All Free Biology MCQs with Answers

2751. A bacteriophage is attached to the receptor site on the host cells:

• A. Slime
• B. Cell wall
• C. Cell membrane
• D. Envelope

Explanation: A bacteriophage is a virus that infects bacteria. It attaches to the receptor site on the host cell's cell membrane. The receptor site is a specific molecule on the cell membrane that the bacteriophage can recognize and bind to.Once the bacteriophage has attached to the receptor site, it injects its DNA into the host cell. The DNA then takes over the host cell's machinery and starts to replicate itself. The replicated DNA then produces new bacteriophage particles, which are released from the host cell.

2752. In Rhizopus zygote is formed by fusion of hyphae of:

• A. Minus mating strains
• B. Minus mating and plus mating strain
• C. Plus mating strain
• D. Same fungus

Explanation: Answer is "Minus Mating strain and plus mating strain"Explanation: In fungi due to homothallic body the terms of male and female cannot be used.

2753. In the life cycle of Rhizopus, the hyphal tips after coming in contact with each are transformed into:

• A. Sporangia
• B. Conidiophores
• C. Sporangiophores
• D. Gametangia

Explanation: Answer is "Gametangia"Explanation: Means bodies containing gametes.Gametangia are specialized structures in fungi that produce gametes, which are haploid reproductive cells. Gametangia are typically found in fungi that reproduce sexually.There are two main types of gametangia: antheridia and archegonia. Antheridia produce male gametes, while archegonia produce female gametes.

2754. In the life cycle of Black bread mold, gametangia after plasmogamy and karyogamy give rise to:

• A. Zygospore
• B. Basidiospore
• C. Ascospores
• D. Conidiophore

Explanation: Answer is "Zygospore"Explanation: It is a diploid resistant body which comes into being by fusion of two haploid nuclei of different strains.

2755. In the life cycle of Rhizopus diploid spores are produced in:

• A. Asexual reproduction only
• B. Sexual reproduction only
• C. Both in sexual and asexual reproduction
• D. Both in fragmentation and budding

Explanation: Answer is "Sexual reproduction only"Explanation: Somatic body of fungus is haploid and it divides by mitosis to produce asexual spores.Diploid spores are produced in sexual reproduction in the life cycle of Rhizopus.Rhizopus is a heterothallic fungus, which means that it requires two different mating types in order to reproduce sexually.

2756. Pick up the true choice with respect to the life cycle of Rhizopus:

• A. Haploid Zygospores mitosis ⎯⎯ →⎯ Haploid spores
• B. Diploid Zygospores mitosis ⎯⎯ →⎯ Diploid spores
• C. Diploid Zygospores meiosis ⎯⎯ →⎯ Haploid spores
• D. Diploid Zygospores meiosis ⎯⎯ →⎯ Diploid spores

Explanation: Answer is "Diploid zygospore ⎯⎯→Haploid spores"Explanation: Diploid zygospore undergoes meiosis to produce four haploid spores, two of plus strain and two of minus strain.Diploid zygospores are created when two haploid fungi fuse together. These zygospores then undergo meiosis, which splits the zygospore into four haploid spores. These spores are then dispersed and can grow into new haploid fungi.

2757. Which one of the following phases of the life cycle of Rhizopus is delayed?

• A. Dikaryotic
• B. Heterokaryotic
• C. Diploid
• D. Meiosis

Explanation: Answer is "Meiosis"Explanation: Zygospore is a resistant dormant body which waits for arrival of favorable conditions and meiosis is delayed. This is because Rhizopus is a heterothallic fungus, which means that it requires two different mating types in order to reproduce sexually. The meiosis phase only occurs when two compatible mating types come together.

2758. Without the activity of _ along with _ all the essential nutrients would soon become locked up in the mounds of dead animals and plants:

• A. Fungi, Saprobic bacteria
• B. Algae, Saprobic bacteria
• C. Fungi, Parasitic bacteria
• D. Algae, Parasitic bacteria

Explanation: Answer is "Fungi, saprobic bacteria"Explanation: Both of them are decomposers and recycler of nature.

2759. Mycorrhizal fungi improve the growth of _ of all kinds of vascular plants through their association:

• A. 95%
• B. 90%
• C. 85%
• D. 80%

Explanation: Answer is "95%"Explanation: Symbiotic association is common in vascular plants.

2760. _ growing on rocks breaks them, setting the stage for other organisms during ecological succession.

• A. Ectomycorrhizae
• B. Endomycorrhizae
• C. Bacteria
• D. Lichen

Explanation: Lichens growing on rocks breaks them, setting the stage for other organisms during the course of ecological succession.Lichens are a symbiotic relationship between a fungus and an alga. The fungus provides the alga with water and minerals, and the alga provides the fungus with food. Lichens are able to grow on bare rock because they secrete acids that break down the rock. This process is called lichenolysis.As lichens break down the rock, they create a small pocket of soil. This soil provides a habitat for other organisms, such as mosses and small plants. These organisms further break down the rock, creating more soil. This process continues until a mature ecosystem is established.Lichens are therefore important pioneer species in ecological succession. They are the first organisms to colonize bare rock, and they set the stage for the establishment of other organisms.