2.1 Scientists reported that a female crocodile in a zoo laid an egg with a developing embryo - NSC Life Sciences - Question 2 - 2024 - Paper 1
Question 2
2.1 Scientists reported that a female crocodile in a zoo laid an egg with a developing embryo. There were no male crocodiles in the zoo for 16 years. This form of re... show full transcript
Worked Solution & Example Answer:2.1 Scientists reported that a female crocodile in a zoo laid an egg with a developing embryo - NSC Life Sciences - Question 2 - 2024 - Paper 1
Step 1
2.1.1 Name the type of meiotic division shown in the diagram above.
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Answer
The type of meiotic division shown in the diagram is called meiosis.
Step 2
2.1.2 Name the type of egg that was laid by the crocodile.
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Answer
The type of egg laid by the crocodile is an amniotic egg.
Step 3
2.1.3 Explain ONE way in which the type of egg named in QUESTION 2.1.2 is structurally suited to survive the conditions on land.
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An amniotic egg has a shell that prevents drying out, and it contains amniotic fluid which protects the developing embryo from mechanical shocks and provides a stable environment.
Step 4
2.1.4 Explain ONE advantage of parthenogenesis.
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One advantage of parthenogenesis is that females can reproduce without males, which increases the chances of survival for the species in environments where males are scarce.
Step 5
2.2.1 State TWO functions of LH during the menstrual cycle.
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LH stimulates ovulation.
LH stimulates the development of the corpus luteum.
Step 6
2.2.2 Besides LH, name ONE other hormone that is secreted by the pituitary gland during the menstrual cycle.
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Follicle-stimulating hormone (FSH) is another hormone secreted by the pituitary gland during the menstrual cycle.
Step 7
2.2.3 Give the name of hormone X.
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Hormone X is progesterone.
Step 8
2.2.4 Use the information in the graph to explain how the level of hormone X will be different in woman B.
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Answer
In woman B, the progesterone levels will remain low because the LH levels are low, indicating that ovulation will not take place, and therefore no corpus luteum will develop.
Step 9
2.2.5 What evidence in the graph suggests that woman A is pregnant?
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The evidence that suggests woman A is pregnant is the sustained high levels of progesterone throughout the luteal phase of her menstrual cycle.
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Answer
(a) The independent variable is age.
(b) The dependent variable is fertility in men.
Step 11
2.3.2 State THREE ways in which the dependent variable was determined.
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The sperm count was determined by counting the number of normal sperm per milliliter of semen.
Progressive motility was assessed to check the ability of sperm to swim effectively in a straight line.
Sperm necrosis was evaluated by counting the number of dead or immature sperm per fresh semen sample.
Step 12
2.3.3 Give TWO reasons why the investigation can be considered to be reliable.
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The investigation was conducted over multiple years with a large sample size of 1,294 men, improving the accuracy of the results.
Standardized methods were used to collect and analyze the sperm samples to reduce variability.
Step 13
2.3.4 Explain why with occupations involving exposure to excessive heat were excluded from the investigation.
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Occupations involving exposure to excessive heat were excluded because high temperatures can adversely affect sperm production and motility, which could confound the results of the investigation.
Step 14
2.4.1 Name: (a) The organelles found in large numbers in part B (b) The part of the testes where spermatogenesis takes place.
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(a) The organelles are mitochondria.
(b) The part of the testes where spermatogenesis takes place is the seminiferous tubules.
Step 15
2.4.2 Identify the following parts during fertilization. (a) A (b) D
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(a) A is the acrosome.
(b) D is the nucleus of the sperm cell.
Step 16
2.4.4 Describe the functional relationship between the organelles in part B and structure C during reproduction.
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The mitochondria (part B) provide the necessary energy for motility of the sperm (structure C) enabling it to swim towards the ovum for fertilization.
Step 17
2.4.5 Calculate the distance (in cm) that a sperm needs to move to reach the ovum. Show ALL workings.
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Distance = speed x time = 5 mm/min x 45 min = 225 mm = 22.5 cm.
Step 18
2.5.1 Identify part: (a) A (b) B
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(a) A is the auditory nerve.
(b) B is the cochlea.
Step 19
2.5.2 State the function of part: C D
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(C) Part C absorbs excess pressure waves from the inner ear and prevents echo.
(D) Part D equalizes pressure on either side of the tympanic membrane.
Step 20
2.5.3 Explain how this condition will affect hearing.
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Answer
Otosclerosis will prevent the ossicles from vibrating, leading to less or no vibrations being transmitted to the oval window, which can result in impaired hearing since pressure waves will not stimulate the auditory nerve adequately.
