Biology Test - 16

Zoophily is defined as pollination via animals. Insects are the most important animal pollinators. Birds, snails, bats, etc. also play an important role. Some lizards, lemurs, etc. also have proven to be important for pollination.

Key Points

• The correct sequence of human embryo development starts with (D) Cleavage in zygote, which is the first step following fertilization. This process involves the division of the zygote into smaller, multicellular stages without the zygote increasing in size.
• Following cleavage, the zygote develops into (C) the morula, a solid ball of cells.
• As development continues, the morula transforms into (A) the blastocyst, a hollow ball of cells with an inner cell mass that eventually forms the embryo.
• The final step in the sequence is (B) implantation, where the blastocyst attaches itself to the wall of the uterus.

The correct answer is option 2: (D), (C), (A), (B).

Additional Information

• Option 1: (C), (D), (B), (A) is incorrect because it suggests that the morula forms before cleavage, which is not the correct order of development.
• Option 3: (D), (B), (C), (A) incorrectly places implantation before the formation of the morula and blastocyst, which is not possible as implantation is the final step in this sequence.
• Option 4: (A), (C), (D), (B) is incorrect as it suggests the blastocyst forms before cleavage and morula formation, which contradicts the actual developmental sequence.

Intra Uterine Devices (IUDs) are not a barrier method for birth control. Barrier methods are designed to prevent sperm from entering the uterus, whereas IUDs work in a different manner.

Key Points

• Diaphragms, cervical caps, and vaults are all examples of barrier methods. They work by physically blocking sperm from entering the uterus.
• Intra Uterine Devices (IUDs), on the other hand, are inserted into the uterus and work primarily by altering the uterine and cervical environment, making it inhospitable for sperm and, in some cases, preventing ovulation.

Additional Information

• Barrier methods are often preferred by individuals looking for non-hormonal forms of birth control.
• IUDs can be hormonal or non-hormonal (copper IUDs). Both types are highly effective forms of birth control but do not function as barrier methods.

Amniocentesis is a medical procedure used for prenatal diagnosis of chromosomal abnormalities and fetal infections. It involves extracting a small amount of amniotic fluid, which contains fetal tissues, for analysis.

Key Points

• Amniocentesis is primarily used to detect the presence of certain genetic disorders. This includes conditions such as Down syndrome, cystic fibrosis, and spina bifida.

Additional Information

• Sexually transmitted diseases: Amniocentesis is not typically used to detect sexually transmitted diseases. Such conditions are usually diagnosed through blood tests, urine tests, or swabs of the affected area.
• Causes of infertility: Amniocentesis cannot be used to determine the causes of infertility. Infertility assessments usually involve a different set of tests for both men and women.
• Presence of pneumonia germs: Although amniocentesis can detect some infections, it is not specifically used for diagnosing pneumonia in the fetus. Pneumonia diagnosis would typically involve chest X-rays or sputum tests in the suspected individual.

Key Points

• In a cross between RRyy (round, yellow seeds) and rrYY (wrinkled, green seeds), the F1 generation will all be RrYy, exhibiting the dominant traits (round and green seeds).
• The F2 generation, obtained by self-pollinating the F1 generation, will show a variety of genotypes due to the independent assortment and segregation of alleles during gamete formation.
• When considering two traits controlled by two genes, each with two alleles (Rr and Yy), the Punnett square method predicts that 16 different genotypes can be formed in the F2 generation.
• However, these 16 genotypes will only result in 4 different phenotypes because the traits are independently inherited and express complete dominance (round yellow, round green, wrinkled yellow, wrinkled green).
• Therefore, the number of genotypes is 9 and the number of phenotypes is 4, which aligns with option 3.

Additional Information

• Option 1 (16 genotypes and 4 phenotypes) incorrectly suggests a reversal in the number of genotypes and phenotypes.
• Option 2 (4 genotypes and 16 phenotypes) also incorrectly reverses the numbers, and it is not possible to have more phenotypes than genotypes in this scenario.
• Options 4 and 5 are not applicable as they either present incorrect combinations or are left blank.
• The correct understanding of Mendelian genetics and the principles of dominance, segregation, and independent assortment is crucial for predicting the outcomes of genetic crosses.

Key Points

• Down's syndrome is not a type of Mendelian disorder. It is caused by the presence of an extra copy of chromosome 21 (Trisomy 21), which is a type of chromosomal disorder.

Additional Information

• Colour blindness is a Mendelian disorder linked to the X chromosome. It is commonly a result of the inability to perceive colors correctly, often red and green.
• Haemophilia is another X-linked Mendelian disorder characterized by the inability of blood to clot properly, leading to excessive bleeding from even minor injuries.
• Thalassaemia is a Mendelian genetic disorder affecting the blood, where the body makes an abnormal form of hemoglobin, resulting in excessive destruction of red blood cells and anemia.

