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The diagram below shows a phase during meiosis in an animal cell - English General - NSC Life Sciences - Question 2 - 2021 - Paper 1

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The diagram below shows a phase during meiosis in an animal cell. Identify part C. Name the phase represented in the diagram. B represents homologous chromosomes.... show full transcript

Worked Solution & Example Answer:The diagram below shows a phase during meiosis in an animal cell - English General - NSC Life Sciences - Question 2 - 2021 - Paper 1

Step 1

Identify part C.

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Answer

Part C is the centromere.

Step 2

Name the phase represented in the diagram.

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Answer

The phase represented in the diagram is metaphase.

Step 3

What are homologous chromosomes?

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Answer

Homologous chromosomes are a pair of chromosomes that have the same structure and length, containing the same sequence of genes. One is inherited from the maternal parent and the other from the paternal parent.

Step 4

Explain the appearance of the chromosomes in the diagram.

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Answer

The chromosomes in the diagram appear as replicated structures. Each chromosome consists of two sister chromatids that are joined at the centromere. During meiosis, crossing over can occur where homologous chromosomes exchange genetic material, leading to genetic diversity.

Step 5

How much DNA (in arbitrary units) was in the parent cell at the beginning of the cell division?

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Answer

Since each daughter cell contains 12 arbitrary units of DNA, the parent cell must have had a total of 48 arbitrary units of DNA at the beginning of the cell division.

Step 6

Identify part B.

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Answer

Part B is identified as a sweat gland.

Step 7

Describe how structure A functions during thermoregulation on a cold day.

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Answer

Structure A, which is a blood vessel, will constrict to reduce blood flow towards the surface of the skin. This reduces heat loss and helps to maintain the body temperature in cold conditions.

Step 8

Explain why temperature needs to be kept constant in the human body.

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Answer

Temperature needs to be kept constant in the human body because enzymes function optimally at a specific temperature (around 37°C). Any deviations can lead to enzyme denaturation or loss of activity, affecting metabolic processes.

Step 9

Name the gland that secretes ADH.

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Answer

The pituitary gland secretes ADH.

Step 10

Describe osmoregulation on a cold day.

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Answer

On a cold day, the body conserves water by reabsorbing it in the kidneys while reducing the amount of sweat produced. This is largely controlled by ADH, which promotes water reabsorption in the renal tubules.

Step 11

Explain why the ADH levels in the body of this person are not normal for this person.

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Answer

In this person's case, the renal tubules are resistant to the effects of ADH. Consequently, water is not reabsorbed effectively, leading to the production of large volumes of dilute urine, which results in abnormally low ADH levels.

Step 12

Name the type of fertilisation in guppies.

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Answer

The type of fertilisation in guppies is internal fertilisation.

Step 13

Explain TWO ways in which the type of fertilisation named in QUESTION 2.4.1 increases reproductive success.

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Answer

  1. Internal fertilisation allows sperm to be deposited directly inside the female, which increases the chances of successful fertilisation by minimizing the risk of environmental factors affecting sperm and eggs.
  2. The fertilised eggs remain in the female’s body until they are ready to hatch, providing protection from predators and environmental dangers, leading to a higher survival rate for the offspring.

Step 14

Why are guppies regarded as being ovoviviparous?

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Guppies are regarded as ovoviviparous because the fertilised eggs develop inside the female's body, and the young are born live, rather than laying eggs externally.

Step 15

Why is the injection of progesterone a good treatment to prevent premature delivery?

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Answer

The injection of progesterone is a good treatment to prevent premature delivery as it maintains the lining of the uterus, thus supporting the pregnancy and preventing contractions that could lead to early labor.

Step 16

Identify: (a) Independent variable.

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Answer

The independent variable is the dosage of progesterone administered to the participants.

Step 17

(b) Dependent variable.

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Answer

The dependent variable is the glucose levels measured in the participants.

Step 18

Describe how the investigators determined whether any of the participants in Group A had developed gestational diabetes.

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Answer

The investigators determined if participants from Group A developed gestational diabetes by measuring their glucose levels daily. A sustained increase in glucose levels would indicate the development of the condition.

Step 19

State TWO factors that were kept constant when the progesterone was administered in Group A.

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Answer

  1. The dosage of progesterone given was kept constant at 250 mg.
  2. The timing of the injection was kept constant for all participants, occurring between weeks 16 and 20 of gestation.

Step 20

Explain the importance of group B in this investigation.

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Answer

Group B serves as the control group, which helps to establish a baseline for comparison against Group A. This allows researchers to determine the effects of progesterone treatment specifically, as any changes in glucose levels can be attributed to the treatment compared to a group that did not receive it.

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