Reading File
Finding Sources
Finding Sources
Reading File
Reading File
The textbook sources give a very clear timeline. Here is the full breakdown:
Question: In humans, up to 6 weeks of pregnancy...
Correct answers (TRUE by 6 weeks):
- Gonadal ridges are formed ✅
- The primordial germ cells migrate to the gonads ✅
Incorrect answers (happen AFTER 6 weeks or are wrong):
- Derivatives of the Müller channel are formed ❌ - Müllerian ducts regress between weeks 8-10 (under AMH/MIS). They aren't forming useful derivatives by 6 weeks.
- Gonads are formed ❌ (partially wrong timing) - The gonadal ridge is present, but the gonads are still bipotential/indifferent until after week 6; macroscopic differentiation into testis vs. ovary occurs at 7-8 weeks.
- Derivatives of the Wolf channel are formed ❌ - The Wolffian (mesonephric) duct derivatives (epididymis, vas deferens) develop under testosterone influence after week 7-8.
- The primordial germ cells migrate to the progenitor of the sex glands - This is essentially a rewording of the correct answer above, so both could be considered true, but "migrate to the gonads" is the standard phrasing.
Full Developmental Timeline (from authoritative sources)
| Week | Event |
|---|---|
| Week 3 | Primordial germ cells (PGCs) arise in the yolk sac wall |
| Week 4-5 | PGCs migrate along the dorsal mesentery toward the gonadal ridge |
| Week 5-6 | Gonadal ridges form; PGCs arrive at the gonadal blastema (~1,000-2,000 cells) |
| Week 6 | Sex cords form; gonad is still bipotential ("indifferent gonad") |
| Week 6-7 | Testicular cords begin forming (if SRY present); Sertoli cells differentiate |
| Week 8-10 | Müllerian (Paramesonephric) duct regression in males under AMH/MIS |
| Week 8-9 | Leydig cells differentiate; Wolffian duct derivatives develop under testosterone |
Key Teaching Points
- By week 6, the embryo is in the indifferent (bipotential) gonad stage - both XX and XY embryos look identical.
- The gonadal ridge is present and PGCs have populated it, but sexual differentiation has not yet begun.
- The Müllerian and Wolffian duct derivatives (fallopian tubes/uterus vs. epididymis/vas deferens) are established much later, after week 7-8.
- If PGCs fail to migrate to the gonadal ridge, the gonads fail to develop entirely.
Sources: Campbell-Walsh Urology, p. 1277 | Campbell-Walsh Urology, p. 428
So give me only correct answer
Based on the textbook evidence, the correct answers for events occurring up to 6 weeks of pregnancy are:
✅ Gonadal ridges are formed
✅ The primordial germ cells migrate to the gonadsThe question asks for the systematic (taxonomic) position of Paragonimus westermani — the lung fluke — in the correct order.
Here is the complete classification:
| Rank | Answer |
|---|---|
| Species | westermani |
| Class | Trematoda |
| Superkingdom | Eukaryota |
| Phylum | Platyhelminthes |
| Kingdom | Animalia |
Full taxonomy in correct hierarchical order:
- Superkingdom - Eukaryota
- Kingdom - Animalia
- Phylum - Platyhelminthes (flatworms)
- Class - Trematoda (flukes)
- Species - Paragonimus westermani
Paragonimus westermani is the lung fluke that causes paragonimiasis, transmitted via ingestion of undercooked crabs or crayfish infected with metacercariae.
photo-1785998089105.jpg
Give me correct answers from this
This is the dropdown options for the previous question about Paragonimus westermani's taxonomy. Here are the correct selections for each rank:
| Rank | Correct Answer |
|---|---|
| Species | Paragonimus westermani |
| Class | Flukes (= Trematoda) |
| Superkingdom | Eukaryotes |
| Phylum | Flatworms (= Platyhelminthes) |
| Kingdom | Animals |
Not used from the list: Turbellaria, Tapeworms, Roundworms, WormsThe question asks for the migration route of Ascaris larva after penetrating the intestinal wall and entering the bloodstream. This is the classic hepato-pulmonary (Löffler's) migration cycle.
The correct order is:
| Position | Structure |
|---|---|
| No. 1 | portal vein |
| No. 2 | hepatic vein |
| No. 3 | inferior vena cava |
| No. 4 | right atrium |
| No. 5 | right ventricle |
| No. 6 | pulmonary arteries |
Full migration path:
Intestinal wall → portal vein → liver → hepatic vein → inferior vena cava → right atrium → right ventricle → pulmonary arteries → lungs (break into alveoli) → trachea → pharynx → swallowed → small intestine (adult worm)
*(left ventricle and left atrium are NOT part of the route - larvae go to lungs via the right side of the heart)*The question asks to match the numbered parts in the chromosome diagram ("Строение хромосомы" = Structure of chromosome).
Looking at the diagram, the numbered parts are:
| Number in figure | Structure |
|---|---|
| 1 | Chromatid |
| 2 | Chromatid |
| 3 | Centromere |
| 4 | Short arm (p arm) |
| 5 | Long arm (q arm) |
The question only asks to select answers for 1, 2, 4 (visible dropdowns). Based on standard chromosome structure diagrams:
| Dropdown | Answer |
|---|---|
| 1 | Chromatid |
| 2 | Chromatid |
| 4 | Centromere |
Standard chromosome structure:
- 1 & 2 = the two chromatids (sister chromatids joined together)
- 3 = Centromere (the constriction point where chromatids are joined)
- 4 = Short arm (p arm) - the smaller upper portion
- 5 = Long arm (q arm) - the longer lower portion
Could you share the dropdown options available so I can give you the exact selections to choose?
photo-1785999181234.jpg
Give me the correct answers
Here are the correct matches for the chromosome diagram:
| Number in figure | Answer |
|---|---|
| 1 | chromatid |
| 2 | chromatid |
| 3 | primary constriction (= centromere) |
| 4 | arm |
| 5 | telomere |
Not used: satellite, euchromatin, nuclear organizing region
(Note: "satellite" and "nuclear organizing region" would apply to acrocentric chromosomes with a secondary constriction - not shown in this standard metacentric chromosome diagram)✅ Correct answer: four chitinous teeth
Ancylostoma duodenale (the hookworm) has a buccal capsule with 4 chitinous teeth (2 pairs of ventral cutting teeth) which it uses to attach to the intestinal wall and feed on blood.
Why the others are wrong:
- Suction cup - that's Taenia (tapeworm) / Echinococcus
- Two chitinous semilunar plates - that's Necator americanus (the other hookworm)
- Vesicle and bulbus of the esophagus - characteristic of pinworm (Enterobius vermicularis)
- Anterior hair-like end of the body - not a fixation organ✅ Correct answer: when resources are most abundant
Interspecific competition is most obvious when resources are most abundant — this is counterintuitive but follows the principle that when resources are plentiful, more species can coexist and actively compete for the same niche, making competition more visible.
Why the others are wrong:
- Among species whose trophic levels are different - species at different trophic levels generally don't compete (they have predator-prey relationships instead)
- In the presence of a keystone species - a keystone species actually reduces competition by controlling dominant species
- When organisms have quite different ecological niches - species with different niches compete less, not more
- When a non-native organism is introduced to a community - this can cause competition, but it's not the primary circumstance where interspecific competition is most obvious
This is a shared conversation. Sign in to Orris to start your own chat.