SECTION B (approx 30 mins). Answer 1 question. USE A SEPARATE ANSWER BOOKLET. Q1
ID: 260781 • Letter: S
Question
SECTION B (approx 30 mins). Answer 1 question. USE A SEPARATE ANSWER BOOKLET. Q1. You have discovered a previously unknown invertebrate animal. Describe the characteristics you would look for to determine the phylum to which the animal belongs Q2. Answer both a) and b): a) Explain, with examples, how small changes in developmental genes can lead to major changes in body plan; and b) Explain, with examples, how changes in the timing and spatial pattern of developmental gene expression can contribute to evolutionary change.Explanation / Answer
1) Invertebrates are the organisms that neither possess nor develop a vertebral column, derived from the notochord.For determining the phylum to which the newly discovered invertebrate animal belongs, following characteristics would be considered- body organization and symmetry, the presence of body cavities and germ layers, body segmentation, the presence and number of appendages, the presence/absence of exoskeleton, digestive and respiratory machinery and habitat.
2)
(a) The developmental plans of the body are coordinated by genes. Small changes in developmental genes can have large effects on the final shape and characteristics of the organism. For example, in Drosophila, "ultrabithorax" (Ubx) gene codes for a mRNA transcript that is spliced 5 different ways, hence is translated into five different transcription factor proteins. Normal expression of Ubx in the third thoracic segment of the fly interrupts the development of a wing and stimulates the development of a larger set of legs on the third thoracic segment. Mutation in Ubx in this segment makes this thoracic segment develop like the second thoracic segment, growing wings and a smaller pair of legs.
(b) Changes in the rate and timing of developmental events significantly affect the evolutionary pattern of organisms, influencing how we end up down the line as fully developed individuals. Take for example humans and chimps.As fetuses, our skulls are actually quite similar to those of chimps. But as we grow into adults, the chimps' jaws grow much faster than those of humans.Because of genetic changes in humans, we have a much slower jaw growth, giving us an adult jaw that is much more proportional to the rest of the head. Our brains also grow much faster after birth, giving us a larger skull than chimps, whose brains grow much slower.Our development is also greatly influenced by where the changes occur ie; where certain genes are expressed or not.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.