When a child is born, the umbilical cord and stem cells can be obtained from it - NSC Life Sciences - Question 3 - 2022 - Paper 2

Stem cells are undifferentiated cells and have the potential to develop into any type of cell in the body. This characteristic allows them to replace damaged or defective cells, making them particularly useful for treating disorders such as heart disease and spinal injuries.

One condition mentioned in the extract that can be treated with stem cells is spinal injuries.

A population is defined as a group of organisms of the same species occupying the same habitat at the same time.

One reason they are considered two different species is because they produce infertile offspring when they interbreed.

Three mechanisms of reproductive isolation are:

1. Breeding at different times of the year
2. Species-specific courtship behavior
3. Prevention of fertilization

The positioning of the thumbs is important because it allows for a power grip and precision grip, which are essential for humans in manipulating objects.

One difference is that humans have small teeth compared to canines, whereas African apes have large teeth and significant gaps between them.

The type of diagram shown is a phylogenetic tree, also known as a cladogram.

There are two genera represented by the diagram.

The species represented by X on the diagram is Homo habilis and the species that shares a common ancestor with Homo erectus is Homo naledi.

The only species of the genus Homo that is in existence today is Homo sapiens.

Two forms of evidence that could have been used are:

1. Fossil evidence
2. Genetic evidence

The difference in cranial capacity is significant as it indicates brain size, which is linked to intelligence and the development of complex behaviors in Homo sapiens compared to earlier species.

The ancestor of whales that most likely lived both in water and on land is Pakicetus.

One reason for this is that Pakicetus had physical characteristics such as limbs suitable for both swimming and walking on land.

Ambulocetus and Dorudon are considered transitional species because they exhibit features that are intermediate between land-dwelling ancestors like Pakicetus and modern whales like Balaena.

According to Lamarck, as whales spent more time in the water searching for food, the legs they originally had were used less frequently, leading to their disappearance in future generations.

The dependent variable is the probability of developing resistance to antiretroviral drugs, while the independent variable is the number of missed treatments.

One conclusion is that the probability of HIV developing resistance to antiretroviral drugs increases with the increase in the number of missed treatments.

The more days a patient misses treatment, the greater the probability of the virus developing resistance to antiretroviral drugs.