Question 1: Define protists and describe two key characteristics that distinguish them from other microorganisms.

Answer: Protists are a diverse group of eukaryotic microorganisms that are neither plants, animals, nor fungi. They typically have a nucleus and are unicellular or simple multicellular organisms.

Question 2: Explain how the protist Plasmodium causes malaria in humans.

Answer: Plasmodium infects human liver and red blood cells after being transmitted by Anopheles mosquito bites, causing symptoms of malaria. It reproduces inside these cells, leading to cell rupture and illness.

Question 3: Identify three safety precautions that must be taken when studying protists in a laboratory setting.

Answer: Wearing lab coats and gloves, avoiding inhalation of aerosols, sterilising equipment after use, and disposing of cultures properly.

Question 4: If a sample of water contains 150 protist cells per millilitre, how many cells are present in 10 millilitres of the sample?

Answer: 150 cells/mL × 10 mL = 1500 cells

Question 5: A scientist observes that 60% of protists in a sample are infected with a parasite. In a sample of 200 protists, how many are infected?

Answer: 200 × 0.60 = 120 protists

Question 6: Describe a practical experiment to investigate the effect of salt concentration on the survival of a freshwater protist.

Answer: Prepare solutions with varying salt concentrations. Place equal volumes of freshwater protist culture into each solution. Observe and record the number of living protists after a set period. Ensure safety by wearing gloves and sterilising equipment after use. Control variables include temperature, volume, and initial protist count.

Question 7: In a study, the number of protists in a sample was recorded as follows: 100, 120, 115, 130, 125. Calculate the mean number of protists in the sample.

Answer: (100 + 120 + 115 + 130 + 125) / 5 = 118

Question 8: Analyse the potential impact of protist infections on aquaculture industries.

Answer: Protist infections can lead to disease outbreaks in fish farms, reducing fish health and yield. This can cause economic losses and affect food supply. Managing infections requires monitoring water quality, implementing biosecurity measures, and using treatments where appropriate.

Question 9: Which of the following protists is known to cause sleeping sickness in humans?

Answer: Trypanosoma brucei

Question 10: Fill in the blank: The protist responsible for causing malaria is transmitted by the ______ mosquito.

Answer: Anopheles

Question 11: Explain why protists are considered both beneficial and harmful in different contexts.

Answer: Some protists, like phytoplankton, produce oxygen and form the base of aquatic food chains, benefiting ecosystems. Others, like Plasmodium, cause serious diseases in humans and animals, posing health risks. Their impact depends on the species and environment.