The correct answer is In vitro fertilization­ - Test tube baby

Key Points

• A large number of couples worldwide, including India, are infertile, i.e., they are unable to produce children despite unprotected sexual cohabitation.
• Specialized healthcare units (infertility clinics, etc.) could help diagnose and treat some of these disorders and enable these couples to have children.
• Where such corrections are not possible, the couples could be assisted to have children through certain special techniques commonly known as assisted reproductive technologies (ART).

Explanation-

• In vitro fertilisation(IVF) - fertilisation outside the body in almost similar conditions as that in the body.
• In vivo fertilisation- fusion of gametes within the female.
• After the fusion of gametes, the zygote is formed which reaches the 32-celled stages within 24 hrs.
• Now, this embryo is transplanted in the normal uterus of same mother or surrogate mother for further development after the completion of the gestation period a normal child take birth.

Therefore The test-tube baby means fertilization in vitro and then transplantation in the uterus.

Additional Information

ZIFT - (zygote intrafallopian transfer)

• The zygote or early embryos (with up to 8 blastomeres) could then be transferred into the fallopian tube (ZIFT–zygote intrafallopian transfer) and embryos with more than 8 blastomeres, into the uterus (IUT – intrauterine transfer), to complete their further development.

IUD - An intrauterine device

• An intrauterine device (IUD), also known as an intrauterine contraceptive device, is a small, flexible, plastic device shaped like the letter T.
• It is inserted into the uterus by a healthcare provider and can remain in place for several years to prevent pregnancy.
• Types of IUDs:
  • Hormonal IUD: Releases progestogen, which thickens cervical mucus, preventing sperm from reaching the fallopian tubes. It may also partially prevent ovulation.
  • Copper IUD: Contains no hormones but releases copper ions, toxic to sperm. It also causes the uterus and fallopian tubes to produce fluid toxic to sperm.
  • Emergency Contraception: Copper IUDs can be used as emergency contraception within five days of unprotected sex.

Key Points

• Inflammation is a signal when the body sends cells to defend against an irritant, an allergen, or a pathogen.
• The signs of inflammation include heat, redness in the skin, swelling, pain, etc.
• It is an important part of the body's immune system defenses.
• The cells involved in inflammatory reactions are basophils.
• Basophils are one of the granulocytes of white blood cells.
• The other two granulocytes are neutrophils and eosinophils.
• Basophils secrete histamine, serotonin, heparin, etc., and are involved in inflammatory reactions.
• Basophils contain cytoplasmic granules and the nucleus has two lobes.
• They play a role in both parasitic infections and allergies.

Additional Information

• Neutrophils:
  • These are granulocytes, a type of white blood cell.
  • Neutrophils are the most abundant cells (60-65
    percent) of the total WBCs.
  • Neutrophils are phagocytic cells that destroy foreign organisms entering the body.
• Eosinophils:
  • These are granulocytes, a type of white blood cell.
  • Eosinophils prevent infections and are also associated with allergic reactions.
• Lymphocytes:
  • These are agranulocytes, a type of white blood cell.
  • Lymphocytes are of two major types - B lymphocytes and T lymphocytes.
  • Both B and T lymphocytes are responsible for the immune responses of the body.

​​Hence, the correct option is (1) Basophils.

The correct answer is Sere.

Key Points

• The entire sequence of communities that successively change in a given area is called Sere.
• The individual transitional communities are termed seral stages or seral communities.
• In the successive seral stages, there is a change in the diversity of species of organisms, an increase in the number of species and organisms as well as an increase in the total biomass.

Important Points

• Ecological succession:
  • ​The gradual and fairly predictable change in the species composition of a given area is called ecological succession.
  • During succession, some species colonise an area and their populations become more numerous, whereas populations of other species decline and even disappear.

The correct answer is An ecosystem which can be easily damaged but can recover after some time if damaging effect stops

• Low Stability: Stability in an ecosystem refers to its ability to resist change or disturbance. In this case, the ecosystem described can be easily damaged, indicating low stability. This means that even minor disturbances or stresses can disrupt its structure and function.
• High Resilience: Resilience is the ability of an ecosystem to recover and return to its original state after being disturbed. The ecosystem described in option 1 can recover after some time if the damaging effect stops. This demonstrates high resilience because despite being easily damaged, it has the capacity to bounce back and restore itself.

In summary, option 1 represents an ecosystem that is prone to damage (low stability) but has the ability to recover effectively (high resilience). This combination of characteristics is typical of ecosystems that are subject to frequent disturbances but can adapt and regenerate over time.