The defecation reflex involves two postive feedback loops. these loops are the stretch receptors in the rectal walls and the sacral parasympathetic system. Defecation reflex empties the rectum by peristaltic movements push fecal matter from the sigmoid colon into the rectum. Then this distension of the rectal walls stimulates stretch receptors which results in defecation.
Answer:
True
Explanation:
Meiosis is a type of cell division that occurs in gametic cells. In this cell division, one cell is divided into four cells and the chromosome number is reduced to half therefore it is also called reduction division.
During meiosis crossing over occurs between homologous chromosomes that allow the exchange of genetic material between them that results in the formation of genetically unique daughter cells.
In spermatogenesis during the first meiosis division, the homologous chromosomes get separated into two daughter cells reducing the chromosome number by half and during second meiotic division sister chromatids separate into two more cells. Therefore four genetically different cells are generated.
1. Ask a question: He thought how traits passed from one generation to another.
2. Form a hypothesis: His hypothesis was "Each plat has two factors for a trait, one from each parent.
3. Test hypothesis: He grew pea plants to see what will happen.
4. Make and record observations: He discovered that one factor alone doesn't determine the expression of the trait in the pea plant.
<span>5. Conclusion: Traits in pea plants are inherited from the parent pea plants.</span>
The process of the scientific method involves making conjectures (hypotheses), deriving predictions from them as logical consequences, and then carrying out experiments or empirical observations based on those predictions. A hypothesis is a conjecture, based on knowledge obtained while seeking answers to the question.
Answer:
- Diploid → Prophase, metaphase, and anaphase
- Haploid → Telophase
Explanation:
During prophase I, chromosomes get condensed. Each of the chromosomes gets in pair with its homologous one. They do so to make the crossing-over possible, a stage where they interchange their parts → 2n
During metaphase I, each of the homologous pairs is driven to the equatorial plane, where they randomly line up → 2n
During anaphase I, occurs the independent separation of homologous chromosomes that migrate to opposite poles of the cell. This separation generates different chromosomal combinations in the daughter cells. There are two alternatives per homologous pair → 2n
In telophase I, half of the chromosomes are already in one of the poles, while the other half is on the other pole. Each group of chromosomes has now half the number of the original cell. The nuclear membrane forms again in each pole → n
Finally, occurs cytokinesis, which involves the invagination of the cell membrane and cytoplasmic division.
The two new cells are ready for meiosis II.
