Animals and plants defend themselves against infection - Edexcel - GCSE Biology - Question 3 - 2017 - Paper 1

The number of deaths from malaria is only an estimate because reporting may vary between countries, some cases might go unreported, and there can be discrepancies in the cause of death determination, especially in regions with limited health infrastructure.

From the data, in the immunisation trial, 64 out of 400 children who were not immunised developed malaria, while only 32 out of 400 immunised children contracted the disease. This indicates that the immunisation reduces the incidence of malaria significantly. The effectiveness can be calculated as:

Substituting the values:

This means that the immunisation appears to reduce the risk of developing malaria by 50%.

The part of an immunisation that stimulates the production of antibodies is B an antigen.

1. Misinformation or distrust about vaccine safety and efficacy.

2. Unavailability of vaccines or accessibility issues in certain regions.

Plants have several defense mechanisms against infections, including:

1. Physical barriers: Thick cell walls, waxy cuticles, and thick bark can prevent pathogens from entering.

2. Chemical defenses: Plants may produce antimicrobial compounds, such as phytoalexins and enzymes, that inhibit pathogen growth.

Additionally, when attacked, plants can also release volatile organic compounds to attract predators of the pathogens.