statement “Sex chromosomes are chromosomes that determine sex in all species” is false.
Why It’s False:
In many organisms—such as humans, mammals, and birds—sex chromosomes play a key role in determining the biological sex. For example:
- In humans and most mammals:
- Males have XY chromosomes.
- Females have XX chromosomes.
- In birds, the system is reversed:
- Males have ZZ chromosomes.
- Females have ZW chromosomes.
These are examples of genetic sex determination using sex chromosomes.
But Not All Species Use Sex Chromosomes:
- Environmental Sex Determination (ESD):
- In some reptiles (like certain turtles and crocodiles), sex is not determined by chromosomes at all.
- Instead, temperature during egg incubation determines the sex of the offspring.
- Haplodiploidy:
- Found in bees, ants, and wasps.
- Males develop from unfertilized eggs and are haploid (one set of chromosomes).
- Females develop from fertilized eggs and are diploid (two sets of chromosomes).
- No distinct sex chromosomes are involved.
- Hermaphroditism:
- Some species (like earthworms and some fish) are hermaphroditic, having both male and female reproductive organs.
- In these cases, sex can be fluid or simultaneous, and not always based on distinct sex chromosomes.
Conclusion:
While sex chromosomes are critical in many species, not all living organisms use them to determine sex. Thus, the statement is false because it overgeneralizes a concept that is not universal across all species.