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Reproduction · Paper 2 — Free Biology HL Practice Questions

1MasterySAQ-SSexual cycles in animals and plants5 marksPaper 2~8 min

Data

- Concentration of egg jelly glycoprotein: 0.5 μg mL−10.5\,\mu\text{g}\,\text{mL}^{-1} - Percentage of sperm undergoing acrosomal reaction at this concentration: 78%78\% - Percentage of sperm undergoing acrosomal reaction in control (no glycoprotein): 2%2\%
In a species of sea urchin (Arbacia punctulata), external fertilization occurs in seawater. Researchers observed that the acrosomal reaction in sperm is triggered by a specific glycoprotein on the surface of the egg's jelly coat.
(a)
Describe the events of the acrosomal reaction in sea urchin sperm upon contact with the egg jelly coat. [2 marks]
(b)
Determine the difference in percentage points between sperm undergoing the acrosomal reaction in the experimental group and the control. [1 mark]
(c)
Predict how the percentage of sperm undergoing the acrosomal reaction would change if the glycoprotein concentration were increased to 2.0 μg mL−12.0\,\mu\text{g}\,\text{mL}^{-1}. Explain your reasoning with reference to receptor behaviour and the consequence for fertilization. [2 marks]
diagram

Solutions

2MasterySAQ-SSexual cycles in animals and plants5 marksPaper 2~8 min
A student investigated sporophyte production in Funaria hygrometrica over two years. The table shows the number of sporophytes counted in sample plots. Year — Rainfall classification — Sporophytes counted Year 1 — Wet — 8484 Year 2 — Dry — 1212 The life cycle of Funaria hygrometrica involves a dominant haploid gametophyte generation. The gametophyte produces gametes by mitosis, and fertilization requires water for sperm to swim to the egg.
(a)
Describe how the gametophyte of Funaria hygrometrica produces both male and female gametes. [2 marks]
(b)
Calculate the ratio of sporophyte production in the wet year to the dry year. Express your answer as a whole number ratio (x:1)(x:1). [1 mark]
(c)
Explain why dependence on water for fertilization limits moss reproduction in terrestrial environments. [2 marks]
diagram

Solutions

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